What happens during an MCS heat-pump site visit in 2026

What the visit is actually for

The MCS site visit produces the data your installer needs to issue a binding quote. It’s not a sales call — you should already have decided you want a heat pump before booking it. The output of the visit is a properly sized system specification and a complete cost breakdown for your specific property.

For comparison: getting a gas boiler quote takes a 15- minute phone call and a Google Streetview check. Getting a heat-pump quote takes 90 minutes of an MCS engineer physically measuring your home. That difference is what the BUS grant + MCS certification framework requires — and why heat-pump quotes are more rigorous than boiler quotes you may be used to.

Step 1: Heat-loss survey (BS EN 12831)

This is the biggest single piece of work in the visit. The installer goes room by room with a tape measure (or laser distance meter), measuring:

• Room dimensions — floor area, ceiling height.
• Exterior wall area + assessed construction (solid wall, cavity wall, internal wall insulation, external wall insulation).
• Window area + glazing type (single, double, triple).
• Floor construction + insulation (suspended timber, solid concrete, screed-on-insulation).
• Roof + loft insulation depth.
• Air-tightness indication (gaps around windows, doors, unsealed loft hatch).

From this they calculate room-level heat-loss in watts. Sum across rooms gives the whole-house peak demand at the local design temperature. Typical 3-bed UK semi: 8–14 kW peak demand. Better insulated → smaller heat pump needed.

Ask for the room-by-room numbers in writing. If you get 2 quotes and the heat-loss figures differ by more than 20%, that’s a flag — one installer is sizing conservatively (which costs you more on the heat pump) or another is sizing tight (which risks comfort problems).

Step 2: Existing-system assessment

The installer checks what’s already in the property:

• Radiators: measured and sized against the room-level heat-loss numbers at the proposed flow temperature (45–55°C typical). Rooms where the radiator is too small get flagged for upgrade.
• Pipework: the existing primary pipework (between boiler and radiators) is inspected for sizing. Microbore (10mm) systems often need upgrading to 15mm for adequate flow with a heat pump.
• Hot water cylinder: if you have one, its size and coil suitability are checked. Most gas- boiler-era cylinders need replacing for heat-pump operation; the heat pump heats water more slowly than a gas boiler, so the cylinder needs to be sized to smooth that.
• Boiler / fuel source:they note what they’ll be removing (combi gas, system gas, oil, LPG, electric, storage) — relevant for cylinder decisions and grant eligibility.

Step 3: Outdoor unit siting

The installer walks the property exterior to identify outdoor unit locations. The key constraints are:

• Permitted-development criteria. Most UK homes can install a heat-pump unit without planning permission IF: the unit is at least 1m from the property boundary, no more than 1m³ in volume, not on a principal elevation facing a road, and not within a conservation area or listed building.
• MCS 020 noise.The unit’s sound pressure at the neighbour boundary, calculated using the manufacturer’s published sound power + distance + screening, must be ≤42 dB(A). Most 5–10 kW units satisfy this at typical garden distances; tight back gardens may need screening.
• Refrigerant pipe distance. Shorter is better for efficiency + lower install cost. Most installers want the unit within 10m of the indoor plant location.
• Access for service + future replacement. The installer needs 0.5–1m clearance around the unit for service. Don’t plan to wall the unit in.

Step 4: Electrical assessment

Heat pumps draw 1.5–4 kW continuously at peak (depending on capacity), with start-up spikes of 6–8 kW briefly. The installer checks:

• Consumer unit capacity. Most UK properties have 60–100A supplies; a heat pump usually adds a dedicated 32A or 40A breaker. Properties with near-capacity consumer units may need an upgrade.
• Single-phase vs three-phase. Most UK homes are single-phase. A handful of larger or older rural properties have three-phase, which makes bigger heat pumps easier. The installer notes which you have.
• Earthing arrangement. Older homes sometimes have TT earthing (earth rod) instead of TN-S or TN-C-S (network earthing). Heat-pump installs generally prefer TN earthing; TT-earthed homes may need earth-rod work.

