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Solar Hot Water


I’ve been thinking about doing a solar hot water system for a long time, but I’ve finally got an upcoming project that looks like a perfect candidate. As I’ve been asking around town about contractors two names keep coming up. Tech Sun Solar and The Solar Man seem to both get good reviews. Basically they both recommend similar systems. The Solar Man has a great website with lots of good information, but I’d say read it with a critical eye because I don’t agree with all his thoughts. He’s obviously slanted towards selling Solar Hot water and dishes on tankless heaters a bit too much. I got a chance to meet with Curtis “The Solar Man” last week and we had a really informative meeting. He’s got a ton of experience doing this in Austin and it’s his main business so I really trusted what he was telling me. He’s the brief summary: The system consists of solar collectors on the roof (cross section photo and installed photo shown), and a two tank system inside the house. The first tank is the solar “pre-heat” tank that’s connected to the collectors on the roof. A non-toxic anti-freeze is pumped through the collectors and into the first tank which heats the water inside. The anti-freeze and the water don’t actually touch so it’s a closed loop system. This first pre-heat tank is roughly 75 gallons and on a sunny day really heats the water to a steamy 140 degrees. Then, when you open a faucet and ask for hot water you pull from tank #2 which is a traditional gas or electric 40 gallon tank. This water is replaced with the pre-heated water (instead of cold from the water supply at 65 degrees it’s 140!) and Curtis tells me this reduces your water heating bill by 80%. I guess that depends on how much hot water your family uses, but that number seems reasonable. He says payback on these $4000-5000 systems are about 5-7 years. Considering solar electric payback (even after rebates) is well above 10 years this seems pretty quick. You need to replace the anti-freeze every 3-4 years and I would guess that your tanks would need replaced every 10-15 years. Overall seems like a good option for renewable energy. Too bad that you need such a large space inside your house for two big tanks (3×5 closet). That’s one of my favorite things about tankless water heater is you can hang them on the outside of the house to save space. You really need to design the house to have a good south facing roof for the collectors and a closet for the tanks from the outset. I like that the payback is much quicker than solar electric, but there’s something to be said about the lack of moving parts in a solar electric array. I like the lack of maintenance required in solar electric and the long-term reliability aspects. Solar electric isn’t as sexy as PV, and it’s pretty old school technology but it’s a great way to reduce your energy usage and I’m really looking forward to installing a system in a Risinger Home soon! -Matt Risinger