Heat pump hot water running costs

Running cost is where a heat pump earns back its higher price, so it is worth understanding properly. The trouble is that no current official calculator covers the whole country. Sustainability Victoria's old running cost calculator is gone (the agency has closed and its pages now redirect). So this page builds the numbers from the published energy figures and lets you plug in your own electricity price.

How much electricity does a heat pump use?

The ACT Government's heat pump guide says heating a standard 300 litre tank to 60°C with an electric element takes about 14 kWh a day, and works through a heat pump with a COP of 3 using about 4.7 kWh to do the same job (ACT Government). Over a year, that is my arithmetic:

Real use depends on how much hot water you use, how cold your water and air are, and how often the backup element runs. A household using less than a full tank a day will use less.

What does that cost at my electricity price?

Find your usage rate (cents per kWh) on your bill. If the heat pump runs on a controlled load or off-peak tariff, use that rate. The rates below are examples to read across from, not quoted prices:

Daily supply charges aren't included, because you pay those whichever system you have. In a free midday power window the energy is free up to the daily cap. On your own rooftop solar, each kWh costs you the feed-in credit you would otherwise have been paid for exporting it. See solar and off-peak timing.

How does a heat pump compare with gas on running costs?

Gas is harder to put in one table because gas prices and daily charges vary so much. The official figures I found:

• Victoria: replacing gas hot water with a heat pump "can reduce annual operating costs by up to $400" (energy.vic.gov.au), and Solar Victoria says households "can save around $400 a year" (Solar Victoria).
• Victoria's buyers guide adds that disconnecting from gas entirely saves around $350 to $400 a year in fixed network charges, which only applies if hot water was your last gas appliance (VEU buyers guide).
• NSW: the government estimates savings of $200 to $800 a year compared with a traditional system (energy.nsw.gov.au).

Your Home also notes that LPG systems are "around two-to-three times more expensive to run" than piped gas (Your Home), so households on bottled gas may save more than those on mains gas. More in heat pump vs gas.

What about the ACT cost table?

The ACT guide includes a full yearly cost comparison, but it is based on 2021/22 prices, so read it for the proportions rather than the dollars:

Even at those older prices the heat pump came in at about a third of standard electric and a little over half of gas.

What pushes running costs up?

• The backup element. Your Home warns costs rise if the boost element is used often, and the federal review found installers sometimes set units to use it. Check the mode.
• Cold mornings. Heating in the coldest part of the day is the least efficient time. Your Home suggests timing heating to warmer afternoons.
• Heat loss. About 30% of a storage system's energy is lost from the tank and pipes (Your Home). Insulate exposed pipes and don't oversize the tank.
• Expensive peak power. Running a heat pump during the evening peak costs the most on a time-of-use plan.