This section gives a more detailed analysis of how to improve the efficiency of your school’s hot water system.
The following sections provide more background and analysis on your hot water efficiency including:
Improving the timing control of your existing hot water system or replacing it completely with point of use electric hot water systems can produce significant savings.
Hot water in schools is generally provided by a central gas boiler which then continuously circulates the hot water in a loop around the school. Sometimes these gas-based systems are supplemented by more local electrically powered immersion or point of use heaters.
Circulatory hot water systems are 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 15% efficient.
Generally, there are two potential options you might have to reduce the costs and carbon emissions of running the hot water system at your school:
The table below provides some indication of the benefits of these two alternatives:
| Annual use | Annual saving | Capital Cost | Payback | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Choice | kWh | £ | CO2/kg | Efficiency | Cost | % | CO2/kg | % | £ | Years |
| Current setup | 370,000 | £18,000 | 67,000 | 7.2% | 0p | |||||
| Improved boiler control | 99,000 | £4,800 | 18,000 | 27% | £13,000 | 73% | 49,000 | 73% | 0p | 0 |
| Point of use electric heaters | 32,000 | £9,400 | 4,900 | 81% | £8,500 | 47% | 62,000 | 93% | £19,000 | 2 |
This is only an approximate estimate as Energy Sparks can only imply this based on a generic school of the same size as yours and the information provided by your school's smart meter data, but it should provide an indication whether investments of this type are worthwhile investigating further.
Our analysis is showing that for your school, investing in point of use electric heaters would save less money each year than improving your boiler control. However, it would reduce your CO2 emissions by more.
Improved boiler control
This option involves changing the timing of your existing boiler potentially at no cost to the school.
It involves reducing the time the hot water is heated to school hours and turning it off during weekends and holidays. This could save you about £13,000 a year and reduce your carbon emissions by 49,000 kg CO2 (73%).
Point of use electric heater
This option often leads to the largest savings but for most schools it does require a significant capital investment.
We estimate a saving of £8,500 per year for your school, and a more significant reduction in carbon emissions of (62,000 kg CO2/ 93%).
We estimate the amount of energy used for hot water in your school by looking at heating over the course of the summer - just before and during the start of the summer holidays. It is assumed that during the summer term, gas is used for hot water but not space heating and during the holidays, gas is used for hot water but very little of that is used.
The chart below gives a demonstration of that assessment for your school. The red bars show energy used to heat the water that is circulated around the school. The blue bars show the energy used to heat the water that is used. Note that if your school has a gas heated swimming pool, it is more difficult for us to assess efficiency.
Theoretically every pupil uses about 5 litres of hot water per day, which for your school with 929 pupils, equates to 905,775 litres of hot water over the 195 days of the school year. In a 100% efficient system about 26,000 kWh of energy is required each year to heat this hot water.
We calculate the efficiency of your hot water system by comparing this calculation of 26,000 kWh for a 100% efficient system with Energy Sparks' estimate of kWh for your current system.
The circulatory gas-based systems in schools are generally very inefficient, averaging about 15%; for your school we estimate 7.2%. These inefficiencies offer significant cost and carbon emission saving opportunities if addressed.
Calculations based on Gas consumed between 07 Jul 2022 and 10 Apr 2025
The following characteristics are used when analysing your school energy data. Temperature compensation uses weather data specific to your school's location.
| Characteristic | Value |
|---|---|
| Floor area | 10881.0m2 |
| Location | CR5 1ES (-0.113905, 51.3002) |
| Pupils | 929 |
| Type | Secondary |
Consumption costs are calculated based on the unit prices of energy and do not take into account standing charges or other fees.
Tariffs may be based on MAT or Local Authority averages, or an Energy Sparks default, if your school has not provided their actual tariffs.
Consumption costs are estimated based on historic tariff information.
Future savings are estimates based on your school's latest tariff information.
Potential cost savings quoted in school comparisons, e.g. for comparable "well managed" and "exemplar" schools are also based on your school's current tariffs.
School comparisons are based on benchmarking your school against comparable schools based on the characteristics outlined below.
"Exemplar" schools represent the top 17.5% of Energy Sparks schools
"Well managed" schools represent the top 30% of Energy Sparks schools