The Energy Sparks Analysis Dashboard provides in depth analysis of a school’s energy consumption via multiple charts.
This is the documentation associated with the Analysis Dashboard and provides more in depth advice and analysis.
To access the detail information, click the ‘+’ sign to the left of each section’s title below.
For schools in the Bath area, this data is then fed to a school’s energy company, which then feeds it onto a council system called ‘SystemsLink’, which then passes it onto the Energy Sparks website. The website then analyses this data, in conjunction with historic temperature and other data and produces advice and charts.
kWh versus kW
Consumers are often get confused by the terms kWh (‘kilowatt-hours’) which is a unit of energy and kW (killowatts) which is a unit of power (a more detailed explanation here). The Energy Sparks website uses both terms, and graphs contain data in both of these units. kW is a measure of your instantaneous usage of energy, so the instance you turn a kettle on it might use 3 kW, but if you turn it off immediately after it is turned on, then you will not have used much energy because that (power) consumption was only for a short period of time.
If however your kettle was very large and took 30 minutes to come to the boil, it would have used 3 kW * 30 minutes of energy, which is 1.5 kWh (3 kW * 1/2 an hour).
Converting kWh to £ and pence
Your electricity supplier will charge you for the amount of electricity you use, for example at 12p/kWh, so in this example boiling the kettle for 1/2 an hour would have cost 1.5 kWh * 12p/kWh = 18p. Energy Sparks provides lots of examples of potential energy savings, and these are presented in both £ and kWh. A simple example might be how much energy you might save through reducing the amount of electricity you use out of school hours (baseload):
Example: upgrading to a new energy efficient ICT server: If your out of hours power consumption is 4kW, but you manage to reduce it to 3.4kW by replacing an old ICT server which consumes 1kW with a new more energy efficient ICT server which only consumes 0.4kW, you would reduce the school’s power consumption by 0.6kW.
Over the course of a year this would save 0.6kW * 8760 hours = 5,256kWh, which is £631 per year if electricity costs 12p/kWh.
As of July 2018 Energy Sparks makes the following assumptions about a schools energy costs:
CO2 – carbon dioxide
Carbon dioxide (CO2) is a greenhouse gas and is emitted into the atmosphere when we burn fossil fuels e.g. gas, oil and coal. In a school these emissions are produced locally by a school’s gas boiler and remotely by power stations supplying the school with electricity via the national grid (the network of power cables which covers the whole of the UK). It’s important that we try to limit our CO2 emissions as CO2 is a greenhouse gas. The more CO2 that gets released into the atmosphere, the more heat is retained by the atmosphere, which leads to the earth heating up. This heating up will lead to ‘Climate Change’ which will have a negative impact on the earth in the future, particularly by the time current school children become adults.
By making a school more energy efficient, it will reduce the amount of fossil fuels burnt to generate the school’s energy, and reduce the impact of climate change.
Energy Sparks currently makes the following assumptions about the CO2 produced when we use energy:
The electricity CO2 value of 282g/kWh of electricity consumed is the latest average value for the last year, but this varies throughout the day. This website provides the current electricity CO2 value for the UK and what sources of energy (gas, coal, nuclear, wind etc.) are contributing to produce our electricity.
For solar PV (solar photovoltaic panels) Energy Sparks assumes carbon emissions of 40g/kWh – which represents the energy used to manufacture the panels, spread out over the lifetime of the panels. So, although once manufactured solar PV panels have no emissions when generating electricity, we still need to consider the embedded energy in the panels.
AMR: Automatic Meter Reading or Smart Meter data – ½ hourly gas and electricity meter readings transmitted to a central database typically by mobile phone type GSM messages – mandated for installation at all schools by the Department of Education in 2010, but not all LEAs have adopted the policy.
BMS: Building Management System. Typically provides electronic, automatic control of various functions of the building including lighting and boilers. These are generally used in large schools, but are often not that effective at controlling a school’s energy consumption because they can be difficult to understand and programme, and often run incorrectly, wasting energy.
CUSUM analysis: Cumulative Sum Control Chart – used for spotting trends in energy consumption patterns particularly when normalised adjustment of temperatures by degree days for heating analysis is required. The methodology basically adjusts gas consumption for temperature, so it is possible to directly compare gas consumption on cold and warm days, which helps spot anomalies.
