This policy explains where the figures on HousyTools come from, how we check them, how often we update them and what happens when we get something wrong. It applies to every calculator, guide and hub page on the site.
Where Our Figures Come From
We use the most authoritative source available for each fact, in this order:
| Priority | Source type | Examples |
|---|---|---|
| 1 | Regulators | Ofgem for the energy price cap, unit rates and standing charges |
| 2 | Government and official statistics | GOV.UK and HMRC for gas conversion and VAT, Eurostat for EU electricity prices, the EU Joint Research Centre (PVGIS) for solar yield |
| 3 | Safety bodies and standards | HSE, the Gas Safe Register, Approved Document P, MCS heat pump design guidance |
| 4 | Manufacturer manuals and data sheets | Coverage, consumption and output figures published by paint, adhesive, flooring and radiator makers |
| 5 | Independent advice bodies | Energy Saving Trust, Citizens Advice |
We do not use competitor calculators, forums or unsourced blog posts as the basis for a figure. If a number cannot be verified from a source like those above, we do not present it as fact. Instead it becomes an input you can edit, with a clearly labelled example default.
How We Check Each Calculator
- The formula is written out from the source and checked by hand before any code is written.
- Every worked example on a page is produced by running the live calculator with the stated inputs, then checked against the formula.
- Each tool is tested with empty, zero and unrealistic inputs, in metric and imperial, and in pounds and euros where relevant.
- Units are always shown next to results, so a figure cannot be read as the wrong unit.
How Often We Recheck Rates and Prices
Energy rates change more often than anything else on the site. We recheck the UK unit rates and standing charges whenever Ofgem announces a new price cap period, and we review every rate based default at least every 3 months even if nothing has been announced. EU figures are updated when Eurostat publishes a new half year release. Other pages are reviewed when a standard, regulation or manufacturer data sheet changes, and at least once a year.
What the “Checked” Date Means
Each page shows a “Checked” line with a month and year and the sources used. It means a person compared the figures and formulas on that page with those sources in that month. Pages also show when they were first published and when they were last updated. We change the “Checked” date only when a real check has taken place, never just to make a page look fresh.
Corrections
If you think a figure, formula or result is wrong, please tell us through report an error. We check the report against the original source. If we made a mistake, we fix it, update the “Checked” date and record what changed and when in our change log. Significant corrections, such as a wrong rate or a formula error that changed results, are also noted on the page itself.
Use of Software and AI Assistance
We use software tools, including AI writing and coding assistants, to help draft text, write and test calculator code, and check pages for consistency. AI is never treated as a source: every rate, formula and safety statement is traced back to a primary source, and every page is reviewed and approved by a person before it is published. The person responsible for the content is named on our about page.
No Commercial Influence
No company pays to appear on HousyTools or to change a default value. Brand names are mentioned only to cite their published data. If we ever use affiliate links or advertising, they will be clearly labelled and kept separate from the calculators, and they will not affect which products or figures we use.
Safety Rules We Follow
- We never give step by step instructions for gas work. In the UK, work on gas appliances and pipework must be carried out by a Gas Safe registered engineer, which you can check on the Gas Safe Register.
- For electrical work, we say clearly when a qualified electrician is needed. In England and Wales, much electrical work in homes falls under Part P of the Building Regulations (Approved Document P).
- Where a job may disturb asbestos, lead paint or silica dust, we point to HSE guidance and recommend professional help.
- Sizing tools for boilers and heat pumps are labelled as guides only. A proper heat loss survey by an installer is needed before you buy.
Read more about the limits of our tools in the disclaimer.