Our Methodology
How we turn open data into useful advice — and how we choose the companies we work with.
The data
Every number on this site comes from official, publicly available government data. We don't make anything up and we don't guess. When we estimate, we tell you exactly how — and we label it clearly.
EPC Register
Every rated property in England and Wales, published by the Ministry of Housing, Communities & Local Government under Open Government Licence v3.0. Scottish EPCs via Energy Saving Trust's epcdata.scot.
Energy prices
Ofgem's quarterly price cap sets the unit rates we use: gas at 5.93p/kWh, electricity at 27.69p/kWh (Q1 2026). We update these every quarter when Ofgem announces new rates.
Solar generation
The European Commission's PVGIS service uses satellite data to estimate solar output at your exact latitude. We model a typical 4kWp system — the most common residential installation in the UK.
Property sales
HM Land Registry Price Paid Data — every residential property transaction in England and Wales since 1995.
Location data
Office for National Statistics postcode data via postcodes.io — local authority, region, rural/urban classification.
How we calculate savings
When you look up a property, we calculate potential savings from three improvements: insulation, solar panels, and heat pumps. Here's exactly how.
Insulation
Your EPC tells us what type of walls you have. We apply standard saving percentages to your actual heating cost: 15–25% for solid wall insulation, 10–20% for cavity wall, 10–15% for loft insulation. These ranges come from Energy Saving Trust research.
Solar panels
We take your latitude, calculate annual solar output using PVGIS satellite data, assume 50% self-consumption (you use half, export half), and price it at current Ofgem electricity rates plus the Smart Export Guarantee rate (typically 12p/kWh) for the exported half.
Heat pumps
We calculate your thermal demand from your gas heating cost (adjusting for boiler efficiency at 85%), then divide by a heat pump COP of 3.0 to find the electricity needed. We only show a saving when a heat pump genuinely costs less to run. When it doesn't, we still show it — because the £7,500 BUS grant often makes the upfront cost worthwhile.
These are estimates, not quotes
Every property is different. Actual savings depend on your home's specific construction, your usage patterns, the system installed, and the installer. Only a qualified assessor can give you exact figures. We show you the ballpark so you can decide whether it's worth investigating.
Estimated potential ratings
Some properties have old EPCs assessed before heat pumps and solar were standard recommendations. For these, we look at neighbouring properties assessed in the last 5 years and show their average potential as a guide. This is clearly labelled with a dashed border and a note that only a qualified assessor can confirm.
How we choose our partners
We work with a small number of commercial partners — companies that install solar panels, heat pumps, and insulation, plus energy suppliers. We're selective about who we feature.
Trustpilot 4★ or above
Every commercial provider we list must have a Trustpilot rating of 4 stars or higher. We do our best to monitor ratings regularly, but scores can change at any time and we can't be held responsible if a rating dips after we've listed a provider. If we spot it, we remove them.
Red flag checks
We review complaint patterns, regulatory standing, and whether the company genuinely fits the type of work your home needs.
Non-commercial options always shown
Alongside our partners, we always include free, independent options: MCS certified installers, Energy Saving Trust, TrustMark, and government grant schemes. We earn nothing from these — they're there because they're useful.
Multiple options, never just one
Every category shows several providers. We never funnel you toward a single company. You compare, you choose.
We earn a commission when you click through to a partner and make a purchase or booking. This costs you nothing extra — the commission comes from the provider. Full details in our affiliate disclosure.
What we don't do
- ✗We don't collect your personal data — no forms, no phone numbers, no email harvesting
- ✗We don't estimate property values — we show Land Registry facts only
- ✗We don't sell leads to installers or energy companies
- ✗We don't use your data for profiling or targeted advertising
Questions about our methodology? Email hello@ukhomeenergyguide.co.uk