DC1100: Satchwell DC1100 controller – is the most common boiler controller used at primary schools (about 75%), it provides sophisticated control, and its features include:
- 7 day control, programming of all holidays up to a year in advance, auto GMT/BST switchover, multiple on and off times during the day
- Optimum start, optimum stop, night time and day time set back
- Compensation control, weather compensation, sophisticated frost protection
- It relies on combinations of room, outside and pipework temperature sensors to control the boiler
- Can control a maximum of 2 zones
Degree Days: metric indicating how cold a particular day was, typically the number of degrees C the average outside temperature was below the balance point temperature of 15.5C. Used for thermostatic analysis and energy consumption estimates. So for example if the temperature outside was 5.5C it would have 10C of degree days (15.5 – 5.5), but if the outside temperature was 10.5C it would have 5C degree days. Typically you would expect heating (gas) consumption on a 10C degree day to be double that of a 5C degree day. Good thermostatic control should show a linear relationship between degree days (how cold it is) and heating energy consumption. The 15.5C set point is an industry default and presents the outside temperature at which the internal gains of a building should be able to maintain an internal temperature of 19C without the need for heating. In schools because of their significant internal gains from high occupation density the balance point temperature is likely to be below 15.5C. Typical annual degree days for schools during days of occupation (number of days x temperature difference below 15.5C) is between 1000 and 1500 for schools in Bath, this compares with 2400 for domestic properties which are assumed to be occupied year round.
Frost protection: Frost protection aims to stop pipe damage from freezing water. The boiler controller turns the heating on if the outside temperature drops close to zero degrees (typically 4C). It then attempts to maintain the internal temperature of the school above a set temperature (typically 10C) until the external temperature rises above freezing again.
ICT: Information and Communication Technology – a generic term used throughout the report for computer infrastructure in schools, this includes computer servers, networking equipment, desktops and overhead projectors and whiteboards. These typically consume between 30% and 50% of a school’s electricity. The growth of ICT is a significant contributor to the 40% increase in schools’ electricity consumption over the last decade.
Optimum start boiler controller: most schools use sophisticated boiler controllers which determine when to start the boiler each morning in order to get the school up to temperature for the start of the school day. So on a cold morning the controller might start the boiler at 5.30am, but on a mild morning as late as 7.15am – this saves energy. Typically these controllers self-learn how long it takes to get the school up to temperature.
R2: Coefficient of determination or R squared is a mathematical metric used to indicate how well a series of points fit a line or a curve. In the context of thermostatic control it provides an indication of how linearly energy consumption varies with outside temperature. The higher the value the better the thermostatic control, a figure of 0.8 or above is considered ‘good’
RHI: Renewable Heat Incentive – a subsidy to encourage renewable heating
Thermal Mass: is the ability of a material to absorb and store heat energy. A lot of heat energy is required to change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to have high thermal mass. So for example schools with high thermal mass take longer to get up to temperature and require more gas on a Monday morning after the heating has been off all weekend. Thermal mass also helps maintain temperatures overnight after the heating is turned off as heat is slowly released into the interior of the building from thermal mass in the walls and floor of the building. Because schools are only occupied 15% of the year, thermal mass is probably less beneficial if you consider both energy efficiency and comfort than other buildings, for example residential homes with greater occupancy
TRV: Thermostatic controlled radiator valve – controls which are connected to the pipework leading into radiators. They control the flow of hot water into the area, shutting the flow off if the room gets too hot, and back on when it gets cold again. TRVs should generally never be set to a maximum setting, as rooms will get too hot. They should be adjusted to a level which provides a good average temperature (e.g. 20C) when the room is occupied.
U-Value: the U value of a building fabric element is a measure of its insulative properties and defines the heat loss per meter squared per degree difference in temperature between the inside and the outside of the building. The lower the U value the better the insulation, for example single pane metal framed windows might have a U value of 6.0 W/m2/K whereas modern UPVC would glazed windows might have a U value of 1.5 W/m2/K and lose only a quarter of the heat of an equivalent sized single pane metal framed window.
Typical U Value for building fabric components are:
|Component||U Value W/m2/K|
|Metal framed single pane window||6.0|
|Old double glazed window||2.8|
|Uninsulated cavity wall||1.4|
|Modern double glazed window||1.4|
|Insulated cavity wall||0.6|
|Modern wall built to 2010 building standards||0.4|
Weather Compensation: Weather compensation is a feature of a boiler controller which changes the temperature of the water circulating in the radiators depending on the outside temperature. The temperature of the circulating water affects the amount of heat being delivered to the building, so very hot water circulating through radiators produces more heat than colder water. If a boiler has weather compensation configured the temperature of the circulating water is varied linearly with the outside temperature, so in cold weather very hot water is circulated (e.g. 70C) and in milder weather cooler water is circulated (e.g. 40C). Weather compensation is thus more efficient as it delivers less heat to a building during milder weather reducing the chances of overheating in classrooms and the necessity to open windows. It may not be compatible with fan assisted radiators. It can however be retrofitted to most boilers relatively cheaply with some pipework, a couple of pumps and a thermostat.
