Questions to ask your solar installer

Before choosing a solar installer, ask the right questions. A good quote should explain the system design, expected solar panel generation, warranties, grid connection and total installation costs.

Are you MCS certified? Check the installer at mcscertified.com. MCS certification provides an important quality and certification framework for domestic solar PV installations. For eligible systems, you may also need an MCS certificate or equivalent evidence when applying for the Smart Export Guarantee (SEG).

1. What is the exact kWp size of the solar PV system?
   Ask how many solar panels the system includes and the wattage of each panel. Then ask why the installer recommends that system size for your home and electricity use. A larger system can generate more electricity, but it also increases the upfront solar installation cost. The right size should match your roof, expected generation and household demand.
2. How much electricity will my solar panels generate each year in kWh?
   Ask for a roof-specific solar generation estimate, not a generic figure. The estimate should account for your roof orientation, pitch, shading, location and panel efficiency. It should also reflect the proposed solar PV system size. Ask the installer to explain the assumptions behind the forecast so you can compare quotes properly.
3. Which solar inverter will you install and what warranty does it have?
   The inverter converts electricity from your solar panels into usable electricity for your home. Ask for the exact make and model, warranty length, expected lifespan and likely replacement cost. Also ask whether the system includes monitoring. Common residential brands include SolarEdge, Enphase, Solis and Growatt.
4. What solar panel warranty is included?
   Check both the product warranty and performance warranty. Many modern panels include long-term output guarantees, often lasting 25 years or more. Ask what power output the manufacturer guarantees at the end of that period. Also check what happens if a panel fails or produces less than expected.
5. Who will handle the DNO notification and grid connection?
   Ask your solar installer whether your system needs a G98 notification or G99 application. For installations up to 16 amps per phase, G98 may apply. Larger systems can require G99 approval before installation. Your installer should explain the process and include the relevant DNO requirements in your written solar installation quote.
6. Will you help me register for the Smart Export Guarantee (SEG)?
   Ask whether the installer will provide the MCS certificate and supporting documents you need to apply for SEG payments. You do not have to use the same company for your electricity supply and SEG payments. Compare available export tariffs because suppliers set their own SEG rates and contract terms.
7. Will my solar installation be registered with MCS and will I receive the certificate?
   Make sure your completed solar PV installation receives the correct certification and documentation. Keep your MCS certificate, commissioning paperwork, warranties and electrical documents in a safe place. You may need them for SEG payments, future maintenance or when you sell your property.
8. Is scaffolding included in the solar panel installation quote?
   Check exactly what the quote includes. Ask about scaffolding, access equipment, electrical work, roof repairs and other potential installation costs. Some solar quotes leave these items out. That can make a low headline price much higher once work starts.
9. What happens if my roof needs repairs or is not suitable for solar panels?
   Ask the installer to inspect your roof before work begins. They should consider its condition, structure, available space and any potential shading. Find out who would pay for roof repairs, strengthening or other preparation work. Also ask whether those costs sit outside your original solar panel quote.
10. Can you show me the solar panel payback calculation using my actual energy usage?
    Ask the installer to show how they calculated your expected solar savings, payback period and return on investment. The calculation should consider your electricity use, expected solar generation, self-consumption and potential SEG income. For comparison, Ofgem’s average electricity price-cap rate for Direct Debit customers was 26.11p/kWh from 1 July to 30 September 2026. Your actual tariff may differ by supplier, region and payment method.