If you plan on running a renewable energy system than it’s a very good idea to run a low cost solar water heater. If you’re looking to save money on heating costs than installing a solar water heater is also a good idea also.
The problem is… how big of a solar water heater do you need? The most popular type of solar water heater available on the market today is an evacuated tube design. There are also flat plate solar water heaters; however, I don’t recommend that you use them for one important reason.
In tests done that have compared the evacuated tube and flat panel designs it has been found that evacuated tube designs are much more efficient at converting solar energy into heat over a wide variety of conditions. If you live in an area where it is sunny all the time (in which case I’m jealous) than a flat panel collector is best for you, but they are only more efficient in full sun. Once some clouds start floating by the evacuated tube design wins every time.
What Size Solar Water Heater?
The next question that comes up is how big of a water heater should you get? There are several ways to go about this, but if you’re just getting started in solar water heating than my recommendation is to start with a 10 or 16 tube solar water heater.
Why? As with all things renewable energy related, solar water heaters are expensive and I’ve thought out a system where you can start small and use the savings to purchase additional equipment. For example, lets say you’re a family of four and you start with a 10 or 16 tube heater. Depending on your hot water usage that can save you anywhere from 25% – 50% of the cost of heating water.
The next month you simply look at your electric (or gas) bill and figure out how much you saved. Put that into a savings account and within 6 months you’re going to have enough to buy another 10 – 16 tube heater… which will save you 50% – 100% of your heating costs! You still spent the same amount of money in the end, but you had a lower up-front cost (typically less than $500).
I Want To Buy A Full Installation… How Big Should It Be?
If you’re looking to build a complete solar water heater installation than you’ll have to look at things a little bit differently. The first thing you need to do is take a look at your current hot water usage habits. On average, each adult in the household will use about 20 gallons of hot water per day; however, if you for example wash your clothes with cold water etc. than you can probably reduce this to 10 – 15 gallons of hot water per day.
Now comes the tricky part. On the solar hot water heaters you’re looking at there should be a BTU rating (daily BTU’s produced in sunlight and cloud). As a rule of thumb 10,000 BTU’s will heat up 10 gallons of water (that’s off by a bit, but it makes the math much easier). So for a family of four you’ll need to produce at least 60,000 BTU’s of heat per day. For reference, a 30 tube collector generally collects 40,000 BTU’s on a sunny day and 25,000 BTU’s on a cloudy day so you will need 2 30 tube solar water heaters.
Where To Buy?
The next question that usually comes up is where can I buy a low cost solar water heater? Although you can head down to a renewable energy store or your local hardware store (some of them do have them now!) I find it’s much cheaper to buy them online from eBay or Amazon.
They both have quite a large variety of low cost solar water heaters. I’d use Amazon if you’re looking for brand new with warranties and I’d use eBay if you’re looking for something used that’s a little cheaper (note that eBay also has new ones as well).
The most important thing to remember in deciding if a solar hot water heater is right for you is this: it’s much less efficient to convert solar or wind energy into electricity and than use that to heat water.