Most complaints about solar panels, home batteries and heat pumps are not really about the technology. They are about the company that fitted it: a system sized wrong, a warranty that turned out to be worthless, or a firm that had dissolved by the time a fault appeared. Spending twenty minutes checking an installer before you sign is the cheapest insurance available on a £8,000-£15,000 purchase.
Here is the full checklist we would use ourselves, in the order we would use it.
1. Check the certification that actually matters
For anything that generates heat or electricity, the certification to look for is MCS (Microgeneration Certification Scheme).
- Solar PV, batteries fitted with solar, air source and ground source heat pumps should all be installed by an MCS certified company.
- Ask for the MCS certificate number and check it on the MCS installer database. The number belongs to the company, not the salesperson.
- MCS is not optional if you want the Boiler Upgrade Scheme £7,500 heat pump grant or Smart Export Guarantee payments for exported solar. A non-MCS install loses you both.
Also reasonable to see, depending on the job:
- NICEIC, NAPIT or ELECSA registration for the electrical work
- RECC or HIES membership, which gives you deposit protection and a dispute route
- Gas Safe if a boiler is being removed as part of a heat pump changeover
- TrustMark for retrofit work carried out under a government scheme
2. Check the company, not just the brand
Company names in this sector change often. Two minutes on Companies House tells you a lot.
- How long has it traded? A firm incorporated three months ago cannot honour a ten year workmanship warranty on its own track record.
- Are accounts filed and up to date? Repeated late filings or a proposed strike-off are a warning.
- Has the same director closed previous companies? A pattern of dissolved companies at the same address is the single biggest red flag in the industry.
- Does the trading name match the legal entity on the quote? The contract, the deposit and the warranty must all name the same registered company.
3. Check insurance and who stands behind the warranty
There are three separate protections and installers sometimes blur them together.
| What it covers | What to ask for |
|---|---|
| Damage to your property or injury during the work | Public liability insurance, usually £2m+, in date |
| Faults in the fitting itself | Workmanship warranty, in writing, typically 2-10 years |
| Faults in the equipment | Manufacturer product warranty, in the manufacturer's name |
| The warranty if the installer stops trading | Insurance-backed guarantee (IBG) certificate |
The one people forget is the last. A "10 year guarantee" from a company that folds in year three is worth nothing unless it is insurance backed.
4. Judge the survey, not the sales pitch
The quality of the survey tells you more than any review.
For a heat pump, a legitimate installer produces a room-by-room heat loss calculation and states the design flow temperature. If someone quotes from your floor area or your old boiler's kW rating over the phone, the system will very likely be oversized and expensive to run. Our heat pump quote checklist covers every line a proper quote should contain.
For solar, expect roof orientation and pitch, a shading assessment, an annual generation estimate in kWh, the inverter make and model, and whether scaffolding is included. See how to compare solar panel quotes for the like-for-like comparison.
For a battery, expect usable capacity in kWh (not just the headline figure), warranted cycles or throughput, where it will be mounted, and how it behaves in a power cut.
5. The red flags worth walking away from
- "This price is only valid today." Legitimate installers hold a quote for 14-30 days. Discount-now pressure is the most reliable sign of a bad deal.
- A large deposit. Anything above roughly 25% is unusual, and any deposit at all should be protected through RECC, HIES or a credit card payment.
- Cash, bank transfer to a personal account, or no VAT number on a job priced in the thousands.
- No written quote, or a single lump sum with no breakdown of equipment, labour, scaffolding and certification.
- Savings promises presented as guarantees. Illustrations are fine; guaranteed bill figures are not.
- A quote before a survey for a heat pump. Always.
- Reviews only on the company's own website. Cross-check an independent platform and look for how they answer negative reviews.
6. Questions to ask before you sign
- What is your MCS certificate number and which body registered your electrical work?
- Which registered company will the contract be with?
- Is the workmanship warranty insurance backed, and can I see the certificate?
- Will your own employees do the work, or subcontractors — and who holds the warranty if so?
- What happens if the system underperforms against your estimate?
- Who handles the DNO application and the MCS certificate afterwards?
- When do payments fall due, and what protects my deposit?
7. Always compare three quotes
Not because the cheapest wins — because three quotes are the only way to see that one system size, one flow temperature or one price is an outlier. Two quotes tell you a difference exists. Three tell you which one is wrong.
Home Energy Match matches you with suitable UK installers so you can compare like for like without ringing round yourself. It is free, there is no obligation, and your details go only to installers relevant to your job.