The best commercial solar quote isn’t always the cheapest.
It’s the one that explains clearly why the system has been recommended, how the expected generation has been calculated, and exactly what is included in the installation.
When you’re comparing quotations, don’t focus solely on the final figure. Look at the assumptions behind the design, the scope of work, and whether the recommendation has been built around your business.
That’s what will tell you which proposal actually offers the best long-term value.
Key Takeaways
- Compare the design behind each proposal, not just the price.
- Make sure every company has worked from the same information — and has actually been to site.
- Check whether a structural engineer’s report is included. It should be.
- Look at how savings are presented. Real figures, not vague ranges.
- Review system size, projected generation and installation scope together.
- Check accreditations: MCS, RECC, NICEIC, TrustMark.
- If you can’t tell the proposals apart, get help. Don’t guess on an investment this size.
Why Can Commercial Solar Quotes Be So Different?
Many businesses are surprised when they receive three commercial solar quotes and no two recommendations are the same.
One company may suggest covering every available metre of roof. Another may recommend a smaller system that better matches your electricity usage. A third may include electrical upgrades, monitoring or project management that the others have priced separately.
None of those approaches is automatically right or wrong.
The important thing is understanding why each recommendation has been made.
A well-designed commercial solar system shouldn’t start with how many panels fit on the roof. It should start with how your business uses electricity, what you’re trying to achieve, and how the building performs across the year.
If two companies have approached the project differently, it’s natural that their quotations look different too.
What Should Every Commercial Solar Quote Include?
Every proposal should explain exactly what you’re being offered and how the recommendation has been reached. If key information is missing, it’s difficult to make a fair comparison.
A detailed quotation should leave very few unanswered questions.
| Area | What to Compare | Why It Matters |
|---|---|---|
| System size | Total capacity (kWp) | Shows the overall size of the proposed installation. |
| Estimated annual generation | Predicted output (kWh) | Underpins projected savings and return on investment. |
| Estimated bill savings | Monthly, quarterly and annual figures | Turns generation into money you can actually plan around. |
| Structural engineer’s report | Included, excluded, or not mentioned | Confirms the roof can safely carry the system. A serious omission if absent. |
| Solar panels | Manufacturer, model and quantity | Explains differences in equipment and warranty. |
| Inverters | Brand, model and configuration | Drives performance, monitoring and future maintenance. |
| Monitoring | Platform, and whether it’s included or optional | Determines whether you can see how the system is performing. |
| Installation scope | Electrical work, access equipment, commissioning | Shows exactly what’s included. |
| Grid application | Who manages it and who pays | A common source of unexpected cost. |
| Warranties | Product, performance and workmanship | Protects the investment after installation. |
| Accreditations | MCS, RECC, NICEIC, TrustMark | Evidence of independently assessed competence. |
| Exclusions | Work not included | Where the real cost differences usually hide. |
Has the Company Actually Been to Site?
We very rarely quote remotely.
If a site is a long way away, or someone tells us straight that they’re only after a rough cost at this stage, we’ll put something together on paper. That’s fair enough. But anything with real intent behind it gets a site visit — often more than one.
There’s too much you can’t see from above. Access. Logistics. And above all, the electrical setup.
That last one is where we differ from most solar installers. We’re electricians first.
Our sister company, Synergy Group Solutions, has been trading B2B since 2018, and between the two directors there is 45 years of commercial electrical experience behind every survey we carry out. Panel boards in large commercial units, metering, earthing arrangements — that’s our bread and butter, not something we subcontract or design around.
It matters more than people expect. Any system of a decent size needs a substantial AC supply, and on a retrofit into an existing building that is frequently the hardest and most expensive part of the whole design to get right. Doing it remotely is guesswork. We’re not prepared to guess and then hand a client a return figure built on top of that guess.
