Using Energy Spark’s Electricity Simulator


Energy Spark’s Electricity Simulator can be used to find out how much electricity appliances in a school use over the course of a year. To do this accurately you will need to carry out an audit of the appliances in a school and enter that data into the simulator. The simulator then simulates how much electricity each appliance uses, by calculating usage for each half hour of the year, and then presents the results as a series of tables or charts. The results provide an estimate of how much electricity appliances are using and the results can be used to determine the economic benefit of replacing appliances with more energy efficient versions. For example, you might be considering replacing an old ICT server with a newer more efficient server; you can use Energy Spark’s Electricity Simulator to work out how much electricity and money you will save by doing this.

The chart below shows an example of this breakdown of usage by appliance:

And in the form of a table:

Once you have an accurate model of your existing electricity use, you can then see the impact of changes you might make to your appliances. So, if for example you decide to upgrade your ICT servers to more energy efficient versions, upgrade to LED lighting and install 24 solar PV panels on the school roof, you can change the simulator configuration to see the impact of these changes. Your breakdown might change to the following:

You can see by comparing the 2 tables that the school’s annual electricity consumption has reduced by about 30,000 kWh or £3,700, so over a 10 year investment period this would be a saving of £37,000 in your electricity costs. You can see by comparing the 2 tables the reduction in server consumption 21,840 kWh/£2,621 to 6,552 kWh/£786, lighting from 14,917 kWh/£1,790 to 7,480 kWh/£895, and solar PV would save 8,148 kWh/£978.

The remainder of this webpage discusses how individual appliances are configured in the simulator, and potential capital costs and savings.

 How to audit your school and configure the simulator accurately

Initially the simulator analyses your current consumption and tries to determine the correct configuration for the simulator parameters (using statistical analysis techniques) and previous experience of audits at typical schools. This process is only a guestimate, and to model the school accurately you need to perform an audit of the consumers of electricity in a school – by going around and counting and documenting appliances in every room. This audit could be carried out by pupils, and Energy Sparks has a number of planned activities which could help with audits (School Kitchens, Science Labs).

Once you have finished an audit you can then type the results into the simulator. So, for example for ICT you might end up with a simulator configuration like this:

Which says the school has 3 (energy efficient servers) consuming 250 watts each, 20 desktops which consume 200W each and are left on over holidays and weekends, and 20 laptops. As you adjust the parameters you compare the simulators prediction of electricity consumption versus the actual consumption in the graphs immediately below:

On you initial audit the aim, if the audit has been accurate is to get the green and orange charts to look very similar. There are sections below which describe how you can do this for each type of appliance.

Why appliances which are switched on all the time have the biggest impact on schools’ electricity consumption

Lets consider and compare the electricity consumption patterns of ICT servers and lighting. Lets, for example compare 2 kW of lighting and servers which consume 2 kW, and how much it costs to run each for a year. To calculate the electricity consumption and cost you need to multiply the power consumption (2kW) by the number of hours each is left on each year, and then multiple the energy consumption (in kWh) by the number of hours. If you would like to know more about the maths behind kW and kWh there is more detail information here.

So, for the ICT servers, which are left on 24 hours a day, 365 days per year the calculation is as follows:

Annual consumption = 24 hours * 365 days * 2 kW = 17,520 kWh

Annual cost = 17,520 kWh * 12p/kWh (electricity cost) = £2102

For the lighting which has the same 2kW power consumption, lets assume the lighting is only on during school days (190 per year), and then only on for half of the school day (4 hours), as lighting gets turned off when it is sunny:

Annual consumption = 4 hours * 190 days * 2 kW = 1,520 kWh

Annual cost = 1,520 kWh * 12p/kWh (electricity cost) = £182

As you can see the lighting uses 8 times less energy over the course of the year than ICT servers, so reducing the energy consumption of appliances which are left on all the time has the biggest potential saving in electricity costs. These savings could either be achieved by replacing appliances with more efficient ones, or could be made by behavioural change – switching equipment off when it isn’t being used.

The simulator mimics and calculates these usage patterns for all appliances, so you can make a more informed decision about the potential electricity savings. The lighting simulator for example knowns about school occupancy, and based on past surveys when lights are likely to be turned on and off, and also looks at how sunny it is outside to determine whether lights are switch on.

