How to Read a Solar Quote Line by Line

Getting three solar quotes through your letterbox (or inbox) and finding they’re laid out completely differently is one of the most common reasons UK homeowners stall on a decision. One installer gives you a single page with a price. Another hands you eleven pages of technical spec sheets. A third quotes “4kW” but never explains what that actually means for your roof or your bills. None of this is your fault — there’s no standard format for a solar panel quote in the UK, which makes genuine comparison hard unless you know what each line is actually telling you.

This guide walks through a typical quote section by section, decodes the jargon, flags the phrases that should make you pause, and gives you a proper method for comparing three quotes side by side rather than just eyeballing the bottom-line figure.

Start with the system size — kWp is not the same as kW output

Every quote leads with a system size, usually written as something like “4.4kWp” or “3.68kW.” kWp stands for kilowatt-peak — the maximum output the panels can produce under lab-standard test conditions (a specific light intensity and panel temperature that rarely occurs exactly on a British roof). It is a nameplate rating, not a promise of daily output.

What actually matters is annual yield, measured in kWh/year, which depends on:

• Orientation and pitch — a south-facing roof at 30-40° pitch is closest to optimal; east/west splits still work but yield less per panel
• Shading — even partial shading from a chimney or neighbouring tree at certain times of day can disproportionately cut output if the system lacks module-level optimisers
• Location — UK yields typically range from around 850 kWh per kWp per year in the north to over 1,000 kWh per kWp in the sunnier south

A good quote states the predicted annual generation in kWh, not just the kWp figure, and ideally references the specific roof pitch and orientation measured for your property — not a generic assumption. If a quote only gives you kWp and a lump sum saving with no generation figure in between, ask for it. The British Solar Blog’s guide to how solar panels actually perform in the UK is worth reading alongside your quote if the generation numbers seem optimistic.

The panel line: brand, wattage, warranty, and technology

This line usually reads something like “16 x 440W JA Solar panels” or similar. Break it down:

• Panel count × wattage — multiply these and you get the kWp figure above (16 × 440W ≈ 7kWp, though real-world DC-to-AC losses mean actual output is slightly lower)
• Brand and model — Tier 1 manufacturers (JA Solar, Trina, LONGi, REC, Jinko and similar) have a long track record; be more cautious of unfamiliar white-label brands with no UK service history
• Technology — most panels quoted in 2026 use N-type cells (TOPCon, HJT or back-contact/ABC designs), which degrade more slowly than older P-type panels — typically around 0.4% efficiency loss per year, versus closer to 0.5-0.7% for older technology. A well-specified N-type panel should still be producing strongly after 25-30 years
• Product warranty vs performance warranty — these are different things and quotes sometimes blur them. The product warranty covers manufacturing defects (often 12-25 years depending on brand). The performance warranty guarantees a minimum output percentage over time (commonly 25-30 years, tailing off to roughly 87-92% of original output). Check both are stated, not just one

If a quote just says “solar panels” with no brand named, that’s worth querying directly.

The inverter line: the part people forget will need replacing

The inverter converts DC power from the panels into AC power your home can use. It’s arguably the single most important line on the quote because, unlike panels, inverters do wear out — typically after 10-15 years, with a replacement costing roughly £500-£1,000 for a string inverter.

Check the quote specifies:

• String inverter vs micro-inverters vs power optimisers — string inverters are the cheapest and most common for straightforward, unshaded roofs; micro-inverters or optimisers cost more but can significantly improve output on roofs with partial shading or multiple orientations
• Inverter warranty length — often shorter than the panel warranty (5-12 years as standard, sometimes extendable). A mismatch between a 25-year panel warranty and a 5-year inverter warranty isn’t a red flag in itself, but you should know you’re likely paying for an inverter swap partway through the system’s life
• Make and model, so you can check it independently rather than take the installer’s description on trust

Battery storage, if included

If a battery is quoted alongside the panels, look for the usable capacity in kWh (not just the headline number, since a small percentage is usually reserved to protect battery health), the chemistry (LFP/lithium iron phosphate is now the standard for safety and cycle life), and the cycle warranty (commonly 6,000-10,000 cycles or a set number of years, whichever comes first). Installed battery costs in 2026 typically run around £400-£700 per kWh — so a Tesla Powerwall 3 at 13.5kWh usable capacity landing around £8,500-£10,500 installed is roughly in line with the market; a much cheaper unbranded battery of similar size is worth extra scrutiny on the warranty terms. For a full breakdown of what drives battery pricing, thecostofsolar.co.uk’s solar battery storage cost guide is a useful cross-reference.

Scaffold, mounting and balance-of-system lines

This is where quotes vary most and where genuine cost differences hide:

• Scaffolding — should be itemised, not buried. A straightforward two-storey semi might need only a few days of scaffold; a complex roofline, dormer windows or a third storey adds real cost. If one quote is markedly cheaper than the others, check whether scaffolding is included at all or quoted as an “if required” extra
• Mounting system — in-roof (flush, more expensive, better aesthetics) versus on-roof (rail-mounted, standard and cheaper) should be specified, along with roof type compatibility (slate, concrete tile, flat roof with ballast, etc.)
• DNO application — for most residential systems this is a formality your installer handles, but larger systems may need Distribution Network Operator approval before connection; the quote should say who’s responsible for this and any associated fee
• MCS certification — this is not optional. Without MCS (Microgeneration Certification Scheme) certification on both the installer and the installation, you cannot claim the Smart Export Guarantee, and some lenders and home insurers may query an uncertified installation. If a quote doesn’t mention MCS at all, ask outright

VAT, grants, and the numbers people get wrong

Residential solar panels and battery storage installed in Great Britain currently qualify for 0% VAT, a relief scheduled to run until 31 March 2027 (after which it’s due to revert to 5%, not the full standard rate). A legitimate quote should already show 0% VAT applied — if you see 20% VAT added to a straightforward domestic installation quote in 2026, query it immediately.

