Hot water accounts for roughly 25% of the average Australian household's energy bill, making it one of the biggest areas for potential savings. But with several hot water technologies to choose from — electric storage, gas storage, gas instantaneous, and heat pump — it can be difficult to know which delivers the best value. Let's compare the real running costs and help you pick the right system for your situation.
Running Cost Comparison: All Hot Water Systems
The following table compares annual running costs for a typical 4-person household using approximately 200 litres of hot water per day, based on 2026 energy prices:
| System Type | Annual Running Cost | COP / Efficiency | Annual CO₂ (kg) |
|---|---|---|---|
| Electric storage (off-peak) | $800–$1,200 | 0.9–1.0 | 2,500–3,500 |
| Gas storage | $600–$900 | 0.6–0.7 | 1,800–2,200 |
| Gas instantaneous | $500–$750 | 0.8–0.85 | 1,500–1,800 |
| Heat pump | $150–$350 | 3.0–4.0 | 400–800 |
| Heat pump + solar PV | $50–$120 | 3.0–4.0* | 100–300 |
*Heat pump + solar assumes daytime operation using rooftop solar generation, with some grid top-up during cloudy periods and winter.
Understanding COP: Why Heat Pumps Win
The Coefficient of Performance (COP) is the ratio of heat energy output to electrical energy input. A COP of 1 means the system converts energy at a 1:1 ratio — one kilowatt of electricity produces one kilowatt of heat. That's what a standard electric element does.
A heat pump with a COP of 3.5 produces 3.5kW of heat for every 1kW of electricity consumed. It achieves this by extracting free heat energy from the ambient air, effectively getting 2.5kW of energy "for free" from the environment.
Gas systems actually have a COP below 1, because some energy is lost through the flue and in combustion inefficiencies. A gas storage system typically converts only 60–70% of the gas energy into hot water — the rest goes up the flue.
Installation Cost Comparison
While running costs tell the long-term story, upfront costs matter too. Here's what each system costs to purchase and install in 2026:
| System Type | Installed Cost | After Rebates | Lifespan |
|---|---|---|---|
| Electric storage | $1,500–$2,500 | $1,500–$2,500 | 8–12 years |
| Gas storage | $1,800–$2,800 | $1,800–$2,800 | 8–12 years |
| Gas instantaneous | $2,000–$3,000 | $2,000–$3,000 | 15–20 years |
| Heat pump | $3,000–$5,000 | $2,000–$3,500 | 10–15 years |
Heat pumps have a higher upfront cost, but government rebates (federal STCs plus state programs) typically reduce the gap to $500–$1,000 more than a gas system. Given annual savings of $400–$600 compared to gas, the payback period is often just 1–3 years.
Total Cost of Ownership Over 10 Years
When you factor in both purchase price and running costs over a 10-year period, the picture becomes very clear:
| System Type | Install (after rebates) | 10-Year Running Cost | 10-Year Total |
|---|---|---|---|
| Electric storage | $2,000 | $10,000 | $12,000 |
| Gas storage | $2,300 | $7,500 | $9,800 |
| Gas instantaneous | $2,500 | $6,250 | $8,750 |
| Heat pump | $2,750 | $2,500 | $5,250 |
| Heat pump + solar | $2,750 | $850 | $3,600 |
Which System Should You Choose?
Choose a heat pump if:
- You want the lowest running costs possible
- You have or plan to install rooftop solar
- You're looking to go all-electric and disconnect gas
- You're replacing a failing electric or gas storage system
- You want to reduce your carbon footprint
Choose gas instantaneous if:
- You have very limited outdoor space (no room for a heat pump tank)
- You need unlimited continuous hot water for a very large household
- You already have a gas connection for cooking and heating that you plan to keep
Avoid electric storage unless:
- You're on a very tight budget and need an emergency replacement
- It's a rental property where the landlord won't invest in a heat pump
For the vast majority of Australian households, a heat pump hot water system is the clear winner in 2026. The combination of low running costs, generous rebates, and environmental benefits makes it the smartest long-term investment. If you already have solar panels, running your heat pump during the day makes it almost free to operate — delivering savings that compound year after year.