The remainder of this webpage explains more about each auditing each appliance type, how to configure the simulator for the appliance and potential ways of saving electricity, and covers the following types of appliances:

  • Lighting (internal)
  • ICT – servers, PCs, laptops and tablets
  • Security lighting
  • Electrical heating
  • Kitchen (general)
  • Air conditioning
  • Electric hot water
  • Boiler pumps
  • Floodlighting (sports usage)
  • Solar PV
  • ‘Unaccounted for baseload’ – all the other appliances which are left on but are difficult to assess

Lighting (internal)

Comparison of efficiency of different lighting types

Different types of lighting have different efficiencies. Lighting efficiency is measured in lumens per watt.  Lumens is a measure of the brightness of a light, and watts being its electrical consumption. The efficiency of different types of lighting varies significantly:

Type Efficiency: lumens/watt
Incandescent 15
Halogen 20
Compact Fluorescent 50
T8 Fluorescent Tube 50
T5 Fluorescent Tube 90
LED Tube 110

The less efficient lighting is the more heat it produces. Apart from modern T5 fluorescent tubes it is generally a good investment for a school to replace all its lighting with LEDs and the cost savings make it worthwhile.

In the example at the start of this webpage the simulator was configured for older T8 lighting and had an annual electricity consumption of 14,917 kWh/£1,790, and a simulator lighting configuration of 50 lumens per watt:

This setting was changed to 100 lumens per watt, to simulate replacing the old T8 fluorescent tubes with LED tubes and the simulator predicted consumption dropped to  7,480 kWh/£895 – a saving of £895 per year, or £8,950 over a 10 year period.

The single figure for the efficiency in the current Energy Sparks web interface, is assumed to be the average efficiency of the lighting for the whole school. So, for example if half the school has 50 lumens/watt T8 fluorescent lighting and half has 90 lumens/watt T5 fluorescent lighting, then enter a weighted average of 70 lumens/watt. The brightness value is also an average, most schools have lighting in the 300 to 400 lumens/m2 of brightness range, recommended levels for classrooms is between 300 and 400 lumens/m2 (lumens per m2 is often called LUX).

Identifying lighting types in schools

It can often be difficult and confusing to identify lighting types in schools. The easiest way is to look at individual spare bulbs and look them up on the internet. Often the building manager or caretaker has some spares and it can sometimes be easier to look at these rather than trying to examine bulbs in the ceiling!

One tip for identifying types of fluorescent tubes: generally described as T5, T8, T12 is to measure their diameter, the number represents the number of eighths of an inch. So, a T8 tube has a diameter of 8 times 1 eighth or 1 inch (25 mm in metric terms).

Advice on lighting and replacing lighting

The energy saving trust has some good general advice on lighting in schools here, however it is out of date as it doesn’t mentioned LEDs. Significant amounts can be saved through behavioural change, turning lights off when they are not needed, Energy Sparks has a number of activities for pupils to carry out which will save electricity consumption from lighting (here, here, here, here,  and here).

In general it is worth considering upgrading older lighting to LEDs, and there are grants and loans available to do this, including the Carbon Trust Green Business Fund (15% capital contribution), SALIX loans, local authority sponsored programmes, however, what is available change all the time, for example this recent 30% grant funded scheme, so its worth checking on the internet what funding is available.

This is the Carbon Trust’s up to date (August 2018) advice on costs and paybacks of some lighting upgrades in schools:

Upgrade Cost Payback Advice
T12 to LED in place lighting upgrade (just replace tube not fitting) £20-£40 per tube 1-5 years Full luminaire replacement should be preferred option to ensure savings/optimal performance is achieved.
T8 to LED in place lighting upgrade (just replace tube not fitting) £20-£40 per tube 1-5 years Full luminaire replacement should be preferred option to ensure savings/optimal performance is achieved.
T5 to LED in place lighting upgrade (just replace tube not fitting) £20-£40 per tube 1-10 years Full luminaire replacement should be preferred option to ensure savings/optimal performance is achieved.
T8/T12 upgrade to LED with replacement luminaire/fitting £100-£150 per luminaire 1-10 years Paybacks for schools are often longer due to low occupancy hours.
Upgrade to T8/T12/T5 with PIR movement sensor and possible ambient light sensors £180 per luminaire 1-10 years Paybacks for schools are often longer due to low occupancy hours.
Upgrade circular D-type fluorescents to LEDs £75 per luminaire 1-10 years Paybacks for schools are often longer due to low occupancy hours.