There’s a simpler reason too. We want to meet the people we’re working for, and we want them to meet us. We’re not looking to put something on a roof and send an invoice. We want to be the fix for a problem, and we want the relationship to still be there in five years.
Ask every company: did you visit the site, and did an electrician attend?
Are These Quotes Really Like-for-Like?
Before comparing prices, ask one simple question. Has every company based its proposal on the same information?
If not, you aren’t comparing like for like.
One installer may have analysed your half-hourly electricity data. Another may have worked from an annual bill. One may have surveyed the site, while another has relied mainly on satellite imagery.
Those differences influence everything from the recommended system size to the projected generation.
It’s also worth asking why different capacities have been recommended. If one company suggests 250kWp and another recommends 320kWp, don’t assume the larger system is automatically better. The recommendation should reflect your electricity demand, your future plans and how the building operates — not simply how much roof is available.
When we review quotations with prospective clients, this is usually where the biggest differences surface. Once the assumptions behind each proposal are understood, the recommendations tend to make a lot more sense.
Do the Generation Estimates Use the Same Assumptions?
Projected annual generation drives the savings figure and the return on investment. If one quotation predicts significantly higher generation than another, it’s worth understanding how that figure was produced.
Ask:
- Has shading been assessed in the same way?
- Have the same roof areas been included?
- Have system losses been allowed for?
- Are the roof pitch and orientation assumptions the same?
- Has different design software been used?
MCS guidance states that its shade assessment method is expected to yield results within 10% of actual annual energy yield for most systems, while noting that unusual systems or environments may produce different results.
The highest generation estimate isn’t necessarily the most accurate. What matters is whether the company can explain how the figure was calculated and what sits behind it.
How Are the Savings Figures Presented?
Generation in kWh is only half the picture. What you actually want to know is what it saves you.
We give estimated bill savings monthly, quarterly and annually — worked against how your site genuinely uses electricity, not applied as a blanket percentage.
A payback figure quoted as a wide range isn’t a return on investment. It’s a guess with a spread on it. You’re making a capital investment, and it should be presented as one: what it costs, what it’s expected to return, and over what period.
If a proposal can’t show you that, it isn’t finished.
Has Each Company Understood Your Business?
A commercial solar system should be designed around your business, not your roof.
Commercial and industrial users accounted for 61% of electricity consumed in Great Britain in 2024, according to the Department for Energy Security and Net Zero. Understanding how that electricity is used is one of the most important parts of designing an effective system.
That’s why the early conversations matter. Before any design work begins, we want to understand how the site operates, when demand peaks, whether the business expects to expand, and whether there are plans for new equipment or EV charging.
Those conversations often shape the final design as much as the roof does.
Ask every company:
- What electricity data did you review?
- Have you accounted for future business growth?
- Why have you recommended this system size?
- How much of the generated electricity do you expect us to use on site?
Has Anyone Mentioned a Structural Engineer’s Report?
This is a big one, and it’s where we hold a firm line.
We will not carry out a commercial installation without a structural engineer’s report. Not usually. Not in most cases. Ever.
Opinions don’t hold up. A report does. It’s based on the actual structure, and it establishes whether the building can safely carry the added weight of the array and mounting system, along with the loads it will see across its life — including snow loading.
Under CDM regulations, the parties designing and installing the system carry a duty to make sure the structure can support what’s being put on it. That is not something to be settled by eye during a site visit. It needs a professional.
It protects the client, and it protects us as the installer. We work with named structural partners, and the fee is passed straight through to you at cost. We don’t mark it up.
If a quotation doesn’t mention a structural report, ask why. If the answer is that the roof looks fine, that’s your answer.
What Equipment Has Been Specified, and Why?
Two proposals can quote the same capacity and specify very different kit.
On large-scale commercial we typically install Solis 5G and 6G string inverters. They’re top of the range and, for commercial applications, they tick every box we need them to.
Where fire safety and panel-level optimisation are priorities, we’ll often specify SolarEdge instead. Different requirement, different tool.
