How much deposit to pay an installer and how to protect it

The consumer code binding every MCS certified installer caps the deposit at 25% of the estimated job cost and names 15% as the reasonable figure. On a £14,000 air source heat pump that is a ceiling of £3,500 and a norm of £2,100. An installer who asks for £7,000 up front is breaking a rule they signed up to. That rule lives in the consumer code, several clicks away from the quotation you are handed.

This guide covers the money layer rather than the usual red-flag checklist. It works through what each certification badge legally certifies, how much cash an installer is allowed to hold before the work is finished, which payment methods keep a legal claim alive, what happens if the company stops answering the phone, and how the picture changes in Scotland and Northern Ireland.

What the badges actually certify

Every certification logo in UK home energy answers one narrow question, and the questions are all different. Read together they look like a single blanket assurance that the company does good work. Read individually, each one covers something much smaller.

MCS, RECC and HIES

Business Companion, the official Trading Standards guidance service, states that businesses carrying out MCS installations must register with one of the two Chartered Trading Standards consumer codes. Those two are the Renewable Energy Consumer Code (RECC) and HIES, the Home Insulation and Energy Systems scheme. MCS certification itself assesses technical competence, record keeping, complaint procedures and quality processes.

According to the Energy Saving Trust’s heat pump installers toolkit, the consumer code side covers customers in vulnerable circumstances, advertising, the behaviour of sales representatives, cancellation rights, the amount of deposit permitted, guarantees and the dispute resolution process. That is the whole money-and-conduct layer, and it belongs to RECC or HIES.

So when a solar or heat pump install goes wrong, “they’re MCS certified” tells you the business was assessed as technically competent. The document setting out how much deposit they were allowed to take, how long they have to answer your complaint and who adjudicates if they refuse is the consumer code. Ask which of the two they belong to before you ask anything else. There is a fuller explanation of the scheme in our guide to the UK MCS scheme.

What TrustMark checks, and how often

TrustMark’s homeowner FAQ says Registered Businesses are inspected no less than every three years by a qualified independent inspector. Their scheme provider checks insurances and documentation annually, and some scheme providers inspect more often than the minimum. That is a vetting regime for the company, and a reasonable one. It carries no promise that anybody looked at the work done on your house.

TrustMark also runs an escrow service, which is the part worth raising at quotation stage. TrustMark Escrow holds agreed funds in a holding account until the contracted works are completed to satisfaction, and TrustMark prices it from as little as £6 per party. Both sides have to agree to use it, so the time to suggest it is before the contract is signed. We cover the scheme itself in more depth in our guide to TrustMark accreditation.

FENSA, Part P and Gas Safe

GOV.UK describes a competent person scheme in exact terms. An installer registered with a scheme can self-certify that their work complies with building standards, and will give you a certificate within eight weeks of completion which can be used as evidence of compliance. That certificate also shows up in solicitors’ searches when you sell, which is when a missing one becomes expensive.

Two separate documents should come out of a window replacement, and only one of them is a guarantee. FENSA describes itself as a government-authorised scheme that monitors building regulation compliance for replacement windows and doors, operating in England and Wales, and the certificate is proof that the installation is compliant, energy efficient and registered. The workmanship guarantee comes from the installer. FENSA verifies that every FENSA Approved Installer’s guarantee is insured, but it does not write that guarantee itself, so ask for both documents at handover. Our comparison of FENSA and CERTASS covers how the competing schemes differ.

Electrical Safety First sets out the equivalent for electrical work. All electrical installation work in a home, garden, conservatory or outbuilding must comply with the Building Regulations, and beyond minor tasks it must either be notified to local authority building control or done by a registered electrician. A registered electrician arranges for you to receive an Electrical Installation Certificate or Minor Works Certificate confirming the work meets BS 7671, plus a Building Regulations Compliance Certificate. Chase both.

Gas is a legal question rather than a commercial one. The HSE is explicit that under the Gas Safety (Installation and Use) Regulations 1998, gas work must be carried out by a Gas Safe registered engineer. A firm advertising Gas Safe registration as a selling point is advertising that it is allowed to trade at all.

Deposits

Citizens Advice gives a general figure for home improvement work: push the deposit down as much as possible, and do not agree to more than 25%. For any MCS installation the RECC code turns that advice into a rule the installer has to follow.

RECC section 6.3 says a deposit “will constitute a reasonable percentage of the estimated overall costs of the work as set out in the Contract, for example 15 per cent”, and that “it should not exceed 25 per cent under any circumstances”. The same section caps the deposit and any further advance payment together at 60 per cent of estimated overall costs, and a further advance payment can only be required no more than three weeks before the agreed delivery date.

Section 6.3 also requires code members to insure all deposits and further advance payments, so that if the installer becomes insolvent or ceases to trade before the contract is complete, another code member finishes the job at no additional cost to you. That deposit insolvency insurance is the thing to ask for by name. Ask who the policy is with, and ask to see the certificate.

A worked example on a £14,000 heat pump

This is an illustrative calculation, not a real customer. Assume an air source heat pump quoted at £14,000 before grant, by an MCS certified business belonging to RECC, with the £7,500 Boiler Upgrade Scheme grant deducted so the homeowner pays £6,500.

