Air conditioning advice & FAQs

A single-room wall-mounted split system in a Cambridge home typically costs between £1,500 and £3,000 fully installed, including the indoor unit, outdoor condenser, refrigerant pipework and commissioning. Multi-room systems covering three or four rooms can run from £5,000 to £10,000 or more, depending on the number of indoor units and how complex the pipework run is. The main price drivers are the capacity of the unit in kilowatts, the distance between the indoor and outdoor units, and how much disruption is involved in routing the pipework through walls or ceilings. The most reliable way to get an accurate figure is a site survey of your property before you commit.

Since 29 May 2025, a reverse-cycle air conditioning system (an air-to-air heat pump that heats as well as cools) can usually be installed at a house in England under permitted development rights, so no planning application is needed as long as it meets the conditions. These include limits on the size and number of outdoor units and meeting the MCS 020(a) noise standard. A system used only for cooling is not covered by these rights and may need planning permission. Listed buildings, conservation areas and flats have extra restrictions, and Cambridge has many listed properties and conservation areas, so check with the local planning authority or ask your installer to confirm before work starts.

A well-maintained domestic split system typically lasts between 15 and 20 years, though the compressor in the outdoor unit is usually the first component to show wear after 12 to 15 years of regular use. Annual servicing, keeping the filters clean, and ensuring the outdoor unit has clear airflow around it all extend the working life considerably. Systems that are undersized for the room they cool tend to run harder and wear out faster, which is why correct sizing at the design stage matters.

A split system has a fixed indoor unit connected by refrigerant pipework to a condenser outside the building, which means no hot air is vented back into the room and efficiency is much higher. Portable air conditioners are self-contained units that sit inside the room and exhaust hot air through a flexible hose pushed out of a window, but this also draws warm air back in around the hose, significantly reducing their effectiveness. For a Cambridge home where you want reliable cooling each summer, a properly installed split system will use less electricity and cool the space far more effectively than a portable unit of the same stated output. The upfront cost of a split system is higher, but the running costs and performance are genuinely better.

Yes. Most modern split systems sold in the UK are reverse-cycle heat pumps, which means they can heat a room in winter as well as cool it in summer. Running a heat pump in heating mode is typically two to three times more efficient than a direct electric heater, because it moves heat from outside air into the room rather than generating it electrically. This makes a well-chosen system genuinely useful all year round in Cambridge, where winters are cold enough to justify supplementary heating in poorly insulated rooms.

Any engineer who handles refrigerant in a domestic air conditioning system in the UK must hold a valid F-Gas qualification, as required under UK F-Gas regulations. It is illegal for an unqualified person to purchase or handle refrigerant, and work carried out without proper certification can invalidate any manufacturer's coverage on the equipment. When choosing an installer, always ask to see evidence that their engineers hold the relevant F-Gas category certificate.

An annual service is the minimum recommended for a domestic system, ideally carried out in spring before the cooling season begins. A typical service covers cleaning the indoor unit filters, checking refrigerant pressure, inspecting electrical connections, cleaning the outdoor condenser coil and testing the unit operates correctly in both heating and cooling modes. Skipping annual servicing is the single most common reason for premature compressor failure, which is also the most expensive repair on any system.

If a system is under ten years old and the repair cost is less than half the price of a new installation, repair is usually the better choice. Once a system is over 12 to 15 years old, uses an older refrigerant such as R22 (which is now banned for use in servicing), or has suffered compressor failure, replacement is normally more cost-effective when you factor in improved efficiency and lower running costs. A useful rule of thumb is that if the repair quote exceeds 50% of a new installed system price, it is worth getting a replacement quote alongside it to compare properly.

First, check that the indoor unit is receiving power and that no circuit breaker has tripped in your consumer unit. Check whether the unit is displaying an error code on its display or remote control, as most modern systems show a fault code that an engineer can look up before attending. If the outdoor unit is running but the room is not cooling, a restricted or dirty filter on the indoor unit is a common cause and can be cleaned by removing the front panel and rinsing the filter. If none of these steps resolve the issue, call an F-Gas qualified engineer rather than attempting to interfere with the refrigerant circuit yourself.

Air conditioning does reduce indoor humidity as part of the cooling process, and in a well-sealed room this can occasionally make the air feel drier, particularly if you are running the system for long periods. Most modern systems include humidity sensors and allow you to set a target humidity level to prevent over-drying. Regular filter cleaning is important for air quality, as a dirty filter can circulate dust and, in poorly maintained systems, mould spores. Some systems also include ionisation or UV filters, which can be useful for allergy sufferers.

Always verify that the company's engineers hold current F-Gas certification before they touch your system, as this is a legal requirement and a basic indicator of professional practice. Ask for a written, itemised quotation that specifies the make and model of equipment, the refrigerant type, the length of the installation run and what electrical work is included. Check whether the company is a member of a recognised trade body such as REFCOM or the Institute of Refrigeration, and ask for references from local residential installations. A trustworthy installer will carry out a site survey before quoting rather than pricing over the phone without seeing your property.

To work out the running cost, check the unit's rated electrical input in kilowatts (shown on its specification sheet), multiply it by the hours you run it, then multiply by the unit rate on your electricity bill. A small single-room system in cooling mode uses far less than its cooling output suggests, because it moves heat rather than generating it. Heat pump mode in winter is more efficient still, typically delivering around 3kW of heat for every 1kW of electricity consumed. Actual running costs vary with the insulation of your home, the outdoor temperature, and how well the system has been sized for the space it is conditioning.