The short answer
Check any solar firm on the MCS search, confirm its consumer code and read its Companies House record. Get three itemised quotes for the same layout. Make sure each performance estimate uses Congleton figures: about 909 kWh per kWp a year on an open south roof, a few per cent below Nantwich. On slate, ask how it will be handled.
Why the choice matters more in the old town
On a modern house with a concrete-tiled roof, most competent firms will do a similar job. Congleton’s older streets ask more of them. The 2010 Moody Street appraisal describes town-centre roofs covered mostly in slate; the West Street conservation area is on Historic England’s Heritage at Risk register with 23 listed buildings (register entry); and the town’s sunlight figures are a little lower than the Cheshire plain’s. A firm that handles slate carelessly, overlooks a consent or overstates output can turn a reasonable project into a poor one.
The three registers
MCS. Certification by MCS shows a firm has been assessed for the technology it installs, and it is required for export payments under the SEG. Search the firm on the MCS installer search and check that its certification covers solar PV, and storage if a battery is part of the job. Look the firm up by name yourself instead of relying on a logo on a leaflet.
A consumer code. Codes such as those run by RECC and HIES set rules on contracts, selling, deposits and complaints, and give a route to resolve disputes. Check membership on the code’s own website. Where a funded scheme asks for TrustMark registration, check that as well.
Companies House. The Companies House search shows when a company was formed, who its directors are, whether its accounts are filed on time and whether there are notices of insolvency. A young company is not a problem in itself, but overdue accounts or a history of directors whose previous companies failed are worth noticing. Make sure the company name on the quote matches the registered name.
What a proper site visit covers
A quote made from a satellite image alone is a starting point, not a design. Before a firm commits to a layout and a price, someone should look at the house, or at least at detailed photographs and measurements you supply. A thorough visit usually covers:
- measuring each usable slope and noting chimneys, vents, roof lights and dormers;
- looking into the roof space at the rafters, the underside of the covering and any loft room;
- checking shade from neighbouring buildings and trees at different times of year;
- examining the consumer unit, the meter and the earthing arrangements;
- agreeing where the inverter, isolators and any battery will go, and how cables will run;
- noting scaffolding access, including any need to use the pavement.
Ask for a layout drawing showing each panel on the roof. It makes the quote easier to compare, and it is the drawing a council will want to see if consent is needed. A firm that declines to visit an older slate roof before quoting is telling you something about how it works.
Getting quotes that can be compared
Ask at least three firms to quote, each after seeing the roof or a good set of photographs. Give them all the same brief: which slopes, roughly how many panels, whether a battery or diverter is wanted, and any planning constraint you know about. Ask for each quote to be itemised, with the make and model of panels, inverter and mounting system, the scaffolding, the electrical work, bird protection if wanted, the network paperwork and VAT shown separately.
Then compare line by line. Totals hide differences in scope. One quote may leave out scaffolding or consent drawings; another may include a battery you did not ask for. Costs in Congleton gives the government’s 2025/26 price per kW as a yardstick.
The performance estimate, using Congleton’s figures
Every quote from a certified firm should include an estimate of yearly output, made using the method MCS sets. Check that it reflects Congleton. In the PVGIS runs for this guide, an unshaded south roof at 35° makes about 909 kWh per kWp a year, the lowest of six Cheshire towns we ran with identical settings and about 5.3% below Nantwich at 959 (PVGIS 5.3). An estimate built from a wider regional figure may run high.
Ask the firm three things: which data the estimate uses, what shade factor it has applied and why, and how each slope has been counted if the array is split. If its figure for a clear south roof is far above the Congleton number, ask it to explain the difference. Output has the full table by direction and pitch to check against.
Questions about slate
Fixing to slate is skilled work. Brackets pass through the covering to the rafters, so slates have to be removed and refitted or replaced around each one, and every fixing has to be flashed so it stays watertight. Ask each firm:
- who does the roof work, its own staff or a roofer it brings in;
- what kind of bracket and flashing it uses on slate;
- how many spare slates it allows for, and where they come from;
- whether it will match replacement slates on a street-facing or listed roof;
- whether it will check the timbers from inside the roof space first.
A firm that answers these clearly, and can show slate roofs it has worked on, is a better bet for an older Congleton house than one that treats every roof the same. Silk town roofs explains why slate is so common in the centre.
Consents and the paperwork before work starts
For a listed building or a conservation-area wall, someone has to prepare drawings and apply. Ask whether the firm does it, how much it charges, and who pays if consent is refused. Ask whether it has made such applications before. A firm should also check, before quoting, whether the building is on the national list. Listed buildings and conservation areas set out when each route applies.
The firm should also deal with the network: notifying within 28 days for small systems, or applying for approval before installation for larger ones. The ENA postcode search shows which operator covers your address, and grid connection explains the two procedures.
Contracts, deposits and warranties
Read the contract before signing, not after. It should name the equipment, the price including VAT, the payment stages, the expected start and finish dates, and what happens if either side cancels. For a contract made at home, consumer law usually gives a cancellation period. Keep the deposit modest and ask how it is protected. Putting part of the payment on a credit card may add a layer of consumer credit protection.
Warranties come in layers: the maker’s warranty on panels, inverter and any battery; the firm’s warranty on its workmanship; and insurance that keeps that workmanship warranty alive if the firm stops trading. Ask who provides the insurance and whether it passes to a new owner if the house is sold.
Warning signs
- A price that is only available if you sign today.
- Claims that the council or the government has sent the firm, or that panels cost nothing because of a grant.
- Reluctance to put the quote, the output estimate or the warranty in writing.
- A large deposit demanded before any work or materials are delivered.
- An output estimate that cannot be explained, or that ignores obvious shade.
After the job
On completion the firm should hand over the MCS certificate, the electrical certificate, confirmation of building regulations compliance, the network notification or approval, and every warranty. Register for an export tariff with the certificate. Keep the whole set together for the day the house changes hands; the papers a purchaser’s solicitor tends to request are set out in buying a home with solar. To check a specific roof or quote, use the roof and route check or send a question.