Electricity supply

What to consider when planning the system’s electricity supply

Power consumption

Power consumption

A mini-split air conditioner’s or heat pump’s power rating is not the amount of electricity it uses. A 3 kW heat ouyput system operating at a 3:1 efficiency will consume 1 kW, not 3 kW. See more information.

The manufacturer’s specifications will state power consumption, and often the required fuse rating for the circuit. This fuse rating is much higher than the average power consumption because of ‘inrush current’. This is the instantaneous high input current drawn by a power supply or electrical equipment at turn-on.

It is normal to see small mini-splits with circuit requirements of 16A, although some newer units are quoting lower figures and state that they can be powered from a 13A plug socket.

Inside / outside power isolator

Rotary power isolator

Most mini-split systems rely on power being supplied to the outside unit. A secondary cable then runs to the inside unit. However, some smaller units are the other way around - the main power goes to the internal unit.

Some electricians prefer an isolator next to the external unit, irrespective of the main feed being to the internal or external unit. Others are happy with an internal isolator if positioned such that someone maintaining the outside unit can be confident it is fully isolated.

Most electricians would recommend an RCD protected separate fused spur for a fixed appliance such as a mini-split unit.

DIY electrics


In England, under Part P of the Building Regulations Opens in a new window, installation of a complete new circuit is classed as ’notifiable work’. This means it must be completed by a competent person (i.e. a qualified electrician) or certified by a competent person on behalf of the non-registered person carrying out the work.

Minor DIY work is permitted under the regulations, including adding a single fused spur to an existing circuit.

There is a useful FAQ on the Institution of Engineering and Technology Website Opens in a new window.

Northern Ireland, Wales and Scotland have differing regulations which should be consulted.

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Notifying the District Network Operator.