The temperature in the school is generally automatically controlled in two ways:
- a thermostat, often installed centrally (often incorrectly in a hall or corridor) which turns the boiler on or off depending on whether the room in which the thermostat has been installed reaches the set point temperature (typically 20C)
- TRVs – thermostatic radiator valves, installed on each radiator which turn the radiators off when a room reaches a temperature set by the TRV
Additionally, windows are manually opened to further control the temperature.
Unfortunately in most schools the automatic and manual management of heating doesn’t work well, and it can easily be improved to save costs, reduce greenhouse gas emissions and improve thermal comfort. At most schools there are opportunities to save 25% of heating costs at no or relatively low cost; on average about 50% of a school’s gas is consumed out of hours- when no one is in the building!
The types of issues commonly found at most schools, which could be improved are as follows:
- boilers are left on unnecessarily over holidays
- some schools leave their boilers on at weekends
- boilers come on too early – before 3:00am in about 30% of schools! And, stay on too late, after the school has closed
- thermostatic control is poor, temperature control is managed by opening windows rather than setting the TRVs correctly
- classrooms are often too hot; for every 1C above the recommended 18C the school’s heating bill increases by about 10%
The following sections go into these issues is much more detail, and provide guidance on how many of these issues can be improved.
A good starting point for analysing whether your school is managing its electricity well is to compare your school’s energy usage with other schools. The first graph on the Energy Sparks dashboard does this, providing comparisons of your usage with regional and national averages, and with ‘exemplar’ schools (those which manage their energy well):
The example above shows a school’s energy use (in £) over the last 3 years compared with schools of the same size (scaled by floor area for gas and number of pupils for electricity), compared with national and regional averages, and with exemplar (well managed) schools. In this example the school seems to be managing its gas consumption well but is using more electricity than you would expect for a school of this size? How does your school compare?
Analysis suggests there is very little difference in energy efficiency between older (for example Victorian) and recently built schools. So, you shouldn’t use the age of your school buildings as an excuse for not trying to improve their energy efficiency!
Another comparison is provided by the third graph on the Energy Spark’s dashboard which breaks down the school’s gas consumption between holidays, weekends, school data, both during school hours and outside school hours:
This shows a school using more than 70% of its gas outside school hours. How does your school compare? At schools with well managed heating and hot water this value would be less than 25%.
The fifth graph on the first Energy Sparks dashboard web page provides a better understanding on how well managed a school’s gas usage is during holidays:
The chart highlights in red the school holidays, you can see for this school that the heating has been left on on every holiday in the last year. Sometimes there are legitimate reasons, for example the school is used during the holidays, or school staff are coming in to do preparation work. However, it is often not necessary to heat the whole school, if one or two staff members are potentially coming into the school for a few half days during the holidays – it is better that they use local heating, for example fan heaters rather than heating the whole school. In our experience, the main reasons for not turning the gas boiler off during holidays:
- the school forgets (Energy Sparks now sends text alerts and emails just before school holidays as a reminder to turn the boiler off)
- the school doesn’t know how to turn the boiler off (most commercial boiler controllers have ‘holiday’ functions to help with this)
- someone is going to be in the building at some point during the holidays (see above)
- the school is worried about burst water pipes; this shouldn’t be a concern as most school boilers have automatic frost protection (see below)
On the ‘Gas Detail’ section of the Energy Sparks Dashboard, there is a breakdown of gas consumption by day of the week:
As you can see at this school it appears the heating is left on both on Saturdays and Sundays, which is probably unnecessary. Look at the dashboard for your school, are you using gas at the weekend? Unless the school is used at weekends (quite rare for most schools) then weekend consumption should be almost zero, the only reason for weekend consumption is potentially frost protection, but that should be a very small amount.
School Day Usage: before and after school hours
Another control issue is boilers coming on too early or staying on too late during school days:
In the example above, the school boiler seems to be coming on at 02:00am in the morning which is too early – it should be coming on on average at about 06:00am. The boiler appears to be turning off at about 14:30pm which is good, but there seems to be some unexpected low level gas usage for the rest of the day through to midnight.
Check how well the timing of your boiler is controlled? Is it coming on at about 6:00am?
The reasons for poor boiler timing can be as follows:
- Mis-programming: – the boiler timer is either set to the wrong time of day, or the times at which the boiler is set to come on and turn off are wrong
- Optimum start control not working: – see the section on this further down this web page
- A faulty thermostat: – for example turning the boiler on erroneously to protect against frost
Most school boiler controllers monitor 3 sensors in order to manage frost and determine when and by how much to turn the heating on. The 3 sensors are:
- An outside thermostat which triggers the heating to be turned on typically when the outside temperature drops below 4C
- An inside thermostat which ensures the internal temperature does not drop below a set level, typically 8C
- A heating return thermostat which monitors the temperature of the return flow on the heating system, typically keeping it above 2C
We would generally recommend that ‘frost protection’ is installed on all school boilers, as it reduces the risk of burst pipes and it means the school doesn’t need to leave its heating on over weekends and holidays in cold weather.
