The system: what is being fitted, and where
The quote should give the size of the system in kW, the number, make and model of the panels, and the make and model of the inverter, plus any optimisers. Two quotes at the same size can use very different kit; the model names let you look up each part's warranty. The Energy Saving Trust says panels can last 25 years or more while the inverter typically lasts around 12 years (Energy Saving Trust), so the inverter's warranty matters more than it first seems.
It should also show the layout: which slope, how many panels, and how they sit around chimneys, vents and roof windows. On a semi or a terrace that drawing is how you know the installer has looked at your roof rather than the street's typical one. If the layout uses two slopes, ask for the output of each.
The estimate: a yearly figure in writing
A good quote gives the expected yearly output in kWh. RECC advises getting the performance estimate in writing and says its members follow strict rules for how it is calculated (RECC). Test the figure against PVGIS: in central Wigan a south roof at 35° makes about 927 kWh a year per kW, an east roof about 737 and a west roof about 743 (PVGIS 5.3). The quote checker does the sum for any size and direction.
An estimate somewhat below PVGIS often means the installer has allowed for shade, which is a good sign. One well above PVGIS should come with an explanation.
The price: itemised, with VAT shown
Ask for the price broken into lines: panels, inverter, any optimisers and battery, mounting, scaffolding, labour, commissioning and VAT. MCS advises checking that the price covers everything you need, commissioning included (MCS). Scaffolding is often a separate line, and on a terrace it is worth asking who arranges any space it needs on the pavement.
Installed solar panels and batteries in homes carry 0% VAT until 31 March 2027, and 5% from 1 April 2027 (HMRC). A quote dated before then for work finished after it should say which rate applies. Divide the panels' share of the total by the size in kW and compare it with the North West mean of £2,021 per kW for systems up to 4 kW (DESNZ). See what solar costs in Wigan.
The paperwork: who does what
Three jobs happen after the panels are on the roof, and the quote should say the installer does each one:
- The network notice. Electricity North West runs the borough's network. For inverters up to 16 A per phase (3.68 kW single-phase) the installer notifies it after commissioning; a larger system, or solar with a battery over that limit, needs an application before connection (Electricity North West).
- The MCS certificate. Registered by the installer; an export tariff needs it.
- The handover pack. Electrical certificates, the warranties, the user manuals and the commissioning record.
If the house is in one of the borough's 23 conservation areas or is listed, the quote should also say whether permission is needed and who applies (planning and conservation areas).
Deposit, payment stages and the right to cancel
The quote or contract should state the deposit, when the rest is due, and how the deposit is protected if the firm stops trading. RECC lists deposits alongside contracts, warranties and complaints among the things its code covers (RECC). Paying the balance on completion, once the system is commissioned and the paperwork is in hand, is the usual pattern to ask for.
Most contracts made at your home or online can be cancelled within 14 days (Consumer Contracts Regulations 2013); the contract should explain how. If a battery is included, the quote should say where it will go: the British Standards Institution's code of practice, PAS 63100, sets out where home batteries may be installed (BSI). Batteries in Wigan homes
Lines a Wigan quote may need on top
- Consent. If the house is in one of the borough's 23 conservation areas, or is listed, who applies for any permission and whether the contract waits for it (planning and conservation areas).
- Grant-funded work. If the job is paid for through GMCA's Warm Homes: Local Grant, for a home at EPC D to G whose household qualifies on income, benefits or postcode, the measures follow a retrofit assessment and the quote should match what it recommends (help with the cost).
- A battery. Its own line, its usable capacity and where it will be fitted (batteries).
- Shared roofs. On a semi or a terrace, whether any fixing, cable or scaffolding crosses onto a neighbour's side, and who will speak to them before work starts.
The checklist
| Line | What it should say | If it is missing, ask |
|---|---|---|
| System | Size in kW; panel and inverter makes and models; optimisers | Which models, and what each warranty covers |
| Layout | Slope, panel count and positions on a drawing | Which slope, and the output of each if two |
| Estimate | Yearly kWh, in writing | How it was calculated, and what shade was assumed |
| Price | Itemised, VAT shown | What the price per kW includes |
| Scaffolding | Included or separate | Who arranges it, and any pavement space |
| Commissioning | Included | Who tests and switches it on |
| Network | G98 notice or G99 application by the installer | Which route, and when |
| MCS | Certificate registered by the installer | When you will receive it |
| Warranties | Panels, inverter, workmanship | Whether workmanship is insurance-backed |
| Money | Deposit, stages, protection | What happens to the deposit if the firm fails |
| Cancelling | How to cancel within 14 days | Where to send the notice |
Before any of this, check the firm itself: checking a solar installer in Wigan.