How to Compare Solar Panel Quotes: A UK Buyer's Checklist
Comparing solar quotes in the UK isn't about finding the cheapest price per watt.
It's about understanding what you're actually buying, how the system will perform on your roof, and whether the installer will still answer the phone in 2029 when your inverter throws an error code.
This guide walks through the specific line items, certifications, and red flags that separate a solid quote from an expensive mistake.
What Every UK Solar Quote Must Include
A legitimate quote should provide enough detail that you could hand it to a different MCS-certified installer and they'd know exactly what's being proposed.
Vague descriptions like "premium panels" or "European inverter" aren't acceptable.
You need manufacturer names, model numbers, and specifications.
Start with the basics: total system capacity in kilowatts peak (kWp), the number and wattage of individual panels, inverter make and model, mounting system type, and whether the quote includes scaffolding.
Many homeowners overlook scaffolding costs until they receive a surprise £800 invoice after signing.
Key figure: Scaffolding typically adds £600–£1,200 to a domestic solar installation, depending on property height and access.
Always confirm whether this is included in the headline price.
The quote should specify panel efficiency ratings, inverter warranty periods, and expected annual generation in kilowatt-hours.
Reputable installers use software like PVSol or SketchUp with location-specific irradiance data to model your roof's output.
A 4 kWp system in Manchester won't generate the same as an identical system in Southampton—your quote should reflect your actual postcode, roof pitch, and shading.
Check for MCS certification details.
The installer must be MCS-registered, and they should provide their certificate number.
Without MCS certification, you can't access the Smart Export Guarantee, and your system won't meet building regulations.
Some installers subcontract the electrical work to MCS-certified partners—this is legal, but you need written confirmation of who holds the certification and who's responsible if something goes wrong.
Breaking Down the Cost Structure
A typical 4 kWp system in 2024 costs between £5,000 and £7,000 before any grants.
Larger systems benefit from economies of scale—a 6 kWp installation might only cost £1,500 more than a 4 kWp, not £3,000.
Understanding where your money goes helps identify inflated quotes.
| Component | Typical Cost Range | What to Check |
|---|---|---|
| Solar panels (per kWp) | £800–£1,200 | Manufacturer warranty (usually 25 years product, 25–30 years performance) |
| Inverter | £800–£1,500 | Warranty period (5–12 years standard, extensions available) |
| Mounting & fixings | £300–£600 | Roof type compatibility, wind load calculations for your area |
| Labour & installation | £1,200–£2,000 | Number of days on-site, team size, insurance details |
| Scaffolding | £600–£1,200 | Duration of hire, whether removal is included |
| Electrical work & DNO | £400–£800 | G99 application, consumer unit upgrades if needed |
Labour costs vary by region.
London and the South East command premium rates, while installers in the North East and Wales often charge 15–20% less for identical work.
This doesn't reflect quality—it's simply regional wage differences.
Some quotes bundle "project management" or "design fees" as separate line items.
These shouldn't exceed £200–£300.
If an installer charges £800 for "technical survey and design," they're padding the bill.
Site surveys are part of standard service.
Pro Tip: Ask installers to separate VAT-rated items from zero-rated items.
Solar panel installations qualify for 0% VAT under current rules, but battery storage added to an existing system is charged at 20%.
A combined quote should show this split clearly.
Panel Quality: Beyond the Wattage Figure
A 400W panel isn't automatically better than a 350W panel.
What matters is efficiency (how much power per square metre), degradation rate (how quickly performance drops over time), and temperature coefficient (how well panels perform in UK summer heat).
Most UK installations use monocrystalline panels with 19–22% efficiency.
Polycrystalline panels are cheaper but less efficient—you'll need more roof space for the same output.
Bifacial panels can capture reflected light from light-coloured roofs or gravel, adding 5–10% extra generation, but they cost more and require specific mounting.
Check the temperature coefficient, listed as a percentage per degree Celsius.
Panels lose efficiency as they heat up.
A coefficient of -0.35%/°C is typical; -0.29%/°C is excellent.
On a 25°C summer day, panels might reach 45°C, losing 7% output with a poor coefficient versus 5.8% with a better one.
Over 25 years, this compounds.
Key figure: Premium panels degrade at 0.25–0.35% annually.
Budget panels may degrade at 0.5–0.7% per year.
After 25 years, that's the difference between 90% and 82% of original output.
Manufacturer matters for warranty claims.
LG, Panasonic, and SunPower have strong UK presence and honour warranties reliably.
Lesser-known Chinese brands may offer identical specs on paper but disappear before year ten.
Check how long the manufacturer has operated and whether they have a UK office.
If you need to ship panels to Shenzhen for warranty replacement, you won't bother.
Inverter Selection and Sizing
The inverter converts DC power from panels into AC power for your home.
It's the component most likely to fail before your panels do, so warranty length and local service matter enormously.
