Hot Water System Cost Calculator
Compare electric, gas, solar and heat pump hot water systems on upfront price and yearly running cost to find the cheapest option long term.
Illustrative default — tariffs vary by retailer, state and plan.
Illustrative default — gas tariffs vary by retailer and state.
Heat pumps typically have a COP around 3–4; gas systems around 0.8.
Your results
Actual prices, usage, efficiency and savings vary by provider, equipment, location and behaviour.
Calculation breakdown
- Energy required
- 200 L × 4.186 × (65 − 20) ÷ 1000 = 37.674 MJ/day
- Annual cost
- $3.44/day × 365 = $1,255.42
Compare system types at the same demand
| System | Daily cost | Annual cost |
|---|---|---|
| Electric resistive | $3.44 | $1,255.42 |
| Heat pump | $1.28 | $467.60 |
| Gas storage | $1.71 | $625.16 |
| Gas instant | $1.63 | $594.83 |
| Solar-boosted | $1.08 | $395.98 |
Assumptions
- Electricity and gas tariffs are illustrative user inputs — actual prices vary by retailer, state, plan and time.
- The comparison table uses default efficiency figures for each system type unless you override the efficiency/COP field.
- Energy required is based on the physics of heating water and ignores pipe losses beyond the entered standing loss.
- Installation and maintenance costs are not included in this running-cost comparison.
How this calculator works
Enter household size, energy prices and the purchase and installation price of each hot water option. The calculator estimates daily hot water energy demand, applies each system's efficiency or coefficient of performance, and compares annual running costs and total cost over the system's life.
Frequently asked questions
Why are heat pumps so efficient?
They move heat from the air rather than generating it directly, delivering roughly three to four units of heat per unit of electricity.
Does off-peak electricity help?
Yes. A storage system on a controlled-load tariff heats overnight at a much lower rate, which significantly reduces running costs.
How long do systems last?
Around 10–15 years for most storage and heat pump systems, and slightly longer for well-maintained solar thermal units.
Actual prices, usage, efficiency and savings vary by provider, equipment, location and behaviour.
Results are estimates only and are not financial, tax, legal or credit advice.