An installer’s free survey and independent advice both start with someone looking at your roof. They end in different places. The survey ends in a quote from a firm that wants to build the system. Independent advice ends in a recommendation from someone who is paid the same whether you build or not. Both are useful, but at different points, and mixing them up is how businesses end up with a specification written by the first bidder.
What an installer’s survey is for
A survey from an installer exists to produce a quote. The surveyor measures the roof, checks direction and shade, and notes obvious problems. The firm then proposes a system size, a price and a savings figure. That is real engineering work and you need it before you buy.
It also sits inside a sales process, which shapes the output in four ways.
- The firm earns only if you say yes. A survey that ends in “don’t build this” means lost time and no sale.
- The design is usually the firm’s own. Panel make, inverter and system size come from what that installer sells.
- The savings figure is a sales figure. Consumer group Which? lists very optimistic savings and extremely short payback estimates among the red flags in solar quotes. It also warns against pressure to decide at once and large time-limited discounts. That advice is written for households, but the incentive behind it applies to business buyers too.
- A certificate is not independence. MCS certification shows an installer meets a quality standard. It does not make the installer neutral. MCS also only covers systems up to 50 kWp, so for a large commercial project it tells you little.
None of this makes a free survey worthless. It answers “what would you build and for how much?” It does not answer “should we build at all, and on what terms?”
What independent advice looks like
The test is simple: does the adviser lose anything if you decide not to proceed? An adviser with no equipment to sell and no commission from an installer has no reason to lean either way.
| Installer survey | Independent adviser | |
|---|---|---|
| Who pays | Built into the system price | You, for the advice |
| Can it say “don’t proceed” | Seldom, as it ends the sale | Yes, that is part of the job |
| Who writes the specification | The installer | A neutral brief any bidder can price |
| What you receive | A quote and a savings estimate | A study, a business case or a tender pack |
| Basis | The installer’s assumptions and products | Your site, your tariff and your finances |
Independence is about incentives, not labels. Ask any adviser how they are paid. If part of their fee comes from an installer, or rises when you buy a bigger system, the advice is not neutral.
Why it matters most on commercial sites
A slightly rosy survey on a house costs a few thousand pounds. However, on a warehouse roof, a farm or a multi-building estate, the decision is worth six or seven figures. Two stages carry the risk.
- The specification. If the first installer writes it, every later bid is measured against their design. Tenders then look competitive but are hard to compare. Our procurement and tender support exists to fix that.
- The go or no-go decision. Some sites should not go ahead: a roof that cannot take the load, a grid connection with no capacity, a payback that misses your hurdle rate. A seller is unlikely to say so. Our guide to what a feasibility study involves shows what is checked.
The same split appears on land, since a landowner deciding between a lease and building an array is hearing from a developer on one side and an installer on the other, and each has a stake in the answer. We set out the choice neutrally in land lease vs on-site solar.
An illustrative case
Picture two quotes for the same warehouse roof. This is an invented example to show the pattern, not a real client.
Installer A proposes the largest array its panels will fit. Its savings figure assumes the whole output is used on site. Installer B proposes a smaller array and an export limit because of the local grid. Without a neutral specification you cannot tell whether B is cautious or A is optimistic. A feasibility study that models your half-hourly use and the connection answer lets you set one brief, and then both quote against it.
Questions to ask before you act on advice
- Does this person or firm sell or install solar equipment?
- Do they earn more if I proceed than if I do not?
- Could they credibly tell me not to do this?
- Is the quote itemised, with scaffolding, grid costs and VAT shown? The same Which? guide recommends getting at least three quotes and checking what is left out.
- Who carries the risk if the grid connection is late or the yield falls short?
If your answers point to a seller, you have had a quote, not advice. That is fine, provided you know the difference. Our due diligence checklist for a solar contract lists what to confirm before you sign.
The sensible order
Get independent advice first, to settle whether and how to proceed. Then collect installer quotes against a specification you control. Our feasibility studies and procurement support are advisory services. They do not include supplying or fitting equipment. For the cost side of the conversation, read how much commercial solar costs.
We are paid by the client and never by installers, so our feasibility studies can end in a no. Our energy and ROI modelling tests the figures in a quote, while procurement and tender support turns a quote into a fair tender. PPA and financing advice does the same for funded offers. Public buyers should also read buying solar under the Procurement Act 2023.