Buyer's guides · Comparing quotes
How do you compare commercial solar quotes like for like?
Three quotes, three different systems: how to put them on the same basis before the board decides.
Written by Harry HainesCEO & Co-Founder, CH Group
Updated · 7 min read
CH Group runs controlled solar tenders for commercial sites of 100 kWp and above.
The short answer
To compare commercial solar quotes like for like, put every quote on the same basis for ten variables before you look at price: system size, generation, self-consumption, fully installed £/kWp, equipment, warranties, savings, payback, programme and commercial terms.
Ask each installer to state its yield in kWh per kWp and name the tool it used. Business Solar Check, a lead-generation site, uses about 950 kWh/kWp as a benchmark in its June 2026 checklist 1, and Solar4Good, an installer, puts the UK average at 850 to 950 2.
MCS certification covers systems only up to 50 kWp DC 3, so on a 100 kWp or larger roof you check accreditation and warranty backing yourself.
Figures checked
Key numbers for comparing quotes
| Figure | Source | |
|---|---|---|
| Variables every quote should state on one basis | Ten | Checklist below |
| Scope of MCS certification | Up to 50 kWp DC | MCS, MIS 3002 (2025) |
| Benchmark first-year yield | About 950 kWh/kWp; UK average 850 to 950 | Business Solar Check and Solar4Good, June 2026 |
| Fully installed price, large roofs | £700 to £1,000 per kWp (Business Solar Check); £750 to £850 at 100 to 150 kW (Solar4Good) | Both June 2026, lead-generation and installer sources |
| Items often missing from a headline price | Scaffold £1,200 to £3,000; structural survey £500 to £2,000; DNO fees £1,000 to £10,000+ | Business Solar Check, June 2026 |
| VAT on commercial installations | 20% standard rate; 0% is for residential and charitable buildings | HMRC Notice 708/6 |
What goes wrong, and what does it cost?
Comparing commercial solar quotes on headline price goes wrong because each installer sizes the system, picks the equipment and models the savings on its own assumptions, so the lowest price often buys the smallest scope.
The board is asked to approve a quote nobody can compare. Three PDFs arrive in three formats, and one number must be defended.
These are the mistakes that cost money.
- Comparing £/kWp across different scopes. Scaffolding, a structural survey and DNO fees can sit outside a headline price. Business Solar Check puts them at £1,200 to £3,000, £500 to £2,000 and £1,000 to £10,000 or more 1. Added together, that is £2,700 to £15,000 or more that one quote includes and another does not.
- Accepting different yield assumptions. The Joint Research Centre's PVGIS tool estimates annual output from installed kWp and losses 4, so every installer can be asked to run the same method.
- Accepting an assumed self-consumption figure. Solar4Good warns that a quote assuming 100% self-consumption is overpromised 2. The figure should come from twelve months of half-hourly data.
- Reading a 25-year warranty as 25 years of cover. Business Solar Check says the headline figure is usually a performance warranty and that product cover is much shorter 1.
- Assuming MCS protects a 150 kWp project. The MCS standard ends at 50 kWp DC 3.
- Believing tax claims in installer content. One installer guide says 0% VAT applies to commercial solar. HMRC limits the 0% rate to residential accommodation and qualifying charitable buildings 5. Commercial work is generally standard-rated at 20%. Check tax treatment with your accountant.
Which ten things must every solar quote state on the same basis?
Every commercial solar quote must state the same ten variables on the same basis: system size, generation, self-consumption, £/kWp, equipment, warranties, savings, payback, programme and commercial terms.
