Solar Hot Water Systems
LESLIE: Well, if you’ve ever felt warm water flowing from a garden hose that’s been stretched across your sunny lawn, you already kind of understand how solar water heating works.
TOM: And if you’ve ever paid a fuel or electric bill, you can understand why using the sun’s rays to warm water is a really good idea. Joining us now with some details about solar hot-water heating systems is Richard Trethewey, the plumbing and heating expert for TV’s This Old House.
RICHARD: Hi, guys.
TOM: And solar heat has been an option for a lot of years but I’m happy to see that lately, everyone has become so much more interested in being more green; it’s really taken on some new life. So, how does a basic system work?
RICHARD: Well, the basic setup consists of a heat-trapping solar collector. That’s either going to be these flat panels or the special tubes that sit outdoors, facing south, usually up on the roof.
RICHARD: And there’ll be some sort of water-storage tank down inside the house.
TOM: So, essentially, there’s a circulating pump that moves the water across the collector and then down to the storage unit.
RICHARD: Now, in cold climates, there’s going to be a circulator pump that doesn’t pump water through the collectors; it’s actually going to be glycol, a non-toxic propylene glycol that is an anti-freeze, really.
RICHARD: And it goes up through those collectors, absorbs energy from the sun, brings that down to the tank and transfers that energy into the water that’s inside the tank.
LESLIE: Now, are there certain areas of the country that really this is a better opportunity for or are there ways to make this work, regardless of your climate?
RICHARD: I think people don’t understand. The sun is out in most parts of this country enough that solar thermal – and that’s the solar to make domestic hot water – makes a lot of sense. You can always get 65 to 70 percent of your domestic hot-water production using the sun, even in the northern climates like we are up here in New England, where I live.
TOM: Now, on some days, I would imagine you are heating far more hot water than you really need to. Do you store that? Is there a way to save it until the cloudy days?
RICHARD: Well, that’s the challenge. There are days you actually have more energy than you know what to do with and sometimes, you have to do a heat dump; you have to get rid of some heat. That’s where it’s often good to have a pool; if you want to heat a pool or something like that, it’s terrific.
We’ve even seen people that have solar systems on vacation houses where they’re not there, where there’s a little device that can actually run the solar backwards during the night to take the super-heated water in the tank and dump it to outside because you actually have too much energy.
TOM: Interesting, interesting.
LESLIE: Mm-hmm. You know, we actually vacationed once in St. Lucia and the entire hotel had the same solar water-heating systems. And every night, we would hear it draining from all the different rooms and the first night, we were like, “What is that?”
RICHARD: That’s right.
LESLIE: And when we called the front desk, they explained to us the whole system.
RICHARD: That’s right. Right.
LESLIE: Now, with solar water-heating systems, I imagine they’re kind of expensive to put in. Do you recoup that kind of quickly or does it really take a long time to get that back?
RICHARD: Well, as is so often the case, you’ve got to spend money to make money. And so, it really depends, I think, also on the local utility rates. For a family of four, you’re going to do a system – typical system – with an 80-gallon tank. It’s probably 5,000 for the materials, another 2,000 or so for installation. And the payback periods could be relatively quick – five, six, seven years – and it really depends on how much hot water you use.
TOM: Now, comparing that to, say, active solar where you have photovoltaics, though, it’s probably a lot less expensive.
RICHARD: Well, it’s got a high efficiency. The thing about photovoltaics is they have some unbelievable incentives that make it – and that – and the cost of that technology is coming down in price every day. It’s often – it’s like what’s happened with computers; there was a time that computers were much more expensive. As more people bought it, the premium came down. We’re seeing that with solar thermal and with solar photovoltaics.
LESLIE: And I think for the pedigree of a home, when you go to sell down the road, to say, “We have solar water heating,” it ultimately makes the house more valuable.
RICHARD: That’s right.
The other metric that’s not in this discussion is the cost of fuel. In August of ’08, fuel prices got to almost $4. Fuel oil was $4.10 around where I live. We couldn’t keep enough solar in stock; everybody wanted to do solar. And then as the price came down, people got a little more complacent. And so, all that stuff is going to be driven a lot by that fossil-fuel cost.
TOM: And there’s really an opportunity issue here, too. You mentioned it briefly before but the rebates, the incentives, the tax credits, they’re always changing. Keep an eye on that, because there could be a golden opportunity to get a system like this installed if you meet those requirements.
RICHARD: That’s right. The government and the local utility can be your friend in that case.
TOM: Great tip. Richard Trethewey from TV’s This Old House, thanks so much for stopping by The Money Pit.
For more great tips just like that, you can visit ThisOldHouse.com.
LESLIE: And you can watch Richard and the entire This Old House team on This Old House and Ask This Old House on your local PBS station.
TOM: And today’s This Old House segment has been brought to you by Lumber Liquidators. Lumber Liquidators, hardwood floors for less.