Heat pump hot water systems are sold on efficiency. Most Perth households want a simpler answer: what will it cost to run each year? The answer depends on a few things. The biggest factors are how the system is set up and whether it runs on solar. This guide works through the real numbers, using current Synergy rates. It shows what heat pump hot water running costs look like in practice, not just in theory. In short, it shows the cost to run a heat pump in Perth. It covers what that costs once solar and tariffs are taken into account.
In short, an iStore heat pump typically costs a few hundred dollars a year to run on a standard tariff. That is a fraction of what an old electric element costs. It costs close to nothing when it runs on surplus solar. The detail below explains why, and how to reach the lower end of that range.
What Determines a Heat Pump’s Running Cost
Three things set the annual cost of running a heat pump hot water system. The first is how much hot water the household uses. More hot water means more energy to heat it. The second is the efficiency of the unit. This is measured as its coefficient of performance, or COP. The third factor is within the household’s control. It is when the system runs and what the electricity costs. That comes down to the tariff and whether solar is covering the load.
The iStore heat pump helps on the second point. It carries a COP of 4.82 on the 270 litre model and 4.37 on the 180 litre model. Both sit at the top of the category. A COP of 4.82 means the system delivers close to five units of heat for every unit of electricity it draws. That efficiency is why a heat pump uses so much less power than a conventional electric element.
How Much Electricity a Heat Pump Actually Uses
A conventional electric storage system heats water with a resistive element. It turns one unit of electricity into roughly one unit of heat. Depending on household size, that adds up to somewhere around 2,000 to 3,000 kilowatt hours a year just for hot water. A heat pump does the same job differently. It moves heat rather than generating it. That is why it uses far less electricity for the same amount of hot water.
For a typical Perth household, an iStore heat pump uses around 500 to 900 kilowatt hours a year. A smaller or more efficient household sits at the lower end. The worked examples below use a figure of around 650 kilowatt hours a year as a middle estimate. The actual figure for any home depends on occupants, hot water habits and the weather. Even so, this level of use is a sound basis for understanding iStore running costs.
What That Costs on Synergy’s Flat Rate (Home Plan A1)
Most Perth homes are on Synergy’s standard Home Plan A1, which charges a single flat rate. That rate is 33.2621 cents per kilowatt hour, at any time of day. On that tariff, running the heat pump from the grid works out at roughly 650 kilowatt hours multiplied by 33.2621 cents. That comes to about 215 dollars a year.
That is the cost with no solar involved. It is simply the heat pump plugged into a standard tariff. For context, an old electric element uses around 3,000 kilowatt hours on the same flat rate. That would cost close to 1,000 dollars a year. The heat pump alone, before any solar, cuts the running cost by roughly two thirds.
The Lowest-cost Way to Run It: On Your Own Solar
The number drops a lot when the heat pump runs on solar. A heat pump draws only a modest amount of power and includes a timer. It can be set to run in the middle of the day. That is exactly when a rooftop solar system is generating its surplus. Instead of exporting that surplus to the grid for a low feed-in rate, the household uses it to make hot water.
Under Synergy’s DEBS feed-in tariff, exported solar earns 2 cents per kilowatt hour outside the afternoon window. Redirecting that same energy into the hot water tank avoids buying it later at 33.2621 cents. Every unit used this way is worth far more self-consumed than exported. For a home with enough daytime solar to cover the heat pump, the running cost of hot water drops right down. It falls to close to zero. This is the single biggest lever on the annual number.
Heat Pump Versus Old Electric Hot Water: The Real Saving
The table below sets out illustrative annual running costs for hot water. It is based on around 650 kilowatt hours of heat pump electricity a year. That is set against an older electric element using around 3,000 kilowatt hours, using current Synergy rates. The figures are worked examples. They show the heat pump versus electric hot water cost difference between setups. They are not a quote.
| Setup | How it runs | Approx. per year |
|---|---|---|
| Old electric element | About 3,000 kWh at the 33.2621c flat rate | About $1,000 |
| iStore heat pump (grid, A1 flat rate) | About 650 kWh at the 33.2621c flat rate | About $215 |
| iStore heat pump (Midday Saver, 9am to 3pm) | About 650 kWh at the 8.85c Super Off Peak rate | About $58 |
| iStore heat pump (own solar surplus) | About 650 kWh self-consumed from solar | Close to $0 |
The pattern is clear. Switching from an electric element to a heat pump is a large saving on its own. Running that heat pump during solar hours, or on a time-of-use tariff, takes it close to nothing. For a solar home, the heat pump hot water savings in Perth are close to the full cost of heating water.
What About Midday Saver and EV Add-On?
Households on one of Synergy’s time-of-use plans have an extra lever. Both Midday Saver and EV Add-On charge a Super Off Peak rate of just 8.85 cents per kilowatt hour, between 9am and 3pm. Timing the heat pump to run inside that window means buying electricity at the lowest-cost rate of the day. This works whether or not the sun is out. At 8.85 cents, the same 650 kilowatt hours costs around 58 dollars a year.
