How to choose a commercial solar installer (2026)

Three schemes get quoted a lot, and they do different jobs. Understanding the distinction is the single fastest way to filter a shortlist.

• MCS (Microgeneration Certification Scheme) is the government-backed quality mark for the installation itself. Crucially, MCS is company certification, not an individual qualification, and it is split into scopes. Many firms that brand themselves "commercial" are only certified for domestic solar PV. Ask to see certification that explicitly covers Solar PV above 50 kWp, and check the named operatives on the certificate.¹
• RECC (Renewable Energy Consumer Code) and MCS 003 are consumer-protection codes. They matter most for micro-businesses and sole traders buying like a consumer; larger B2B contracts are usually governed by your own commercial terms instead.
• TrustMark is the government-endorsed quality scheme that sits alongside MCS for many domestic and mixed-use schemes. It is a useful signal but is not a substitute for the correct MCS commercial scope.

A quick VAT note that trips up many buyers: the 0% VAT rate applies to domestic solar only. Commercial solar PV is charged at 20% VAT, which a VAT-registered business normally reclaims through its return.² Treat any installer quoting "0% VAT" on a commercial job as a red flag on their commercial competence.

Almost every commercial system exports or has the capacity to export, so it needs approval from your Distribution Network Operator (DNO) under engineering recommendation G99. Anything above roughly 16 A per phase (about 3.68 kW single-phase, 11 kW three-phase) falls under G99 rather than the simpler notify-after-install G98 route, which captures virtually all commercial sites.³

A capable installer should own this process on your behalf: preparing the single-line diagram, protection settings, inverter datasheets and MPAN details, and managing the back-and-forth with the DNO. Typical DNO turnaround is 5–11 weeks, and longer where the network needs a capacity study or reinforcement.³ On constrained networks you may be offered an export limitation (capping how much you send to the grid) so the project can proceed without expensive reinforcement.

The most important input to a commercial solar design is your own half-hourly (HH) consumption data — the 48 readings per day your meter records. A serious installer will ask for 12 months of HH data (or your MPAN and letter of authority to pull it) before sizing anything.

Why it matters: solar economics on a business are driven by self-consumption — the share of generation you use on site rather than export. Because on-site use is worth your full import price (often 20–30 p/kWh) while export earns far less under the Smart Export Guarantee,⁴ a system sized to your daytime load pays back faster than an oversized one. Typical commercial self-consumption runs 60–85% depending on sector: a single-shift office is lower, a 24/7 cold store or manufacturer much higher.

Use these industry sanity anchors to pressure-test any quote — and ask the installer to cite their own current figures:

See worked economics by size on our 10 kW, 50 kW, 100 kW and 250 kW pages, or by sector for a warehouse, factory or farm.

A 25-year asset needs support for 25 years. Separate two very different warranties that are often blurred in sales conversations:

• Product warranty — covers physical failure of the panel or inverter (commonly 12–25 years on panels, 5–12 years on inverters, often extendable).
• Performance warranty — the manufacturer's guarantee that panels retain a minimum output over time (typically around 85–92% at year 25). It is separate from, and weaker than, the product warranty.
• Workmanship warranty — the installer's own cover on labour, mounting and waterproofing. This is only as good as the installer's solvency, so company track record matters.

Then look at O&M and monitoring. Ask whether you get inverter-level (or string-level) monitoring, who watches the alerts, response times for faults, and the annual O&M cost. Panels are low-maintenance, but inverters are the component most likely to need attention over the system's life, so a clear maintenance and monitoring plan protects your return.

Watch for these warning signs:

• MCS scope that only covers domestic solar, or no MCS at all for commercial work.
• A price quoted before your half-hourly data or roof survey has been reviewed.
• "0% VAT" claimed on a commercial job, or unqualified "up to X% savings" headline maxima with no assumptions shown.
• No mention of the G99 / DNO application, or a promise it "won't be needed".
• High-pressure discounts that expire today, or large deposits with no staged payment schedule.
• No structural assessment of the roof and no O&M or monitoring plan.

Ten questions to put to any installer:

1. Does your MCS certification cover commercial solar PV above 50 kWp?
2. Will you design from my 12 months of half-hourly data?
3. What self-consumption percentage are you assuming, and why?
4. Will you manage the full G99 DNO application, and have you checked my capacity?
5. What yield (kWh/kWp) and degradation have you assumed?
6. What are the product, performance and workmanship warranties, in years?
7. What monitoring is included and who responds to faults?
8. What does annual O&M cost?
9. Is the price ex-VAT, and confirm commercial VAT is 20% (reclaimable)?
10. Can you share references from comparable commercial sites?

Our how-to-choose checklist and buy-vs-PPA guide go deeper on each.

A well-run commercial installation typically runs 2–6 months from enquiry to switch-on, with the grid application usually the longest single item. Indicative stages:

Steps 1–2 can overlap, and the DNO application can often run in parallel with final design, which is where an experienced installer shortens your calendar.

PlutoHome is a neutral introducer, not an installer. We do not install, finance or own systems, and we do not take a view on which panel or inverter brand you should buy. Our role is narrow and useful: we understand your site and match you with one MCS-certified commercial installer suited to your roof, load and location — never a list of five firms competing to call you first.

Every installer in our network is checked for the right MCS commercial scope, insurance and track record on comparable sites, so the credentials work above is done before you speak to anyone. You still own the decision: you review the design, the warranties and the numbers, and you can walk away. Because we are neutral, we have no reason to push a bigger system than your data supports.

All savings and payback figures across PlutoHome are estimates for a typical site; your figures depend on your load, roof and tariff, and any tax treatment should be confirmed with your accountant.