Energy adviser: Solar water heaters work in Northwest

Thursday, May 6, 2010

Solar Hot Water

I’m interested in solar water heating? How does it work and is it feasible here?

On average, a solar water heating system properly installed here can provide more than half the hot water needed by a typical home throughout the year. From May to September, it should provide almost 100 percent. Since water heating accounts for about 15 percent of a home’s energy costs, these systems can save you money. But they don’t come cheap. We recommend you research the technology and talk to a couple of quality installers before investing in a system.

• How they work

A roof-mounted solar collector is made up of tubes of circulating liquid that absorb the sun’s radiant heat. The heated liquid is pumped through a heat exchanger where it preheats water in a solar tank, typically located next to your water heater. The preheated water is fed into your water heater, reducing the amount of energy needed to bring the water to the desired temperature.

• Heat exchangers

You can install a separate solar tank with a heat exchanger or choose to replace your water heater with one with an internal heat exchanger.

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“If you have an efficient water heater, you probably want to hang onto it, and go with a separate solar tank,” said Heath Kearns, sales manager with Mr. Sun Solar in Portland, which makes and installs the Sol-Reliant system. “Water heaters with a heat exchanger cost between $300 and $400 more, but are substantially more efficient. With a two-tank system, you have to use hot water before the preheated water can enter the tank. In a single tank, it’s being preheated no matter if you’re using water or not.”

John Lutes of Simple Solar Solutions in Vancouver sells three brands of systems, ranging in price from $4,000 to $9,000. He typically installs an external heat exchanger, which allows him to use a “plain old water heater.” That’s much less expensive than an internal heat exchanger.

• Incentives

Solar water heating systems certified by the Solar Rating and Certification Corporation are eligible for a 30 percent federal tax credit and a $1,000 rebate from Clark Public Utilities, if installed by an approved contractor.

Kearns said the incentives mean a $9,200 system would carry a net cost of $5,740. In addition, Washington residents pay no sales tax on solar equipment.

• How it pencils out

Lutes, who is a former accountant, makes a financial argument for solar hot water systems.

“It takes nine and a half years to pay back the system, so that’s a 10.5 percent return on your investment,” he said.

Although incentives and tax credits do not apply, solar swimming pool heaters can reduce pool-heating costs considerably.

The Energy Adviser is written by Clark Public Utilities energy counselors, who provide conservation and energy use information to utility customers. Send questions to energyadviser@clarkpud.com or to Energy Adviser, in care of Clark Public Utilities, P.O. Box 8900, Vancouver, WA. 98668. Past topics are available at www.clarkpublicutilities.com.