About this site

1 What we are not

We are not heating engineers, and we hold no heating qualifications or accreditations. Nobody here is MCS certified, Gas Safe registered or a chartered engineer.

That matters, so we would rather say it plainly than bury it. What this site offers is not professional judgement about your property. It is published data and arithmetic, applied carefully and shown openly, so that you can check it and so that you can hold an installer’s quote up against something.

MCS requires a room-by-room heat loss calculation to BS EN 12831‑1:2017 before anyone installs a heat pump. Nothing here replaces that, and nothing here is a quote.

2 Why you might trust it anyway

• Every figure names its source and its date. Scroll to the bottom of any calculator and you will find a table of every constant used, where it came from, and when it was last checked against that source.
• The arithmetic is on the page. The heat loss table shows each area, each U‑value and each multiplication. You can check any line with a pocket calculator. We would rather be checked than believed.
• We use measured data, not manufacturer ratings. Heat pump efficiency comes from a government field trial of 428 real installations, not from the figure on the box. Boiler efficiency comes from a field trial too, so both sides of the comparison are judged by the same standard. This produces smaller savings than most calculators show.
• The gaps are published. Each calculator has a section listing what it cannot tell you and which of its inputs are assumptions rather than sourced figures. A page claiming no limitations would deserve less trust, not more.
• The calculations are tested. The formulas run against a suite of automated tests, including worked examples checked by hand.

3 How this site makes money

If that changes, it will be stated here, in the footer of every page, and next to any button that earns us something. We will not take money to recommend a particular installer or manufacturer, and no commercial arrangement will ever change a number produced by a calculator on this site.

We do not sell your details. The calculators collect no personal information at all, which you can read more about in the privacy policy.

4 If you think something is wrong

Tell us. Energy prices, grant rules and published datasets all change, and a page that was right in October can be wrong by January.

If you can, say which figure, which page, and what you think it should be. If you are an installer and our estimate disagrees with your survey, we would genuinely like to know — that is the most useful correction we can get, and a real room-by-room calculation beats an estimate every time.

5 When pages were last checked

Energy prices are reviewed every quarter, when Ofgem announces the next cap. Grant rules and installation cost statistics are checked at the same time. The date at the top of every page is the date its figures were last verified against their source, not the date the words were edited.