Hot water tank sizes

Our handy hot water sizing table sets out which size and type of hot water system you'll need for your household to run it on an economy tariff.

Tariff 31 Super Economy

This tariff is for electric hot water systems of 250 litres or more.

Household size Electric storage
1 - 3 people

250L

3 - 5 people

315L

5 - 8 people

400L

Tariff 33 Economy

This tariff is for electric hot water systems holding 125 litres or more, heat pump systems holding 270 litres or more and solar hot water systems holding 160 litres or more.

Household size Electric storage Heat pump Solar hot water

1 - 3 people

125 L

270 L

160 L

3 - 5 people

160 L

270 L

300 L

4 - 6 people

250 L

270 L

440 L

6 - 8 people

315 L

340 L

440 L

If the heating element or rated electrical input for the hot water system is greater than 1800 watts, the system can't exceed the following ratios.

Electric storage systems:

  • 13.5 watts per litre for heat exchange systems
  • 15.5 watts per litre for other systems

Solar hot water and heat pump systems:

  • 13.5 watts per litre
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