Nigel Ramsay

Wellington, New Zealand

Energy efficiency after 1 week

06 June 2020

It’s been about week since we replaced our gas-fired central heating system with an electrical heat-pump based system.

The new system operates a little differently to our previous one. The main difference is how they heat:

Gas - it’s either on or off. The radiators are either heating up, or cooling down.

Heat pump - like a regular heat pump, the system can run at a variety of power levels.

This means that the radiators run at lower, but consistent temperatures as the house reaches it’s target temperature.

The numbers

Electrical heat pump system

For the last 6 days (June):

Consumed energy: 88 kWh

Delivered energy: 312 kWh

Efficiency: 355%

Cost to purchase energy: 88 kWh * 17.4c = $15.31

Daily energy cost: $2.93 (fixed daily charge covered by existing energy requirements)

Carbon emitted over 6 days: 10.8 kg (source: Ecotricity)

Note: need to reduce these figures, as daytime energy usually covered by solar PV panels. Will need another month or so, for comparison with new/old metered electicity usage.

Gas powered boiler

Energy required: 312 kWh

Cost to purchase energy: 312 kWh * 4.83c = $15.07

Daily energy cost: $4.11 (include $1.60 daily charge as only use for heating)

Carbon emitted over 6 days: 61 kg - (source: Ecotricity)