However, a reasonable proportion of school frost protection systems are misconfigured, aren’t working well or are overly pessimistic:
- Configuration doesn’t check the internal temperature: some boilers are set to come on at 4C whatever the internal temperature – this is wasteful of energy as the thermal mass of the building will retain heat and reduce the requirement for heating potentially up to 48 hours after the heating has been turned off
- Configuration doesn’t check the external temperature: this is often a setup used by complicated, expensive BMS’s (Building Management Systems). They can be particularly wasteful, as they are often configured to maintain a building’s internal temperature at all times above a minimum temperature, typically 10C. This is wasteful because unless the external temperature drops below 4C, there is no chance of frost damage, and so it is often unnecessary to maintain a minimum internal temperature in this circumstance
- Internal temperature settings too pessimistic its not uncommon for the internal temperature setting to be set as high as 14C, this means that the heating is often on all the time in cold weather
Our general advice is that frost protection systems need to be set as low as possible, so at 4C for the external temperature and 8C for the internal temperature. Set temperatures can depend a little on the configuration of the school – if there is a particularly cold section of the school, a long way from a thermostat, then we would recommend a higher temperature. You could also consider using localised trace heating on pipework to reduce the risk of burst pipes particularly in out buildings. One way to be confident the settings are working well in vulnerable rooms is to install a min-max thermometer and check it regularly for the minimum temperature.
Checking how well the frost protection is working at your school can be a little tricky, and involves interpreting the 3 ‘frost protection’ graphs on the ‘Boiler Control’ page of your Energy Spark’s Dashboard. It’s is probably best illustrated by examining a few examples:
No frost protection
It’s likely this school has no frost protection, as in this example the temperature has been below 4C for most of the weekend, and you would expect by some time on Sunday the school would have cooled down enough for frost protection to start the heating, but the heating doesn’t come on until the normal time on the Monday:
The frost protection at this school is working better than the example above, as the heating stays off for most of the weekend, despite it being cold, and then turns on at 18:30 on the Sunday, when the school has cooled down sufficiently for the heating to be turned on to protect the pipework:
Have a look at the graphs for your school, do you think they suggest your frost protection control is working well? If you have any doubt, please contact us and we will get our energy expert to provide advice.
The chart below shows this working at a school (apart from starting a little early in the morning):
You can see that the boiler (gas consumption) starts later in the morning on the milder day (orange gas consumption line and yellow temperature line) compared with the colder day (green gas consumption and black temperature line).
In theory this should save the school energy if the functionality is working well. Unfortunately at many schools, because it is poorly installed or configured it works badly:
The main problem with optimum start control is that the boiler comes on too early in the morning:
Typical reasons for this problem are:
- The main boiler thermostat is situated in a cold, poorly insulated space, typically a corridor or a hall which in cold weather never gets up to temperature
- The space containing the thermostat is also under-radiatored, and cannot provide enough heat to ever compensate for the fabric and ventilation heat losses in the room
- The school tries to save energy by turning the heating off in unused, or occasionally occupied rooms e.g. the hall, without realising this is actually causing an increase in energy consumption as a result of the boiler coming on for the rest of the school much earlier in the morning than it should
- Fan convector radiators in the rooms where the thermostats are installed are not functioning properly or clogged up with dust, or their TRVs are set to a lower temperature than the main thermostat, meaning that the room never gets up to temperature
- The optimum start is misconfigured as the time set in the controller, is not the occupancy time but a time someone programming the boiler misunderstood to be the boiler start time. This means the boiler starts up earlier than expected.
In all these circumstances the optimum start control starts the boiler as early as possible in a vain attempt to get the room containing the thermostat up to temperature. To fix this problem it is probably best to start by installing some temperature loggers (can be borrowed from Energy Sparks) to get feedback on how quickly classrooms are heating up in the morning; generally you would expect them to take up to 2 hours with conventional radiators and about 30 minutes with fan assisted radiators. Once you have established the school’s heating patterns in the morning and diagnosed the problem, the most likely courses of actions might include:
- move the thermostat to somewhere more representative of the majority of the school (e.g. move it from an under heated corridor or hall) to a classroom
- ensure that the radiators are working properly in the room with the thermostat
- switch the optimum start off on the controller altogether, perhaps setting the (non optimum start) boiler start time to 06:00am.
Whatever, you decide to do, you can monitor how effective the results are by looking at Energy Sparks a few days later to see if your changes have improved the control of the boiler?
