Thermal versus electric solar

I am wondering if anyone compared thermal verses electric solar. I read a few articles claiming electric is now better(cheaper.) I heat with hot water, and I can build a thermal solar system compared to buying the panels and building an electric system. Either way I would be installing and assembling the system. What are peoples recent experiences?

The cost of PV just keeps falling and from a financial standpoint it makes sense to put up panels and use the electricity to heat water to circulate in your existing system. I've got a grid-tied 4.4 KWp array and use a Paladin diverter to dump excess power into the hot water cylinder instead of exporting at the measly feedin tariff that our retailer offers. On a sunny day I get 300 litres of water heated up to 78 C for nothing.

I have been studying in depth and personal opinion is that solar thermal done correctly still wins.  If you are going to go buy a collector, heat exchangers, glycol etc then the answer is no.  But if you adhere to KISS and truly keep it simple solar thermal still wins.  DYI collectors built as drain back, non pressurized storage tanks etc that solar thermal can still win for cost effectiveness.  The key points are 60% to 80% efficiency gathering heat vs 20% for solar panels along with being something I can build nearly totally from scratch.  The other major key point is water while space consuming is a really cheap battery.  Remember that you need storage too.  Where you already have the storage(pressurized I asssume) you may be better off with PV.  But if you were buying batteries too then I would argue solar thermal can still lead.  I have about 2/3 of my write up ready on this for people to check my thinking.  Will try and get it finished and posted.

Hi Eric,
I'll have to start by asking: better for what?
Because it always depends.
Hot water? Heating? Where? What type of house? What use? How many people? Cost efficiency or self reliance as a goal?

In general I am of the opinion that PV systems are superior in most setups. My main reasons are:

You can use electricity for almost anything, hot water only for warm water and space heating.

You need electricity also in summer, hot water not really.

No plumbing, just some cables

No maintenance

But of course there's also reasons to have solar water setup. For example DIY or resilience, as C describes.

Eric Rothoff wrote:I am wondering if anyone compared thermal verses electric solar. I read a few articles claiming electric is now better(cheaper.) I heat with hot water, and I can build a thermal solar system compared to buying the panels and building an electric system. Either way I would be installing and assembling the system. What are peoples recent experiences?

Eric, as a longtime solar guy I will just say it depends. Here are some rough numbers for you. Approx 20-23 percent of the light hitting a solar electric panel is transformed to electricity. When you are using manufactured evacuated tube heated water system you will transform 80-90 percent of the light to heat. It seems light an easy comparison right? It gets complicated though. To get that high conversion for solar thermal you need to be the type of person who can trouble shoot plumbing, pumps, thermostats, holding tanks, vapor locked runs, failing mechanical valves, etc so all that efficiency comes at a cost. Then there is the financial. Retail solar panels are going for 30-50 cents per watt whereas the cost of solar thermal arrays have not changed much in the last 2 decades. Then you have the issue with all you get from the solar thermal array is heat which is considered a low end energy versus electricity which is very flexible. Add in the recent gains in heat pump technologies which give you a 3 to one gain in heat generation over simple resistance heaters and you have efficiencies that are virtually identical... One is more high tech, one is more prone to requiring maintenance. I have not fielded any inquiries about solar thermal in 5 years which corresponds with better heat pumps and the drop in solar electric panel prices.
Cheers,  David