Pay less for hot water
Estimate what it costs to heat your water, then see how insulation and daytime solar heating could reduce that cost.
Your hot-water setup
Your hot water uses about 12.1 kWh a day and 4,428 kWh a year
Each day you heat about 200 litres of water from 15°C to 60°C. That takes about 10.5 kWh. A 180-litre cylinder also loses about 1.7 kWh a day while keeping the water hot.
$1,550per year
Taking 30-second shorter showers
At about 9 litres per minute, each person uses roughly 5 litres less. This household would heat 20 fewer litres each day.
Save $134Pay $1,416 per year
The saving starts as soon as less hot water is used.
- You pay
- $0
- Electricity saved
- 382 kWh/year
- Pays back in
- Immediately
Insulating the cylinder and pipe
Reduce the heat lost through the cylinder and the hot-water pipe above it.
Save $74Pay $1,475 per year
Reduces heat escaping through the pipe above the cylinder.
- You pay
- ~$10
- You save each year
- $11
- Pays back in
- 11 months
Assumes a 30% reduction in cylinder standing heat loss.
- You pay
- ~$100
- You save each year
- $64
- Pays back in
- 19 months
Approximate material prices only. Installation costs are not included.
Installing a hot-water heat pump
A hot-water heat pump takes heat from the outside air and transfers it into the water. This estimate assumes it uses one-third of the electricity used by a standard electric cylinder.
Save $1,033Pay $517 per year
- You pay
- ~$5,000
- You save each year
- $1,033
- Pays back in
- 4.8 years
- You pay
- ~$7,000
- You save each year
- $1,033
- Pays back in
- 6.8 years
The $5,000 option is a rough lower-cost estimate. EECA uses about $7,000 as its typical purchase-and-installation figure.
Adding solar for daytime water heating
A timer or smart switch turns the hot-water element on only between 10am and 3pm, when solar production is usually highest.
Save $1,162Pay $387 per year
Other savings means solar used by the rest of your home plus surplus exported to the grid. We value that electricity at an average of 20¢/kWh—a mix of avoided imports and export credits. Once the system has paid for itself, it continues reducing your bills and exported surplus can put credits back on your power bill. Under these assumptions, its lifetime savings can exceed the original installation cost. Most of that return is electricity you no longer need to buy, rather than cash income. This estimate assumes each installed kW generates about 1,200 kWh a year; actual production, household use and export credits vary.
What we would do
Use less hot water first. Reducing daily use by 5 litres per person saves electricity immediately and requires no investment. Shorter showers and efficient shower heads are the simplest place to start.
If you already have an electric hot-water cylinder, insulate it next. Wrap an older cylinder and insulate the first metre of hot-water pipe. It is the cheapest upgrade here and has a short payback.
If your roof gets good sun, consider solar next. Use a timer or smart switch to run the cylinder element between 10am and 3pm. The cylinder stores surplus solar as hot water, helping you use more generation at home rather than exporting it.
If the roof is not suitable, consider a hot-water heat pump. It makes more sense for households using around 100 litres of hot water a day or more, particularly when the existing cylinder already needs replacement.
Check the payback against the equipment life. EECA gives a hot-water heat pump an indicative life of around 15 years. If its payback is already 8–10 years, the remaining lifetime savings may not justify replacing a working cylinder early.
Solar and a hot-water heat pump can work together, but we treat them as alternatives here. A heat pump minimises electricity use. A standard resistance cylinder uses more surplus solar and acts as a larger thermal battery. The better choice depends on whether your priority is efficiency or maximum solar self-consumption.
Safety and installation
Keep stored water at least 60°C to control legionella. Never wrap a gas cylinder. Use an electrician for timers or smart switches and a licensed plumber for plumbing changes.
About these estimates
The calculator uses the energy needed to raise water to 60°C, published cylinder heat-loss benchmarks, and the prices you enter. Use the result as a guide, not a quote.
Sources:hot-water systems,hot-water heat pumps,using solar, andsafe temperatures.