Daytime Setback: this is a feature of some boiler controllers which turns the boiler off when the outside temperature reaches a set temperature typically 15C. At this point the internal heat gains within the building (human beings, sunshine, electrical equipment) are enough to maintain a good working internal temperature (e.g 20C) without the use of heating. This control works well at most schools and rarely goes wrong. It is particularly helpful in the Spring when it is cold overnight because of cold ground left from the winter, and temperatures rise rapidly during the day. The boiler will come on before school in the morning, to heat the building up, but will turn the heating off during the morning when the outside temperature has risen sufficiently for heating not to be need.
Optimum Stop: this is similar to ‘Optimum Start’ but works at the end of the day, turning the school heating off 30 minutes to an hour before a school closes when it knows that the school is warm enough for temperature to be maintained at a reasonable temperature without the need for heating. Although this functionality works well in other commercial buildings, in our experience it doesn’t work in schools, as temperatures drop in classrooms as pupils exit the building en masse and doors are left open. This causes a rapid temporary drop in temperatures which tend to confuse the Optimum Stop’s self-learning algorithm. We would recommend it is not configured in schools.
A building with good thermostatic control means the heating system brings the temperature of the building up to the set temperature, and then maintains it at a constant level. The heating required and therefore gas consumption varies linearly with how cold it is outside. The heating system can adjust for internal heat gains due to people, electrical equipment and sunshine warming the building. It can also adjust for losses due to ventilation. Poor thermostatic control is likely to cause poor thermal comfort (users feel too hot or too cold), and excessive gas consumption as the thermal comfort is often maintained by leaving windows open.
Unfortunately, many schools have poor thermostatic control. This can be due to poorly located boiler thermostats. A common location for a thermostat in schools is in the school hall or entrance lobby whose heating, internal gains and heat losses are not representative of the building as a whole, and particularly classrooms. Halls are often poorly insulated with few radiators which means they never get up to temperature, causing the boiler controller to run the boiler constantly which causes the better insulated classrooms to overheat.
Poor thermostatic control can also be due to a lack of thermostatic controls in individual rooms, which leads to windows being opened to compensate.
Fixing thermostatic control issues can be difficult, but it can make a school more comfortable and save money.
Overly hot classrooms
The ideal temperature range for learning is 18C for normal classrooms, 15C for areas of the school with high levels of activity (eg sports halls) and circulation spaces (eg corridors), and 21C for Special needs schools, low activity
areas or areas with very young children. Above and below these temperatures students’ learning performance reduces. Additionally, classrooms should have good ventilation of between 5 and 7 litres of air per student per second. As a rule of thumb for every 1C increase in classroom temperature there is a 10% increase in gas consumption.
Energy Sparks recommends a classroom temperature for most schools of 18C, which reduces gas consumption and provides a good learning environment for students. We often find when visiting schools that some classrooms are too hot e.g. above 23C, which is both detrimental to students’ alertness and is more expensive to heat. We also find that thermostatic radiator valves (TRVs) are often not adjusted correctly often set to their maximum settings, and that when a classroom gets too hot, rather than being turned down, windows are opened.
Fixing this in an existing school is difficult, and is best dealt with through behavioural change, which could include:
- a prominently displayed large thermometer in each classroom, with a recommended temperature drawn on it, which pupils can monitor
- a school or eco-team exercise to measure classroom temperatures, and the presentation of results to the whole school (See the relevant Energy Sparks activity links for appropriate activities: KS1/KS2 and KS3)
- a weekly or monthly check by the caretaker or building manager of all TRVs to make sure they are not set to maximum
The amount of gas required to heat a building is linearly proportional to the difference between the inside and outside temperatures. So if the internal temperature of a buildings is 20C, and the outside temperature drops from 10C to 0C, the temperature difference doubles and the amount of gas required to heat the building doubles. The Energy Sparks dashboard illustrates this through a series of graphs.
The weekly gas consumption graph with degree days provides a good indicator of how well gas consumption is linked with outside temperature:
Gas usage is highest in the winter, when it is coldest (degree day line highest), and gas consumption goes up and down as the outside temperature varies.
Another way of looking at this is to plot the daily gas consumption against the degree days:
As the temperature gets colder (degree days – x axis), the gas consumption increase (y axis). This graph is at a school with good thermostatic control because the points on the graph are close to the trend line (regression line). How close the points are to the line is measured by the mathematical value R2, and for this school the value is 0.78, which is a good value.
Contrast the graph above with a school where thermostatic control is poor:
This school has an R2 of 0.39, which is poor – you can see that the points are more spread out and further from the trend line, indicating that the thermostatic control is not as good as the first school.
The R2 value for your school is included in the text below the thermostatic scatter plot graph in the Energy Sparks Dashboard.
The Energy Sparks dashboard also tries to show how well a school’s thermostatic control is performing by displaying the gas consumption on a day when there is a wide diurnal temperature range i.e. the outside temperature varies significantly during the day:
The boiler comes on briefly early in the morning for frost protection, and then again at 06:00am to heat the school up ready for the school to open at 08:15am. As the outside temperature rapidly rises the boiler rapidly reduces the amount of heating.
