Great for electricity production—not for heating water.In our last column, we showed why solar water heating is the single most effective way that you can save energy and money at home, reduce your use of fossil fuels and shrink your “carbon footprint.”
How about using the “other” solar technology—photovoltaics—to make electricity and use that solar electricity to heat water?
This is definitely not a good idea. Yes, photovoltaics work, and they work well in sunny locations across the Valley Isle. Yes, a solar electric system makes electricity silently, with no emissions, for decades. Yes, photovoltaic-generated electricity can be cheaper than the kilowatt-hours you now buy from MECO.
But photovoltaics should be used to do what they do best—make electricity for computers, microwaves, stereos, lamps, and all the other things in your house which require electricity. They should not be used to heat water. For that simple task, use a solar water heater—it heats water directly and inexpensively by collecting and storing the sun’s heat.
Why not use photovoltaics to heat water? For one thing, it’s far more expensive. After tax credits, you’re likely to pay only about $1,400 to $2,100 for a solar water heating system. To make the same amount of hot water with a solar electric system, however, you’d probably need to pay more than $40,000, after tax credits! Photovoltaics are, quite simply, more expensive per unit of energy produced than solar water heaters.
Also, solar water heaters take much less space. A family normally needs only two collectors and perhaps 50 to 80 square feet of space. To do the same job as the solar heater, a photovoltaic system might require more than 30 modules and perhaps 450 square feet of roof space.
It’s a far better idea to install a solar water heating system first, and also implement all the electricity-saving measures you can (such as changing light bulbs to compact fluorescents, and replacing major appliances with Energy Star or other efficient models) to reduce the amount of electricity you use. Then, when your electric consumption is as small as you can make it, invest in a solar electric system. You’ll get more bang for your buck.
In partnership with the state’s energy office, the Maui Weekly provides this feature to help Valley Isle homeowners reduce their utility bills and increase their environmental awareness. For more information, visit www.hawaii.gov/dbedt/info/energy.