School Energy Saving Estimate Assumptions
This page explains the modelling assumptions used in Energenie’s indicative school energy-saving proposals. It is designed to make the calculation basis transparent before a school proceeds to a review call, funding report or full site survey.
1. Energy Baseline
Where actual school energy usage is available, this is used as the preferred baseline. Where actual usage is not available, public DEC / EPC data or school-size benchmark assumptions may be used to estimate annual electricity and heating energy use.
Where public data is provided in kWh, tariff assumptions are applied to convert usage into estimated annual spend.
| Baseline source | How it is used |
|---|---|
| Actual school energy usage | Preferred source where recent electricity and gas / heating bills or kWh usage are available. |
| Public DEC data | Used where public operational energy data is available for the school or relevant building. |
| Public EPC / floor-area benchmark | Used where certificate data supports a floor-area or rating-based estimate. |
| School-size benchmark estimate | Used where actual usage and certificate data are unavailable. |
| Manual estimate - needs validation | Used as an indicative placeholder pending bills, survey or further school-provided evidence. |
2. Tariff Assumptions
Electricity and gas tariff assumptions are used to convert kWh usage into estimated annual cost. These assumptions are indicative and can be updated once the school provides actual bills or contract rates.
3. Gas / Wet-Radiator Heating Savings
For schools with gas or wet-radiator heating, heating savings are estimated from the gas or heating spend, adjusted by the assumed proportion used for space heating, then multiplied by the EPC / DEC-linked heating control saving percentage.
The current space-heating allocation assumption is 61%. This can be reviewed if the school provides more detailed energy or operational data.
4. Electric Radiator Heating Savings
For electrically heated schools, electric radiator or electric panel heating is treated as a heating-control opportunity, not as normal electrical equipment switching.
The model uses the estimated annual electricity spend, applies an electric space-heating allocation, and then applies the EPC / DEC-linked heating control saving percentage.
This avoids double-counting by separating electric heating savings from non-heating electrical equipment savings.
5. EPC / DEC-Linked Heating Saving Percentage
The heating control saving percentage is linked to the building’s EPC / DEC rating. The assumption reflects the principle that poorer-rated buildings are more likely to have greater avoidable heating waste and therefore a larger opportunity from improved control.
| EPC / DEC rating | Applied heating saving % |
|---|---|
| A | 5% |
| B | 13% |
| C | 20% |
| D | 25% |
| E | 30% |
| F | 30% |
| G | 30% |
These percentages are Energenie modelling assumptions for indicative proposal purposes. They should be validated against actual bills, operating schedules, existing controls and site survey findings.
6. Non-Heating Electrical Equipment Savings
Non-heating electrical savings are estimated separately from heating savings. The model considers the number of controllable electrical devices, assumed avoidable load, avoidable out-of-hours runtime and electricity tariff.
Examples of equipment included in this part of the model include:
Electrical equipment savings are sensitive to whether devices are left fully on, left in standby, or already switched off. This is why final savings should be validated through school operating patterns, site review and available usage data.
7. Combined Savings
Combined savings bring together the applicable heating saving and the non-heating electrical equipment saving. The model avoids double-counting by separating gas heating, electric heating and non-heating electrical equipment.
8. ROI Basis
The ROI period shown in the proposal is based on the full 3-year package cost divided by the estimated annual saving. This means the ROI period reflects the total 3-year investment package, not only the upfront hardware or installation cost.