Blog Post Monday 18 May 2020
Most of us probably take the hot water that runs out of our taps for granted. Yet if you stop to think about it, you’d miss having hot water on demand if your hot water system happened to break down. In Australian households with electric hot water systems, we pay a considerable amount for the privilege: our water heating accounts for about 25% of total energy usage. So what if you could generate your own water-heating power from solar and cut your power bills by one-quarter? Investing in solar water heating is one way you could do it.
Currently, around 13% of Australia’s hot water systems are solar water heaters. Solar water heating uses the free and abundant energy of the sun to heat your residential water. Two common types of systems are solar PV and solar thermal. Both harness the energy of the sun to heat your hot water, and both feature rooftop panels.
Solar photovoltaic (PV) systems convert solar energy into electricity, which is then used to power your hot water system to heat water. One of the big advantages of solar PV systems is using this electricity to power anything in your home, not just your hot water system. You could potentially generate all of your hot water electricity demand from your solar panel system.
Solar thermal water heating systems, on the other hand, use sunlight to directly heat water. Solar thermal panels incorporate copper tubes for collecting water and heating it using sunlight before sending it back to a storage tank.
Solar thermal can be more space efficient than solar PV, and it’s highly efficient, able to turn as much as 90% of radiation into heat in contrast to the 15% or 20% associated with solar PV systems. While solar thermal could be the cheaper option of the two, you can’t use it to power anything else in your house. Additionally, with solar PV you can sell excess electricity back to the grid through the feed-in-tariff system.
With a solar hot water system, the cold water flows from your tank to the solar collector, which is usually situated on the roof. In split systems, cold water gets pumped up to the collector. In thermosiphon systems, the tank is located on the roof. The cold water runs into the collector as it’s heavier than hot water. When the cold water travels through the solar collector, the heat of the sun as conducted by special materials heats up the water before it’s returned to the water and ready to use when you turn on the tap.
Gas, electric, and solar are the main options for hot water systems in Australia. Solar water heaters are the most efficient option, better than gas or electric heaters for energy efficiency and running costs.
Ultimately, how much money you’ll save with solar and gas depends on what type of system you currently use. It also varies depending on how much hot water you use and the specifications of your new system. Things like the location and orientation of your house and the amount of sunlight can also impact how much you save.
While solar water heating systems will cost you more to buy and install, their payback period can be as little as seven years. Depending on the size of your system and other factors, a solar hot water system might cost you around $3,000 to $7,000 fully installed. Note you might be able to claim a rebate or be eligible for other incentives depending on your state or territory, in addition to the federal government-regulated Small-Scale Technology Certificates.
A four-square-metre solar collector (two panels) and a 300 to 360 litre tank might be sufficient for the average four-person household. However, if you’re in a region with less sunlight or if your property isn’t optimally oriented for sunlight, you might opt for a larger tank to cover you for cloudy days.
When it comes to solar water heaters, you have a lot of options, and it’s important to take into account your household size, climate, house type and orientation, roof design, and available space. Within solar hot water systems you can consider a range of additional features like natural gas, LPG, or electricity boosted for backup and extra peace of mind. Solar will typically be a more cost-effective option than gas or electric, but if solar is not an option, gas hot water systems can be the next best choice.