How much heat a patio needs
Heat output in kilowatts sets how big a patch a heater can warm, and outdoors that patch is smaller than the room sizes quoted for indoor use. As a rough guide, up to 2 kW suits a balcony or a table for two, 2.5 to 3 kW a table for six, and 4 to 6 kW electric or a gas heater a large terrace. Wind strips warmth from people, so exposed spots need more heat than sheltered ones.
Gas flame or electric infrared
Electric infrared gives off no fumes, so it can sit under a canopy or a covered terrace, reaches full heat almost instantly and on many models can be dimmed or switched by remote. Gas gives more heat from a single heater and a cylinder model needs no mains power, but it releases combustion fumes, so use it only where there is plenty of open air. Fixed gas heaters suit large, open commercial terraces, while electric suits homes and covered seating.
Wiring, gas supply and weatherproofing
Electric heaters up to about 3 kW can plug into a weatherproof outdoor socket, while bigger ones and any fixed wiring need a qualified electrician, and the higher the IP (ingress protection) rating, the better a heater resists rain. Fixed gas heaters are connected by a Gas Safe registered engineer, and a portable one needs the right cylinder and regulator. A 2 kW electric heater on full uses 2 units of electricity an hour, and a winter cover protects a freestanding heater.
