Hot Water Energy Calculator

hot liquid water use hot water shower

  • What does hot water cost you now?
  • How much hot water, power and money can be saved with efficiency?
  • What savings can be made with an efficient shower head and tap aeration?
  • What savings can be made with solar hot water?
  • Calculate your answers here.

Hot Water Savings Ideas

Replace a shower head for a water efficient one and Save 55% and associated heating costs.
Install tap aerators and Save 75% and associated heating costs.
Fix water leaks fast and save up to 20000 litres per year.

Hot Water Calculator

Calculate your yearly hot water consumption and hot water costs.
See what a different efficient shower heads and aerators can make.
Evaluate if solar hot water capital costs compare with 20 years of hot water savings.
Fill in the values in the top 3 tables.
Press Get Results button.
See you hot water annual costs and possible water efficiency savings.

Water Use

Consumption Guide: Open tap 20 l/min, 3 star shower head 9 l/min, aerator tap 5-7 l/min. Time the filling of a known sized container for more accuracy. Consider trying to keep showers to 4 minutes each.

Description Time in
minutes per day
e.g. 10
Proportion Hot Water
(0-1) e.g. 0.5
Normal use in
Efficient use in

20 litres per minute
9 litres per minute
Hand washing
dish rinsing etc.

20 litres per minute
5 litres per minute

Water Use continued

Consider only using the dishwasher when full. Compare water use of a shower versus a bath.

Description Quantity per day Proportion Hot Water
Total Litres


Hot Water Power Cost

Power Cost in Dollars per kWh example 0.15
Power costs for off peak tariff will be cheaper.

Press button after completing or adjusting fields in the top tables. Results in lower table.

Water and Energy Use Results

The power and cost calculations is based on a conventional electric storage water heater. Water efficient shower heads cost about $40, tap aerators cost about $10.
See how much savings can be made by their use in the short and long term. The return on investment should be good in most cases.
Solar hot water can save even more. The capital cost must be compared to the potential savings. Do you still use enough hot water to make a case for its installation?
Calculate all possible power efficient activities and see which ones are easiest to implement.

Parameter Normal Values Water Efficient Values Water Efficient Savings
Total Hot Water Use for year in litres


Hot water power consumption per year estimate
(kWh) not including reheating


Electricity hot water costs per year ($)


Potential Solar Hot Water at 80% savings over 20 year (kWh)


Potential Solar Hot Water at 80% savings over 20 year ($)


Does the water calculator show savings in power and money?

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