What air conditioning costs to run

The maths

A unit's input power, not its output, is what you pay for. Divide the output kW by the efficiency figure to get the electrical input, then multiply by your unit rate.

A 3.5 kW unit at an SEER of around 7 draws roughly 0.5 kW. At 25p per kWh that is about 12–13p an hour at full tilt — and inverter units spend most of their time well below full tilt once the room is at setpoint.

Heating is the interesting half

In heating mode the same unit moves heat rather than making it, so it typically returns three to four units of heat per unit of electricity. Over a mild shoulder season that often undercuts running a gas boiler for a single room, which is why reverse-cycle systems get used far beyond July.

What actually moves the bill

• Setpoint — every degree lower in cooling costs noticeably more
• Correct sizing — an oversized unit short-cycles and wastes energy
• Filters — a clogged filter forces the fan and compressor to work harder
• Doors and blinds — cooling a room with the door open cools the hallway

Keeping it efficient

Clean the filters monthly in season, keep the outdoor unit clear of leaves and fencing, and have the system serviced annually so the charge and airflow are checked. Our workmanship guarantee runs for 5 years, parts and labour, when the annual service is kept up.