We’re not precious about manufacturers. But we will always tell you why we’ve specified what we’ve specified, and what the alternative would have done differently. If a company can’t do that, they may not have made a decision at all, they may just be quoting what they always quote.
One thing we include as standard: remote monitoring. On some inverters it’s an optional extra, and it gets left out to shave the price. We put it in every proposal regardless, because we want to be able to see how your system is performing, and so should you. Whether you think you’ll use it or not, you’ll want it the first time output drops and nobody can say why.
What’s Included Beyond the Solar Panels?
It’s easy to compare panel counts and system size, but those aren’t what separate two proposals. Two quotations can recommend near-identical systems while including very different amounts of work.
| Item | Why It Matters |
|---|---|
| Solar panels | Manufacturer, efficiency and product warranty all affect long-term performance. |
| Inverters | Affect performance, monitoring and future maintenance. |
| Structural engineer’s report | Should be included and passed through at cost. Check whether it’s in the price or listed as an exclusion. |
| Electrical work | Confirms whether switchgear upgrades, cabling or distribution board modifications are included. |
| AC supply and integration | On larger retrofits this is often the most expensive single element. It should be priced, not assumed. |
| Grid application | Clarifies who manages the process and whether the associated costs are included. |
| Access equipment | Scaffolding, MEWPs and edge protection are regularly excluded and added later. |
| Monitoring | Shows how you’ll track performance once the system is live. |
| Product and workmanship warranties | Cover different things and should be considered separately. |
| Exclusions | Where later costs come from. Read this page as carefully as the specification. |
One thing we always encourage businesses to do is read the exclusions as carefully as the specification. Two quotations can look almost identical until you reach the final page. That’s usually where additional electrical work, access equipment or grid-related costs are sitting.
Is the Company Properly Accredited?
Accreditation isn’t a formality. It’s independent evidence that someone else has assessed the work, and it determines what protection you have if something goes wrong.
Synergy PV Renewables holds the following:
| Accreditation | What It Covers |
|---|---|
| MCS | Certification of the installation and the products used. Required for most export and incentive schemes. |
| RECC | Renewable Energy Consumer Code. Sets standards for how customers are treated, from quotation through to aftercare. |
| NICEIC | Independently assessed electrical competence — the underlying trade behind every solar installation. |
| TrustMark | Government-endorsed quality scheme covering standards, trading practice and customer protection. |
| IWA | Independent Warranty Association. Insurance-backed warranty cover, protecting the workmanship guarantee beyond the installer. |
Ask every company which of these they hold, and ask for certificate numbers. It takes a minute and it’s worth doing.
Compare Your Quotes Side by Side
The easiest way to compare commercial solar quotations is to stop reading them individually and start comparing them against the same checklist.
Once they’re lined up, the differences are usually obvious, and they’re rarely where you expected them to be.
| Compare | Quote A | Quote B | Quote C |
|---|---|---|---|
| System size (kWp) | |||
| Annual generation (kWh) | |||
| Estimated annual saving | |||
| Electricity data used | |||
| Site visit carried out | |||
| Structural report included | |||
| Panel specification | |||
| Inverter specification | |||
| Monitoring included | |||
| Electrical / AC works included | |||
| Grid application included | |||
| Accreditations held | |||
| Warranties | |||
| Exclusions | |||
| Total price |
What If You Can’t Tell the Difference Between Them?
Here’s the honest problem with everything above.
Most people reading three commercial solar proposals won’t be able to tell the figures apart. That isn’t a criticism — unless you work in this industry, why would you?
And that’s the risk. It would be very straightforward for a sharp installer to flatter a set of numbers knowing full well that nobody is going to check them.
So check.
- Ask the installer to walk you through the calculation, and see whether the explanation holds together.
- Bring in a colleague with an engineering, facilities or energy background.
- Ask a second installer what they make of a competitor’s assumptions.