Step 5: Cylinder + plant location

Where the hot water cylinder + buffer vessel + controls will live. Three typical options:

• Airing cupboard. Standard for most UK homes — the old hot-water cylinder location. Usually fits a 200–250 L heat-pump cylinder with controls.
• Utility / garage. If the airing cupboard is too small or you want it back as storage, some installers can locate the cylinder in a utility room or attached garage.
• Loft. Less common but possible. Loft locations need accessible servicing routes + insulation + freeze protection.

Step 6: The quote conversation

After the survey work, the installer typically sits down with you to discuss what they’ve found. Topics covered:

• Indicative heat-pump capacity + brand they’d recommend.
• Which radiators (if any) need upgrading + why.
• Cylinder choice + location.
• Outdoor unit siting + MCS 020 confirmation.
• Indicative pre-grant + net-of-grant cost ranges.
• BUS application timing + paperwork.
• Install timeline if you proceed.

Don’t commit on the day. You should receive a written quote within 1–2 weeks for considered review.

What to prepare before the visit

1. EPC certificate.Download from gov.uk/find-energy-certificate. Check expiry — fresh one needed if >10 years old.
2. Last 12 months of gas + electricity bills. Helps the installer calibrate the heat-loss assumption against actual usage.
3. Loft access.Confirm you can open the loft hatch + that there’s safe access. Some installers bring their own ladder; most prefer your existing access.
4. Consumer unit access. Usually in a meter cupboard or under the stairs. Clear anything in front of it.
5. Outdoor unit location idea. Walk your garden / side return + identify candidate spots for the outdoor unit. The installer will refine, but knowing your preference saves time.
6. Questions list. Prepare 4–6 questions on what you care about — efficiency, brand preference, warranty, install timeline, finance options.

What to look out for during the visit

• Does the installer measure every heated room? A proper BS EN 12831 calc requires it. If they skip rooms, the heat-loss number is approximate at best.
• Do they ask about your usage pattern? Heat-pump sizing depends on how you actually use your home — out at work all day vs WFH, large family vs single occupant. A good installer asks; a bad one assumes.
• Do they walk you through the MCS 020 numbers? Outdoor siting + noise is a frequent quote blocker. The installer should explain the calculation.
• Are they pushy on signing the same day? Good installers issue written quotes for considered review. High-pressure tactics aren’t standard and are a flag.

After the visit

Expect the written quote within 1–2 weeks. It should include:

• Room-by-room heat-loss calculation as an appendix.
• Specific heat-pump make + model with MCS product ref.
• Gross install cost + £7,500 BUS deduction + net amount.
• Radiator/pipework/cylinder/electrical line items.
• Warranty terms + extended warranty options.
• Install timeline + payment schedule.
• Finance options if relevant.

Compare 2–3 quotes side by side. If the heat-loss figures differ by more than 20%, query the discrepancy with the installers directly. Heat-pump quoting variance is mostly about sizing assumptions, not unit pricing.

The pre-survey shortcut

Before booking any installer visit, run the free pre-survey at propertoasty.com/check:

• BUS eligibility confirmed (or flagged for clearance).
• Property heat-loss indication (informs which sizing range to expect).
• Roof + outdoor space check for siting.
• Installer-ready report to send with quote requests.

Doing this before the site visit saves the first 30 minutes of the installer’s time (and yours) on eligibility / orientation questions — they can dive straight to the heat-loss survey.

The summary

An MCS heat-pump site visit is a 60–120 minute survey that produces a binding-quote-grade specification for your specific property. The five things they check — heat-loss room by room, existing system, outdoor siting, electrical supply, cylinder location — feed a quote you receive within 1–2 weeks. Prepare your EPC, gas bills, and a candidate outdoor location; ask for the heat-loss calculation in writing; compare 2–3 quotes before committing. Variance between quotes is mostly about sizing assumptions — query 20%+ gaps directly.

Related reading

• MCS 020 noise rules explained — the most common reason a site visit produces a “planning permission needed” flag rather than permitted development.
• BUS grant application walkthrough — the grant paperwork side that follows from the site visit’s quote.
• ASHP vs GSHP comparison — if the site visit flags issues with MCS 020 or outdoor siting, GSHP becomes the natural alternative.