Worked example
A new build with a heat pump and an EV — should they add solar and a battery?
Illustrative worked example
This worked example uses invented household figures to demonstrate how future case studies and recommendations will be presented. It is not evidence from a real household, and its costs, savings and performance figures must not be used for a purchasing decision.
An invented four-bedroom new build with an air source heat pump, one electric vehicle and no solar. Every figure below is made up to demonstrate how a case study will be presented once real, consented households are involved.
Last updated 5 August 2026
Total electricity use
11,240 kWh
Illustrative example only — invented figure, not measured
Heat pump share
4,180 kWh
Illustrative example only — invented figure, not measured
EV share
2,690 kWh
Illustrative example only — invented figure, not measured
Share on cheap rate
61%
Illustrative example only — invented figure, not measured
The house
- Property
- Four-bedroom detached new build, EPC B (invented example property)
- Occupants
- Two adults, two children, one adult working from home two days a week (invented example household)
- Systems
- 8 kW air source heat pump with weather compensation
- Electric vehicle with moderate annual mileage
- 7.4 kW smart charger
- Time-of-use tariff with a cheap overnight window
How the example unfolds
Year one
Moving in with a heat pump and no idea what it costs
In this worked example the developer's default settings run a high flow temperature. Recommissioning to weather compensation at a lower flow temperature cuts heat pump consumption with no comfort penalty and no spend. The size of that reduction is illustrative and not measured.
Year two
Charger and tariff change
Moving to an EV time-of-use tariff and shifting the dishwasher, washing machine and hot water reheat into the overnight window does more for the annual bill than any hardware purchase. This is the shape of the argument, not a measured result.
Year three
Considering solar and storage
The example household weighs solar only, battery only and both together. The comparison below shows how we will present that decision when it is based on genuine prices and genuine consumption data.
Illustrative quotations (invented figures)
| Item | Quoted | Our read |
|---|---|---|
| 5.2 kWp solar array | £7,450 | Illustrative example price. Modelled payback at the long end of acceptable — self-consumption is the constraint, not the roof. |
| 9.5 kWh battery, retrofit | £5,100 | Illustrative example price. Better standalone case than the solar, driven by the overnight tariff spread. |
| Solar plus battery bundle | £11,900 | Illustrative example price. Best absolute saving, longest payback. A preference question, not a purely financial one. |
What this example is meant to show
- Commissioning a heat pump properly costs nothing and is the first thing we would check.
- The tariff normally decides the battery case, not the roof.
- Bundled quotations hide which component is earning the return — always ask for them separately.
Where these figures come from
Nowhere. Every number on this page is invented for the purpose of demonstrating the format. No smart meter data has been collected, no household has been followed and no quotation reproduced. Once we work with real, consented households, this page will state how each figure was measured — see our methodology.