Lighting usage patterns in schools

If you look at the graph of your annual electricity use on Energy Sparks analysis ‘Electricity Detail’ page:

You will notice that electricity usage gradually increases during the winter and decreases during the summer. This is increase is mainly due to increased lighting usage, as its darker outside lights are left on for longer. At some schools this increase is caused by electrical heating, put in most schools this seasonal effect is caused by lighting.

The pattern of electricity usage during the day can be seen on another dashboard chart which compares power consumption average power consumption over 2 weeks 6 months apart:

You can see that the electricity consumption during the day is much greater in the winter.

The ‘simulator detail’ webpage for your school provides graphs separates this usage out to  just the lighting:

You can see that average power consumption from lighting is higher in the mornings and evenings when it is darker particularly in winter.

The maths behind lighting power consumption calculations

It is possible to roughly calculate how much power the lighting in your school will consume if all the lighting is turned on, using just 3 numbers:

  • the floor area of the school (in m2 – which can be found at the top of the Energy Sparks analysis page for your school)
  • the average brightness of the lighting in lumens/m2
  • the efficiency of the lighting in lumens/watt

So, for the example school above the floor area is 5000m2, the average brightness  is 450 lumens/m2 (this is a good average value to use for most schools) and the lighting efficiency in this school is 50 lumens/watt – as the school has lots of old inefficient lighting.

The peak lighting power requirement is therefore:

Peak power = floor area (m2) * brightness (lumens/m2) / efficiency (lumens/watt)
Peak power = 5000 * 450 / 50 = 45,000W = 45 kW

which seems about right if you look at the graph above (which is averaged, so the average value is likely to be slightly lower as not all lighting will be on at times of peak usage in mornings and evenings).

If you are interested you could try repeating this calculation for your school (find the floor area from the Energy Sparks ‘analysis’ webpage for your school), do a quick survey of your school and decide how efficient the lighting might be on average (should be in range 30 to 100 lumens/watt), use a default brightness of 450 lumens/m2 and then repeat the calculation above and compare it with the Energy Sparks analysis and simulator graphs for your school?

ICT (Servers, Desktops, Laptops and Tablets)

ICT is often the largest consumer of electricity in a school, it is also the cause of the almost doubling in school electricity consumption in the last 20 years with the prevalence of more computers being used in schools. However, for the last 3 to 4 years there has been a general reduction in electricity use from ICT as older less efficient computers are replaced by more modern energy efficient ones.

Type Power consumption per appliance
Server 200W to 1000W
Desktop 40W to 400W
Laptop 15W to 35W
Tablet 2W

Consumption varies widely, from a server which might consume 1000W to a tablet which might only consume 2W.


Generally, its very cost efficient to replace servers as generally left on 24 hours per day, 365 days per year, and so replacing an older less efficient server can be very cost effective. A server which consumes 1000W costs over £1,000 per year to run, replacing such a server with a more energy efficient 100W server costing £1,000 to buy would provide a payback of 1 year, and end up saving £4,000 over the 4 year life of the server. You could also save by consolidating servers – reducing the number of servers, or follow the modern trend of moving your servers off-site to the cloud where the savings are much more significant (you save all your on-site electricity costs, and its much better for carbon emissions as a server shared between a number of schools in the cloud is significantly more efficient than having your own which is probably only being used about 15% of the year.

It can be quite difficult to assess the power consumption of an existing server, the best way to do it is to install an appliance monitor. This plugs into a 3 pin mains socket and then the server is plugged into it. Energy Sparks can send you one to borrow if you contact us. The monitor can be used to determine instantaneous power and how much energy is consumed in kWh (you will need to take two readings 24 hours apart to get a good estimate). You will probably need to coordinate with your ICT support staff to install the appliance monitor.

