Answer first

Compare heat loss, design temperatures, unit output, emitter schedule, seasonal-efficiency assumption and included work. Mark every difference as included, excluded, provisional or unknown.

Then compare who owns design and aftercare, the warranties and MCS route, payment stages, funding documentation and what happens if the property reveals an unforeseen constraint.

3 installers

Home Energy Scotland recommends seeking at least three quotes

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Itemised

Funding applications require an itemised installer quote

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One design

Equipment, emitters, hot water and controls must work as a system

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Normalise the technical assumptions

One quote may assume a different room temperature, fabric condition or flow temperature. Until those are aligned, price and efficiency comparisons are not like for like.

Request the room schedule and unit performance at design conditions. A bigger model number is not automatically a stronger design.

Build an inclusion table

List outdoor unit, cylinder, radiators, valves, pipework, electrics, controls, drainage, lifting, scaffolding, waste and making good. Add survey, MCS registration, EPC or funding documents where relevant.

If an item is provisional, ask for the pricing basis and what evidence will turn it into a fixed decision.

Check the performance calculation

The annual estimate needs heat demand, seasonal efficiency and tariff. Look for the hot-water and backup-heater assumptions.

Treat unexplained savings percentages cautiously. The best proposal shows a range and how design choices change it.

Value aftercare and accountability

Confirm who commissions the curve, balances emitters and explains controls. Ask how comfort or faults are handled after handover.

Product warranty is only one part of protection. Check workmanship cover, installer continuity, monitoring options and service availability.

What to read next

Related answers and services

Quote checklistSee the evidence a proposal should contain.Free quote guideUnderstand the route to a surveyed proposal.Installer questionsTest design, delivery and aftercare.All 60 heat-pump answersFind the next question in the FLO knowledge library.

Questions people also ask

Should both installers calculate the same heat loss?+

They should be reasonably aligned when assumptions match; large differences need explanation.

Is the longest quote always best?+

No. Clarity, correct design and accountable scope matter more than page count.

Can FLO review another quote?+

FLO can discuss the assumptions, but a property survey may be needed to verify them.

Evidence used for this answer

Figures are explained in context and links go to the independent source. Prices, tariffs, scheme rules and standards can change, so check the source again before making a financial or technical decision.