Solar quotes become comparable when the equipment, installation scope and financial assumptions are written down on the same basis. Keep the original proposal and use a generic label such as Quote A in the solar quote checker. No account, upload or email is needed to see its findings.
Work through a labelled example
This is a synthetic example, not a real installation or market price. Quote A offers nine 450 W modules, a stated 4.05 kWp array and a GBP 6,000 installed cash total including applicable tax. It forecasts 3,600 kWh annual AC generation against 4,000 kWh household use, with 40% directly used solar. Its example rates are 30p import and 15p metered export, with zero annual operating cost assumed.
The panel arithmetic is 9 x 450 / 1,000 = 4.05 kWp. If the same quote claimed 5 kWp, the checker would ask the installer to reconcile the count and module rating. Its rounding tolerance is the larger of 0.05 kWp or 1%; this is a tool rule, not a technical installation standard.
Direct use is 1,440 kWh. That avoids GBP 432 of imports. The remaining 2,160 kWh of exports earns GBP 324, so annual benefit is GBP 756 before additional costs. Simple payback is about 7.9 years. A five-year claim needs an explanation of different costs, benefits or projection assumptions, rather than being accepted because it appears in a polished chart. Test the same inputs in detailed payback.
Record scope as included, excluded or not stated
If scaffolding is absent from the proposal, record not stated. Do not convert that into excluded or assign a zero price. Ask which elevations are covered, whether an extension needs bridging and what happens if access work changes after survey. The same distinction applies to electrical upgrades, roof repairs, monitoring, commissioning and certification.
A useful written question is: ?Does the total include scaffold design, erection and removal for the surveyed access, and what remains provisional?? Another is: ?Who handles the network application or notification, and what happens if the proposed export limit is not accepted?? The installation guide explains why those differences can change the total.
Separate direct use from battery delivery
A second proposal may claim 80% self-consumption including a battery. That is not the same input as 80% direct solar use. Ask how much is used immediately, how much solar enters storage, how much emerges after losses and how much is exported. Without that split, the checker marks the financial comparison incomplete; it does not give the stored energy a second credit.
A combined solar-and-battery total also cannot establish an additional battery price. Ask for the same solar design without storage and an itemised additional storage scope. A whole-system savings number is not the battery’s own return. Read battery cost boundaries before comparing unlike bundles.
Keep finance and warranty promises distinct
If one quote gives only a monthly finance payment, request the cash installed price and total repayable separately. Do not compare that monthly payment with another contractor’s cash total. State whether tax is included and ask how qualifying supplies are treated.
Product warranty, workmanship warranty and panel performance warranty cover different obligations. Record who provides each, the term, exclusions, registration requirements and labour or scaffold charges. A long performance warranty does not mean an installation fault will be repaired without cost for the same period.
Use the findings as questions, not a verdict
The checker cannot survey a roof, verify an installer?s honesty or establish a market price from one quote. Its findings should produce a clearer proposal. Edit the entries and rerun after the installer answers, print the comparison and keep the agreed version with your contract.
Verify the contracting business through the MCS guidance and read the installer comparison checklist. Missing evidence is a reason to ask; a cheaper total is not automatically a better purchase.
Research checked 1 November 2026. Primary references: Energy Saving Trust solar guidance and Ofgem SEG guidance. The numerical example is illustrative and uses model solar-ac-1.0.0, not a supplier forecast.
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