What Should You Buy First? Solar Hot Water or Solar PV?

Solar Hot Water is fast becoming the poor cousin of Solar PV (AKA Solar Electricity). Consumers just seem to prefer solar PV to solar hot water these days. In fact solar hot water has gone from almost zero to 1,000,000 roofs in about 30 years, whereas PV has gone from almost zero to 500,000 roofs in about 5 years. Soon there will be more PV than Solar HW out there! Unbelievable.

It doesn’t help that retailers prefer to sell PV over hot water – for a whole bunch of reasons that I’ll go into in a future blog post.

Here’s a video where I answer the question posed in the title: Should you buy Solar Hot Water or PV first?, But first I answer a much more fundamental question that creates an enormous amount of confusion out there:

And here’t the transcript for the video-phobes amongst you:

Okay so this is a rarely fundamental question that I get asked. A lot of people out there think the answer is obvious, but it’s also has a lot of confusion about this. The question is:

What is the difference between a solar hot water panel and a solar electricity panel?

They are completely different things okay?

A solar hot water often has an integrated tank so it stores the water on the roof with the panel, you can also get them without the tank, where the tank is on ground level.

How do these panels work? It’s really simple, you pump cold water literally through the panel, the sun comes in hits the glass -  hits the water, heats the water –  the hot water gets pumped the hot tap, simple as that.

There are two main types of technology for solar hot water panels. First is the flat plate collector, called… “Flat plate”. The other is a funkier looking technology and I get into all sorts of trouble with so hot water dealers if I say they are more efficient. They are called Evacuated Tube and they’re more expensive, as generally they convert more of the sun’s heat into heat in the water. Hence, why they’re more efficient certainly more efficient at lower temperatures.

So, if you live somewhere chilly like Melbourne or Tasmania, you probably looking at evacuated tubes wheras  if you live somewhere like Brisbane, like Northern New south Wales, evacuated tube is probably a bit over the top. So that’s the solar hot water panel.

The second type of solar panel is thetype of solar panel that people generally are thinking about when they think about solar – and that’s the solar electricity panel.

You get between 6 and 60 on a roof.  They are much smaller than solar hot water panels and all they do is they take the sunlight in and use a mixture of semi conductors and silicon to convert the sunlight into electricity, so you get sun in and electricity out.

What should you get first?

Another common question when we’re talking about hot water and solar electricity is which type should you get first. The really simple answer to that question, is it depends how you heat your water at the moment. If you use electricity to heat your water, get solar hot water first and the payback will be between 5 and 6 years and that will probably be a faster payback in solar electricity, which would be between 6 and 10 years.

So get solar hot water first, if you have an electric hot water system at home.

If you have a gas hot water system at home then it’s completely the other way around. Gas heats water really efficiently anyway, so solar hot water will make it more efficient. But the payback if you retrofitting solar hot water to an existing gas system will probably be 15 to 20 years whereas if you get a PV system, the payback will be between 6 and 10 years.

So that’s the difference between solar hot water and solar PV and the answer to question which should you get first.