How to reduce hot water energy costs

There is no better time than winter to assess the costs associated with hot water usage, which have the potential to make up an increased component of household electricity spending during the colder months.

As a rule, household electricity usage increases during winter, which is due to a combination of factors. Heaters are often the immediate focus of this increased usage, however it is also important to consider hot water costs, as longer, hotter showers and baths can in turn result in increased power bills.

The Electricity Authority has found that water heating accounts for 30 per cent of typical household electricity usage, and there is certainly significant monetary incentive to ensure more efficient usage, not only during the winter months, but all year round.

There are a number of ways to limit spending on hot water, and cutting down on usage is an obvious first step, while it is also worthwhile paying attention to the water efficiency of household appliances, from dishwashers to washing machines, along with shower and tap fittings.

It is additionally worthwhile determining the efficiency of your current hot water system, making sure that it has been properly maintained, and also investigating other hot water system options that may deliver savings in the long term.

First steps: Limiting hot water usage

tap dispensing hot water with steam

For households concerned about hot water usage costs, a logical first port of call is to assess current usage habits and to determine whether changes can be made to deliver greater efficiency and savings.

While changes to usage may appear small in isolation, over the course of a year the savings gained have the potential to add up.

The Energy Efficiency and Conservation Authority Energywise website provides the following tips on limiting hot water usage:

  • Wash clothes in cold water – a hot water wash can use 10 times more electricity than a cold wash, and at four loads a week, this could provide savings of around $60-80 per year
  • Fill the sink – rather than leaving hot water running, such as when shaving
  • Shower rather than bath –  which will typically use only half as much water and energy
  • Skip the hour-long shower – each minute you add to your shower time in a household of three is about $70 per year
  • Use cold water – if rinsing dishes before loading the dishwasher
  • Run the dishwasher when fully loaded – on an “eco” wash setting, if available

It is also worthwhile considering your hot water usage patterns in the context of your electricity tariff. For instance, if your tariff is divided into peak and off-peak hours, timing as much of your hot water usage as is possible to take place during off-peak hours will help cut down on costs.

Go with the flow: Appliance, shower and tap efficiency

man having a hot shower

If you are using an older-style shower or tap fitting, your water consumption rates may in turn be higher, and when assessing methods to reduce hot water electricity usage this should also be a consideration.

The New Zealand Water Efficiency Labelling Scheme (WELS) provides consumers information at the point of sale related to products that use water across six product classes: clothes washing machines, dishwashers, lavatories, showers, taps and urinals.

As advised via the Ministry for the Environment website: “The labelling provides clear information on a product’s water efficiency and water consumption in a standardised form, and helps you to choose products that use less water but are still functional.”

The website notes that using water more efficiently has both environmental and economic benefits, potentially reducing water charges in areas with water meters, while “choosing a product that uses less heated water will help to reduce your energy bills”.

The labels include a star rating, indicating the product’s relative water efficiency, with each label displaying a rating out of six, and a water consumption or water flow figure.

Showers currently only have a maximum rating of three stars, while the other product types can achieve up to the six stars, due to New Zealand and Australia not yet having a laboratory test to ensure very low-flow shower products will deliver acceptable performance, the website advises.

The New Zealand government’s Smarter Homes website also advises that households can:

  • Fit flow restrictors to existing taps and shower mixers
  • Fit aerators to kitchen taps, simulating high pressure by dragging air through and cutting the flow of water by 50 per cent without reducing water pressure
  • If you have a very strong shower, have a plumber fit a pressure-limiting valve, reducing flow to the whole plumbing system

Hot water system maintenance

hot water system settings

Ensuring that your hot water system is running to its potential will help to both potentially extend its lifespan and drive down electricity usage and costs, and it is worthwhile undertaking regular maintenance, especially for older models.

When assessing maintenance costs, it is important to consider the short-term costs in the context of potential long-term savings. Energywise recommends the following hot water system maintenance measures:

  • Wrap the hot water cylinder and hot water pipe – pre-2002 electric hot water cylinders aren’t insulated very well and should have a cylinder wrap, while the first 1-1.5 m of hot water pipe coming off the hot water cylinder should also be insulated
  • Check your hot water temperature – which should be 60°C at the cylinder (to prevent the growth of Legionella bacteria) and no more than 55°C at the tap so you don’t get burnt, while depending on the cylinder, you may need an electrician or plumber to adjust the thermostat
  • Maintain your hot water system regularly – maintenance includes gently moving the easing lever of the temperature/pressure relief valve every six months, preventing it from sticking, while glass-lined water cylinders should have their anode changed every five years (more frequently in hard water areas)

Hot water heater options: Time to install a new system?

When it comes to installing a new hot water system, there are a number of factors that should be taken into consideration in determining the right system for your household, from your budget to your current and potential future patterns of usage.

There are a range of hot water system options available – from electric and gas hot water cylinders, to heat pumps and solar heaters – and it is worthwhile assessing all of your options in the context of your usage requirements.

The Energywise water heating systems tool is a useful guide as to the different options available, comparing the upfront costs (purchase and installation), annual running costs and lifetime costs of the different types of hot water systems.

As with any such purchase, research your options, shop around and talk to experts within the field. It is important to keep in mind that the potentially higher upfront costs of a more energy efficient system may be cancelled out by the savings it delivers over the longer term.

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