THI Solar
Solar cost and savings
What decides the cost of solar panels and a battery, how a savings estimate is put together, and the questions that show whether a figure means anything.
You won’t find a “from” price or a headline saving on this page. A number that leaves out your roof, your electricity use and your tariff doesn’t tell you much, so we explain what decides them. You get a written, itemised price after your survey.
The price
What affects the cost
| Factor | Why it matters |
|---|---|
| System size | How many panels your roof can take, and how many your electricity use justifies. More panels aren’t always better if most of the output would be exported. |
| The roof | Its shape, condition, pitch and covering. Some roofs take longer to work on, and some need attention before panels go on. |
| Battery | Whether you want one, and at what capacity. A battery is a large part of the price, so it’s worth seeing the numbers with and without. |
| Inverter | The type suited to your roof layout, any shading and any battery, now or later. |
| Scaffolding | Access varies a lot from house to house. Your quotation should say whether it’s included. |
| Electrical and network work | Consumer unit work, cable routes, and anything your network operator requires. |
| VAT | Qualifying installations in homes are zero-rated until 31 March 2027, and 5% from 1 April 2027. Your quotation states the treatment. |
VAT position taken from VAT Notice 708/6, checked 3 November 2026.
The government publishes official cost data for solar installations, drawn from MCS records. It’s a useful way to sanity-check a quotation. It isn’t THI’s price.
The quotation
What a good quotation includes
- The make and model of the panels, inverter and any battery
- A total price including VAT, and what could change it
- What’s excluded, such as scaffolding or electrical upgrades, if it is
- A performance estimate for your home, with its assumptions
- What you pay and when, and how any deposit is protected
- Guarantees and warranties, each with its length and provider
- Your cancellation rights
Be wary of
- A price that’s only good for today
- “Free”, “eliminate your bills” or “pays for itself in N years” with nothing behind it
- An “up to” figure that doesn’t say how many customers actually get it
- A monthly payment with no lender, APR or total repayable beside it
Savings
How an estimate should be built
What solar saves you depends on five things. Change any of them and the answer changes, which is why neighbours with similar houses can get very different results.
What the system generates
Set by size, direction, pitch, shading and the weather. It varies through the year.
How much you use at home
Power you use yourself replaces power you’d otherwise buy. Being home in the day usually helps.
Your import tariff
What each unit you don’t buy would have cost, and when. Tariffs change.
Your export rate
What your supplier pays for what you send to the grid. Each sets its own rate.
Whether there’s a battery
A battery moves some use to the evening. Results with and without one should always be shown separately.
Payback
Why you won’t see one number
Published payback figures vary widely, partly because they rest on different assumptions about price, tariffs and how much electricity is used at home. A single figure hides all of that.
So we’d rather show you the method for your home, with its assumptions and a date, and let you test it. If your circumstances change, you’ll be able to see what that does to the answer.
Questions worth asking any installer
- What unit rate and export rate did you assume, and when were they checked?
- What share of the output do you assume I use at home?
- Does this include a battery? What’s the answer without one?
- Is this first-year only, or have you assumed prices will rise?
Grants and finance
What we can say today
Grants
There’s no general grant for solar. ECO4 is a supplier-led scheme for low-income or poorly insulated homes, and runs to 31 December 2026.
Lower-rate loans
The Warm Homes Loan Scheme offers lower-rate loans through participating lenders and needs an MCS installer. It’s a loan, not a grant.
Finance
Finance isn’t offered through this website. If you’re offered finance by anyone, check the lender, the total cost and your cancellation rights before you sign.
Checked 3 November 2026. Scheme rules change, so check the current position before relying on this.
Keep reading
Related pages
How solar installation works
Each stage, and what you receive at it.
Battery storage
What a battery does, and when one may suit.
Request Your Solar Assessment
A survey and an itemised quotation are how you get a real number. Start with your name, postcode and how you’d like us to get in touch. “Not sure” is always fine.
We reply as soon as we can.