There are additional opportunities for saving energy with servers:

  • Consolidating network equipment: servers are connected to the rest of school networks via ethernet (generally black, cabling). Historically almost all computers in a school were connected via ethernet, but now most are connected by Wi-Fi. What we have found is that schools often forget to uninstall their network switches (boxes which have lots of ethernet connections in an out distributed around a school) when Wi-Fi is installed. In our experience many schools often have multiple switches with very few active ethernet cables going in and out, and that these switches can be turned off by consolidating fewer switches. Older switches can use 5 times as much electricity as more modern switches and cost £25 per year more to run than the most efficient modern switches which might only cost £25 to buy
  • Improving the efficiency of air conditioning in server rooms: servers are often installed in air conditioned rooms to stop them getting too hot. It is often possible, at no cost to significantly reduce server air conditioning energy consumption by changing the temperature settings in a server room and re-organising the air flow; more information and suggestions are available here


Desktop are generally less energy efficient than laptops, so if you are planning on replacing desktops consider purchasing laptops.

However, if you have desktops and want to reduce electricity consumption the best approach is to enforce a site-wide ‘standby policy’ on all desktops. This is simply a matter of configuring each desktop to switch to standby mode when the PC has not been used for a period of time – we would recommend 15 minutes; reconfiguring a PC only takes 20 seconds. In addition we suggest you enforce a policy of turning PCs off on Fridays before weekends and holidays. On average in our experience about 50% of PCs at schools are not set to automatically switch into standby mode. We would recommend carrying out a survey of all desktops, once per term to ensure that they are configured to switch into standby mode.

Laptops and tablets

Laptops and particularly tablets are generally very efficient, and it is not cost effective to upgrade them to more efficient versions.

Auditing ICT for entering data into Energy Sparks

In order to audit ICT for Energy Sparks you need to count each item of ICT, work out how much power it consumes and


Kitchens are often a hidden source of electricity consumption in schools and often significant amounts of electricity and gas can be saved through behavioural change.

Commercial kitchen refrigeration equipment  is often inefficient, in fact when purchasing such equipment it can be quite difficult to find an energy rating, often commercial equipment has B to E ratings, compared with most new domestic refrigeration which is rated between A and A++. This can mean the difference between consuming 1,800kWh/£200 of electricity per year and 200kWh/£24 per year; a £175 saving per year can quickly payback the purchase costs of new more efficient equipment.

Behavioural change in a kitchen can significantly reduce electricity and gas costs, it is very common for kitchen staff to turn all cooking equipment on as soon as they arrive in the morning at 8:00am, even if they don’t need to use it until 11:00am for cooking; ovens generally take less than 15 minutes to heat up, and hobs less than 10 minutes to boil a pan of water! This means hobs and ovens are can be consuming 2 to 3 times more energy than necessary; this saving could be between £200 and £500 per year at no cost to the school.

The simulator supports a basic representation of a kitchen:

The example value of 4.0 kW labelled ‘Power’ above is a representation of the average oven and hob usage between ‘Start time’ and ‘End time’. Ovens can range in (average) power consumption from 1kW to 10kW, hobs are generally 2 to 3 kW per ring on full power, and about 0.5kW per ring on simmer. If your school doesn’t cook onsite, and has no ovens and rings you could set this to zero.

The ‘Warming Warmer Oven’ represents the heating plates and ovens most schools have for keeping the food warm prior to serving whether the food is cooked onsite or not.

The refrigeration represents the average power of the fridges and freezers in the kitchen – to calculate this either use an appliance monitor and calculate the average power across the year, or lookup the ‘Energy Rating’ for the appliance – at the bottom of the G to A+++ chart which (domestic) retailers have to provide for all products on sale, this gives you a kWh/year figure, which you need to convert into an average power figure by dividing by the number of hours in the year. So, for example 1000 kWh/year rating would be 1000kWh/year / 8760 hours in a year = 0.114 kW – you need to add all of these up for the various refrigeration units. If you don’t know them a good guess might be 0.1 kW per old fridge, 0.2kW per old freezer, 0.05 kW per new fridge and 0.1 kW per new freezer – although it would be better to get a more accurate figure.

If you go to the ‘Simulator Detail’ results page you will see a graph for the kitchen which looks like this example:

You can see the cost by time of day across the year, with the out of hours usage being the refrigeration, in this example about 80kWh per 1/2 hour, the peak starting at 8:00am the ovens and hob, with the jump at 11:30am being the warming plates/ovens being turned on.

Energy Sparks has a number of activities which pupils can carry out in schools to improve the energy efficiency of kitchens (here, here, and here).

Electric Heating

There are 2 types of electric heating commonly used in schools, heat pumps (either air conditioning type systems, or air (to water) heat pumps) which can be very efficient, and traditional electric fires, or fan heaters which are expensive to run compared with heating from gas boiler powered radiators.

