What a quotation should contain

Two quotations for the same job frequently look nothing like each other, which makes comparing them difficult and choosing between them a matter of instinct. The standards help here, because they fix what the numbers have to be based on, so a quotation can be read against a list of what ought to be in it.

Common to both technologies

• The company's MCS certificate number, and the technology it is certified for. A company certified for solar PV is not thereby certified for heat pumps.
• Its consumer code, and its insurance-backed guarantee provider.
• An itemised price, with what is included and what is not. Scaffolding, making good, electrical upgrades and disposal of the old system are the usual omissions.
• Which equipment, by make and model, so it can be looked up on the MCS product database.
• Warranties, separated into product, workmanship and insurance-backed, with lengths.
• Deposit terms and cancellation rights.

A heat pump quotation

The room-by-room heat loss calculation. Not a summary. Every room, with areas, U-values, design temperatures and totals. This is the foundation of everything else, and if it is not offered it should be asked for.

The design flow temperature. The most consequential number in the document, and the one most often left out. It determines the running cost, and it should be a specific figure, not "low temperature".

The emitter schedule. Which radiators are being kept, which replaced, and what each delivers at the design flow temperature in the room it serves. This is where you find out whether the flow temperature is achievable or aspirational.

The heat pump's output at your design conditions. Not its headline rating. A unit sold as 8 kW may deliver 5.5 kW at −3 °C outside and 50 °C flow, and it is that figure that has to cover your heat loss, without an immersion heater making up the difference.

The SCOP at the design flow temperature. A SCOP quoted at 35 °C for a system designed at 50 is not a figure about your installation.

The hot water arrangement. Cylinder volume, coil area, storage temperature, and how the legionella cycle is provided for.

The noise assessment. Where the unit will stand, the MCS 020 calculation for the assessment positions, and the resulting figures against the 37 dB(A) limit.

Whether an alternative was offered. If the design proposes a flow temperature above 55 °C, MIS 3005-D requires a design at 55 or below to be provided alongside it, with the difference in efficiency and running cost explained. A hot design with no cool alternative has not met the standard.

A solar PV quotation

The five inputs to the estimate. Capacity in kWp, postcode zone, pitch, orientation, shade factor. All five, so the arithmetic can be repeated.

The annual output estimate, as an AC figure in kWh.

The shading assessment, where one was needed, or a statement that the horizon is clear. A shade factor of 1.00 on a roof with a chimney is a claim worth questioning.

The string layout. Which modules are on which inverter input, and whether optimisers are fitted. On a partially shaded roof this matters more than the choice of panel.

The mounting system, by name, and confirmation that it is certified with the modules being used. MCS 012 covers this, and mounting components are approved to work together as a set, not individually.

The structural check. MIS 3002 requires the roof structure to be checked by a competent person. On an older roof this is not a formality.

The network operator route. Whether the system falls under G98 or needs a G99 application, and whether any export limitation is proposed.

Self-consumption, if a battery is quoted. The MGD 003 figures, with the occupancy pattern and consumption they were derived from.

Things that should give pause

A performance figure with no working behind it. Both technologies have prescribed methods. A number that cannot be traced back to one has come from somewhere else.

Pressure to sign today. A discount that expires at the end of the visit is a sales technique, and the consumer codes take a dim view of it.

A heat pump sized to the old boiler. "You had a 24 kW boiler so you need a 16 kW heat pump" is not a calculation, and boiler sizing is exactly the guesswork the heat loss standard was written to replace.

Savings quoted without assumptions. A saving depends on fuel prices, on the flow temperature, on how the house is run. A figure with none of those attached cannot be checked.

A large deposit. Deposits are normal; deposits approaching half the contract value are not, and they should be protected.

Reluctance to provide the calculations. They exist, because the standard requires them. A contractor unwilling to share them is telling you something.

Comparing like with like

Get the same scope from each quoting company, or the comparison is between different jobs. If one includes new radiators in four rooms and another does not, they are not the same installation, and the cheaper one may become the dearer one in March.

For solar, compare kWh per kWp instead of kWh, which removes system size from the comparison and shows whether the two are estimating the same roof the same way.

For heat pumps, compare design flow temperatures. Two systems at the same price with flow temperatures of 45 and 55 are not equivalent purchases; one of them will cost noticeably more to run for the next twenty years.