Conservatory air conditioning: the best way to cool and heat one

Air conditioning is usually the only thing that reliably makes a conservatory usable in a heatwave, and the best choice for most homes is a wall-mounted reverse-cycle split. It cools the room properly in summer, holds a set temperature, and because it is an air-to-air heat pump it heats the same room in winter, when a glass box is otherwise freezing. Expect to pay roughly £1,500 to £3,500 supplied and fitted. A portable unit will get you through a single hot week, but it is a stopgap, not a fix, for the hottest room in the house.

Blinds, fans and roof vents all have their place, but none of them lowers the temperature of a conservatory the way air conditioning does. A conservatory overheats because of solar gain through all that glass, and the only way to be comfortable is to actively remove that heat. This guide explains why conservatories get so hot, walks through the best options, and covers the two things that trip people up: sizing (a conservatory needs more cooling than a normal room) and where the units actually go when the walls are made of glass.

Conservatory air conditioning options at a glance

For most people the real decision is a fixed split versus a portable, and being honest about that saves a disappointing summer. A fixed split cools the whole room to a temperature you set and costs pennies more per hour to run than the cheap alternatives that do not actually work. A portable helps a little in one part of the room and vents warm air back in through the window it needs for its hose.

Why does a conservatory get so hot?

A conservatory overheats because of solar gain. Sunlight passes straight through the glass as shortwave radiation, is absorbed by the floor, furniture and air, and then cannot escape back out through the glass as quickly as it came in. That is the greenhouse effect, and it works on your conservatory exactly as it works on a greenhouse. On a warm July afternoon the inside of a conservatory can reach 35°C or higher.

The roof is the worst offender. It is the largest surface facing the sun, so it collects the most heat, and older polycarbonate or plain glazing with no solar-control coating lets a room heat up fast even on a moderate day. A south or west-facing conservatory gets the strongest, longest exposure, which is why orientation matters so much.

The same glass that traps heat in summer is a poor insulator in winter. Heat pours out through the glazing far faster than it would through an insulated cavity wall, so the conservatory that is unbearable in July is often too cold to use from October onwards. That double problem, too hot then too cold, is exactly why a unit that both cools and heats makes so much sense here.

Why air conditioning beats blinds and fans

Passive fixes take the edge off, but they do not solve the problem, and it helps to know why before you spend money on them.

Blinds sit a few centimetres away from the glass, so the sunlight still passes through and the heat is still trapped inside, now behind the blind. They cut glare and soften the worst of it, but the room keeps warming. Solar-control window film does better because it works at the glass itself, and can cut a lot of incoming heat, but it cannot remove heat that is already in the room or hold a comfortable temperature. Roof vents and open doors rely on the outside air being cooler than the inside, which on the hottest, stillest days it often is not, so ventilation alone frequently fails when you need it most.

A fan does not cool a room at all. It moves air, which helps sweat evaporate off your skin and feels cooler up to about 35°C, but the room stays exactly as warm. Inside a solar-loaded conservatory that can tip past 35°C, a fan stops helping.

Air conditioning is different in kind, not degree. It uses a refrigerant circuit to actively pull heat out of the room and move it outside, then holds the temperature you set, and dries the air as it goes, which also cuts the condensation conservatories are prone to. It is the only option on this list that genuinely makes a glass room comfortable on the worst days. For the wider picture on staying cool, see our guide to keeping your house cool.

A wall-mounted split system is usually the better option if you use the room a lot. It is quieter and much more effective than a portable.

The best air conditioning for a conservatory

There are four sensible routes, plus the portable stopgap. The right one depends on how you use the room and, crucially, what wall and outdoor space you have.

Wall-mounted split (reverse-cycle). One indoor unit on the wall, one outdoor condenser. This is the standard recommendation and the best answer for most single conservatories: quiet, efficient, and because it is reverse-cycle it heats the room in winter as well as cooling it in summer. An air-to-air heat pump like this delivers roughly three to five units of heating or cooling for every unit of electricity, so running a glass room year-round stays affordable. Best for: most conservatories.

Multi-split. Several indoor units run from a single outdoor condenser. This is the one to consider if you want to cool the conservatory and neighbouring rooms, such as an open-plan kitchen-diner, without bolting a separate outdoor box on the wall for each. It also neatly solves the problem of having only one good spot outside. Best for: cooling the conservatory plus adjoining rooms. Browse multi-split systems to see the format.

Floor-standing (console) split. A split where the indoor unit sits low, under the windows or on a dwarf wall, instead of high on a wall. Because a conservatory is mostly glass, there is often nowhere to mount a normal wall unit, and a console unit is the natural fit. It still cools and heats like any other split. Best for: conservatories with little or no high solid wall. See floor-standing units.

Self-contained unit with no outdoor part. If there is genuinely nowhere to put an outdoor condenser, a monobloc-style unit that vents through two cored holes in an outside wall, with no separate outdoor box, can be the answer. It is less common and a little less efficient, but it removes the siting problem. We cover this fully in air conditioning without an outdoor unit.

