Sources and methodology

Why this page exists

Solar advice online mixes real physics with sales copy. A homeowner cannot always tell them apart, because both sound confident. This page explains how we try to keep the two separate.

Our aim is simple. Each fact in a guide should trace back to a named publisher. If a fact cannot be checked, we leave it out, or we say plainly that it varies. Our editorial and evidence policy sets out the wider principles. This page covers the working method.

The source hierarchy

We rank sources by how close they are to the rule or the data. The order below is the one we follow when sources disagree.

1. Law and regulator pages. Examples are legislation.gov.uk, GOV.UK, HMRC, Ofgem and the Competition and Markets Authority.
2. Technical standards and scheme operators. The main one is MCS and its installation standard, MIS 3002. The Renewable Energy Consumer Code (RECC) sets sales rules for its members.
3. Public advice bodies. These include the Energy Saving Trust, Home Energy Scotland, Nest in Wales and nidirect in Northern Ireland.
4. Supplier pages. We use these only for live tariff rates.

Commercial pages, such as installer blogs, can help us explain a product. However, we never use them as the only proof of a technical or price claim. A company’s own performance claims are not independent evidence either, since the firm has a stake in the result.

How we check a figure

Every guide and post goes through the same steps before it is published.

1. We open the primary page for each rule or number. We do not rely on a summary or on memory.
2. We compare the wording against what we wrote. If our sentence says more than the source, we cut it back.
3. We name the publisher in the text or in the source list at the foot of the page.
4. We label anything that changes fast with the month and the source.

Money figures get extra care. A cost figure needs at least two independent sources. If we only have one, we give a range and name where it came from, because a single number can mislead. Our guide on how much solar panels cost follows this rule. The wider costs and savings hub does too.

Where we could not open a page in full, we treat it as a weaker source. As a result, we keep the claim modest or leave it out.

Rules that change quickly

Some facts have an end date or a recent change. We state the date and the source so you can see how current the fact is. For example, here are three items as of October 2026:

• VAT. HMRC says the zero rate for solar panels and batteries in homes runs to 31 March 2027. The rate then returns to 5% from 1 April 2027. See 0% VAT on solar panels.
• Planning in England. The Planning Portal says the permitted development rules for solar changed on 27 August 2026. A 12-month transition lasts until 27 August 2027. See planning permission for solar panels.
• Installation standard. MIS 3002 issue 6.0 is dated 18 March 2026. We explain what it means for buyers in MCS certification explained.

Funding rules move fastest of all. For that reason, our grants and funding hub points you to the official scheme page for the current terms.

Four nations, different rules

The UK has four sets of rules in some areas. Planning and building regulations differ between England, Scotland, Wales and Northern Ireland. Grants differ too. When a rule applies to one nation, we say which, while a UK-wide rule, such as the MCS standard, is marked as UK-wide.

Export tariffs and rates

Ofgem sets the framework for the Smart Export Guarantee. Each supplier then sets its own rates. Because of that, we do not quote a “standard” rate. If we name a rate, we name the supplier and the date we checked. Our guide to the Smart Export Guarantee explains how to compare offers. The batteries and export hub puts them in context.

Tools and estimates

Any interactive tool on this site shows its inputs. Its results are indicative only. They are not a quote and they do not replace a survey, because a real design depends on your roof, shading and use of power. The roof and property suitability hub shows what an installer will assess. Our guide to choosing an installer shows how to ask for a written estimate on your own home.

Review dates

Each guide shows an “updated” date. We change it only after a real review or a material edit. Posts show the date they were published, plus an updated date when we revise them.

This page was last reviewed in October 2026. Earlier versions of the guides carried older dates, such as a July 2026 review. We recheck time-sensitive facts at each review, and we recheck them sooner if a scheme or rule changes. Our plan your installation hub and the maintenance and lifespan hub both carry their own dates.

Plain-language terms

We keep language simple, but solar has jargon you cannot avoid. Our glossary defines the main technical terms we use, in everyday words, so you can follow a quote or a standard.

Corrections and AI-assisted drafting

Tools may help us organise research and draft structure. A page is not published just because a tool wrote it. Every claim must fit its cited source. If you spot a mistake, tell us through the complaints and corrections page. We correct pages in place and update the review date when the fix is material.