Solar Water Heating – The Facts

Growing demand

Solar PV energy is increasingly requested in the domestic market, especially in new home builds.
Around 1.6% of home owners in New Zealand have now installed solar water heating systems, and currently there are around 2000 new solar water heating systems installed each year. This number is growing at around 30 – 40% annually.

Can you use solar water heating anywhere in NZ?

Solar water heaters function well from Invercargill to the Far North, although the solar contribution varies depending on your location and the time of year. Standard solar water heating systems can produce around 75% of your household’s water heating in summer and between 25 – 45% in winter.

How does solar water heating work?

The free energy of the sun is harnessed in a special solar collector/panel usually mounted on the roof of your house. Water is pumped from your hot water cylinder to the collector where it is heated by the transferred energy and then returned to the cylinder.

What is evacuated tube technology and how does it compare with flatplate systems?

Evacuated tube collectors consist of rows of transparent twin glass tubes. When each twin tube is manufactured, air is evacuated from the space between the two tubes, forming a vacuum. The absence of air eliminates convective or conductive heat loss, which means greater efficiency at achieving higher temperatures in both direct and diffused solar radiation.

Evacuated tube collectors are typically more efficient at producing higher temperatures than flat-plate collectors, and will not freeze in frosty conditions.

Evacuated tube collectors produce extremely high temperatures, which makes them more appropriate for commercial and industrial applications.

What equipment is needed?

The Solar Technology installer will supply all of the necessary components including the solar panels which collect the energy, the hot water cylinder, if a new one is required, the pumps and controllers.

How much money will I save?

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.

Generally recovering the costs of a solar water heating installation may take anywhere from 3 and 6 years. Once it has paid for itself, it’s like having a pay rise!

It’s been estimated that, for an average household, an effective system will:

  • provide up to 75 % of annual hot water needs
  • cut about 2200kWh from annual electricity use
  • provide savings of at least $450-$700 a year (depending on the cost of your electricity or gas supply).

For motels, hotels, rest homes and other large users of hot water, installing solar water heating makes even better sense with payback periods as short as 3 to 4 years.

Are the products under warranty?

Yes we offer a comprehensive warranty.

Is solar water heating only for new houses, or can existing houses be converted?

Solar water heating is an excellent solution for both new and existing homes. Often homeowners will take the opportunity when renovating to also install a new solar system which is integrated with household electricity and gas supplies.

How much does it cost? New build homes vs existing home conversions?

Because each installation is different, the costs of solar water heating can vary widely. We assume that a cylinder is already in place or budgeted for in a new house build. The cost to install a solar system typically ranges from $3,000 to $6,000 however talk to us about your particular circumstances so we can provide a firm quote.

Can I use a solar collector with my existing hot water system?

In most cases yes. We would naturally need to understand your specific requirements before confirming this.

Is this the only form of water heating I will need?

There can be times when there isn’t enough solar energy to heat the water and this is when ‘booster heating’ is used to heat up the water in the cylinder to the right or optimum temperature. This secondary booster heating may be via a wetback, electric, and sometimes gas.

Does solar energy help reduce negative impacts on the environment?

If you install solar water heating, you’ll be helping to reduce New Zealand’s dependence on non-renewable energy sources. If each household in New Zealand had its own solar water heater, carbon dioxide emissions from electricity generation would be reduced by about 2 million tonnes per year. Using solar water heating more widely throughout New Zealand would also take a huge load off our other energy resources.