Quick answer: how much do solar panels cost for a house depends first on system size in kilowatts peak (kWp), then on how the quote splits panels, inverter, labour and extras. Compare quotes line by line, not by headline total.
The dollar figures below come from US installers and surveys. They show how price scales and splits, not what a UK installer will charge in pounds. For the wider picture, including storage, see our guide to home solar panels and battery storage.
Choosing a system size
System size is the biggest driver of the total, because larger systems with more panels have higher up-front costs. The kilowatt peak (kWp) rating is the figure installers use to describe array size, so it is the number to pin down before comparing prices.
- Start from your bills. Historical utility bills help determine the optimal system size, so size the array to your own use before you look at totals.
- Expect the total to rise with size. Moving up a size adds panels and therefore adds cost, so ask installers to price two neighbouring sizes side by side.
- Compare on a per-watt basis. Dividing a quote by the array’s capacity lets you compare a small system with a large one. A UK quote expresses the same idea as a price per kWp.
What a 4kW, 6kW and larger system costs
The table gives quote ranges from a US survey, in dollars, before the 30% US tax credit. Treat them as a guide to how the price climbs with size.
| System size | Typical quote before credit | Planning use |
|---|---|---|
| 4 kW | $14,000 to $16,000 | The reference point for the average cost of a 4kW solar system. A sensible first quote to request if your bills are modest. |
| 6 kW | $19,000 to $22,000 | The step up for a household whose bills justify more panels. Ask the installer to explain what the extra capacity adds. |
| 8 kW | $24,000 to $28,000 | Totals are large enough that small differences between line items matter, so insist on an itemised quote. |
| 10 kW | $28,000 to $32,000 | The largest size in the survey. Only worth pricing if your usage supports it. |
These ranges come from a US residential solar quote survey, in dollars, before the 30% credit.
Other US benchmarks sit in the same band. The same survey cites national costs from $2.50 to $3.50 per watt in 2025 data from EnergySage. A California installer puts a typical 6 kW system at $15,000 to $21,000 before incentives. At the large end, most Texans need an 11.5 kW system, which averages $36,570 at $3.18 per watt before the federal credit.
For a typical house system in the UK, ask for the total in pounds and the price per kWp. Judge both against the pattern above: bigger arrays cost more in total, and a per-watt price shows whether a quote is out of line for its size.
Where the money goes in a quote
A quote bundles panels, an inverter, labour and several smaller items, and breakdowns differ. One California installer breakdown puts panels at 30-40% of the total price and inverters at 10-15%. A separate guide says panels can make up only roughly 12% of the total installation cost. Use these as ranges to test a quote against, not as fixed shares.
Solar panels
The panel line is usually the most visible item, but the wide gap between those two breakdowns shows it does not decide the bill alone. Check the panel count and type against the array size you agreed. If you want to see what each component does before judging its price, read how do solar panels work.
Inverter and electrical work
The inverter line was 10-15% of the total price in the same California breakdown. The inverter converts the array’s output into usable household electricity, and its price depends on the type you choose. Settle that choice first using our comparison of string inverter vs microinverter, then check the quote names the inverter model.
Labour, mounting and scaffolding
Labour is the next biggest piece after equipment, often 20-30% of the total system cost. Mounting hardware and scaffolding are the lines most likely to be folded into that figure or into a lump-sum price. Ask whether each is listed separately. A quote that names them is easier to compare with another installer’s.
How roof and site change the price
Roof layout changes the cost through the number of panels and the work of fitting them. South-facing roofs with minimal shading offer the best efficiency and may require fewer panels, which can mean a smaller panel line for the same output. In the other direction, a steep roof may require extra time and work, and that falls under labour.
Neither effect has a universal price. If your roof is steep, shaded or awkwardly shaped, ask the installer to show any roof-related uplift as its own line rather than hiding it in the total.
Checking a quote line by line
An itemised quote lets you test each line against the shares above. Work through it in this order.
- Confirm the size. Find the array size in kWp and the total price, and work out the price per kWp.
- Read the panel line. Check the panel type and count, and see whether they match the size stated.
- Find the inverter line. Look for the model and type, not just the word inverter.
- Locate labour. See whether it is its own line, and whether it looks consistent with the share ranges earlier.
- Look for the extras. Scaffolding, mounting hardware and certification should each be visible, either as lines or as items the installer confirms are included.
Keep the same layout for every installer, so a missing line is obvious.
When a quote looks off
- The panel line is far from the ranges. The shares in different breakdowns vary widely, so a gap is a reason to ask questions, not proof of a bad quote. Ask what the panel line includes.
- The total is low but vague. A single lump sum can hide excluded items. Ask for an itemised version and check which of scaffolding, mounting and electrical work are left out.
- Labour is missing as a line. It is probably folded into other items. Ask the installer to separate it so you can compare it with other quotes.
- Two quotes differ by a lot at the same size. Compare price per kWp, then compare the inverter and panel lines to find where the difference sits.
Frequently asked questions
What does kilowatt peak mean on a quote?
Kilowatt peak (kWp) is the rating used for the size of the array. A higher kWp means more panels and, as larger systems carry higher up-front costs, a higher total.
Do monocrystalline panels cost more than polycrystalline?
Yes. Monocrystalline panels typically cost more upfront but generate more electricity per square foot.
Are permit costs included in a quote?
Usually, from professional installers. Permit costs vary by locality, and some areas have specific installation requirements that can affect pricing, so confirm the quote states them.
