How we work
Every number in our calculators comes from a published source, and every result shows its workings.
Our rules
We do not type in a price from memory or copy one from another website. Each figure is recorded with where it came from and the date we last checked it. The site will not build if a figure is missing either.
Every result has a "Show the workings" button with each step of the sum, so you can check it yourself.
Our calculators give information, not advice. They estimate from what you enter and cannot know everything about your home.
When prices change
Ofgem sets a new price cap every three months. We read the new prices from Ofgem's own tables and add them beside the old ones, so every page updates together and earlier periods stay on record.
Corrections
We have not had to correct any figure yet. When we do, we will list it here with the date. If you spot a mistake, email max@youellsystems.co.uk.
Figures we use
Energy prices
Prices are Ofgem's energy price cap: the unit rate and standing charge for electricity and gas, for each of 14 regions and the Great Britain average, for three ways of paying. We hold July to September 2026 and October to December 2026. We last read them from Ofgem on 13 November 2026.
| Figure | Value |
|---|---|
| Electricity unit rate | 26.32p per kWh |
| Electricity standing charge | 54.83p a day |
| Gas unit rate | 7.97p per kWh |
| Gas standing charge | 29.68p a day |
All regions and ways of paying
Fuel prices
Petrol and diesel prices are the average UK pump prices DESNZ publishes every week. We use the latest week, which is now the week beginning 9 November 2026, and keep every week since 2018.
Heat loss
Heat loss figures for the radiator size and BTU calculators (design temperatures by postcode area, U-values, air changes and ground floor tables) come from the MCS Heat Pump Calculator, which takes them from CIBSE Guide A and the Domestic Heating Design Guide. See them all.
Postcodes
Postcode lookups use Ofgem's own postcode table, including its list of the 17,469 postcodes that are in a different region from the rest of their district.
Typical use
| Figure | Value | Source | Checked |
|---|---|---|---|
| Typical yearly electricity use, low user | 1,600 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly electricity use, medium user | 2,500 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly electricity use, high user | 3,800 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly electricity (multi-rate meter such as Economy 7) use, low user | 1,900 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly electricity (multi-rate meter such as Economy 7) use, medium user | 3,400 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly electricity (multi-rate meter such as Economy 7) use, high user | 6,100 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly gas use, low user | 6,000 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly gas use, medium user | 9,500 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
| Typical yearly gas use, high user | 14,000 kWh a year | Ofgem: Review of typical domestic consumption values, decision (Table 1) | 13 November 2026 |
Grants, loans and rules
| Figure | Value | Source | Checked |
|---|---|---|---|
| Boiler Upgrade Scheme grant towards an air source heat pump | £7,500 | GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get | 13 November 2026 |
| Boiler Upgrade Scheme grant towards a ground source heat pump | £7,500 | GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get | 13 November 2026 |
| Boiler Upgrade Scheme grant towards a biomass boiler | £5,000 | GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get | 13 November 2026 |
| Boiler Upgrade Scheme grant towards an air-to-air heat pump | £2,500 | GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get | 13 November 2026 |
| Extra Boiler Upgrade Scheme grant for an air or ground source heat pump replacing oil or LPG heating with no mains gas | £1,500 | GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get | 13 November 2026 |
| Warm Homes: Local Grant, usual household income limit | £36,000 a year | GOV.UK: Apply for the Warm Homes: Local Grant | 13 November 2026 |
| Warm Homes Loan Scheme: reduction in interest rate compared with regular loans, up to | 5 percentage points | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for solar panels | £15,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for an electrical storage battery | £15,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for an air-water source heat pump | £20,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for an air-air source heat pump | £10,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for a ground source heat pump | £35,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for a biomass boiler | £20,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for a heat network connection | £7,500 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Warm Homes Loan Scheme: largest loan supported for a micro-renewable system | £20,000 | GOV.UK: Warm Homes Loan Scheme factsheet | 13 November 2026 |
| Largest alternating current output of a plug-in solar device allowed under the 2026 regulations | 800 W | The Plugs and Sockets etc. (Safety) Regulations 1994 and Electricity Safety, Quality and Continuity Regulations 2002 (Amendment) Regulations 2026 | 13 November 2026 |
Fixed figures
| Figure | Value | Source | Checked |
|---|---|---|---|
| Declared voltage of a low voltage electricity supply in Great Britain | 230 V | The Electricity Safety, Quality and Continuity Regulations 2002, regulation 27 | 13 November 2026 |
| One British thermal unit (IT) per hour, in watts | 0.2930711 watts | NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically | 13 November 2026 |
| One UK gallon, in litres | 4.54609 litres | Weights and Measures Act 1985, Schedule 1 | 13 November 2026 |
| Watts in one horsepower (550 ft·lbf/s), the horsepower used for UK cars | 745.6999 watts | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Watts in one metric horsepower (PS) | 735.4988 watts | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Watts in one electric horsepower, used for motors | 746 watts | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Megajoules in one kilowatt hour | 3.6 megajoules | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Megajoules in one therm (EC), the therm used for UK gas | 105.506 megajoules | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Joules in one British thermal unit (IT) | 1055.056 joules | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Cubic metres in one cubic foot | 0.02831685 cubic metres | NIST Guide to the SI, Appendix B.8: factors for units listed alphabetically | 13 November 2026 |
| Temperature and pressure correction for household gas meters | 1.02264 | The Gas (Calculation of Thermal Energy) Regulations 1996, regulation 2 | 13 November 2026 |
| Average gross calorific value of natural gas used in the UK, 2025 | 39.56 MJ per cubic metre | DESNZ: Digest of UK Energy Statistics, calorific values (Table A.1.3) | 13 November 2026 |
| Kilometres in one mile | 1.609344 km | Weights and Measures Act 1985, Schedule 1 | 13 November 2026 |
Appliance power ratings
The typical power of 30 common appliances is from Centre for Sustainable Energy: How much electricity am I using?, checked 13 November 2026. Your own appliance may differ, so check its rating plate.