String inverters (one unit for the whole array) cost less but create a single point of failure.
If it breaks, your entire system stops generating.
Microinverters (one per panel) cost more but isolate failures and optimise each panel individually—useful if you have shading or multiple roof orientations.
Inverter capacity should match your panel array.
A 4 kWp system needs a 3.6–4 kW inverter.
Undersizing by 10% is acceptable and can save money—panels rarely hit peak output simultaneously.
Oversizing wastes money and may void warranties.
Check the inverter's efficiency rating.
Quality units achieve 96–98% efficiency.
Cheaper models sit at 93–95%, losing 2–3% of your generation as heat.
Over 25 years on a 4 kWp system, that's 600–900 kWh lost—worth £180–£270 at current electricity prices.
"We replaced a customer's failed inverter after six years.
The original installer had used a budget model with a five-year warranty.
The customer paid £1,200 for a replacement that should have been covered.
Always check warranty terms and whether extensions are available at installation." — MCS-certified installer, West Midlands
Hybrid inverters cost £300–£600 more than standard models but allow battery addition later without replacing the inverter.
If you're considering storage within five years, a hybrid inverter makes financial sense now.
Battery Storage: When the Maths Works
Battery quotes vary wildly.
A 5 kWh system might cost £3,500 from one installer and £5,800 from another for functionally identical storage.
The difference often lies in battery chemistry, warranty terms, and whether the installer is pushing a specific brand for commission.
Lithium iron phosphate (LFP) batteries cost more upfront but last longer and handle more charge cycles than lithium nickel manganese cobalt (NMC) batteries.
LFP units typically warrant 6,000 cycles versus 4,000 for NMC.
If you cycle daily, that's 16 years versus 11 years of warranted life.
Key figure: Battery storage adds £1,200–£1,800 per kWh of usable capacity.
A 5 kWh battery costs £6,000–£9,000 installed.
Payback depends on your electricity tariff and usage patterns—typically 12–18 years at standard rates, 8–12 years on time-of-use tariffs.
Usable capacity differs from total capacity.
A 10 kWh battery might only provide 9 kWh usable storage—manufacturers limit depth of discharge to extend lifespan.
Your quote should specify both figures.
Battery warranties cover capacity retention, not complete failure.
A typical warranty guarantees 70% capacity after ten years.
If your 10 kWh battery drops to 6.8 kWh in year nine, that's within warranty terms.
Read the fine print.
Pro Tip: If adding battery storage to an existing solar system installed before 2022, check whether your current inverter supports DC-coupled batteries.
AC-coupled batteries work with any inverter but are less efficient.
Replacing the inverter might cost less than the efficiency loss over ten years.
Installation Timeline and DNO Approval
Your installer should explain the G99 process.
Systems under 3.68 kW (roughly 10 panels) qualify for G99 Fast Track—the Distribution Network Operator (DNO) has ten working days to respond, and approval is usually automatic.
Larger systems require full G99 application, taking 30–65 working days.
Some installers submit G99 applications before you've signed the contract.
This speeds things up but means you're committed before DNO approval.
Others wait until after deposit payment.
Clarify the sequence and who pays if the DNO refuses connection (rare, but possible in areas with grid constraints).
Installation typically takes one to two days for a standard domestic system.
Scaffolding goes up the day before, panels and inverter are fitted on day one, electrical connection and testing happen on day two, and scaffolding comes down on day three.
Delays happen—weather, material shortages, or DNO inspection scheduling—but your quote should include a realistic timeline.
Ask about building control notification.
MCS installers self-certify electrical work, but you still need a Building Regulations Compliance Certificate.
Reputable installers handle this automatically and provide the certificate within two weeks of completion.
Without it, you may face problems selling your property.
Warranties, Insurance, and Long-Term Support
Panel warranties typically cover two things: product defects (25 years) and performance degradation (25–30 years, guaranteeing 80–85% output).
Inverter warranties range from five to twelve years, with paid extensions available.
Installation workmanship warranties should cover at least two years, ideally five.
Check who honours each warranty.
If the installer goes bust, can you claim directly from the manufacturer?
Some panel makers require claims through the installer, leaving you stranded if they've dissolved.
Others handle claims directly—this is preferable.
Insurance-backed guarantees protect your deposit and workmanship warranty if the installer ceases trading.
They cost the installer £100–£200 and should be included automatically.
If not mentioned, ask why.
Confirm the installer's public liability insurance covers at least £5 million.
This protects you if installation damages your roof or causes injury.
Request a copy of their insurance certificate—legitimate installers provide this without hesitation.
Smart Export Guarantee Rates and Optimisation
The Smart Export Guarantee (SEG) pays you for surplus electricity exported to the grid.
Rates vary from 1p/kWh (token payments from some suppliers) to 15p/kWh (Octopus Outgoing Fixed).
Your installer should discuss SEG options and help you choose a tariff that matches your usage pattern.
