How we work it out
Each person in a house runs through about 50 litres of hot water a day. Heating that from a 20°C mains supply, the NHMRC's mid-range figure for Australian reticulated water, up to the 60°C minimum storage temperature AS/NZS 3500.4 requires (the plumbing standard that exists to stop Legionella growing in the tank) takes around 2.3 kWh. An electric storage tank heats it with a resistive element, plus roughly 1.2 kWh a day for the heat that leaks out of an insulated cylinder overnight, a real loss every storage tank has. A heat pump does the same job for about a third of the power: the Australian Government's energy.gov.au states heat pump water heaters use 30% of the energy of a conventional electric system, the ratio behind every heat-pump figure here. A solar system with electric boost only pays for the cloudy days, modelled here as the boost covering 35% of the load, an estimate rather than a registry figure since that share depends on your roof and climate. We turn those figures into dollars at your state's rate.
Worked example: a family of four on an electric storage tank in NSW uses around 11.4 kWh a day, which is about $3.70 a day or $1,350 a year. The same family on a heat pump would use around 4.3 kWh a day, closer to $500 a year.
If your tank is due for replacement
The numbers above are the whole argument for heat pump hot water. The saving for a family commonly lands between $700 and $1,000 a year, and federal STC incentives plus state rebates knock a fair chunk off the purchase price. If your electric tank is over ten years old, price a heat pump before it fails, because the day it dies you'll take whatever the plumber has on the truck.
Common questions
How much of my power bill is hot water?
For homes with electric storage tanks, typically 20 to 30% of the whole bill. It's usually the biggest single energy user in the house after heating and cooling.
Are heat pump hot water systems worth it in Australia?
For most households replacing an electric tank, yes. They use 60 to 70% less power, rebates reduce the upfront cost, and the saving typically repays the difference within a few years.
Does an off-peak hot water tariff change these numbers?
Yes, controlled load tariffs heat your tank overnight at a lower rate than the one used here, often around 20 cents per kWh. Check your bill for a controlled load line. The heat pump still wins, just by a smaller margin.
Does mains water temperature affect the running cost?
Yes. The NHMRC's Australian Drinking Water Guidelines put Australian reticulated water anywhere from 10 to 30°C depending on state and season, and the figures above assume 20°C, the middle of that range. In the coldest conditions the energy needed to heat a tank runs about 25% higher than shown; in the warmest conditions it runs about 25% lower. Your own bill will sit somewhere inside that band depending on your climate and the season.
How much does a shower cost per minute?
With a standard 9 litre-a-minute showerhead, the maximum flow allowed on anything sold since June 2022, heating the water costs roughly 6 to 8¢ a minute depending on your state's electricity rate. See our shower cost per minute guide for the full breakdown by shower length and showerhead type.
What this costs, state by state
A three-person household on an electric storage tank.
| State | Rate | Per day | Per year |
|---|---|---|---|
| New South Wales | 32.4¢ | $2.87 | $1,049 |
| Victoria | 29.8¢ | $2.64 | $965 |
| Queensland | 31.2¢ | $2.77 | $1,010 |
| South Australia | 38.1¢ | $3.38 | $1,234 |
| Western Australia | 33.6¢ | $2.98 | $1,088 |
| Tasmania | 28.9¢ | $2.56 | $936 |
| Australian Capital Territory | 27.4¢ | $2.43 | $887 |
| Northern Territory | 31.7¢ | $2.81 | $1,026 |
Reference rates for 2026–27. Your row is highlighted once you set your location.
Sources
Electricity rates: AER Default Market Offer (NSW, SA, south-east QLD), Victorian Default Offer, and each remaining state's regulated tariff, current for 2026–27. Appliance figures: the energyrating.gov.au registration database (July 2026 snapshot). Methods and assumptions are described on each page.