Warm air heaters: fan heaters and unit heaters explained
By Dale @ ukaircontracker · facts checked
Quick answer
A warm air heater blows air across a heating element to warm a space quickly. Plug-in fan heaters are usually 2–3 kW (53p–79p an hour at the price cap). Wall-mounted unit heaters for garages and workshops run from about 3 kW up to 9 kW or more; anything above 3 kW needs a dedicated circuit, and the largest need a three-phase supply.
| Type | Typical power | Per hour at full power | Use |
|---|---|---|---|
| Plug-in fan heater | 2 – 3 kW | 53p – 79p | Quick heat in one room |
| Wall-mounted fan heater | About 2 kW | 53p | Kitchens, utility rooms, bathrooms (rated models only) |
| Garage / workshop unit heater | 3 – 9 kW | 79p – £2.37 | Garages, workshops, outbuildings |
At 26.32p/kWh (Ofgem cap, Oct–Dec 2026).
When warm air heat makes sense
Fan-driven heat warms the air in a room within minutes, which suits spaces you use for short spells: a garage, a workshop, a bathroom first thing in the morning. For rooms you sit in all evening, a heater with a thermostat that holds a steady temperature, such as an oil radiator, is more comfortable.
Safety and wiring
- Bathrooms need a heater rated for the zone it is fitted in, installed by an electrician.
- Garage heaters above 3 kW need a dedicated circuit; very large unit heaters need a three-phase supply.
- Choose models with overheat cut-outs, and keep them away from flammable materials and dust.
FAQ
Common questions
- Are fan heaters expensive to run?
- A 2 kW fan heater costs 53p an hour at full power at the current price cap, the same as any 2 kW electric heater. It is cheap for short bursts and dear for all-day heat.
- What size heater do I need for a garage?
- It depends on the size and insulation. Uninsulated garages lose heat fast, so a 2–3 kW plug-in heater only takes the chill off; workshops used daily often need a fixed unit heater.
- Can I use a fan heater in a bathroom?
- Only a heater designed and rated for bathroom use, fixed in the right position by an electrician. Never use a portable plug-in heater in a bathroom.