What does your house actually cost to run?

Because the answer changes. Not by a rounding error — by enough to reverse which system you should buy. A household on a 22c retail offer and a household on a 45c standing offer are looking at different winners for the same house, and a calculator that quietly assumes a national average cannot tell either of them that.

Where to find these numbers on your bill — the usage rate, the supply charge and the off-peak rate, and which line on the bill each one is.

Most comparisons of hot water systems publish one table and leave it there. That table is wrong for most of the people reading it, because four things that vary enormously across Australia all move the answer at once.

Electricity costs 52% more in Adelaide than in Melbourne

South Australia's reference rate is 41.9c per kilowatt hour. Victoria's is 27.5c. That single difference is enough to change which system wins. It is also why a calculator that hardcodes a national average is not really a calculator.

Two states have no off-peak hot water tariff at all

Western Australia and the Northern Territory have no residential controlled load rate. Everywhere else, an electric storage tank can run overnight at roughly two thirds of the standard price. In Perth and Darwin it cannot, so it runs at the full rate around the clock — and the cheapest way to heat water with electricity disappears.

A heat pump works better in Brisbane than in Hobart

A heat pump moves heat out of the outside air, so it does less well when there is less heat in the air to move. The same unit that manages an effective coefficient of performance of 2.55 in Darwin manages 2.14 in Hobart and Canberra. Both are still far better than an element — but the gap between them is a real difference in your bill, and no other Australian tool shows it.

Gas is a connection charge as much as a fuel, and it decides the answer

This is the one that surprises people, and it is the reason the calculator asks a question no competitor asks.

If hot water is the only thing you use gas for, the daily supply charge — $300 to $350 a year in most states — is part of what hot water costs you. Switching to a heat pump saves the whole thing, and on our figures the heat pump then wins in every single state — comfortably enough that servicing does not change it anywhere.

If you also cook and heat with gas, the connection stays whatever you do. Hot water should carry only a share of it, gas instantaneous drops to between $319 and $513 a year depending on the state, and the two systems land close enough together that the heat pump's annual service decides it in three of the six states with mains gas. Same house, same appliances, and a conclusion that turns on whether the gas bill would disappear or merely shrink. The full table shows the servicing separately, because a $50 line item deciding a comparison ought to be visible rather than folded into a total.

These are the government reference rates that apply from 1 July 2026 — the Default Market Offer in New South Wales, south-east Queensland and South Australia, the Victorian Default Offer, and the equivalent regulated or standing rate elsewhere. Retail market offers are often below them, which is why every rate on this site is yours to overwrite.

Heating and cooling is about 40% of household energy on the Australian Government's figures, and the largest usage line on most of the bills this site models. Everywhere south of Brisbane the heating half of it dwarfs the cooling half — in Melbourne by nearly nine to one. Households worry about the air conditioner in February and the money leaves in July.

More on heating and cooling running costs, or go straight to the heating and cooling cost calculator.

Every calculator on this site answers one question. If what you want is the shape of the whole thing — where the money actually goes before you decide what to change — start here instead:

The highlighted rows are the part no comparison site shows you: what you pay before switching anything on. It is between $228 and $1,000 a year depending on where you live and whether you hold a gas connection, and nothing you turn off touches it. What it costs to run a house, and what to do about it in order.

Rooftop solar used to be an export business: you sold what you did not use and the feed-in tariff did the work. In May 2025 the Victorian Parliament amended the Electricity Industry Act so that the Essential Services Commission no longer sets a minimum feed-in tariff at all. The last figure the commission calculated before the change was 0.04 cents per kilowatt hour.

So what a system is worth now depends almost entirely on the share of its generation you use yourself rather than sell — and that ratio is between three and seventeen to one depending on where you live:

Which has a consequence the industry has been slow to say out loud: past a certain size, a bigger system pays back more slowly, because the extra generation has nowhere to go but the grid. What solar is actually worth now, or work out the payback for your roof.

A pool changes the shape of a household's bill more than anything else in this list. The Australian Government puts pool pumping at around 18% of a typical electricity bill, and as much as 30% for a home with an in-ground pool — more than the fridge, the dryer and the television together.

Most of that is one motor, and a large part of it is avoidable without buying anything. Filtration is measured in turnovers of the pool, not in hours: the standard is one a day, and the pump beside most Australian pools does one in about three hours. Most timers are set to eight.

What a pool costs to run, or put your own pool in the calculator.

Anyone can publish a calculator. The question is whether its output is right, and almost nothing in this market gives you a way to check.

Sustainability Victoria publishes measured annual water heating running costs for a Melbourne household. It is the closest thing to an independent benchmark in Australia, and this calculator's constants are fitted to reproduce it — within two per cent on every system type it covers:

The most consequential thing that fit tells us is about heat pumps. The number on the box is a coefficient of performance between 3.0 and 4.5. The effective annual figure, once you count cold mornings, compressor cycling and standing losses, is a little over 2 in Melbourne. A calculator using the nameplate figure understates what a heat pump costs to run by about a third. Ours does not, and the methodology page shows the working.