What Size Electric Hot Water System Do I Need?

What Size Electric Hot Water System Do I Need?

“What size electric hot water system do I need?” This is a question we often hear at Botanical Plumbing. We get it, choosing the right hot water system can seem like a hassle. Not only do you need to select the best type of hot water system for you, but also the correct size. Here are a few guidelines to remember when choosing the size of your hot water system.

Questions To Ask

Installing Electric Hot Water

How much water do you need?

The suitable capacity and volume of the electric hot water system will depend on the number of people living in the household and how much water is used at peak times.

In short, you need to look at two separate factors:

  • The volume of the tank
  • The capacity it can deliver at peak times

How’s the energy rating?

When choosing the right electric hot water system, it’s not as simple as size. Make sure you look at the energy-efficiency star rating too. Heating water can use up to 35% of the average Queensland household’s energy, so it pays off to choose well. An energy-efficient system will save you money in the long run. Especially in Queensland, solar-assisted electric hot water systems are becoming increasingly popular to cut long-term costs further.

How much space do you have?

You must also ensure sufficient physical space for the electrical hot water system. The tank itself requires space and space on either side, and excess water can run off somewhere. If you plan to get a solar electrical-boosted system, you must ensure enough room for the panels on the north-facing side of your roof.

Electric Hot Water System Sizing Table

Use this table as a rough guide to what size electric hot water system you need based on the number of people in your household.


Number of people served Capacity (litres)



Number of people served Capacity (litres)


Source: Choosing a hot water system, Sustainable Energy Authority Victoria, 2002.

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