Take the heat off your energy bills
Water heating makes up around a third of your household energy bills. This means that you can make some serious savings by being smart with how you heat and use hot water.
Ways to save
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Invest in efficient technology
Make energy and water efficiency a priority when buying new appliances, because this will make it much cheaper to run.
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Fine tune your system
You can improve your hot water energy efficiency by adjusting your tap flows, fine-tuning temperature settings, and insulating your hot water cylinder.
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Adopt low-energy habits
Being smart about how you use hot water will save you energy and money. Check out our tips for simple changes you can make to the way you use hot water, that will make a difference over time.
Make a good investment
As well as upfront and running costs, consider these when you choose a new system.
- Renewable energy – Electricity in New Zealand is around 80-85% renewable, making an electric hot water system a low-emissions choice. Solar panels can be a great option for water heating to keep running costs down, and wood-fired wetbacks are also a sustainable option.
- Energy efficiency – A more efficient system is cheaper to run over time, so can be worth the upfront investment over less efficient options.
- The right size for you – The number of people in your house, the number of showers and baths, and whether your system feeds the dishwasher or washing machine will impact the required equipment size.
- Opportunities when building or renovating – Group together spaces that need hot water, (bathroom, kitchen, toilets and laundry). There’ll be less hot water left sitting in pipes, and it’ll reach your taps more quickly.
Comparison of household water heating options
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Electric water heaters/Hot water heat pumps
Electric water heaters generally have lower running costs and lower emissions than gas water heaters. Hot water heat pumps are the most efficient option, requiring significantly less electricity to run than traditional electric water heater systems.
Hot water cylinders can be installed inside or outside the home. Rooftop solar can be used to power electric water heaters/hot water heat pump systems, further reducing running costs and emissions. -
Wood/wetbacks
Wetback systems circulate water from your hot water cylinder through pipes at the back of your firebox, using heat from your fire to warm the water.
Many wood or pellet fires, ranges or burner systems can have wetbacks fitted, making the most of a plentiful, renewable biofuel. -
Gas/LPG
Natural gas and bottled liquid petroleum gas (LPG) are fossil fuels, so directly generate greenhouse gas emissions. There are cylinder and continuous flow options – the most efficient is a condensing gas continuous flow system.
LPG is the most expensive option in terms of fuel costs. For gas water heating systems, there are fixed charges to consider for main gas supply, or bottle rental, as well as the energy costs.
Hot water heat pumps
Hot water heat pumps are highly energy-efficient compared to traditional electric hot water cylinders or gas hot water systems. This means they can have a lower lifetime cost for the average New Zealand household*, and are particularly cost-effective for households that use a lot of hot water.
If you’re building a new home or considering a replacement or upgrade to your current hot water system – a hot water heat pump could be the way to go.
Solar PV vs solar thermal for water heating
There are two ways you can use solar energy to heat the water you use at home.
- Photovoltaic solar panels (solar PV) convert energy from the sun into electricity which can be used to power an electric hot water system (including heat pump water heaters) as well as other electric appliances in the home.
Rooftop solar PV - Solar thermal systems produce heat rather than electricity. Solar thermal panels installed on your roof transfer heat from the sun to water stored in your hot water cylinder.
Thermal solar(external link)
Choose efficient appliances that use hot water
When buying appliances that use hot water, like clothes washers and dishwashers, make energy and water efficiency a priority. This will help you save money on running costs. Check the Water Efficiency Labelling Scheme (WELS) rating and the Energy Rating Label to see how different models perform in these areas.
The Gen Less Efficient Appliance Calculator allows you to find the most efficient and cost-effective products.
Fine tune your hot water system
- Reduce your shower flow – The ordinary showerhead typically makes up the largest percentage of indoor water use, accounting for about 30% (Source: BRANZ). If your shower fills a 10 litre bucket in less than a minute, it's wasting water. Change your shower head for one with a more efficient flow rate of 8 to 9 litres a minute or less (Water Labelling Scheme Rating of 3 star or higher). Or, install an inexpensive shower flow restrictor.
- Ease your tap flow – Flow control aerators for taps cost between $10 and $30 and can halve the volume of water you use while still giving good pressure. They’re great for taps over sinks or tubs that aren't regularly filled up, so the water flow volume is less important.
- Fix dripping hot taps – Replace the washer or fitting - a new washer only costs a few dollars.
- Set mixer taps to cold – Mixer taps can use hot water without you even knowing it, as the hot water will flow into the pipes automatically if it’s not set to cold.
- Wrap your hot water cylinder and pipe – Pre-2002 electric hot water cylinders aren't well insulated and should have a cylinder wrap. You should also insulate the first metre of hot water pipe coming off your cylinder. Cylinder wraps cost around $60 and pipe insulation is about $5 a metre from hardware stores. Note that you can't put a cylinder wrap on a gas hot water system.
- Install a smart thermostat – Thermostats map your hot water use and will automatically turn your cylinder off or down when hot water isn’t needed. Talk to your electrician about which smart thermostat is suitable for your hot water cylinder. Make sure the one you select has the capability to communicate with the grid and respond to electricity price signals.
- Maintain your hot water system – Check the hot water system manufacturer’s instructions and owners guide for your hot water system to find out the recommended maintenance and time frames required to keep your hot water system working efficiently.
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How hot is safe?
Hot water should be a minimum of 60°C at the cylinder (to prevent the growth of legionella bacteria), any temperature higher than 60°C will be adding heating cost that could be avoided and no more than 55°C at the tap so you don't get burnt.
Be extra careful about children. Some cylinder thermostats can only be adjusted by an electrician or plumber.
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When to switch off
If your house is empty for an extended period, consult your hot water system’s manual and consider turning the water cylinder off completely if it’s safe to do so.
Easy hot water savings checklist
- Use a cold wash more often – A hot water clothes wash can use almost 10 times more electricity than a cold wash. Switching to cold water can save you around 25c per wash.
- Turn off the tap – Fill the sink with hot water instead of leaving the tap running when doing things like shaving.
- Shower rather than bath – Showers typically use half as much water and energy, and cost half as much.
- Time your showers – Cutting your shower time from 15 minutes to 5 minutes can save you around 66c per shower – that’s around $5 per person per week!
- Fill the dishwasher – Only run full loads in the dishwasher and washing machine. Use the eco setting on your dishwasher if it has one. Pre-rinse dishes if required, in cold water.
It pays to go electric
Powering your home with efficient, electric appliances can save you thousands in energy costs – and slash your carbon footprint.
We’ve done the math on key household energy uses such as heating, water heating, cooking and driving. The numbers show that the most efficient electric options make sense financially – both in terms of monthly running costs and overall lifetime costs.
Discover how your household might stand to benefit from going electric.
Read next
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