Contrast this with another school:
At this school the gas consumption varies little throughout the day despite the outside temperature rising by 11C.
How does your school’s thermostatic control look in the charts on the Energy Sparks Dashboard?
Suggestions for improving thermostatic control include
- making sure TRVs are not set to maximum with temperatures controlled by opening windows. If windows are opened to control temperature, then in milder weather, there won’t be a drop in gas consumption, and as in the chart above gas consumption won’t reduce
- ensuring that the main thermostats for the boiler are located in good locations in the school, representative of the majority of the school’s rooms e.g. classrooms, rather than in halls and corridors
- install weather compensation on your boiler (see below)
Most modern school boilers support ‘weather compensation’ – which is often the best way of maintaining good thermostatic control across the whole school. Weather compensation reduces the temperature of the water circulating through the pipework from 80C in colder weather to perhaps 45C in milder weather, and as a result automatically changes the heating output of the radiators.
This means the thermostatic control in individual rooms is less reliant on the TRV settings. It also means classrooms are less likely to overheat in milder weather, and can save a significant amount of energy. Most commercial boilers already support weather compensation, but it is often not enabled in schools. Energy Sparks recommends that a school checks with their boiler service engineers whether this is enabled at their school next time their boilers are serviced.
Storage heaters uses cheap rate overnight electricity (between midnight and 06:00am) to store heat in radiators which is then released later in the day to keep rooms warm. They are often installed in temporary buildings or at schools without a mains gas supply.
They can be expensive to run and provide very poor thermostatic control. At most schools they run throughout the winter including weekends and holidays as they often do not have 7 day timing control.
The graphs below show the typical electricity consumption patterns for a school with storage heaters.
The first is the school’s intraday usage, notice its electricity consumption is dominated by electricity use between 00:30am and 06:00am:
And as a result of poor controls (24 hour timer, rather than a 7 day timer) and the difficulty of implementing frost protection the heating runs at weekends and holidays:
Given over the course of the winter about 50% of the days are either holidays or weekends, up to 50% of the electricity used in storage heaters can be wasted.
If you have storage heaters and would like some advice on how you can reduce your electricity consumption, please contact us as we may be able to provide a solution.
Hot water is schools is generally provided by a central gas boiler which then circulates the hot water around the school, or by more local electrically powered immersion or point of use heaters. This section of the dashboard attempts to help analyse gas based hot water heating where a gas boiler, generally in the boiler room circulates hot water around the school. These systems are often quite inefficient, because they circulate hot water permanently in a loop around the school so hot water is immediately available when someone turns on a tap rather than having to wait for the hot water to come all the way from the boiler room. The circulatory pipework used to do this is often poorly insulated, and loses heat. Often these types of systems are only 20% efficient compared with direct point of use water heaters which are often over 90% efficient.
Energy Sparks attempts to automatically assess this efficiency by examining the gas consumption just before and at the start of the school holidays:
You can see that there is little difference in gas usage between school days and school holidays, the blue represents the excess gas usage in school days, which is hot water that is being used, versus the usage over the holidays where there is no hot water being used and the gas is just heating the hot water pipework. This is a common pattern at many schools.
Energy Sparks assesses the efficiency based on this information. For an example school:
- An average school day consumption of 384 kWh
- An average weekend day consumption of 26.25 kWh
- An average holiday day consumption of 278 kWh
- Estimate of annual cost of hot water: £3,068 (102,282kWh)
Benchmark usage for school of same size 11,375 kWh (assumes 5 litres of hot water per pupil per day)
The gas consumption for hot water at this example school would be enough to provide 50 litres of hot water for every pupil every school day – this is equivalent to a hot bath every day for each pupil.
Our general advice is for schools to gradually move away from using centrally controlled gas hot water systems, towards point of use electric hot water systems. This can typically be achieved by gradually replacing the hot water supply every time toilets are refurbished and providing kitchens with their own direct gas heaters.
This inefficiency occurs both in older schools and in newer schools.
However, there is one caveat to this suggestion, and that is Legionella, which can proliferate in water between 25C and 50C. By turning your hot water system off you might either increase or decrease this risk depending on the configuration of your hot water pipework at your school.
If schools follow standard post holiday flushing and cleansing regimes then turning your hot water system off during the holidays is unlikely to increase your risk of legionella. However this is not Energy Spark’s area of expertise, so you would need to take professional advice, for example from whoever provides your Legionella testing, or look at the advice provided to us by the Health and Safety Executive below.
Energy Sparks asked for some formal advice from the Health and Safety Executive and here is their response:
Thank you for your enquiry relating to the management of water systems in schools during holidays.
