Simple ways to save on hot water
Whatever hot water system you have, there are some easy ways to reduce your energy use without impacting on your lifestyle.
Check your shower flow rate
Around 80% of a home's hot water is used in showers, but many showers use a lot more water than they need to - which means wasted energy, water and money.
If your shower fills a 10 litre bucket in less than a minute at normal showering temperatures, install an efficient shower head. Get a shower head with a flow rate of 9 litres a minute or less - you can compare the efficiency of new showerheads at www.waterrating.gov.au.
For a typical family household on mains pressure, a good efficient shower head could:
- cut your hot water use by around 25%
- cut your greenhouse gas emissions from household energy by about 400 kg a year
- cut your household energy bill by around $160 a year [1]
- reduce your water bills, if you're on metered water.
Efficient shower heads can be retrofitted onto most showers. Different products can give you a different showering experience - discuss the options with your plumber or shower head supplier.
Consumer NZ has carried out a user trial of 7 low-flow mains-pressure shower heads, to judge comfort and effectiveness (July 2010). Read the results.
Streamline your system
There are some more simple things you can do to cut your energy and water waste, and make your existing hot water system as efficient as possible.
- Wrap your hot water cylinder and pipes. Hold the heat in by wrapping your electric hot water cylinder (you can't put a cylinder wrap on a gas hot water system) and insulating your hot water pipes. Wraps cost from around $60 and pipe insulation is about $5 a metre from hardware stores. For an older (pre-1987) cylinder and pipes, you could save up to $80 a year.
- Fix dripping hot taps. These can waste up to 200 litres of water every day, or hundreds of dollars of energy each year. Replace the washer or fitting - a new washer only costs a few dollars.
- Ease your tap flow. Where the volume of water doesn't matter - like sinks or tubs that aren't regularly filled up - flow control aerators for taps cost between $10 and $30 and can halve the volume of water used while still giving good pressure.
- Check your hot water temperature. It should not be more than 55° Celsius at the tap so it is low enough not to burn, and it must be 60° Celsius at the cylinder to prevent the growth of Legionella bacteria. Don't have the thermostat on your hot water system higher than necessary - an extra 10° Celsius could cost you $20 to $30 a year. You might not have noticed it's too high if, as with most modern systems, yours has a tempering valve to add cold water to the hot water coming from your cylinder to prevent scalding. And without a tempering valve, a hot water thermostat set higher than necessary is a scalding risk. You may need an electrician or plumber to adjust your thermostat.
- Maintain your hot water system regularly. This includes gently moving the easing lever of the temperature/pressure relief valve (if you have one) every six months. Glass-lined water cylinders should have their anode changed every five years, more frequently in hard water areas. A plumber can help you do these things if you're unsure. Depending on the type of system you have, further maintenance actions may be required - check your manufacturer's instructions.
Easy hot water habits
With some easy, everyday hot water habits you can cut your energy use - and your environmental impacts - even more.
- Use cold water for washing your clothes. At four loads a week, this could save you around $50 - $75 each year.[2]
- Rinse dishes with cold rather than hot water.
- Only run the dishwasher when it is fully loaded, and then on an ‘eco', ‘half load' or ‘fast' wash setting if available.
- Fill the sink with hot water rather than leaving the hot water running when doing certain tasks like shaving.
- Shower rather than bath where practical - it typically uses only half as much water and energy.
- Shorter showers can save you money. In a household of three, each minute you add to your shower time is about $80 a year.[3]
And remember, if your water use is metered, then every litre you save is saving you more money.
More information
Notes:
[1] Compared to an efficient shower head flow rate of 9l/min. Assuming three showers per day, shower duration of 9min, electric water heating at 23.7 cents per kWh. Calculated using the HERS hot water rating tool, documented in BRANZ report EC1475C "ANZHERS - Upgraded hot water rating algorithms", March 2009.
[2] Based on Consumer NZ report "Appliance running costs", updated 2 July 2009.
[3] Assuming three showers per day, shower flow rate of 9 l/min, electric water heating at 23.7 cents per kWh. Calculated using the HERS hot water rating tool, documented in BRANZ report EC1475C "ANZHERS - Upgraded hot water rating algorithms", March 2009.