At the 15% example rate the deposit is £2,100. At the ceiling it is £3,500. An installer asking for 50%, or £7,000, is outside the code they are required to follow, whether or not they mention the code in the sales meeting.

There is a real question about which of the two figures the percentage runs on, and it is worth settling before you sign. RECC section 6.3 ties the calculation to “the estimated overall costs of the work as set out in the Contract”. GOV.UK requires the Boiler Upgrade Scheme deduction to appear on your quotation and invoice, so the sum written into a grant-funded contract is the net £6,500. On that reading the 15% example rate produces £975 and the ceiling produces £1,625, and a deposit demand of £2,100 on a grant-funded job needs explaining. The gap between the two readings is £1,125 of your money, so get the basis stated in the contract rather than assumed.

The 60% combined cap works the same way. On a £14,000 gross contract, £8,400 is the absolute maximum that can be held by the installer before the system is delivered. Against the £6,500 the homeowner actually pays, the balance held back until completion is the only pressure you can apply if commissioning is poor.

Then the payment method. Citizens Advice states that if you paid any part of the cost by credit card you can use Section 75, as long as the total cost of the item is more than £100 and no more than £30,000. A £14,000 install falls inside those thresholds, so putting the £2,100 deposit on a credit card makes the card provider jointly liable alongside the installer. The same £2,100 by bank transfer leaves nobody jointly liable. A credit card deposit costs nothing extra unless the installer passes on the merchant fee, and some add 1% to 2%, which on £2,100 is £21 to £42.

How you pay decides whether the money comes back

Citizens Advice is direct about method: pay for the work by debit or credit card if you can, use a bank transfer only if you cannot pay by card, and do not pay with cash. The reason is that these methods rank in a clear order of protection.

The £30,000 ceiling catches large retrofits. A fabric-plus-heating package quoted at £42,000 falls outside Section 75 completely, and no amount of credit card payment brings it back. The other trap is the installer who takes a card for the small deposit and then asks for the balance by transfer to save the fees, which quietly moves the bulk of your money outside every statutory route. Citizens Advice also notes that a trader can challenge a chargeback after a refund is issued, and advises holding refunded money for a few weeks in case it is reversed.

If they go bust

This is the scenario the whole ladder exists for, and the order in which you pull the levers matters.

1. The deposit insolvency insurance. Under RECC section 6.3 the money you paid in advance should be insured so another code member completes the contract at no extra cost. Find the policy document you were given at contract stage.
2. Section 75, if any part went on a credit card. The claim is against the card provider, and it survives the trader ceasing to exist. That is the strongest single argument for putting a deposit on plastic.
3. Chargeback, if you used a debit card. Weaker, time-limited and reversible, but real.
4. The insurance-backed workmanship guarantee, for defects that appear after the work was finished but while the guarantee still runs.
5. The consumer code’s dispute route, which continues even where the individual business has failed, and can point you to the right insurer.

Pay a 50% deposit by bank transfer to a firm outside any consumer code and none of the first four apply. You are an unsecured creditor in the insolvency, which in practice means pennies.

Insurance-backed guarantees

An insurance-backed guarantee (IBG) is insolvency cover. It typically responds only once the original installer has ceased trading or become insolvent, so it will not send an engineer out while the company is still going. While the installer trades, your route is the installer.

RECC section 8.1.2 sets the minimum: a written guarantee against faults arising from the installation process and workmanship, valid for at least two years, and transferable to a new owner if you move home. If the code member becomes insolvent during the guarantee period, they must have arranged for the full term to be honoured through an insurance-backed workmanship guarantee.

Get the detail in writing before signing. Ask how long the workmanship guarantee runs and whether it beats the two-year RECC minimum. Ask who underwrites the IBG, and whether you receive the policy document or only a certificate number. Confirm the guarantee transfers to a buyer if you sell, as RECC requires. Then ask which faults belong to the product manufacturer’s warranty rather than the installer’s workmanship guarantee, and who you call first. Our explainer on insurance-backed guarantees goes through what a policy typically excludes.

That last question separates the two documents people conflate. A failed compressor is a product claim. A leaking flow pipe through a badly sealed roof penetration is workmanship. An installer who cannot draw that line on the doorstep will not draw it in year three either.

Grant-funded work moves the money before you see it

GOV.UK sets out the mechanics of the Boiler Upgrade Scheme. The installer applies on your behalf on the Ofgem website, you must get quotes from MCS certified installers, and the value of the grant is taken off the amount you pay, shown on your quotation and invoice. Query any quote that does not show the deduction before you sign, because that deduction defines the contract sum your deposit percentage runs on.

The grant is worth £7,500 towards an air source heat pump, £7,500 towards a ground source heat pump, £5,000 towards a biomass boiler and £2,500 towards an air-to-air heat pump, one grant per property. Until March 2027 an extra £1,500 is available where the property is heated by oil or LPG and has no mains gas connection, taking the heat pump figure to £9,000.

