Start with insulation, not the heater

Before you spend a penny on a heater, it is worth being honest about how well your cabin is insulated. A well-insulated garden room with a 100mm insulated floor, walls and roof, plus double-glazed doors and windows, can often be kept comfortable with a modest 1kW heater. The same building with a single-skin timber shell and no floor insulation will laugh at a 2kW heater and still leave you in a coat. Insulation is the cheapest heat source you will ever buy: every improvement slows the rate at which warmth escapes, so your heater runs less often and for shorter periods.

Think about air tightness too. Draughts around doors, gaps at the wall-to-floor junction and unsealed cable entries can strip heat out of a cabin faster than poor insulation. A tube of sealant and a decent draught excluder cost very little and often make more difference than upgrading the heater.

Electric heating: simple, cheap to install, costly to run

Electric heaters are the default choice for most UK garden cabins because they need almost no installation work. If your cabin already has a supply from the house, you can plug in a heater the same day.

• Panel convection heaters — around 1kW to 2kW, quiet, slim, good for background warmth in a well-insulated room used for a few hours at a time.
• Oil-filled radiators — slower to warm up but they hold heat after switching off, which suits occasional evening use.
• Infrared panels — they warm people and surfaces rather than the air, so they feel effective almost instantly. Ideal for a workshop or a cabin where you sit in one spot. Less useful for heating the whole room evenly.
• Fan heaters — quick, noisy, best as a short-term boost rather than a permanent solution.

The catch is running cost. Electricity is roughly three to four times the price of gas per unit of heat, so a 2kW heater running four hours a day adds up quickly. Electric heating makes most sense in a small, well-insulated cabin used for short sessions. If you plan to work in there all day, every day, expect the meter to spin.

Wood burners: charm and real heat, with practical strings

A small wood-burning stove turns a garden cabin into somewhere genuinely special. A 4kW to 5kW stove will heat a typical 12 to 16 square metre cabin comfortably, and there is nothing quite like the radiant warmth of a real fire on a cold afternoon. Running costs can be low if you have access to seasoned logs, and the stove doubles as a focal point.

There are conditions, though. You need a suitable flue, correct clearances to combustible materials, and a heat-resistant hearth. In smoke control areas you must use an exempt appliance and burn approved fuel. Building regulations and, in some cases, planning permission may apply, and your cabin insurer will want to know. Never treat a stove as a fit-and-forget purchase — get it installed and signed off properly.

Heat pumps: the efficient option for year-round use

An air source heat pump works like a fridge in reverse, moving heat from outside air into your cabin. For every unit of electricity it uses, it delivers two to four units of heat, which makes it far cheaper to run than a plain electric heater. It also provides gentle, even warmth rather than a blast of hot air.

Heat pumps perform best in a well-insulated, reasonably airtight space, and they suit cabins used regularly rather than occasionally, because they prefer to run steadily rather than in short bursts. They need an outside unit with good airflow, a power supply, and somewhere for condensate to drain. Expect a higher upfront cost than a panel heater, but lower bills over the years. If your cabin is large, used daily, or split into rooms, a small split system or a mini air-to-air unit is often the sensible choice. Some models also cool in summer, which is a genuine bonus in a south-facing garden room.

Matching the heater to how you actually use the cabin

Ask yourself three questions: how big is the space, how often will it be used, and how well insulated is it?

• Small cabin, occasional weekend use, decent insulation — a 1kW to 1.5kW panel heater or oil-filled radiator is plenty.
• Workshop or studio, one person in one spot — infrared panels give fast, targeted comfort at low cost.
• Everyday office or hobby room, well insulated — a small heat pump is the most economical long-term choice.
• Characterful retreat, access to logs, no smoke control restrictions — a 4kW to 5kW wood burner, installed properly.

Whatever you choose, add a thermostat or timer so the cabin is warm when you arrive rather than hours after. And consider a little supplementary heating: a heated desk mat, an electric blanket on a garden bench, or a good pair of slippers can mean you run the main heater at a lower setting. Get the insulation right, size the heater to the room, and your cabin will be usable right through the British winter.