Comparing air-source heat-pump quotes

Make the design basis comparable

Start by placing each quotation against the same description of the property and the work required. A lower price may reflect a different building case, fewer heated rooms, a retained cylinder or less making good.

Record for every proposal:

• heated floor area and rooms included
• intended room temperatures
• external design temperature
• existing or proposed insulation and glazing
• proposed air-to-water ASHP arrangement
• hot-water occupancy and draw-off assumptions
• existing equipment to be removed or retained
• electrical, groundwork and building work included

If one design assumes future insulation, identify the measure and when it will be completed. Do not compare that heat load with another quotation based on the current building without marking the difference.

Use a copy of the floor plan and photographs to check that each survey covered the same extensions, roof spaces, unheated boundaries and unusual construction. The home heat-pump installation guide explains the complete design and work sequence.

Heat-loss calculation

Ask for the room-by-room heat-load report rather than only the final building kW figure. Under the applicable MCS design standard, the calculation uses BS EN 12831-1:2017 with the applicable MCS method.

Compare:

• room dimensions and element areas
• construction and insulation assumptions
• U-values
• ventilation and infiltration
• design room temperatures
• local external design condition
• treatment of party walls, floors, roof spaces and unheated rooms

Differences may be legitimate, but the installer should be able to explain them from evidence. A recent boiler size, EPC demand or watts-per-square-metre allowance is not an equivalent calculation.

Look at the room results as well as the building total. They determine the radiator or underfloor-heating requirement and may reveal a copied or omitted room. The heat-loss survey entry gives a detailed check of survey inputs.

Heat-pump selection at the design condition

Put the exact manufacturer and model into the comparison. A family name without the model code can cover units with different outputs, refrigerants, electrical requirements and controls.

For each unit, ask for:

• declared output at the design outdoor temperature
• flow and return temperatures used for that output
• building heat load being served
• any allowance for defrost
• any assumed supplementary electric heat
• minimum output or modulation evidence
• maximum electrical input used for the supply assessment
• sound-power data used for siting

The number in a model name is not a constant output across all conditions. Product selection should use the applicable manufacturer map or declared data.

An apparent capacity margin may simply reflect the available product steps. Ask the designer to show the next smaller unit and why it was rejected. Also ask how the selected unit will behave during mild weather, when the building needs much less heat.

Where the quotation is hybrid, the share and control priority of each heat source must be stated. Do not compare it as though it were the same design as a heat-pump-only proposal.

Flow temperature and emitter schedule

The design flow temperature affects heat-pump capacity, predicted performance and the emitter size required in every room. Put it near the top of the comparison.

Each quote should include an emitter schedule showing:

• room heat load
• existing emitter and its condition
• proposed emitter changes
• corrected output at the design water and room temperatures
• assumptions for underfloor heating or fan-assisted emitters
• valves and controls

An installer may reasonably retain more existing radiators if the calculation shows adequate output. Another may propose larger emitters to reduce the flow temperature. These are not the same technical offer, even if both keep the home warm at the design condition.

Check that quoted radiator outputs have been corrected from the manufacturer’s declaration condition. A standard catalogue output cannot normally be copied directly into a low-temperature design.

Where a proposal uses a flow temperature above 55°C, the applicable MCS design standard calls for an alternative at 55°C or below with an explanation of the energy and efficiency differences. The requirement is tied to the standard and should not be turned into a claim that every system must operate below one fixed temperature.

Pipework and hydraulic arrangement

Ask for a schematic. Component names are less useful without showing how the water moves through them.

Compare:

• primary pipe sizes and routes
• required design flow
• calculated circuit resistance
• available pump head
• retained microbore or other small-bore circuits
• system and additional pumps
• minimum-flow path
• active water volume
• buffer, volumiser or low-loss header
• bypasses, zone valves and TRVs (thermostatic radiator valves)
• water treatment and insulation

A buffer vessel may be used for hydraulic separation, minimum water volume, defrost support or another defined purpose. Ask the designer to state that purpose and show the expected temperatures and flows on each side.

Likewise, microbore should be assessed from actual bore, route and resistance. A blanket promise to retain it or replace it is not a calculation.

DHW (domestic hot water) cylinder and controls

Compare the complete DHW proposal:

• exact cylinder model and volume
• vented or unvented arrangement
• heat-exchanger performance
• assumed draw-off pattern
• recovery method and time basis
• standing loss
• cold-main test for an unvented cylinder
• immersion heater
• hygiene strategy
• safety discharge route
• service and replacement access

Two cylinders of the same nominal volume can have different heat exchangers and standing losses. A coil-area figure by itself does not prove the transfer rate at the proposed water temperatures.

If an existing cylinder is retained, ask for the evidence that its heat exchanger, volume, controls and condition are suitable. If it is replaced, include cupboard changes, discharge pipework and making good in the price comparison.