There is a reasonably foreseeable legionella risk in a water system if:
i. water is stored or re-circulated as part of the system and;
ii. water temperature in all or some part of the system may be between 20–45 °C.
Therefore, regardless of whether a school switches its hot water system off, if the school is:
i. not using the water system frequently and;
ii. unsure of the water temperature in any part of its water system, the school should ensure all outlets throughout the system are flushed once a week for several minutes to control legionella risks. Further information is available in HSG274 Legionnaires’ Disease Part 2: The control of legionella bacteria in hot and cold water systems (§2.78, p. 30).
Alternatively, if a school ‘mothballs’ its water system (i.e. ensures it is unused over a longer period), weekly flushing is unnecessary. However, the systems should be recommissioned as though they were new (i.e. thoroughly flushed, cleaned and disinfected) before returned to use. Further information on mothballing is also available in Part 2 of HSG274 (§§2.50-252, p. 24).
Where the hot and cold water system is not used for a prolonged period and has not been flushed (for as little as 2 to 3 weeks), then flushing, cleaning and disinfection is also required. §§2.126-2.137 (p. 42) provide further information on cleaning and disinfection.
I hope this information clarifies how legionella risks can be controlled in water systems during school holidays.
Paula Stam | Advice Officer | Concerns and Advice Team | Operational Services Division
Health and Safety Executive | 1.G Redgrave Court, Merton Road, Bootle L20 7HS
Thank you for your further enquiry to the Health & Safety Executive.
I forwarded your enquiry onto a specialist team and they have provided the following advice to you below:
Thank you for your follow up enquiry in which you ask 3 specific questions which I will try and answer below:
1. Can you confirm that no flushing would be required by a school for its hot water systems at the end of a weekend (i.e. 2 days of non-use) whether or not water system is being heated (calorifier, circulatory pipework)?
As a general principle, outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow and minimise the chances of stagnation. If a water system was used within the last week, then generally it is unnecessary to flush all the outlets throughout the system before use again. (However, ultimately the specific conditions relating to the water system must be considered to ensure a sensible and proportionate approach is taken).
2. Can you confirm that for all holidays of 2 weeks or less, whether or not the hot water heating system has been left on, flushing is required before the school is re-opened?
If a water system was unused for more than a week, it is recommended that all outlets throughout the system are flushed for several minutes before use.
3. It’s unclear to me what a school should do at the end of a 6 week unoccupied summer holiday? Chemical disinfection is unlikely to be possible. What would you advise a school to do, and would this advice be different whether or not a calorifier/circulatory HW system was left on or not?
If a water system will not be used for several weeks (e.g. during 6 weeks of the summer holidays), consideration should be given to implementing a suitable flushing regime or other measures. Other measures may include using thermal disinfection to raise the hot water system temperature to a level at which legionella will not survive, drawing it through to every outlet, and then flushing at a slow flow rate to maintain the high temperature for a suitable period. This method is only applicable to hot water systems and is commonly used as a rapid response. It may be less effective than chemical disinfection and may not be practicable where the hot water supply is insufficient to maintain a high temperature throughout.
Please note that HSE is only able to provide generic information on health and safety issues. HSE cannot provide specific advice on individual cases as the circumstances of each situation will be different. HSG274 outlines typical frequencies for dutyholders to help them control legionella risks. However, as every water system is unique, the dutyholder is ultimately responsible for ensuring compliance with current legislation.
If a dutyholder is not confident in their ability to manage health and safety, they may require a consultant. The Occupational Safety and Health Consultants Register (OSHCR) helps dutyholders find consultants with relevant skills and experience in their area.
I hope this reply goes some way to addressing your follow up questions.
Paula Stam | Advice Officer
Concerns and Advice Team | Operational Services Division
Health & Safety Executive | Redgrave Court, Merton Road, Bootle, L20 7HS
The two main consumers of electricity in schools are ICT (servers, desktops, laptops, network equipment) and lighting with the remainder being made up of a miscellany of smaller consumers:
About 50% of this consumption is from ‘baseload’ = appliances which run all year round, including overnight, weekends and holidays::
The biggest and most cost effective electricity saving measures are to upgrade your lighting to more energy efficient LED lighting and to reduce your baseload, which generally means switching off appliances which are unnecessarily left on and switching to more efficient ICT servers.
Minimising baseload is probably the easiest way to save electricity costs in a school
Baseload costs about £1,000 per kW per year (i.e. 365 days * 24 hours * 1 kW * 12p/kWh), so if you compare the electricity consumption for two similar size primary schools:
The first has a baseload of about 6 KW (above)
And the second a baseload of about 2.5 kW. The difference between them is 3.5 kW, which is an additional cost of about £3,500 per year to the first school, despite both schools providing education to about the same number of pupils.