If a quote cannot state an item, send it back before you compare price.
| Variable | What to demand like for like | Why it moves the answer |
|---|---|---|
| System size | kWp DC and inverter kW AC, on every quote | A different DC to AC ratio changes clipping and £/kWp. |
| Generation | kWh/kWp per year, the tool named (PVGIS or other), plus tilt, azimuth and shading inputs | A higher yield assumption makes a dearer quote look cheaper per kWh. |
| Self-consumption | A stated percentage built from twelve months of half-hourly data | It decides how much output earns the import price, not the lower export price. |
| £/kWp | Fully installed, ex-VAT, same scope | Scope gaps hide cost. |
| Equipment | Panel, inverter and mounting makes and models | It sets output, lifespan and product backing. |
| Warranties | Product years against performance years for panels and inverter, workmanship years, and who backs each | A headline 25 years is usually performance cover only. |
| Savings | Annual saving on your verified tariff, prices shown | A quote that assumes a price your site does not pay overstates the saving. |
| Payback | Fully installed price divided by the savings above, shown with the inputs | It is only as good as the savings and scope behind it. |
| Programme | Weeks on site, the G99 and DNO plan, and who lodges the application | It sets disruption and the date savings start. |
| Commercial terms | Deposit, stage payments, retention, completion tied to commissioning, and quote validity | Terms set your cash exposure before the system works. |
Best for: any buyer holding two or more quotes who must defend one to a board.
What does a headline price per kWp leave out?
A headline £/kWp can leave out scaffolding, the structural survey, DNO and G99 fees, roof repairs, asbestos work, cable runs and operations and maintenance, so you must ask each installer to list inclusions and exclusions line by line.
Public price ranges disagree, and none is a primary source above 50 kWp. Business Solar Check gives £700 to £1,000 per kWp on large warehouse roofs 1. Solar4Good gives £750 to £850 at 100 to 150 kW 2. Both are installer or lead-generation sources, so treat them as ranges. Our commercial solar cost guide covers price by size.
Ask every installer to answer in writing:
- Is scaffolding, G99 and DNO work, and any grid reinforcement included?
- Is a structural survey included, and who pays for roof repairs, asbestos work and the grid application?
- Are cleaning, monitoring and inverter replacement included? The Solar Energy UK buyers' guide says operations and maintenance belong in the investment model 6.
Compare prices ex-VAT, and confirm your VAT position with your accountant.
Does MCS certification protect a commercial solar project above 50 kWp?
MCS certification does not protect a commercial solar project above 50 kWp, because the MCS standard applies to systems up to a maximum DC output of 50 kWp and MCS describes its certification scope as a maximum of 50 kW 37.
Many installers keep MCS above that size, but neither the MCS scope nor the Smart Export Guarantee requires it 9. Check other things yourself.
- Accreditation. Ask for MCS or another named accreditation, plus public liability, employers' liability and professional indemnity insurance.
- Workmanship warranty backing. Solar4Good treats 25 years panel performance, 10 years inverter and 5 years workmanship as standard for UK commercial work, with workmanship backed by an industry scheme 2. That is one installer's view.
- Export arrangements. The Smart Export Guarantee covers solar up to 5 MW. Ofgem's 2019 generator guidance shows that above 50 kW the SEG licensee handles eligibility rather than relying on an MCS certificate 8. Confirm the current process with your chosen SEG licensee.
The installer, broker or consultant guide covers who is accountable for these checks.
How long does a like-for-like comparison take, and when do you not need one?
A like-for-like comparison has no published benchmark, but Kelston Sparks went from site survey to contract award in 22 days with three comparable proposals, and you may not need a formal comparison if you already hold comparable quotes and trust one installer.
The slowest part is usually not the comparison. It is the grid application: Solar Energy UK's 2022 guide says a DNO needs a minimum of 45 working days to consider a connection application 6. Treat that as a floor and ask your DNO for current timescales. Ask for a written plan. The timeline guide sets this out.
Kelston Sparks, a plant and machinery hire business in Bristol, ran a tender with three suitable contractors, one consistent brief and three comparable proposals. Kelston Sparks invited all three contractors to visit the site, and the contract was awarded 22 days after the site survey. Its 116 kWp system has a projected annual saving of £20,075 and a projected payback of 2 yrs 10 mths.
When this is not for you. A formal comparison is more than you need for a small, simple system, or if you already hold comparable quotes and a trusted installer. In that case, run the table above yourself. It is the same checklist.
The payback guide shows how to check quoted savings.
