Good Houses
Solar panel cost calculator
Step 1 of 3
Where's the roof?
A postcode gives you a generation estimate for your actual region. You can also skip this and get a national average.
Start with the payback, because it is the least attractive part and everyone else saves it until last. Realistically you are looking at fifteen years or more before the system pays for itself, and longer again if your roof faces east or west, is shaded, or you are further north. Unless this is the house you plan to stay in for a long time, that is a hard number to justify, and we would rather say so here than after three companies have been round.
If you are staying, it gets more interesting. Most roofs face more than one direction, so panels can go on more than one side and catch the sun across the day.
A battery deserves a straight answer. It lengthens your payback rather than shortening it, because it costs more than the extra electricity it saves. What it buys is usefulness: in summer your own generation can run air conditioning and charge a car instead of being exported cheaply. That can be well worth paying for, but it is not a way to get your money back faster.
How we size a solar system
The system size comes from your usable roof area, either the figure you give us, or an estimate from your property type. That size is capped at a common domestic limit unless you choose to go higher, and if you do, the calculator flags that a network operator application is needed.
Generation is then estimated from four things, in order of how much they matter: where you are in the country, which way the roof faces, its pitch, and how much shading it gets. A south-facing roof in Cornwall and a north-east-facing roof in Aberdeen are genuinely different investments, and a national average would flatter one and insult the other.
Cost is built from the panels and inverter, scaffolding, installation labour adjusted for your area, an optional battery, and the network application where the system is large enough to need one.
Savings depend heavily on how much of what you generate you actually use. Without a battery, much of it is exported; with one, considerably less. The calculator uses different self-consumption assumptions for each, values the rest at the export rate, and gives you a payback period from those.
The result is always a range, never a single figure. A precise number would be a false promise, because two builders quoting the same job honestly can land a long way apart. Everything is rounded rather than shown to the pound, for the same reason.
Every figure behind this comes from a table we maintain by hand and review on a schedule. The date of the last review is shown on this page, so you can judge how current it is rather than take our word for it.
What the solar figure covers
The figure covers:
- Panels and inverter, sized to your roof
- Scaffolding
- Installation labour, adjusted for your area
- A battery, where you have chosen one
- A network operator application, where the system size requires it
What the solar figure leaves out
Not in the figure:
- Roof repairs, or replacing tiles that break during installation
- Strengthening a roof that will not take the load
- Removing and refitting panels later if the roof needs work
- Upgrading your consumer unit if it cannot accommodate the system
- Tree work, where shading is the limiting factor
- Scaffolding beyond a standard domestic arrangement on a difficult site
Why your location matters twice over
Location matters more here than on any other calculator, and for two separate reasons. Labour costs vary by region, as everywhere. But sunlight varies too, and by considerably more. The same system generates substantially less in the north of Scotland than on the south coast, and pretending otherwise would make every payback figure wrong.
The calculator uses a regional generation figure alongside the labour adjustment, so both effects are in the answer.
Taking this to solar installers
Take it to real quotes, and treat it as the shape of the answer rather than the answer. Get three written quotes from MCS-certified installers, and compare what each one includes before you compare the totals, because the cheapest number on the page is often the one leaving the most out.
If a quote comes in below our range, that usually means a newer business building a reputation, or work that cuts corners. Above it usually means limited local supply, or a firm with higher overheads. Both can be the right choice. The question worth asking is what is included, not why the number differs.
Worth asking every firm you speak to:
- What annual generation are you predicting for my roof specifically?
- What is the inverter, and what is its warranty?
- What happens to the panel warranty if you go out of business?
- Is scaffolding included, and for how long?
- Have you applied for the network connection, if one is needed?
Common questions
Is a battery worth it?
It depends almost entirely on how much of your generation you would otherwise export. A battery lets you use far more of what you make, which is worth more than exporting it, but it is a large part of the total cost. The calculator lets you see both, which is the only way to answer it properly.
What if my roof faces east-west?
It still works, with a real reduction. The calculator applies it rather than glossing over it. East-west roofs generate over a longer, flatter day, which can suit a household that uses power in the morning and evening.
How accurate is the payback figure?
It is as accurate as the energy prices and export rate it is built on, and those change. Treat the payback period as a comparison tool between options rather than a promise about the next fifteen years.
Is this a quote?
No. It is an estimate built from typical costs, and no contractor is bound by it. Use it to know whether a quote you have been given is roughly where it should be, and to walk into that conversation knowing what questions to ask.
Why do you show a range instead of one number?
Because one number would be misleading. The answer to "what will this cost" is a range, and where you land inside it depends on your property, your area and who you hire. Any tool giving you a single figure to the pound is telling you something it cannot know.
Do you save what I type in?
No. The calculation runs and the answers are discarded. Nothing is written down unless you explicitly ask us to email or save a result. We do not build a profile from calculator use.
How current are the figures?
The date of the last review is shown on this page. The costs behind the calculator are maintained by hand rather than scraped, and reviewed on a schedule.