Outdoor works, noise and planning

Mark the proposed unit location on a plan. Compare:

• base or wall brackets
• airflow and manufacturer clearances
• service access
• pipe and cable route
• wall penetrations and sealing
• condensate and defrost-water drainage
• vibration treatment
• impact protection
• lifting and delivery access
• visual screening
• planning responsibility

For an English permitted-development proposal, ask for the MCS 020 a) calculation and confirmation of the other current Class G conditions. A passing noise calculation is only one part of the planning route. Scotland, Wales and Northern Ireland have separate rules.

The noise document must use the selected unit and final position. A calculation for another model or a location moved during installation should be revised.

If full planning permission or an acoustic assessment is required, the quotation should state who prepares, submits and pays for it. The same applies to listed-building consent or landlord and freeholder permission.

Electrical work and DNO registration

Heat-pump electrical scope can differ substantially between quotations. Include:

• new final circuits
• consumer-unit or distribution-board work
• isolation and protective devices
• immersion and supplementary-heater supplies
• earthing and bonding work
• maximum-demand assessment
• meter-box or service-head work
• Building Regulations notification
• Electrical Installation Certificate

The DNO route is also part of the offer. Heat pumps require registration in Great Britain and some installations need approval before connection.

Ask who makes the submission, what electrical data and site demand are declared and what happens if the DNO requires a limit or network work. A provisional quote should identify which resulting costs are included.

Controls and performance estimate

List the proposed controls rather than accepting “smart controls included”. Identify:

• main heat-pump controller
• outdoor sensor
• room sensor or room influence
• weather compensation
• zones and TRVs
• DHW controller and sensor
• immersion or supplementary-heater control
• app, gateway and internet dependency
• energy and heat metering

Ask which controller has authority over each function. Third-party thermostats and zone controls can change water flow or force on/off operation, so they need to be designed as part of the system.

MCS 031 or MCS 031 a):2025, as applicable, provides the hydronic pre-sale system performance estimate. It is an estimate based on defined inputs, not a promise of the household’s future bill. Compare the assumed space-heating demand, DHW demand, flow temperature, product data and electricity price basis.

An attractive SCOP or annual-cost figure cannot compensate for different heat-loss or comfort assumptions. Put the inputs alongside the result.

Installation scope and exclusions

Use one checklist for every bidder:

• old boiler, tank and cylinder removal
• radiator and valve replacement
• primary-pipe and distribution work
• flushing and water treatment
• outdoor base and drainage
• electrical work
• asbestos and hazardous-material handling
• scaffolding, lifting or ground works
• decoration and making good
• waste removal
• temporary heating or hot water
• commissioning and return visits

Ask how hidden defects and design changes are priced. A written variation process is preferable to an open allowance that becomes clear only after the old system is removed.

Note the expected period without heating and hot water. Project duration can vary with the property and work, so compare the sequence and dependencies rather than relying on a generic number of days.

MCS, BUS and commercial protection

Confirm the MCS certification of the contracting business for the proposed technology. Check that the name on the contract, certification record, deposit payment and warranty is the same legal entity.

If BUS (Boiler Upgrade Scheme) is used, check the live eligibility and current process. The installer applies and the property owner confirms consent directly with Ofgem. The quote and invoice should show how the grant is deducted.

Record separately:

• deposit and stage payments
• cancellation rights
• consumer-code membership
• deposit or payment protection
• insurance-backed workmanship cover
• heat-pump product warranty
• cylinder and other component warranties
• labour included in warranty repairs
• annual service requirements
• grant failure or expiry terms
• ownership of removed equipment

A long product warranty may be conditional on registration, servicing, water treatment or approved labour. Ask for those conditions before signing.

Commissioning and handover

Make the handover pack a contractual deliverable. It should include:

• final heat-loss report
• emitter schedule
• hydraulic schematic and design data
• exact equipment schedule
• applicable MCS 031 estimate
• MCS certificate
• DNO response
• planning and noise documents
• electrical records
• commissioning results
• final control settings
• owner accounts and administrator access
• warranties, user instructions and service requirements

Ask whether a cold-weather return visit or remote review is included. Some controls cannot be properly assessed during mild weather.

The owner demonstration should cover normal heating, DHW, a temporary temperature change, holiday or absence mode, manual hot-water boost, fault reporting and the safe isolation procedure. Installer menus and safety limits need not be handed over as routine owner controls.

Resolve differences before choosing

Create a written question list for each installer. Ask them to revise the quotation or design document where the answer changes the scope. Do not rely on an unrecorded assurance that a missing radiator, cable route or planning check will be dealt with later.

A useful final comparison has four columns:

1. the common requirement
2. each installer’s design or included work
3. evidence supplied
4. unresolved exclusion or decision

The lowest total may still be the right choice. The comparison simply establishes what that total buys and whether the design can be checked before installation.