Be wary of quotes that lean on grant claims that don’t exist. There is no universal government grant for home solar installations in England. What genuinely exists:

• ECO4 and Warm Homes schemes — means-tested support tied to low income and low EPC-rated homes, not a general homeowner grant
• Home Energy Scotland — interest-free loans (not a straight grant) for Scottish homeowners
• Boiler Upgrade Scheme — £7,500 towards an air source or ground source heat pump. It does not cover solar PV, despite occasionally being mentioned in the same breath by less scrupulous salespeople

If a quote or salesperson references a “solar grant” for an ordinary homeowner in England with no mention of income or EPC eligibility, that’s a red flag worth pressing on.

Smart Export Guarantee — don’t accept a headline rate without a name

Nearly every quote will quote a Smart Export Guarantee (SEG) rate to make the payback figures look better. SEG rates are set by individual energy suppliers, not government, and vary widely — from a few pence up to around 12-20p/kWh at the top end for the best tariffs. A quote that assumes the top-of-market rate without naming the supplier or tariff is quietly inflating your payback projection. Ask which specific SEG tariff the calculation is based on, and check it’s still available (rates move).

Payback period and savings projections — check the assumptions

Most quotes include a projected payback period and lifetime savings figure. These are only as good as the assumptions behind them. Ask what import electricity price they’ve used (the current Ofgem price cap puts typical unit rates around 25p/kWh, though this moves with each price cap review), what self-consumption percentage they’ve assumed (i.e. how much of your generation you actually use rather than export — a battery significantly raises this), and whether they’ve factored in any panel degradation over the system’s life. If you want to sanity-check the numbers independently, thecostofsolar.co.uk’s solar panel payback period calculator lets you run your own figures against the installer’s projection.

Red flags worth naming directly

• Pressure to sign today for a “discount” — a legitimate installer’s price shouldn’t expire at midnight
• No MCS number for the installer or the specific installation
• Vague generation figures — “save up to £X” with no kWh generation, no assumed import price, and no stated system size behind it
• AggregateRating-style review claims that can’t be verified against a real review platform — ask where the reviews are hosted and check them yourself
• A single all-in price with no line-item breakdown — makes genuine like-for-like comparison against other quotes almost impossible
• Unnamed panel or inverter brands anywhere on the paperwork
• A grant or “government scheme” reference that doesn’t match anything above — if in doubt, ask the installer to name the specific scheme and cite it

Comparing three quotes properly

Once you have three quotes in front of you, build a simple table rather than comparing headline prices. It looks something like this:

That last row — price per kWp — is often the most revealing single number once scaffold and battery costs are stripped out, because it neutralises the effect of one installer simply quoting a smaller or larger system than the others. As a rough sense-check, a straightforward 4kW residential system installed in 2026 typically runs somewhere between £6,000 and £8,000, with a 3kW system nearer £5,000 and a 10kW system in the £13,000-£17,000 range — so if a quote sits well outside that band without an obvious reason (complex roof, premium in-roof mounting, large battery), ask why.

It’s also worth getting a fourth opinion where none of the three quotes has been particularly forthcoming with detail. Installers who are used to fielding detailed questions tend to answer them properly on paper the first time. In the South Yorkshire area, ElectriFusion Solutions and AMP Pro Electrical both provide itemised residential quotes as a matter of course; in Central Scotland, Ecoaim does the same, and in South Wales, FLD Electrical is a solid local reference point if you want a quote to compare your existing ones against. None of this is a recommendation to use any particular installer — it’s simply worth having a properly itemised comparison quote in hand before you commit to anyone.

If you’re weighing up a battery alongside the panels

Quotes that bundle a battery in with the panels from day one deserve extra scrutiny on the assumptions, because the payback maths for a battery is a different calculation from the panels themselves — it depends heavily on your evening usage pattern and any time-of-use tariff you’re on or planning to switch to. If the household runs any home business or has particularly heavy usage, it’s also worth understanding how commercial-scale thinking differs — Solar Panels For Commercial Property and Battery Storage For Business cover the equivalent decision at larger scale, which can be a useful reference point even for a large domestic system, since the same red flags (unnamed cycle warranties, inflated SEG assumptions) apply regardless of size.

The bottom line

A solar quote is a technical document dressed up as a sales one. Once you know that kWp is a lab rating rather than a promise, that the inverter warranty usually runs shorter than the panel warranty, that VAT should already be at 0%, and that any grant reference needs a name you can check, most of the ambiguity in a typical quote disappears. Build the comparison table, ask for the two or three figures that are missing, and don’t sign anything the same day it’s presented. A legitimate installer will always be happy to leave a proper, itemised quote with you for a few days — if one isn’t, that alone tells you something.

For more on what “good” panels actually look like technically, see thebritishsolarblog.co.uk’s guide to the best solar panels available in the UK, and if long-term upkeep is on your mind before you even sign, our solar panel maintenance guide explains what a properly installed system needs (and doesn’t need) over its lifetime.