Wattcheck
Installers · guidance

The installer decides the money, not the kit.

Whether you get paid for the electricity you export, whether you can claim the £7,500 heat pump grant, and even what VAT rate you pay all turn on who installs it, not what you buy. This page explains why, and shows you how to check an installer’s certificate yourself on the official registers. Facts checked 29 August 2026.

Buying the parts yourself costs more, not less

It sounds like the savvy move: buy the panels and battery at the trade prices we list, then hire someone to fit them. For anything that needs installing, the tax rules make it the expensive route.

When an installer supplies and fits the equipment as one job, the whole job is charged at 0% VAT. When you buy the same equipment yourself, you pay 20%. That is not a quirk of one shop — HMRC’s own guidance says the sale of energy-saving materials by a retailer is always standard-rated. The zero rate belongs to the installation, not the products. (The rule is VAT Notice 708/6; the 0% rate runs to 31 March 2027, then becomes 5%.)

In numbers, from our own catalogue: ten 445 W panels and a 3.6 kW inverter cost about £1,250 before VAT. Buy them yourself and you pay about £1,500. On an installer’s supply-and-fit quote the same materials go in at £1,250, zero-rated. On a system with a battery — £4,000–6,000 of materials — doing it yourself hands HMRC an extra £800–1,200.

And the VAT is only the start. Most installers will not warrant equipment you supplied. Your electricity supplier will want to see MCS certification before paying you for exports. And telling your local electricity network company about the installation is the installer’s job — unbundle it, and it becomes yours.

So what are our parts prices for? Leverage. If a quote says £8,400 and the parts cost about £3,100 at trade, the difference is what you are paying for scaffolding, labour, certification, the zero VAT rating and the paperwork — and now you can ask whether it is fair, and get another quote against it. The exception is equipment that needs no installer at all: plug-in solar and portable batteries, where buying retail is exactly what the rules intend.

What “MCS certified” actually gets you

MCS is the certification scheme for the people and products that generate energy at home. It reads like a quality badge. It is really a gate on three sums of money.

  • Getting paid for what you export. Electricity suppliers require MCS certification (or equivalent) of your installation before they will pay you an export tariff — the scheme is called the Smart Export Guarantee. No certificate, no payments, however well the system works.
  • The £7,500 heat pump grant. The Boiler Upgrade Scheme requires MCS certification of both the installer and the product, and since 28 April 2026 it is the only route to the grant — the alternative-scheme wording was removed from the regulations. Full detail on our heat pumps page.
  • The 0% VAT rate, in practice. The VAT relief does not name MCS — but it attaches to professional installation, and the installers doing this work to the standard the other two schemes require are MCS certified ones.

Certification is per technology, and this catches people out. A firm certified for solar panels is not thereby certified for heat pumps, or for batteries. The certificate that matters is the one covering the technology you are actually having fitted — ask which technologies it covers, and check it yourself before you sign anything.

How to check an installer yourself, today

Every check below is free, takes minutes, and uses the official source directly. Do all four before handing over a deposit.

  1. Look them up on the MCS register. mcscertified.com/find-an-installer lists every certified company with its certificate number (they look like “NAP-11766”), the technologies covered, and whether the firm is registered for the Boiler Upgrade Scheme. If a company’s website claims MCS certification and the register cannot find them, that is your answer.
  2. Check the technologies on the certificate match your job. Solar panels, batteries and each kind of heat pump are certified separately.
  3. Look them up on TrustMark. trustmark.org.uk/find-a-tradesperson is the government-endorsed quality scheme. It covers the standard of the work and the consumer protection around it — a different assurance from MCS’s technical certification. A firm may hold either, both or neither.
  4. Look the company itself up at Companies House. find-and-update.company-information.service.gov.uk shows, free, how long the company has actually existed, whether its accounts are overdue, and whether it is being struck off or wound up — worth knowing before you pay a deposit to a firm whose warranty depends on it still trading in year eight. (A trading name and a registered name often differ; ask for the company number and search that.)

The installers we list

None yet — and here is exactly why, because the reason is the same standard we apply to everyone else.

The two registers that matter are public to read, but neither is licensed to republish. MCS’s terms prohibit copying or commercial use of their content without written permission — and their public search also omits the one fact you most need, whether a certificate is current. TrustMark asserts copyright and database rights and requires written permission. We could technically copy both registers; we have not, and will not.

We have instead asked both organisations for their licensed datasets — MCS’s own data-request process offers an installer dataset that includes certification dates, which is what would let us print “certificate NAP-11766, active, checked on this date” rather than “we found them on a list”. That is the only version of a directory worth publishing, and until it exists the honest state of this section is empty. In the meantime, the checks above give you the same facts from the registers’ own pages.

What we will not do instead: scrape the registers, or pad this page with a proxy — “registered at Companies House as an electrical contractor” and “MCS certified” are different facts, and you came here for the second one.

The registers behind this page

The same rule as every other register on this site: we say what each one is, who runs it, and honestly whether we hold a copy.

MCS certified installer register

Lists installation companies certified under the Microgeneration Certification Scheme, by technology. It is the certification a household needs for the money: Boiler Upgrade Scheme grants require MCS certification of both the installer and the product, and since 28 April 2026 MCS is the only route to that grant - the alternative-scheme limb of the BUS regulations (SI 2022/565 Schedule 4 para 1(b)) was removed by SI 2026/390. MCS certification is separately what a supplier requires before paying a Smart Export Guarantee export tariff. Certification is per technology: a firm certified for solar PV is not thereby certified for heat pumps.

Run by MCS Service Company Ltd (Microgeneration Certification Scheme). We do not hold a copy — search it directly at the source. mcscertified.com ↗

TrustMark registered businesses

The government-endorsed quality scheme for work in and around the home. A TrustMark registration is a live state with a start date and an active flag, held through a scheme provider. It is a different assurance from MCS: MCS certifies technical competence for a specific microgeneration technology and is what the Boiler Upgrade Scheme requires; TrustMark covers the standard of the work and the consumer protection wrapped around it. A firm may hold either, both or neither, and the two must never be presented as interchangeable.

Run by TrustMark (2005) Limited. We do not hold a copy — search it directly at the source. trustmark.org.uk ↗

Where this comes from

Nothing on this page is a recommendation of any installer, and we operate no certification scheme. Facts checked 29 August 2026; the VAT rate changes on 1 April 2027, so if you are reading this after that date, the 0% figures above have become 5%.