Some quotes include SEG registration as part of the service.
Others expect you to arrange it yourself after installation.
Registration requires your MCS certificate and meter readings—straightforward, but time-consuming if you're unfamiliar with the process.
Export limiters reduce the amount of power your system can send to the grid, sometimes required by DNOs in areas with high solar penetration.
If your quote mentions an export limiter, understand how it affects your SEG income.
A 4 kWp system limited to 2 kW export might generate 4,200 kWh annually but only export 800 kWh instead of 1,500 kWh, costing you £70–£100 per year in lost SEG payments.
Red Flags That Should Stop You Signing
Pressure tactics are the clearest warning sign. "This price expires today" or "We can only offer this discount if you sign now" means the installer prioritises sales over service.
Legitimate companies give you time to compare quotes and ask questions.
Quotes that don't itemise components hide problems.
If you can't see the panel model, inverter brand, or mounting system type, the installer is either disorganised or deliberately vague.
Either way, walk away.
Unrealistic generation estimates suggest dishonesty or incompetence.
A 4 kWp south-facing system in Birmingham generates roughly 3,400–3,800 kWh annually.
If a quote promises 5,000 kWh, the installer is either lying or doesn't understand solar modelling.
Both are disqualifying.
Missing MCS certification is non-negotiable.
Some installers claim they're "applying for MCS" or "working with an MCS partner." Unless they can provide a current MCS certificate number you can verify on the MCS website, they cannot legally install your system to building regulations standards.
Deposits exceeding 25% of the total cost are unusual.
Most installers request 10–20% to secure materials.
Anything higher suggests cash flow problems.
Never pay the full amount before installation is complete and signed off.
Your Quote Comparison Checklist
Use this framework to evaluate each quote systematically:
- System capacity (kWp) and number of panels clearly stated
- Panel manufacturer, model, efficiency rating, and warranty terms
- Inverter manufacturer, model, capacity, efficiency, and warranty period
- Mounting system type and compatibility with your roof material
- Scaffolding costs included or itemised separately
- Labour costs and estimated installation duration
- DNO application (G99) included and timeline explained
- MCS certification number provided and verifiable
- Building control notification process explained
- Workmanship warranty period (minimum two years)
- Insurance-backed guarantee included
- Public liability insurance certificate available
- Annual generation estimate based on your specific location and roof
- SEG registration assistance offered or explained
- Payment schedule (deposit, progress payments, final payment)
- Cooling-off period clearly stated (14 days minimum for distance sales)
- Post-installation support and monitoring options
Grants, VAT, and Financial Considerations
Solar panel installations currently qualify for 0% VAT, reducing costs by 20% compared to the standard rate.
This applies to panels, inverters, mounting equipment, and installation labour.
Battery storage added simultaneously also qualifies for 0% VAT, but batteries retrofitted to existing systems are charged at 20%.
The ECO4 scheme provides grants for low-income households, but solar panels aren't directly funded.
However, ECO4 may cover insulation or heating upgrades that improve your home's energy efficiency, making solar more cost-effective.
Check eligibility through the Simple Energy Advice service.
Some local authorities offer solar grants or interest-free loans.
Availability changes frequently, but it's worth checking your council's website or contacting their energy team.
Scotland's Home Energy Scotland offers interest-free loans up to £7,500 for renewable energy installations.
The Boiler Upgrade Scheme doesn't cover solar panels but provides £7,500 grants for heat pumps.
If you're considering both solar and a heat pump, the combined installation may qualify for better rates from installers handling both technologies.
Making Your Final Decision
The cheapest quote rarely represents the best value.
A £6,000 system using budget panels and a five-year inverter warranty might cost you £2,000 more in replacements and lost generation over 25 years compared to a £7,500 system with premium components.
Focus on total cost of ownership: initial price, warranty coverage, expected maintenance, and realistic generation estimates.
A system that generates 3,800 kWh annually at £7,000 costs £1.84 per kWh over 25 years (95,000 kWh total).
A system generating 3,400 kWh annually at £6,500 costs £1.91 per kWh over the same period (85,000 kWh total).
The more expensive system is actually cheaper.
Trust matters enormously.
You're inviting someone to work on your roof, penetrate your weatherproofing, and connect to your electrical system.
Check reviews on Trustpilot, Checkatrade, and Which?
Trusted Traders.
Look for patterns—one bad review might be an anomaly, but multiple complaints about poor communication or shoddy workmanship are warnings.
Ask for references from installations completed 2–3 years ago.
Recent customers are still in the honeymoon period.
Customers whose systems have run through a few winters can tell you whether the installer responded to problems and whether generation matches predictions.
Finally, remember that solar panels are a 25-year investment.
The installer you choose today should still be operating in 2030 when you need support.
Company longevity, financial stability, and reputation matter more than saving £500 on the initial quote.
Choose the installer you trust to answer the phone in five years, not the one offering the lowest price today.