The cost of fitting solar panels: what is in the quote and what is not

Most complaints about solar pricing are not about the headline figure. They are about something that appeared afterwards, was described as standard, and had not been mentioned when the price was agreed.

The fix is to ask for the exclusions in writing before you sign. Here is what to ask about, which of these are legitimate extras rather than padding, and the checks that cost nothing but catch the expensive problems: certification, grid paperwork, VAT treatment and deposit protection.

Always included in a competent quote

• The panels, mounting system and inverter, each identified by manufacturer and model rather than “tier one panels”.
• Installation labour and commissioning.
• Scaffolding, in almost all cases.
• The network operator notification or application.
• MCS registration and the certificate.
• The handover pack, warranties and monitoring setup.

If any of those is absent, that is not a cheaper quote. It is an incomplete one, and the difference will arrive later.

The certification line deserves a moment, because it is the one with money attached. Export tariffs under the Smart Export Guarantee require the installation to be certified under MCS or an equivalent scheme, and suppliers check before they register you. An uncertified install can therefore lock you out of export income for as long as you own it. You can check any installer’s registration yourself on the MCS register before you sign, which takes two minutes and filters out the worst outcome available in this market.

The grid paperwork, decoded

Every grid connected system involves the local network operator, and the quote should say which of two routes applies, because one of them affects your timeline:

• G98 covers systems up to 16 amps per phase, which is 3.68kW of inverter capacity on a single phase supply. The installer fits the system first and notifies the network operator within 28 days. No fee, no waiting.
• G99 applies above that. The application goes in before installation and the network operator must approve it, which typically adds weeks and can occasionally require network reinforcement discussions.

Two things follow. A quote for a larger system that promises next week’s installation date without mentioning G99 has skipped a step you will pay for in delay. And a system sized at exactly 3.68kW of inverter may have been sized to the paperwork rather than to your roof, which is worth a direct question: what would the price and timeline be for the size my roof can actually take? The difference matters over twenty five years, as the worked example on 4kW system costs shows.

Commonly excluded, and legitimately so

Consumer unit work. If your board is old, full, or lacks the right protection, it may need upgrading. A surveyor can tell you before the day. Ask.

Roof repairs. An installer who finds a cracked tile or rotten batten cannot proceed as though it were sound. Reputable ones flag it and price it separately rather than absorbing it silently.

Bird protection. Mesh around the array edge stops pigeons nesting underneath. It is not always specified as standard, it is much cheaper fitted at the same time as the panels, and retrofitting means paying for scaffolding twice.

Long cable runs. Where the inverter has to sit a long way from the board.

Tree work. Nobody’s installer prunes your neighbour’s oak.

These are real costs, not invented ones. The question is whether they were identified at survey or discovered on the day.

Things that should not be extra

Be more sceptical about:

• A charge for the MCS certificate itself, separate from the installation.
• A charge for the G98 notification, which is administrative.
• A “commissioning fee” on top of installation labour.
• Removal of packaging and waste.

None of these are unusual costs. Seeing them itemised as additions is usually a sign the headline price was set low to win the comparison.

VAT: the check that takes ten seconds

The installation of energy saving materials in residential accommodation, including solar panels, is zero rated for VAT from 1 May 2023 to 31 March 2027, after which it reverts to the reduced rate of 5%. Battery storage qualifies too, including batteries retrofitted on their own, from 1 February 2024. The rules are in HMRC’s VAT notice 708/6.

The practical check: a domestic supply-and-install quote today should carry no VAT on the qualifying work. If it shows 20%, ask why. Mixed jobs, where non-qualifying work such as general roof repair is done at the same time, can legitimately have a mixed treatment, and a good quote will show which line is which rather than blending them.

The exclusions question

There is one question that surfaces most of this at once:

“Please confirm in writing everything that is excluded from this price, and what the likely cost would be if it turned out to be needed.”

A surveyor who has looked at your roof and your consumer unit can answer that in a paragraph. One who quoted from an aerial photograph cannot, and the answer will tell you which you are dealing with.

Payment terms are part of the price

Two things worth checking that are not line items:

Deposit size. A modest deposit is normal. A very large one shifts risk onto you for work not yet done.

What the payment schedule is tied to. Payment on completion and commissioning is different from payment on delivery of materials.

Deposit and workmanship protection come through the consumer code your installer belongs to: MCS requires membership of one, and RECC is the largest. Check which code your installer belongs to and what its deposit protection actually covers, rather than assuming the word “protected” on the quote does the work.

Compare like with like: a worked adjustment

Once you have the exclusions from each installer, add the likely extras back onto each quote before comparing. An illustration with two quotes for the same nominal 4kW system:

• Quote A: £7,400, including scaffolding, bird protection and a consumer unit upgrade the surveyor identified.
• Quote B: £6,300, excluding all three. Add realistic figures for the same three items once they arrive as extras and the adjusted total lands above Quote A, with the work now negotiated from a weaker position, after the scaffolding is already up.

The adjusted total, divided by system size in kilowatts peak, is the figure to judge, and you can hold it against the government’s published medians for what solar installations actually cost rather than against advertising.

Then judge that adjusted cost against what the system will actually save on your usage and your tariff, rather than against the savings figure the quote came with. Installer projections routinely assume rising energy prices; our calculator deliberately does not, so you can see the return in today’s money. Put each adjusted quote through the ROI calculator with your own usage and rates, and compare paybacks instead of totals.