Compare air conditioning quotes only after making their scopes equivalent. Each proposal should identify models and capacities, pipe and drain routes, outdoor-unit location, electrics, access, VAT, commissioning, warranty and exclusions. Verify required F-gas credentials and ask how the system was sized. The lowest total can be poor value if it omits electrical work, access equipment, condensate management or making good, while the highest price is not proof of better design.
Make them price the same job
Describe the rooms, the hours you actually use them, whether you want heating as well as cooling, what noise you will not accept, and what the outside of the house can take. Say if the home is leasehold, listed, in a conservation area, or sitting on a consumer unit you already know is full.
Ask each firm to look at the same preferred wall and the same fallback. If one quote puts the condenser on the ground and another puts it on the roof, you are not comparing installers. You are comparing two different buildings works, two different risks, and often two different planning questions.
Photos help, and they do not replace the visit. Send the indoor wall, the outdoor elevation and the consumer unit so the first number is about your house. Then still expect the survey to change the pipe length, the drain and the electrical allowance. A price given from a floor plan alone should stay marked as provisional.
Read the model codes before the total
The quote should name the manufacturer and the full indoor and outdoor model references, not a range or a brochure photo. Capacity, indoor sound at a fan speed you would actually use at night, and the efficiency figures should belong to that model, not to a different size in the same family.
Ask why that capacity, in words. Floor area is a weak guide in Britain. A south-facing room under a roof, a glazed extension, or a shop with the door open is not the same load as a shaded box room of the same square metres. If the only reasoning is a watts-per-square-metre rule, ask what was left out.
Two quotes can differ by hundreds of pounds because one specified a quieter indoor unit and a smaller outdoor, and the other specified the cheapest pair that meets a nominal kilowatt. That is a real choice. It is not visible if both documents only say "2.5 kW wall unit".
- Exact indoor and outdoor model codes.
- Room-by-room sizing rationale, not floor area alone.
- Who supplies the electrical circuit and the isolator.
- How the outdoor unit is isolated from the wall.
- What commissioning record you get on the day.
A cheaper total often omitted a line
Put the quotes side by side and tick the same list: equipment, included pipe length, extra-metre rate, trunking, condensate route, pump if any, outdoor bracket or ground stand, isolator, new circuit or board work, scaffold or access, core drilling, making good, waste removal, commissioning, VAT. The gap between two totals is often one of those lines, not a kinder installer.
A common pattern is a low figure that assumes a back-to-back hole and an existing spare way in the consumer unit, next to a higher figure that includes a dedicated circuit and a condensate pump because the surveyor saw the room is on an internal wall. Add the missing lines back before you decide the higher quote is expensive.
Provisional sums are fine if they are labelled. A quote that says "electrics by others" or "making good by client" can be the right shape if you have those trades. It is a bad surprise if you thought the headline was the cost to walk away with a working system.
Money, timing and the warranty that is actually on offer
Ask for a VAT-inclusive total and a short list of what would be extra. Check the deposit, the stage payments, what happens if equipment is delayed, how long the job is expected to take, and who pays for parking, permits or scaffold. There is no universal fair deposit. It should match equipment that has to be ordered, and it should be traceable.
Split the manufacturer's parts warranty from the installer's labour cover. Ask who registers the equipment, what maintenance keeps the warranty valid, whether a call-out in July is included or charged, and whether travel or a diagnostic fee applies before anyone opens the unit. A long parts warranty with no labour, and no one local who will attend, is a thinner promise than it looks on the last page.
Be wary of pressure to pay a large share in cash before a survey, of a model that changes after you have accepted, and of a price that only lasts until the end of the phone call. Keep the accepted quote, any drawings, the certificates and the payment records together.
Credentials and consents are separate from the price
Regulated work on the refrigerant circuit needs a certified company and appropriately qualified people. Ask for the company certificate and who on the day will do the F-gas tasks. An electrician can do the supply. They should not be assumed to be allowed to braze and charge the system unless those qualifications are there too. Insurance should match the job, including work at height if that is what your wall needs.
No quote removes your duty to get planning, freeholder or listed building consent where it applies. In England, Class G permitted development for an air source heat pump includes a condition that the unit is not used solely for cooling, and it does not apply to a listed building. Flats often need an application as well as a licence under the lease. A good proposal names the outdoor position and says who will check those points. It does not promise that the council has already agreed.
Decide on the job you will still like in January
Score the proposals on whether the design matches the rooms, whether the scope is complete, how much of the house gets opened up, whether you can reach the filters and the drain later, how the outdoor unit sits relative to bedrooms, and what the warranty looks like when something fails on a hot Friday. Price is one column.
Ask the remaining questions in writing. If one firm sized a bedroom at 2.5 kW and another at 3.5 kW, you want the reason, not an average. When you accept, the document you pay against should be the detailed scope, not a one-line "supply and fit".
Frequently asked questions
How many air conditioning quotes should I obtain?
Three comparable proposals are often enough to expose major differences, but quality matters more than count. Use the same brief and ask bidders to explain conflicting recommendations.
Should I choose the cheapest quote?
Only if it provides the right design and complete scope. Add omitted electrics, access, drainage, VAT and making good before comparing totals.
What deposit is reasonable?
There is no universal percentage. It should be proportionate to equipment ordered and project risk, documented in the contract and paid through a traceable method.
Can an installer guarantee planning permission?
No. The local planning authority decides applications and lawful development questions. An installer can supply drawings, specifications and noise data.
What documents should I receive after installation?
Request the final invoice, model and serial details, commissioning record, controls instructions, warranty registration, refrigerant records where applicable and electrical certification for relevant work.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.