Illustrative example, not a real tender
One roof, two quotes, one basis
Two installers quote the same roof against a verified baseline of 22.0p per kWh import and 6.0p per kWh export. Installer A claims a £44,800 annual saving based on a 30p import price. Prices are illustrative only, chosen to show the method, not market rates. Savings are generation × self-consumption × 22p, plus generation × the remainder × 6p.
- Installer A: 210 kWp, 189,000 kWh a year, 70% self-consumption. 189,000 × 0.70 × £0.22 = £29,106. 189,000 × 0.30 × £0.06 = £3,402. Total £32,508, about £32,500.
- Installer B: 180 kWp, 162,000 kWh a year, 88% self-consumption. 162,000 × 0.88 × £0.22 = £31,363.20. 162,000 × 0.12 × £0.06 = £1,166.40. Total £32,530, about £32,500.
- £/kWp: A costs £113,400 for 210 kWp, which is £540. B costs £104,400 for 180 kWp, which is £580.
- Payback: A is £113,400 ÷ £32,508 = 3.5 years. B is £104,400 ÷ £32,530 = 3.2 years.
Installer A's claimed saving was about £12,300 higher than its saving on the verified baseline. On one basis, the two savings match and B pays back sooner.
Your next steps
Get twelve months of half-hourly data Ask your supplier for it before you brief anyone.
Send one written brief Give every installer the same roof access, prices and the ten variables to state.
Build the table and send gaps back Put each quote in the ten-variable table. Any "not stated" is a question.
Check accreditation and warranty backing Ask for named accreditation, insurance and who backs the workmanship warranty.
How CH Group handles this
Three proposals that cannot be compared leave a finance director defending a number nobody can check.
CH Group starts with twelve months of half-hourly data, verified before anyone quotes. We run one controlled tender to our panel of vetted installer partners, all bidding against the same brief. Every proposal is then compared on the same ten variables, with projected results only. Kelston Sparks went from site survey to contract award in 22 days.
Our fee is agreed in writing before you commit to anything. Installer partners also pay CH Group, and every partner bids against the same brief, so no installer can buy a better place in your comparison. If you already hold quotes, we can put them on a single basis. See the projects for the evidence.
Questions buyers ask next
Is the cheapest commercial solar quote the best?
Not necessarily. A lower headline price can exclude scaffolding, grid work or roof repairs, or assume a higher yield. Put every quote on the same scope and basis first.
How many commercial solar quotes should I get?
No public standard sets a number. Kelston Sparks compared three comparable proposals against one brief. Brief every installer identically.
Do I need MCS for a 150 kWp solar system?
No, because MCS scope ends at 50 kWp DC. Check the installer's other accreditation, insurance and who backs its workmanship warranty instead.
What happens after you sign a commercial solar contract?
After signing, the installer's programme, the G99 application to the DNO and commissioning set when savings start, so confirm in writing who lodges the G99 application. Check the contract for monitoring, cleaning and inverter replacement. Business Solar Check says inverters are typically replaced after 10 to 15 years.
Can an independent party compare solar quotes for me?
Yes. Independent consultants and procurement partners, including CH Group, can put quotes you already hold on one basis. Ask how they are paid before you start.
Sources
Public figures are from the sources below, as published on the dates shown. CH Group project figures are projections supplied for each case study. This guide is general information, not financial, tax or legal advice.
- Business Solar Check, How to compare commercial solar quotes (12-point checklist), June 2026.
- Solar4Good UK Ltd, Commercial Solar Buyer's Guide 2026 (PDF), 1 Jun 2026.
- MCS, The Solar PV Installation Standard (MIS 3002), 1 Jan 2025.
- European Commission Joint Research Centre, PVGIS photovoltaic geographical information system, 10 Oct 2025.
- HMRC, VAT on energy-saving materials and heating equipment (Notice 708/6), 31 Jan 2024.
- Solar Energy UK, Corporate buyers' guide (PDF), May 2022.
- MCS, Notifying DNOs, undated.
- Ofgem, Smart Export Guarantee: guidance for generators (PDF), December 2019.
- Surge PV, MCS vs non-MCS, 14 Sep 2026.