- Put the proposals through an AI tool and ask it what questions you should be asking. It’s better than nothing.
Do whatever you need to do to understand it rather than assume it. This is a significant capital investment and the entire case for it rests on the return. That’s the one you have to get right.
What Questions Should You Ask Before Choosing a Commercial Solar Company?
A quotation should leave you confident about the recommendation, not uncertain about what you’re buying. Ask every company the same questions.
- Did you visit the site, and did an electrician attend?
- Why have you recommended this system size?
- What electricity data did you use when designing the system?
- What assumptions have you made about shading and system losses?
- Is a structural engineer’s report included, and is the fee marked up?
- What are the estimated bill savings monthly, quarterly and annually?
- Why have you specified this inverter, and what would the alternative have changed?
- Is remote monitoring included or optional?
- What is included in the quoted price, and what is excluded?
- Which warranties apply to the equipment and to the installation?
- Which accreditations do you hold?
The answers are often worth more than the quotation itself. A company that understands its own design can explain it clearly and without hesitating.
Which Commercial Solar Quote Represents the Best Value?
The best commercial solar quote isn’t simply the one with the lowest price.
It’s the proposal that shows a clear understanding of your business, explains how the system has been designed, and gives you confidence in what will actually be delivered.
Price is always part of the decision. It shouldn’t be the only part. A higher quotation may include additional work, stronger warranties, or a system better matched to how your business operates. Equally, a lower quotation isn’t automatically poor value, it just needs to be understood in the context of what’s included and what isn’t.
Our installation at Wenzel’s the Bakers in Watford is a reasonable benchmark for what a well-matched commercial system looks like: 228.8 kWp across 558 Canadian Solar 410W panels, two Solis 100kW inverters, around 188,000 kWh generated annually and a 4.5 year payback. That system was designed around how the bakery uses electricity, not around how much roof was available.
At Synergy PV Renewables, we think businesses should understand exactly why a recommendation has been made before deciding whether it’s the right investment.
If you’re comparing commercial solar quotations and you’re not sure why they differ, we’ll happily talk you through them. Sometimes the differences are significant. Sometimes they’re simply the result of different design assumptions. Either way, understanding them before you decide usually leads to a better outcome.
Call us on 01442 921055 or email hello@synergypvrenewables.co.uk.
Frequently Asked Questions
How many commercial solar quotes should I obtain?
Three detailed quotations are usually enough to compare different design approaches and understand how each company has assessed your site. Three well-prepared proposals are far more useful than a large number of basic estimates.
Why do commercial solar quotes vary so much?
Different companies use different electricity data, design assumptions and installation scopes. They may also recommend different system sizes or include different levels of work within the quoted price, which is why it’s important to compare more than the final cost.
Can a commercial solar company quote without visiting the site?
They can, but it’s guesswork on anything substantial. Access, logistics and the existing electrical setup all affect the design and the price, and none of them can be assessed properly from aerial imagery. A remote figure is fine as an early indication. It shouldn’t be the basis of a decision.
Should a commercial solar quote include a structural engineer’s report?
Yes. Any commercial roof installation should be supported by a structural engineer’s report confirming the building can safely carry the system, including snow loading. It protects the building owner and the installer. If a quotation doesn’t mention one, ask why.
Should every commercial solar company recommend the same system?
No. Two experienced installers may recommend different solutions based on how they interpret your electricity usage, future plans and site conditions. What matters is that each can clearly explain why.
Is the cheapest commercial solar quote usually the best value?
Not necessarily. A lower price may reflect a narrower installation scope, alternative equipment, or exclusions that aren’t immediately obvious. Comparing the full proposal gives a much clearer picture of overall value.
Can I ask a company to review or amend its quotation?
Yes. If you’ve spotted differences in scope or assumptions, it’s perfectly reasonable to ask a company to explain or revise its proposal. It usually makes a like-for-like comparison far easier