GOV.UK also states that the installer must commission and install the heat pump within 120 days of applying for the grant or it will not be eligible. Ofgem states separately that ECO4 applies to measures installed from 1 April 2022 and runs until 31 December 2026 after a nine-month extension. TrustMark oversees quality assurance of those ECO4 retrofits as Ofgem’s delivery partner, so an ECO4 job carries a second complaints route that a privately funded job does not.

Where you live changes the rules

MCS, RECC and HIES apply UK-wide, so the 25% ceiling, the 60% combined cap and the two-year workmanship guarantee minimum follow the code rather than the postcode. So do Section 75, chargeback and the Consumer Rights Act 2015, section 49(1) of which says every contract to supply a service includes a term that the trader must perform the service with reasonable care and skill, in Cardiff and Coleraine alike.

The funding splits. GOV.UK states that the Boiler Upgrade Scheme is open to people in England and Wales. mygov.scot sets out the Scottish route, the Home Energy Scotland Grant and Loan, at up to £7,500 for clean heating systems such as heat pumps and up to £7,500 for energy efficiency improvements such as insulation, plus up to £1,500 extra on each for eligible rural households. GOV.UK points Northern Ireland residents to NI Direct and records the Northern Ireland Boiler Replacement Scheme as closed.

Building Regulations are devolved too. FENSA operates in England and Wales, while Scotland and Northern Ireland run separate building standards systems. A Scottish homeowner replacing windows should be asking about the Scottish certification route instead of looking for a FENSA number.

Where this advice stops

The deposit rules bind code members. A small local firm that is not MCS certified and belongs to no consumer code is bound by contract law and the Consumer Rights Act, but there is no 25% ceiling to point at. On a £900 job with a good local tradesperson that may be an acceptable trade. On a £14,000 install the absence of a consumer code is itself the reason to walk away.

Section 75 has hard edges. Above £30,000 it disappears, and below £100 it never starts. On a large whole-house retrofit, escrow and staged payments do more work than a credit card.

Cooling-off rights are narrower than they sound. Citizens Advice states the 14-day cooling-off period applies where the business approached you away from its premises and the service costs £42 or more, running from the day after you enter the contract. If you ask for work to start inside that period, the business can keep what is necessary to cover services already provided. RECC section 6.2 runs a different clock for code members’ customers: 14 days from the date the last item of goods is delivered, and refunds due within 14 days of cancellation. Work out which clock you are on before you rely on either. Our guide to doorstep selling cooling-off rights goes through the detail.

If it goes wrong, in order

1. Put the complaint in writing to the installer. RECC section 9.1 requires the code member to arrange to inspect your system within 5 working days of being notified, or within 24 hours where you are left without heating or hot water, and to report the findings clearly to you within 10 working days.
2. Withhold the final payment if it is still outstanding and the work is defective. Citizens Advice notes that paying in stages means problems can be put right before you make the final payment, which is the practical argument for staging in the first place.
3. Escalate to the consumer code administrator for mediation if the installer’s response is inadequate.
4. Renewable Adjudication Service for a binding decision where RECC mediation fails. Our walkthrough of the MCS dispute resolution process covers what each stage asks of you.
5. Section 75 or chargeback in parallel, since these run against the card provider rather than the trader and are not blocked by the trader stalling.

Above the code level there is now a regulator with direct powers. The CMA reported that in the first year of its direct consumer enforcement regime, April 2025 to April 2026, it opened investigations into 14 businesses, reached two settlements, ordered £760,000 in consumer refunds, imposed £4.7 million in fines and issued 157 advisory and warning letters. Drip pricing, where costs surface late in a sale, is one of its stated enforcement priorities, which bears directly on a quotation that grows after signing.

What to do before you sign

Do these in order, before any money moves.

• Get three written quotes rather than estimates. Citizens Advice defines the difference precisely: a quote is a fixed price, an estimate is a rough guess and you might end up paying more. Ask for the word “quotation” on the document.
• Check the consumer code membership on the code’s own register rather than taking the logo on the installer’s website at face value, and note whether it is RECC or HIES.
• Agree the deposit in writing at the 15% example rate, and pin down which contract figure the percentage runs on if a grant is involved.
• Get the deposit insolvency insurance provider named in writing, with the policy or certificate handed to you before you pay anything.
• Put at least part of every payment over £100 on a credit card, and refuse a bank-transfer-only structure.
• Keep a meaningful final payment for satisfactory completion. Staging the balance that way holds you inside the 60% RECC cap without having to argue about it.
• Confirm the grant deduction appears on the quotation if the job is BUS funded, and diarise the 120-day install deadline from the date your installer applies.
• Ask for the compliance certificate with a deadline. GOV.UK sets the competent person certificate at within eight weeks of completion, and a missing certificate surfaces in solicitors’ searches years later when you sell.

If you are heated by oil or LPG with no mains gas connection and want the extra £1,500, that uplift closes in March 2027, so get quotes in hand well before the end of 2026. If you are relying on ECO4, that scheme runs to 31 December 2026. Neither deadline changes what an installer is allowed to ask for up front.