Costs and benefits

Reduced energy bills

In summer, it may be possible to heat all the water you need with solar energy. In winter, or on cold cloudy days, solar water heating will meet part of your hot water needs - you'll also need some supplementary heating from your booster system.

The exact amount you save from solar water heating will depend on a wide range of factors including how much hot water you use, the solar water heating system you install, and the quality of the installation. But it's been estimated that, for an average household, an effective system will:

• Provide between 50 percent and 75 percent of annual hot water needs. 
• Cut about 2200kWh from annual electricity use. 
• Provide savings of $350-$450 a year (depending on the cost of your electricity or gas supply).

Environmental benefits

If you install solar water heating, you'll be helping to reduce New Zealand's dependence on non-renewable energy sources, and you'll be helping to cut greenhouse gas emissions.

Every residential solar water heating system installed is estimated to save, on average, about 1.4 tonnes of carbon dioxide emissions a year (assuming a mix of coal and gas fired electricity generation is avoided).

Installation costs

Because each installation is different, the costs of solar water heating can vary widely. At present, solar water heaters (including the cylinder) typically cost between $4000 and $8000 installed.

In general, it's more expensive to install solar water heating in an existing house than in a new house. This is because, in an existing house:

• You may need to add pipes in parts of the house that are hard to access.  
• You may need to add structural framing in the roof so it can carry the weight of the solar water heating cylinder - if you choose to have the cylinder on your roof.

You may be eligible for government finance assistance. To check whether you qualify, and how to apply, see www.energywise.govt.nz.