Gas boilers cost about 3p/kWh of heat produced compared with electric fan heaters which cost 12p/kWh – i.e. electric powered heating can cost 4 times more to run. A single 2kW fan heater running during the winter during school hours can cost up to £200 per year to run.

The simulator tries to automatically work out how much electricity is being used by heating by looking at (the correlation) how the school’s electricity consumption varies with how cold it is outside (degree days).

How to configure the simulator for electric heating

Configuring the simulator manually for electric heating requires a little bit of knowledge……

The configuration looks like this:

And is a reasonable default for an average sized primary school. The simulator assumes (for this configuration), that electric heating is turned on between 05:30am and 05:00pm on every school day when the outside temperature (balance point temperature) goes below 15C. And, when the temperature is below 15C, 4kW of electricity is always consumed plus 0.5kW of electricity for every degree the outside temperature is below 15C. So for example if the outside temperature was on average 5C on a given day, then for 11.5 hours, the school would consume 4 kW + (15C – 5C) * 0.5kW = 9 kW of electricity, so 9 kW * 11.5 hours = 104 kWh of electricity costing about £12. Over the course of the winter this could add up to £900 assuming average temperatures.

If you want to provide a more accurate estimate than this for your school you will need to audit all electrical heating equipment – which means going around and finding all fan and other electrical heaters, checking their electrical consumption (normally written on the bottom or side – typically 2 kW or 2000W for most fan heaters) adding all the power consumptions up. You also need to ask the users of the heaters when they turn them on and at what outside temperature. If they say ‘most of the winter’ add the total into the ‘Fixed power’ field, if they say only when it gets cold then enter a value of about 20% of the capacity of the heaters into the ‘Power per degreeday’ field (e.g. for two 2 kW fan heaters, you would enter 2 * 2kW * 20% = 0.8 kW/degree day). Typical locations for fan heaters are in the admin staff offices, the headteacher’s office, staff rooms and above entrance doors.

Generally, Energy Sparks advise against using fan heaters as they are very expensive to run compared with gas. The one exception is outside school hours, when if there are very few people in the building, where they can provide local heating which will cost less to run than heating the whole school.

Checking the result of a reconfiguration

Once you have changed the configuration, updated the simulation, you can go to the ‘Simulation Detail’ page to see the result in a graph:

The graph unsurprisingly looks quite similar to that of a graph of annual gas consumption broken down by week of the year, with consumption peaking on the coldest weeks of the year (when the black degree day line is at its highest/coldest).

Air Source Heat Pumps or Air Conditioning Units

Air source heat pumps and air conditioners are about 3 times more energy efficient than fan heaters. They are however more difficult to configure in Energy Sparks because they are much better controlled and its probably best to contact Energy Sparks to get advice on their configuration. The automatic fitting process which Energy Sparks uses to configure the default parameters should however be reasonable accurate.

Storage Heaters

As with Air Source Heat Pumps, please contact us to discuss. We are however planning on doing further development on Energy Sparks to specifically analyse storage heaters during the winter of 2018/2019 – we will let you know via our newsletter when this becomes available.

Security Lighting

Security lighting, typically installed around the perimeter of a school can be quite expensive to run because depending on the controls it can be on for 12 hours a day on average for 365 days of the year. So 1kW of security lighting can consume 4,400kWh of electricity at a cost of £500 per year.

There are 2 main ways of reducing costs:

  1. the change the controls which decide how and when the lighting is turned on
  2. to install more efficient lighting

Lighting Controls

There are typically 4 ways of controlling security lighting:

  • Fixed timer: turning on an off at a fixed time of day – for example between 5:00pm and 6:00am
  • Ambient lighting level detector: which has a light sensor which turns the lights on when it gets dark
  • Sunrise/Sunset Timer: these know when sunrise and sunset for every month of the year
  • Movement Detector: this turns on and off when movement is detected – often called a PIR (Passive Infrared Sensor)

Generally, the first 3 controls on this list use about the same amount of electricity; on average 12 hours per day. We generally recommend Movement Detector sensors as they are very efficient, using less than 10% of the electricity of the other types, and in most circumstances can provide better security – they are more likely to alert neighbours if they suddenly switch on.

