Traditional solar thermal hot water isn't always the best option.
They're super simple & reliable but heavy and can have problems with frost bursting the collectors, boiling water in summer and even hail damage.
Heat pumps require a broader solar power system to make them work.
Though they're very efficient if you do have a power system capable of supporting around a 750watt load.
So when you need something that is self-contained
Finding the right device to heat your water using solar electricity can be difficult, particularly given the limited options if you really want something that is a stand-alone device. The market is niche, which often means you need to double-check for local compliance if you find products from overseas.
The Risks of DIY Solar Water Heating
You may be tempted to go the DIY route and directly hook up DC from your solar array to your hot water unit. Word to the wise: don't. Doing so will burn out your thermostat in just a handful of cycles. Not only that but operating sheathed elements in water with a single polarity can cause corrosion.
In actual fact, running DC through a steel frame is a great way to grow an artificial coral reef—not what you want in your hot water system.
Looking Over the Ditch: New Zealand Solutions
What's available from our friends in New Zealand relies on a grid-connect style inverter that outputs AC to the hot water element. These units are designed to comply with ANZS 3000 wiring rules and are particularly useful for those looking to upgrade their existing solar power with a new grid-connect system.
The old array for your 1 or 2kW system can be repurposed just for hot water.
This also means you can have more solar without any impact on grid connection approval, export limits, or feed-in tariff.
You can check out the HotPV package from EasyWarm for more information.
Closer to home, Sunflux offers devices that switch DC current into a "modified waveform." However, their availability is a bit murky. If you're opting for a local solution, it might be worth giving this a look.
In summary, wherever you find a product, always ensure it's compliant with Australian and New Zealand standards. As the saying goes, "better safe than sorry," especially when it comes to complex systems like solar hot water heating.