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Our data

Every figure on this site comes from public data. Here is each source: who publishes it, what we use it for, when they last updated it, when our figures last changed because of it, and when we last checked it. The headline costs are also in our UK Home Upgrade Price Index, with a CSV.

How we use it

  1. We take published data. Government statistics, the energy regulator, the Energy Saving Trust and suppliers' own price pages. Where no published figure exists, we make an assumption and list it below.
  2. We build it into one model. Heat use, energy bills, insulation costs and heat pump costs each live in one file that every calculator and guide reads, so no two pages can give different answers for the same home. Our methodology explains each step.
  3. We check every page against it. Before any change goes live, 35 automated checks compare the figures on every page with the model and the calculators, and a page that disagrees is held back.
  4. We refresh it when a source changes. The price cap every quarter, grants when the rules change, and costs when the publisher revises them.

Every source we use

82 sources, with their dates. "Our figures last changed" comes from our own publishing history, so it moves by itself when we update a figure.

Our own assumptions

Where there is no published figure, we say so.

What the figures are

Estimates for a typical home of each kind. They use the median or typical figure from each source, so your own home will differ.

A survey, a quote or an EPC assessment is what turns an estimate into a price or a rating. If a figure looks wrong or out of date, tell us and we will check it against its source.