One thing to avoid is running the heat pump during the 3pm to 9pm peak period on those plans. The rate then rises to 55.33 cents per kilowatt hour. A simple timer setting keeps the system firmly in the low-cost window. For a household weighing up these plans, there is a guide that helps. The Synergy A1 versus Midday Saver versus EV Add-On guide covers how each one works in detail.
Real-World Factors That Change Your Number
The figures above are a guide, not a guarantee, and a few things move the number for a particular home.
- Household size. More people means more hot water. That means more energy, so larger families sit at the higher end of the range.
- When it runs. A heat pump timed to run overnight, on a flat tariff, costs more. The same unit costs less when run on midday solar, or in the Super Off Peak window.
- Whether there is solar. A home with enough daytime solar pays close to nothing to run the heat pump. A home without solar pays the standard grid rate.
- The weather. A heat pump runs more efficiently in warmer air. Real-world efficiency is a little higher across Perth’s long warm seasons, and a little lower on cold winter mornings.
How Positive Energy Solutions Helps You Hit the Lower Number
The difference between a heat pump costing 215 dollars a year, and close to nothing, comes down to sizing and setup. That is where the design work matters. Positive Energy Solutions sizes the iStore system to the household. The team sets the timer to run on solar, or the low-cost window. For homes with solar and a battery, the team makes sure the whole system works together, rather than against itself.
Positive Energy Solutions is an iStore Elite Partner and a Perth-based team, with accredited installation teams across the metropolitan area. Every installation is backed by a 10-year installation workmanship warranty, on top of the iStore product warranty. It is also backed by Positive Energy Protection, powered by Omnidian, so the system stays supported well after it is switched on.
Frequently Asked Questions
How much does a heat pump cost to run per year in Perth?
On Synergy’s standard flat rate, an iStore heat pump typically costs 200 to 350 dollars a year to run from the grid. That is based on around 650 kilowatt hours of electricity. Run on surplus solar, or timed to the 8.85 cent Super Off Peak window on a time-of-use plan, the annual cost drops. It falls to somewhere between close to zero and about 60 dollars.
How much lower-cost is a heat pump than an electric hot water system?
A heat pump uses up to 65 percent less electricity than a conventional electric element, for the same amount of hot water. On the same flat tariff, that is roughly the difference between two figures. About 1,000 dollars a year for an old electric system, and about 215 dollars a year for a heat pump. This is before any solar is taken into account.
Can I run my heat pump on solar alone?
Close to it. A heat pump uses only a modest amount of power. It can be timed to run in the middle of the day, when a rooftop solar system is generating surplus. For a home with enough daytime solar to cover it, the running cost of hot water falls to close to zero. Otherwise, that energy would export for only 2 cents per kilowatt hour.
Does a time-of-use plan make a heat pump lower-cost to run?
It can. Both Midday Saver and EV Add-On charge 8.85 cents per kilowatt hour, between 9am and 3pm. Timing the heat pump to run in that window buys electricity at the lowest-cost rate of the day. This is well below the standard flat rate, provided the heat pump is kept out of the 3pm to 9pm peak period.
How much electricity does an iStore heat pump use?
A typical Perth household uses around 500 to 900 kilowatt hours a year to run an iStore heat pump. Compare that with around 2,000 to 3,000 kilowatt hours for a conventional electric element doing the same job. The exact figure depends on household size, hot water habits and the weather.
Work Out Your Own Number
The best way to know what a heat pump will cost a particular home is to look at three things. Look at that home’s hot water use, tariff and solar setup together. Positive Energy Solutions can work through the numbers, and recommend the right iStore system and setup, as part of a quote.
Request Your Quote today: positiveenergy.com.au/contact/
About the Author
Jason Wiktorowicz
Sales Manager, Positive Energy Solutions | Perth, WA
Jason has been at the centre of Western Australia’s energy transition for over a decade. He was Orchestration Lead on Project Symphony, WA’s largest virtual power plant pilot. He was also Stream Lead on Project Encore. In these roles, he worked directly with AEMO, Western Power and Energy Policy WA. Together, they shaped how distributed energy resources connect and operate on the SWIS. That work included developing and rolling out CSIP-AUS, now mandatory for all new WA grid connections. He also led Emergency Solar Management, the first program of its kind in WA. He led VPP for Schools too, which provided direct market benefits through Supplementary Reserve Capacity. He also led REBAR, the WA Residential Battery Rebate scheme.
At Positive Energy Solutions, Jason leads sales with a focus on system design accuracy and long-term performance. Positive Energy Solutions installs solar and battery systems, EV chargers and heat pumps. The company holds partner accreditations with Fronius, SigEnergy, iStore and SunPower.
10-year installation workmanship warranty. Positive Energy Protection, powered by Omnidian, performance monitoring included on all systems.