Portable. Cheap, instant and no installation, which is why it is the heatwave panic-buy. But it is less powerful, noisier, takes up floor space, and needs a window cracked open for its exhaust hose, which lets warm air straight back in. It is the least efficient option and never the long-term answer for the hottest room in the house. Fine to survive one summer; see portable air conditioners if that is where you are. For a full comparison of the types, read how to choose an air conditioning system.

Sizing: a conservatory needs more cooling than a normal room

This is the mistake that ruins conservatory installations. All that glass means far more heat gets in, so a conservatory needs more cooling capacity per square metre than an ordinary room of the same size. Undersize it and even a good unit will run flat out and never quite win.

As a rough guide, a normal room is sized at around 150 to 220 watts of cooling per square metre. A sun-exposed or south-facing conservatory is commonly sized nearer 300 watts per square metre, which is about 20 to 30% more. So a 12 m² conservatory that might take a 2.5kW unit as a bedroom could need something closer to 3.5kW as a conservatory. A glass roof pushes you up another notch.

These are starting points, not a specification. The real figure depends on orientation, the roof type, the glazing spec and any shading, so the sizing is best confirmed by an installer's survey. For the full method and a room-by-room breakdown, use our guide to what size air conditioning you need. The one rule to remember: size for the glass, not just the floor area.

Where the units go: the installation realities

Two practical questions decide whether a conservatory install is straightforward or fiddly.

The indoor unit. A conservatory is mostly glazing, so wall space is scarce. If you have a solid gable end or a section of house wall, a wall unit mounts high on it for even air circulation. If not, a floor-standing console unit that sits on the dwarf wall or under the windows is usually the better fit. A good installer will work out the best position on a site visit; do not assume there is a spot until they have looked.

The outdoor condenser. A split needs its outdoor unit on an external wall or on the ground nearby, positioned for airflow and, importantly, sited to keep noise away from neighbours' windows. On many homes the house wall next to the conservatory is ideal. Where there is no good spot, a multi-split shared with other rooms, or a self-contained no-outdoor-unit system, gets round it. The pipework between indoor and outdoor units is slim and most installs are done in a day or two.

Any split contains a refrigerant circuit, so by law it must be fitted by an F-Gas certified engineer, and the electrical connection is notifiable work. That is not a DIY job. The simplest route is to compare quotes from local F-Gas registered installers who will survey the room and handle the lot.

What conservatory air conditioning costs

A single wall-mounted split, supplied and fitted in a conservatory, typically costs between £1,500 and £3,500, with a standard installation often landing around £1,750 to £2,000. Larger or higher-capacity units, premium brands or an awkward installation can take it to £4,500 or more. A multi-split covering the conservatory and other rooms costs more, scaling with the number of indoor units. A portable, by contrast, is £300 to £700 to buy with no installation.

Running costs are lower than most people fear, because a reverse-cycle split is efficient. Using the Ofgem price cap for 1 July to 30 September 2026 of 26.11p per kWh, a split rated around 3.5kW cooling that draws roughly 1kW of electricity at moderate load costs about 1 kW multiplied by 26.11p, so around 26p an hour, or roughly £1.30 for a five-hour hot afternoon. Once the room is at temperature the unit modulates down, so in practice it usually costs less. From 1 October 2026, VAT on domestic electricity is cut from 5% to 0%, which will trim these figures slightly. Redo the sum with your own unit's power draw for a personal figure.

Prices and rates correct as of July 2026. The energy price cap changes quarterly (the next cap is expected around 26 August 2026), so check the current rate before budgeting.

For the full breakdown of what moves the price up and down, see our guide to home air conditioning costs.

Planning permission and grants

For a conservatory, the planning rules give you a reason to choose reverse-cycle anyway. A reverse-cycle unit, which heats as well as cools, can qualify as permitted development in England (under rules in force since 29 May 2025) if it meets the conditions. A cooling-only unit cannot, because the rules require it not to be used solely for cooling, so it generally needs full planning permission.

The main conditions are that each outdoor unit is no larger than 1.5 m³, with up to two units on a detached house or one on a semi, terrace or flat, and that noise stays within 37 dB(A) measured one metre from a neighbour's habitable-room window. Flats, listed buildings and conservation areas are treated more strictly, and the householder planning fee from 1 April 2026 is £548. Scotland, Wales and Northern Ireland differ, so always check with your local planning authority. Our full guide to planning permission for air conditioning has the detail.

On grants, be realistic. A £2,500 air-to-air heat pump grant exists for England and Wales, but it only applies to reverse-cycle units fitted by an MCS-certified installer to replace an existing fossil-fuel or electric heating system, one per property. Adding cooling to a conservatory while you keep your gas boiler will not usually qualify, and portables never do. It is a real scheme, not free air con, so check GOV.UK and Ofgem for current eligibility before you count on it. Permanently fixed, qualifying air-to-air heat pumps also carry 0% VAT until 31 March 2027.