How to compare solar quotes

Compare the design, not just the price

Two quotes can both say solar panels and still be completely different products. One may use a smaller inverter, cheaper panels, no optimisers and a shorter workmanship warranty. Another may include better monitoring, a stronger inverter and a more cautious generation forecast.

Start with system size in kWp, inverter AC rating, estimated annual kWh, battery capacity in kWh and the proposed export limit. Put those numbers side by side before you compare payback.

Interrogate the savings claim

If a quote says you'll save a large amount each year, ask what import rate, export rate and self-consumption percentage they used. If those assumptions don't match your household, the savings claim won't either.

A human test works well here: if you're out all day, have no battery and the quote assumes very high self-consumption, ask why. If the export rate is higher than the tariff you can actually access, change it in the calculator.

Paperwork to ask for

The paperwork isn't a side issue. It's how you prove the system exists, switch export suppliers and sell the home later.

• MCS certificate or accepted equivalent evidence.
• Electrical installation certificate.
• DNO G98 notification or G99 approval evidence.
• Panel, inverter, battery and workmanship warranties.
• Monitoring login and system handover pack.
• Clear VAT treatment on the quote and invoice.

Red flags

Be careful with pressure discounts, vague equipment descriptions, savings based on huge energy price inflation, or promises that a battery will pay for itself without showing the maths.

A good installer should be able to explain why the system is sized as proposed, what happens in winter, what gets exported, and what would change if you add an EV or heat pump later.