Working out how to heat a garden room is what turns a summer retreat into a space you can actually use in January. A garden room that is freezing from November to March is a garden room you stop walking down to, so the heating decision matters as much as the build itself. The good news is that a well-insulated room needs surprisingly little heat, and the running cost can be modest if you choose the right system.
This guide compares nine ways to heat a garden room on cost, warmth and practicality, then sets out which suit most UK homeowners and roughly what they cost to run.
Why insulation comes before heating
Before you choose a heater, get the insulation right, because it changes everything that follows. A room with well-insulated walls, floor and roof, decent glazing and no draughts holds warmth so well that a small heater keeps it comfortable. The same heater in a thin, single-glazed shell will run flat out and still feel cold, costing you far more for a worse result.
If your garden room is already built and underperforming, improving loft-style roof insulation, sealing gaps around doors and adding heavier curtains often does more for winter comfort than upgrading the heater. Heat you never lose is heat you never pay to replace.
The heating options for a garden room
There are nine realistic ways to heat a garden room, each with a clear trade-off:
- Electric panel radiators: wall-mounted, thermostatic, tidy. A reliable default for a home office.
- Oil-filled radiators: cheap to buy and portable, but bulky and slow to respond.
- Infrared heating panels: warm people and surfaces directly, efficient and quick to feel, ideal for single rooms.
- Fan heaters: cheap and instant, but noisy, drying and expensive to run for long spells.
- Air conditioning (air-to-air heat pump): heats in winter and cools in summer, the most efficient electric option over a year.
- Electric underfloor heating: invisible, comfortable background warmth, best fitted during the build.
- Wet underfloor heating from the house: possible if the room is close to the main system, but costly and disruptive to run out.
- Wood burners: cosy and characterful, but need a flue, clearances and careful safety, and are overkill for a small room.
- Portable gas heaters: avoid. They release moisture and combustion products into a small sealed space and bring real safety concerns.
The best options for most garden rooms
For the majority of UK garden rooms, three options do the heavy lifting.
Infrared panels are hard to beat for a home office or studio. They warm your body and the surfaces around you rather than heating the whole air volume, so you feel the benefit quickly and can run them only when you are in the room. They are slim, silent, mount on a wall or ceiling and are efficient because every unit of electricity becomes usable warmth.
Air conditioning, in the form of an air-to-air heat pump, is the standout if you want one system for the whole year. It heats efficiently in winter and cools in summer, and because it moves heat rather than simply making it, it delivers more warmth per unit of electricity than a plain radiator. It costs more to install and needs an outdoor unit, but over years of use it is often the cheapest to run.
Electric panel radiators are the dependable middle ground: lower upfront cost than air conditioning, tidy and thermostatically controlled, and perfectly adequate in a well-insulated room. If you want simple, proven and inexpensive to fit, this is it.
What it costs to run a garden room heater
Running cost comes down to three things: the power of the heater, how long you run it, and the price of electricity. Under the Ofgem energy price cap for July to September 2026, electricity is capped at 26.11p per kilowatt-hour plus a daily standing charge, though the exact rate varies by region and tariff.
A simple worked example shows how manageable this can be. A 1kW heater run for four hours a day uses 4kWh, which at the capped rate is roughly £1.04 a day, or about £31 over a 30-day month if used every day. In a well-insulated room a thermostat means the heater cycles off once it is warm, so real usage is usually well below the maximum. Infrared and air conditioning tend to beat a plain resistive heater in practice because you heat only when and where you need it. You can check the current unit rates on the official Ofgem energy price cap page before you estimate your own costs.
Electrics and safety
Almost all of these options are electric, which means the supply to the garden room matters. Running a new circuit out to an outbuilding is notifiable electrical work under Part P of the Building Regulations, so it must be installed and certified by a registered electrician rather than improvised with an extension lead.
- Size the supply properly: a garden room running heating, lighting and office equipment needs an adequately rated armoured cable and its own consumer unit, not a socket borrowed from the house.
- Fix heaters, do not trail cables: wall-mounted panels and radiators on their own circuit are safer and tidier than portable units on leads.
- Keep gas out: portable gas heaters in a small, sealed, insulated room are a genuine hazard and should not be used.
Which heating should you choose?
Match the system to how you use the room:
- For a home office used in bursts, infrared panels give quick, targeted warmth with low waste.
- For year-round comfort and hot summers, air conditioning that heats and cools is the best single investment.
- For a simple, low-cost fit, thermostatic electric panel radiators are dependable and cheap to install.
- For invisible background warmth, electric underfloor heating is lovely, but plan it into the build rather than retrofitting.
Whatever you pick, spend on insulation first and the heater second. A tight, well-sealed garden room with a modest heater will be warmer, cheaper and more pleasant than a draughty one with the biggest heater you can buy.
Frequently asked questions
What is the cheapest way to heat a garden room?
Over a full year, an air-to-air heat pump (air conditioning) is usually the cheapest to run because it delivers more heat per unit of electricity than a plain radiator. For lower upfront cost, infrared panels are efficient and cheap to fit. The single biggest saving, though, comes from good insulation, which cuts how much heating you need in the first place.
Do I need planning permission to heat a garden room?
Heating itself does not need planning permission, but the electrical supply must comply with the Building Regulations. Running a new circuit to an outbuilding is notifiable under Part P and must be carried out and certified by a registered electrician. If the garden room is used for sleeping or has extensive services, additional building regulation requirements can apply.
Are infrared panels good for a garden room?
Yes. Infrared panels heat people and surfaces directly rather than warming the whole air volume, so you feel warm quickly and can run them only when the room is in use. They are slim, silent and efficient, which makes them well suited to a home office or studio where you want targeted, on-demand warmth.
Can I use a portable gas heater in a garden room?
No. Portable gas heaters release moisture and combustion products into a small, sealed and insulated space, which causes condensation and poses a real safety risk. Stick to fixed electric heating on a properly installed circuit, and keep any gas appliance out of a garden room entirely.
How much does it cost to run a garden room heater?
It depends on the heater’s power and your usage. As a guide, a 1kW heater run for four hours a day uses 4kWh, which at the capped rate of around 26p per unit is roughly £1 a day. A thermostat in a well-insulated room means the heater cycles off once warm, so real costs are usually lower than the maximum figure suggests.
Planning a garden room you can use all year? Read more expert guides on insulation, costs and build quality on the Best Garden Room homepage.