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What Size Hot Water System Do I Need?

It should be simple: turn on the faucet and get hot water. But when your water heater dies and you need to replace the system, it's not quite that easy. There are several considerations to look at, from the cost of running the system to your household water usage. Let's walk through the basics.

Types of Hot Water Systems

There are several different types of water heaters. The size of your tank will depend on what type you decide to purchase.

Electric. These tanks usually cost between $300-$1,500 but can be expensive to use, especially if running at the continuous rate on your electric bill. If buying an electric tank, you'll need a 125-160-litre tank for a four-person household.

Gas. If you have a natural gas connection, it is less expensive to run; the tank costs between $900-$2,000. A four-person home would require a tank from 135-170 litres. This system is usually installed outside because of venting requirements with gas.

Solar. These tanks are more expensive up front, between $2,000-$7,000, but cost relatively little to run. There are government rebates to help offset the initial costs. The tank will need to be fairly large, 300-360 litres, to allow for days with less available sunlight.

Heat Pump. Much more efficient than electric water tanks, heat pumps take heat from the air and utilise that heat to warm the water in the tank. They need to be installed outdoors or in a well-ventilated area. Tanks cost between $2,500-$4,000, but there are government rebates to help with the initial purchase cost. You will need a larger tank for this system as well, around 270-315 litres for a four-person home.

Heating Method

Storage tanks and continuous flow systems both have a place in hot water heating. Let's look at the differences.

Storage Tank. This works with any of the above systems. There are two types: mild-steel and stainless steel. They can both corrode over time, the mild-steel more quickly, but often last 10 or more years. The tanks can lose heat even though they are insulated, costing you money when running the system.

Continuous Flow. These systems heat only the water needed when the "hot water" tap is turned on. They can be natural gas or electric units. The size will depend on how many hot water taps you have in your home. A supplier or plumber can help find the right size for you.

Household Size and Water Usage

On average, water usage is about 50 litres of hot water per person. This also depends on laundry and dishwasher usage and the length of your showers. You may also need to consider when your family uses the water. If a family of five all shower at night and you run the dishwasher at the same time, you will need more hot water available.

If you have questions or are unsure about what you need, a plumber or supplier can help you determine the right water heater system for your household. They can also help set you up with the right size system for your home.