The Energy Sparks simulator allows you to experiment with all 4 types of lighting control:

You need to complete a survey in order to determine the power consumption of your lighting to complete this configuration. Sometimes it’s possible to see the lighting usage by looking at the Time Of Day/intraday charts on the Energy Sparks ‘Electricity Detail’ analysis page for your school:

You can see the impact as a slight reduction in overnight consumption prior to the school opening in the morning i.e. the overnight consumption is high because of the security lighting until it turns off when the sun rises. In this example the overnight power consumption is about 6.4kW, which drops to a low of 5.0kW at about 06:00am, which suggests the security lighting is consuming 1.4kW or about £700 per year. If the school also has solar PV installed it’s often difficult to distinguish between security lighting turning off at dawn and solar PV reducing the school’s consumption as the sun comes up.

More efficient lighting

We would suggest that installing more efficient security lighting should be a priority over upgrading internal lighting because its potentially on for more hours in the year e.g. 4000 hours versus 900 hours for classrooms, which generally means the paybacks are at least 4 times better depending on the cost of installation.

The table below shows the relative efficiency of differing types of security lights:

Type Efficiency: lumens/watt
Incandescent 15
Halogen 20
HID 40
Compact Fluorescent 50
Sodium (orange street lighting) 90
LED 100

So upgrading a compact fluorescent to LED would halve the electricity consumption. It would also have the benefit of having to replace the bulb less often as they last longer, and most of the other types of lighting particularly HID and fluorescent tend to become less bright the older they are. In the example of the school above switching from fluorescent to LEDs would save £350 in electricity and perhaps several hundred pounds more in maintenance costs, as they should last 4 times longer.

The Carbon Trust has provided the following information (as of August 2018):

Upgrade Cost Payback Advice
Upgrading security lighting – either lighting technology e.g. halogen to LED, or controls e.g. sunrise/sunset to PIR £2-3k per kW LED 1-3 years LED luminaires with automatic controls.

We would recommend this as a very good value upgrade. As a minimum, try to replace existing bulbs with compatible LEDs when the existing bulbs stop working.

Electric Heated Hot Water

We generally recommend all gas hot water systems in schools are replaced by electric point of use hot water, apart from in kitchens and for showers, as gas based hot water heating is generally very inefficient – below 10% at many schools. If you have gas hot water heating at your school – Energy Sparks provides an estimate of its efficiency and annual running costs at the bottom of your school’s ‘Analysis->Advanced Boiler Control’ webpage.

If you have electrically heated hot water systems at the school, or are interested in seeing the annual running costs of a hot water system, you can do this my adjusting the Energy Spark’s simulator hot water configuration:

The ‘Percent of Pupils’ indicates what percent of the number of pupils are served by electrically heated hot water. To provide an estimate of the percentage the easiest way is to count the number of taps with hot water provided by gas versus those provided by electricity. So, for example if the school has 8 electrically supplied taps and 12 gas supplied taps, you should enter 40% (8/20).

5 litres of hot water (at 38C) is the typical usage per pupil in schools for washing hands. The standby power is the power consumption of the hot water heating out of school hours – typically from heat loss of the small cylinders associated with point of use hot water heaters. The start and end time settings have very little effect on the overall annual predicted electricity consumption from hot water, just how the usages is distributed throughout the school day.

Set the ‘Percent of pupils’ to 100% if all the hot water is provided by electricity, and to 0% if it is all provided by gas.

You can compare and contrast the difference in cost between gas and electricity by comparing the cost estimates for gas on the ‘Analysis->Advanced Boiler Control’ webpage, and the predicted electrical consumption on the table/pie chart of the appliance breakdown on the simulator results page.

Boiler Pumps

Boiler pumps are used to circulate central heating and hot water through pipework in a school, and are often overlooked as consumers of electricity, and their energy efficiency can often be significantly improved by installing more energy efficient pumps.

It’s often possible to spot the impact of boiler pumps but looking at the electricity consumption in the early morning in the winter (Energy Sparks:: Analysis->Electricity Detail web page):

For this school there is a jump in electricity consumption of about 4 kW at 3:30 in the morning, which corresponds to about 14,000 kWh per year of consumption at a cost of  £1,600 per year.

The Energy Sparks simulator tries to automatically analyse boiler pump consumption by looking for a jump in electricity consumption in the early hours of the morning when the gas consumption jumps as a result of school boilers turning on. It also simulates the use of the boiler pumps automatically when the gas consumption is high at your school.

