Solar water heating devices have been around for over a century in one form or another. And it’s always been known that using free energy from the sun via a solar water heating system is a great way to substantially reduce water-heating costs over a period of time. But it’s the advancements in absorber coating technologies that we’ve seen in recent years that allows modern solar collectors to reliably convert more than 50% of available sunlight for domestic hot water supply! No wonder they have been increasing massively in popularity in New Zealand homes. Here are a few things you need to know if you’re considering installing solar hot water at your place.
What is it and how does it work?
Solar water heaters do not generate electricity. This is a common misperception. Solar water heating systems use the solar energy from the sun to generate heat. They absorb the sun’s energy in collector panels on the roof and transfer it to the water stored in your hot water cylinder.
Is it all I need?
Solar water heating systems can operate independently but are better when backed up by a booster system such as a heat pump, wetback, electric or gas heater. This is because there is not always enough sun/solar energy in a day to heat the water. When this happens, the booster system kicks in to finish getting the water to the right temperature.
Will it save me money?
By offsetting the use of other energy sources, a solar water heater is one of the most effective ways of cutting your carbon footprint and reducing your energy costs. On average, a well-designed and installed system can provide up to 75% of a household’s water heating needs during summer. It goes down in winter to about 25-45% simply because daylight hours are shorter and sunny days are fewer.
Do I have to be building new to install solar?
New builds do enjoy some advantages, such as allowing more freedom to design a system that will achieve maximum efficiency. However, it is also possible to retrofit solar water heating systems into certain existing homes or work premises; consult with a supplier to find out if it can be done at your place.
Things to consider
In comparison with other hot water systems, the upfront cost of installing solar water heating is high.
You need to live in an area that sees a decent amount of sunshine hours.
Check with your electricity retailer to see if a cheaper night rate is available. If so and you intend to use night rate electric back-up, make sure your storage tank is big enough.
It is imperative your system is correctly set up by a professional to ensure the water regularly reaches 60C (to prevent the growth of legionella bacteria).
They require annual maintenance.
Best case scenarios
These two situations make solar particularly worthwhile:
Use it in conjunction with a wetback on a wood or pellet burner during winter; that way you’re heating your home and the water.
Use it as a very simple pre-heater with no controllers, or pumps, and plumbed into the pipe going into the water-heating cylinder.