Choosing a solar water heater is hard work!
There are hundreds of different configurations and brands to choose from. Thermosyphon, evacuated tube, flat plate, drain back, closed loop - it's like something from an old B grade science fiction movie.
And then, just to increase the mind-boggling options, you also get something called a heat pump water heater which takes heat from the surrounding air warmed by the sun and transfers it very efficiently to the water in your tank to make it hot.
Not to mention the fact that you could also build your own solar hot water system very cost effectively if you are proficient at handiwork.
I know how difficult it is to choose as I went through the same decision confusion after wanting to go solar for my own domestic hot water.
But I finally found a solution which makes it much easier to put your hard earned cash down. Here's how...
Your decision becomes a lot clearer when you know exactly what the actual performance of a solar water heater is after its installation. Sounds simple enough doesn't it?
But how do you know what the real, in the field, practical, everyday water heating efficiency of Brand X is, without actually having it installed at your own home?
Well, here's where the problem comes in, because even the people selling the water heating systems can't tell you accurately because there are just too many variables involved, such as the amount of hot water you consume and the weather conditions at your particular location.
"Bruce", they say, "you can save between 30 and 50% of your total power consumption bill with this system."
Ok...sounds very promising, but 20% is a pretty big spread, especially when I'm trying to work out what the payback time really is. You can't calculate it with much accuracy on this basis, you would be roughly estimating at best.
So, frustrated by this inaccuracy, I've started collecting better performance information from helpful home owners who already have these systems installed and are willing to share their results
And I'm displaying the results on this website so that you and I will know exactly what the performance of Brand X is in the field for that system owner and their particular situation. You can then compare it to your situation and get a better idea of how the system could perform if you were to install it.
It won't ever correspond exactly because many of the variables at your home are unique such as hot water consumption, cloud cover, daily temperatures and roof angle, but it will give you a clearer insight into what you can reasonably expect from a solar or heat pump water heater performance wise.
Laboratory testing has its place, but field measurement after installation gives a truer reflection of solar hot water performance.
There are two major performance metrics or indicators used to measure the efficiency of already installed solar water heaters...
In the case of a heat pump water heater, electricity and not the sun provides the power for it to function, even though it does use thermal energy in the air generated by the sun to heat water.
So measuring these metrics will tell you exactly how efficient a particular system is in the field and what kind of performance you could reasonably expect from it.
Here are the results of the latest measurements using a number of different energy monitors