What is actually in a solar quote
Roughly a third of what you pay is panels. The rest is scaffolding, labour, an inverter, electrical work, paperwork and margin — which is why the price per kW falls as the system grows, and why a quote that will not itemise is hiding the part you can actually negotiate.
Most of a solar quote is not panels.
The clearest evidence is in the official cost data. If the price were mostly panels, the cost per kW would be roughly flat across system sizes. It is not:
| System size | Median £/kW | Mean £/kW | Installations |
|---|---|---|---|
| 0-4 kW | £1,595 | £1,808 | 158,512 |
| 4-10 kW | £1,546 | £1,622 | 91,953 |
| 10-50 kW | £1,204 | £1,267 | 14,277 |
Source: Solar photovoltaic (PV) cost data, Department for Energy Security and Net Zero, release 2025-26, published 28 May 2026. OGL v3.0. Derived by the department from the MCS Installation Database — prices paid, not prices advertised.
A 10–50 kW system costs £1,204 per kW against £1,595 per kW at 0–4 kW. Panels cost the same per panel whatever the roof. Something else is being spread over more kilowatts — scaffolding, the visit, the survey, the inverter, the electrical work and the paperwork.
The fixed half and the variable half
Think of a quote as two components.
Costs that barely change with system size — the site survey, mobilising a team, scaffolding erection and hire, the DNO notification, MCS registration and certification, the electrical connection into the consumer unit, and the design work.
Costs that scale with size — the panels themselves, the mounting rails and fixings, the roof labour, and DC cabling. The inverter sits in between: bigger systems need bigger or additional inverters, but not proportionally.
This is why the marginal panel is cheap and the first panel is expensive, and it is the single most useful thing to understand before negotiating. Asking “what would another four panels cost?” is a far better question than “can you knock something off?” — the first is priced at marginal cost, the second comes out of margin and will be resisted.
We can go slightly further than “some costs are fixed”, but not much further, and it is worth being clear about the limit.
If you take the band medians and treat them as points on a line, the implied fixed component is somewhere in the low thousands and the implied variable cost is somewhere around £1,100–£1,500 per kW. But the bands are wide — “4–10 kW” is a big range — and we do not know the distribution of sizes within each one, so any single number from that exercise would be false precision.
What the data supports without qualification: a substantial part of your quote does not depend on how many panels you buy. What it does not support: a pie chart. If you see one, ask where it came from.
VAT: a date worth knowing
Installation of solar panels in residential accommodation is currently zero-rated. HMRC’s VAT Notice 708/6 sets the relief running from 1 May 2023, and states that from 1 April 2027 these installations “will revert to the reduced rate of VAT of 5%”.
Two consequences:
There is a deadline. On a £6,400 installation, 5% is about £320. That is not a reason to rush a decision you are not ready to make, but it is a real number and it has a date on it.
Supply-only does not qualify. The notice is explicit: “if you supply energy-saving materials without installing them your supply will be standard-rated.” So buying panels yourself and paying someone to fit them separately can cost you the relief — relevant to anyone considering a self-managed installation.
Where other work is genuinely ancillary to the installation, the notice contemplates it being treated as part of a single zero-rated supply. Where it is not ancillary — a re-roof, say — it is its own supply with its own VAT treatment. That is a question for the installer’s accountant, and a reason to have the work itemised.
The line items a quote should separate
| Line | Why it must be separate |
|---|---|
| Panels — make, model, count, total kWp | The kWp is what you divide the price by |
| Inverter — make, model, rated output | Decides G98 or G99, and future expansion |
| Optimisers or microinverters, if fitted | A real cost, only sometimes a real need — see shading |
| Mounting system | Roof type drives this |
| Scaffolding | Often the largest single non-panel item |
| Electrical work | Consumer unit changes, earthing, cable runs |
| Battery, if included | A separate product. Bundled prices cannot be compared |
| EV charger, if included | Likewise |
| Making good and waste | Where “extras” appear later |
| Certification and registration | MCS, building regulations notification, DNO |
| VAT | Zero-rated now; 5% from 1 April 2027 |
A quote that gives you one number and a system size is not a quote you can compare. See comparing quotes for how to normalise two that are structured differently.
What the paperwork must contain
Separate from the money, an MCS-certified installer must give you a performance estimate in a prescribed format before you commit, along with the rest of a specified pack. We cover what that contains, and the one section it may legitimately omit, in what a good quote looks like.
Two points that belong here rather than there:
The estimate is not a guarantee, and it is required to say so. Treat it as a modelled number to be checked against an independent one — ours is at generation by region.
Information given to you can bind the trader. Under the Consumer Rights Act 2015, information a trader gives about the service becomes a term of the contract in defined circumstances. That is a reason to keep every version of the quote, and to get changes in writing rather than over the phone — the ground covered in proving underperformance.
Using this when you negotiate
- Divide by kWp and compare with the benchmark.
- Ask what more panels cost, not for a discount.
- Ask what is excluded, specifically scaffolding, electrical work and making good.
- Get the battery priced separately, or leave it out of the comparison entirely.
- Check the VAT position if the work will run past 31 March 2027.
- Ask which items would change if the survey finds something — that is where the costs that are not in the headline come from.
Sources
- Solar photovoltaic (PV) cost data Release 2025-26, published 28 May 2026. Total Installed Capacity basis.
- VAT Notice 708/6: energy-saving materials and heating equipment Last updated 31 January 2024. Guidance, not the legislation itself.
- MIS 3002: The Solar PV Standard, issue 6.0 Read locally. MCS restricts reproduction, so we cite clauses and quote sparingly.
Contains public sector information licensed under the Open Government Licence v3.0.
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