Single form entry primary schools like these should aim to keep their baseload below 2.5 kW
There are a number of strategies for reducing baseload in schools:
- Complete an audit of appliances at your school: work out what appliances are being left on overnight. You can use an appliance monitor to check how much energy/power an appliance is using (they can be borrowed from Energy Sparks). You can also look up their power consumption online
- Replace energy inefficient appliances: identify energy inefficient appliances, work out how much they are costing you in electricity per year, and replace them with newer more energy efficient ones – particularly ICT servers (see specific advice later)
- Ensure appliances go into standby mode or are switched off overnight
- Switch from timed security lights to movement detectors (PIR) – they often provide better security and they are much more energy efficient as they are not on all night, they can also be more wildlife friendly
Monitor your school’s baseload
On average schools’ baseload has been either stable or reducing over the last few years mainly because ICT servers have become more energy efficient. However, it is not uncommon for baseload to change over time, for example at this school:
In this example baseload has increased by 4 kW, or £4,000 per year over the last 4 years, when the number of pupils at the school hasn’t changed.
At this school there was a big unexplained jump in baseload this winter, which didn’t happen during the previous winter:
The Energy Sparks alert system can be configured to email or text you automatically if it notices your baseload increasing.
There are two main ways to reduce your lighting costs:
- Switch lighting off when it isn’t necessary; this can be done via behavioural change, for example encouraging pupils to turn lights off (Energy Sparks has some good pupil guided activities to help with this)
- Upgrade to more energy efficient LED lighting. This can either be done piecemeal by replacing a few bulbs at a time, when your existing fluorescent tubes stop working or on a more wholesale basis. The table below shows the relative efficiency of various types of bulbs:
Primary schools typically have 3 servers each of between 200W and 500W, which are left on 24×365.
Recommendations: There are 6 obvious solutions to reducing this demand:
- Replacing the servers with more modern more efficient versions: A server consuming 500W consumes about £500 of electricity each year. Replacing it with a new more modern energy efficient server consuming 250W would save £250 per year, and considering a new server is likely to cost £500 to £700 per year, then it is possible to get a return on your investment within 2 to 3 years.
- Server consolidation: some schools have multiple servers which independently service authentication, file systems, printers and remote hosting; it is possible with the power of today’s computers that all these functions could be consolidated onto one server. During visits to schools it has often been noted that an old server is being used just to service a printer, with the users unaware that this might be costing hundreds of pounds per year.
- Moving servers to the cloud: By making the use of cloud technology schools can reduce their costs whilst increasing the potential for collaboration and increased flexibility.
- Putting servers into standby out of school hours: it is possible in most circumstances to configure servers to go into standby mode when not in use particularly out of school hours e.g. outside 06:00 to 22:00 on school days, the servers could then be configured to automatically wake up at set times or to wake up when clients log in (WOL – Wakeup On LAN). To accommodate this change, backup schedules could be switched to faster incremental backups and organised to run round outside periods
- Admin servers: some primary schools have an admin server which supports admin staff and can provide LEA and regulatory services. If such a server is still used in your school, you could approach your local authority about making use of cloud technology.
- Network consolidation; Many schools are in the process of switching from desktops with direct Ethernet connections to the school’s network to laptops and wireless connections, reducing the need for network switches. Unfortunately when this has happened the network switches have not been retired or consolidated.
If your servers are installed in air conditioned rooms then there are a couple of simple ways of reducing the cost of running the air conditioning:
- Making sure the server room is not too cool: to save energy you want to minimise the cooling in the server room. Unfortunately if the servers get too hot their reliability reduces, but you can over-cool servers – hard disk drives for example become less reliable the cooler they are. The following paper which looks at hundreds of thousands of servers suggests that the optimum hard disk drive temperature for reliability is 35C to 40C (fig 4 p6). This paper suggests the optimum inlet temperature for servers is 24C to 27C , so you could run the server room as high as 27C without significantly impacting the servers reliability.
- Optimising cooling airflow: It might also be worth thinking about the positioning of the server cabinet to maximise the airflow. Ideally you want the cold air from the air conditioner dropping down into the intake of the server and the warm air from the outtake rising back to the extract of the air conditioner to avoid mixing with the cold air. This may require the server cabinet to be turned through 180 degrees. If it is orientated the wrong way then you are mixing warm air with cool air before feeding it into the servers which is not very efficient. There are quite a few papers on the internet about server room design. Ensuring the cabinet containing the servers is fully enclosed by panels may also improve the air flow.
Desktops are considerably less efficient than laptops, often consuming 2 to 3 times as much energy, so if you are planning on replacing your desktops it is worth considering replacing them with laptops. Additionally, you should ensure that all desktops are setup to go into standby mode, within a short (15 minute) period of inactivity.