So, in general you don’t need to change the initial configuration unless the school doesn’t have gas smart meter data fed into Energy Sparks.

The configuration looks like this:

These are the default settings, but for most schools the Energy Sparks fitting process have set the ‘Pump power’ to something other than 0.5, in which case you don’t need to do anything. Pump power typically ranges from 300W (0.3 kW) at a small primary to up to 10 kW at a large secondary.

The annual usage is displayed on the Energy Sparks: Simulator Results Appliance Breakdown pie chart and associated table.

Modern variable flow boiler pumps can be significantly more efficient than older fixed flow pumps – your building manager, caretaker or boiler maintenance company should be able to tell you what type the school has (they are normally found in the boiler room).

The Carbon Trust (as of August 2018) suggests the following costs and paybacks:

Upgrade Cost Payback
Replacing boiler pumps with automatic variable flow pumps pump size dependent, £1,500 upwards 2-5 years


There currently aren’t any schools signed up to Energy Sparks which have floodlighting, so we have limited the configuration choice to just the power of the floodlighting and an ambient light threshold:

The underlying model is quite sophisticated allowing bookings on different days of the week, at weekends, both term-time only and during school holidays; reflecting ambient lighting conditions during the course of an evening. If you contact us we can manually configure the correct settings for your school.

Summer Air Conditioning

Some schools have air conditioning which runs during the summer where rooms get too hot. Ideally if the school has been designed well this shouldn’t be necessary as its not a very good use of energy – it’s often cheaper to install brise soleil shading above windows if there is too much heat gain from the sun, or more efficient PCs in computer labs than installing air conditioning and both are a lot more energy efficient.

If you have air conditioning lease contact us and we will help you to configure it. The model takes into account outside temperatures and varies the cooling during the course of the day, but it’s often difficult to convert the air conditioning setup a school has into the above configuration parameters without help.

Solar PV

Energy Sparks simulator allows you to see the impact of your existing solar PV panels, or the impact of you were to install panels. On the simulator configuration web page, you can type in the ‘kWp’ (capacity of solar panels, roughly 4 panels of 15.m x 1m represents 1 kWp) into config page and see the impact:

This shows the config without solar PV:

If you type 20 kWp in you can see the impact on the graph below:

And if you go to the results page you can see the savings in electricity costs (Solar PV internal consumption), and income you would get from exporting electricity (but not the solar FIT income which you would need to calculate manually by adding up the 2 x kWh figures, and multiplying them the relevant FIT payment):

On the Simulator Detail page you can then see the impact across the year, with more solar electricity being generated in the summer, and more electricity being exported during holidays (e.g. August) when demand is low in the school:

The simulator does this calculation using real local solar PV data sourced for every half hour or the year from Sheffield University.

Unaccounted for baseload

Unaccounted for baseload is a catchall for all appliances which are left on 24 hours per day 365 days of the year, either on standby or left on on full power. It is often quite difficult identify these appliances in detail, but can include:

  • photocopiers
  • security camera systems and alarms
  • fire exit lights
  • displays in reception
  • boiler water heaters in the staff room
  • fridges and freezers in the staff room and medical rooms
  • computer network (ethernet and Wi-Fi) equipment

All of these can be reduced by replacing them with more efficient modern versions, and the paybacks can be quite short as most are on all the time, so, for example replacing fire exist lights with new LEDs versions can pay their investment back in under 2 years.

Savings can also be made by putting some of these on 24 hour timers, so,  for example photocopiers which quite often have high standby consumption (you can check either in the manufacturers specification or using an appliance monitor) can be automatically turned off between 06:00pm and 07:00am.

Once you have audited the rest of the appliances in a school and configured them in the simulator, you will need to adjust the ‘unaccounted for baseload’ so the real and simulated baseload match. You can do this on the configuration screen:

The first chart shows the configuration (1.0 kW) where the simulator and actual baseloads don’t align (see the yellow and green lines in the graph at the bottom in the early hours of the morning:

The second chart shows the graphs after they have been aligned – in this case by typing a value of 8 kW into the box at the top, and then clicking the ‘Update Simulation’ button.

Ideally, when auditing a school you should look to minimise the ‘unaccounted for baseload’, and identify as many consumers as possible.