How we check our numbers
Every figure on Warm Home Numbers should be traceable to a source you can open yourself. This page explains where our numbers come from, how we keep them current, and what to do if you find a mistake.
Where our numbers come from
We use primary and official sources first:
- Ofgem for the price cap, unit rates, standing charges and the administration of the Boiler Upgrade Scheme.
- GOV.UK and the Department for Energy Security and Net Zero for grant rules, grant values and official statistics.
- HMRC for VAT rules.
- Independent research organisations, such as Nesta, for analysis of official data.
When we use a commercial source, for example an installer’s published price analysis or an energy supplier’s forecast, we name it in the text and say that it is a commercial figure. Every guide ends with a list of the sources it uses.
Our own calculations
Many figures on the site are calculations, for example the running cost of a heat pump at current prices. When we calculate something we say so, show the formula and state the assumptions (such as boiler efficiency or annual gas use), so you can repeat the sum or change it with our calculators.
How often we update
- Every guide shows the date its figures were last checked.
- Guides that use the price cap are reviewed when Ofgem announces a new cap, every three months.
- Grant and VAT guides are reviewed whenever GOV.UK, Ofgem or HMRC change their guidance, and at least once a quarter.
- If a scheme ends or changes, we update the guide rather than leave an old version online.
How we use AI tools
We use AI tools to help research, draft and check our guides. Every figure is checked against its linked source before a page is published, and the editor decides what is published and is responsible for it and for any corrections. We do not publish pages generated automatically in bulk, and we do not use AI tools to invent experiences, reviews or quotes.
What we don’t do
- We don’t accept payment for coverage or for a better mention.
- We don’t rank or recommend specific installers or products in exchange for money.
- We don’t give personal financial, legal or technical advice. For your own home, get quotes from certified installers and, where needed, independent advice.
Corrections
If you think something is wrong or out of date, contact us with the page and, if you can, the source. We check every report. If we change a figure because of a mistake, we correct the page and update its date.