What types of hot water systems are there?

 

• Electric storage

Electric storage systems are used by around 50% of Australian households. They are the cheapest to buy and install and are generally more expensive to run, unless powered by a solar PV system.

• Solar

Solar hot water systems consist of solar panels or evacuated tubes, and a storage tank unit which is either installed on the roof or at ground level.

In areas with less mid-year sun and long cold nights, solar hot water units may require a booster using gas or electricity.

• Heat pump

Heat pump water heaters are highly efficient and use 30% of the energy of a conventional electric hot water system. These systems use a refrigeration cycle to extract heat from the air to heat the water.

There are 2 main types:

• Integrated with the tank and compressor combined.
• Split with the tank and compressor separate.

The compressor can be noisy, like that of an air conditioner system.

Not all models are designed for cold locations where it regularly drops below 5°C.

Heat pumps are expensive to purchase and install but are cheap to run.

• Gas

Gas hot water heaters are usually installed outdoors because of venting requirements. They have medium-to-high purchase, installation and running costs.

Continuous flow (also called instantaneous) is the most common type of gas water heater.

Gas storage systems are particularly inefficient, especially in cold climates. They have very high heat loss because it’s not possible to insulate at the point where the gas flame is heating the tank.

Installation

Installation of your hot water system must be installed by a licensed local plumber therefore it is important that you check the license of the plumber to ensure it is installed safely and the work is insured.

Energy performance requirements

Minimum energy performance standards (MEPS) are required for:

• electric and gas storage water heaters
• gas instantaneous water heaters.

MEPS are not in place for solar, heat pump or electric instantaneous water heaters.

Regulations do not require water heaters sold in Australia to display an Energy Rating Label. The energy label found on gas water heaters is industry run and not regulated by government.

Household size and water usage

Typically, one person uses about 50L of hot water a day; more if you take very long hot showers or often wash clothes in warm or hot water.

Get a hot water system supplier to analyse your home and usage and recommend some options. To determine the right size of system, a supplier should ask a few key questions to figure out how much hot water your home uses, and when.

• How many people live in your home?
• What’s the usual time for showers or baths? Morning, evening or both? How many showers and how long?
• Do you wash clothes in hot or cold water? Many front loader washing machines take cold water only (and heat it themselves), so they don’t use your HWS. But if your washing machine is connected to a hot water tap, and you use hot wash cycles, that’ll be drawing on the water in your HWS.
• Do you use a dishwasher, or do you mainly handwash your dishes? Dishwashers usually take cold water only (and heat it themselves), so they don’t use your HWS, while handwashing does.
• Is there a long pipe run from the HWS to the main outlets (e.g., the kitchen sink or the shower)? That can be inefficient, and it means long waits for hot water to arrive and wasted energy and water. A shorter run is better, and at the least, the hot water pipe should be insulated. A good installer/plumber can help with that, but of course it will add to the cost of the work.

Energy star ratings 

• Minimum Energy Performance Standards(MEPS) currently apply for electric hot water storage systems, gas hot water storage and gas instantaneous systems. However, they aren’t required to have energy star rating labels.
• You will see star rating labels on gas hot water systems, but that’s an industry-managed scheme and isn’t regulated by government. It’s unrelated to the energy efficiency star rating labels that applies to products such as fridges and air conditioners.
• MEPS are currently under consideration for other water heater types. This will help to remove inefficient models from the market and may see star rating labels appear on all hot water systems.