Harness the Sun

That perception was further eroded when the NAHB Research Center tested PV-equipped homes in New York and Arizona to compare the electricity generated by a 2kw system. The East Coast homes conjured about a third less energy than their desert counterparts, but still enough to off set peak rates in the summer months. “With an intelligent design and a thoughtful process, you can put it anywhere,” says Bres. And have it look good … or at least not bad.

Cost Efficiencies. The day when the costs to install solar hot water and photovoltaics run even with utility rates is on the horizon but is not quite here yet. In the meantime, federal tax credits of up to $2,000 for qualified systems and utility rebates up to $4.50 per watt, mandated by state energy legislation to encourage alternative and energy-efficient use (see www.dsireusa.org for a state-by-state listing of incentives), help offset the premium up-front expense of adding solar.

The cost, while declining, is still steep. Current estimates run about $7,000 to $10,000 per kilowatt (1,000 watts), with most residential systems in the 2kw to 5kw range to effectively supplement the power grid. With federal tax credits and incentives, however, the cost of a 2kw system might drop by a third.

Assuming a peak-hour electric rate of $0.22 per kilowatt-hour (kwh) and an annual average of five hours of sunlight per day, a $9,000 system (after applying the tax credits and rebates) would pay for itself in about 11 years—assuming the utility rate stays constant. “We're already seeing peak-use and time-of-day rates in the high 30s,” says Reedy. “At that point, you're making money with PV.”

Other factors and strategies are also at work to reduce costs. Not only are manufacturing processes and materials use becoming more efficient, says Bres, but also builders are learning that PV is not an all-or-nothing proposition. “The goal should not be to pick up the entire [electrical] load of the house,” says Bres, but instead to design systems that offset peak loads (and rates, which, coincidentally, occur when the sun is highest in the sky, beating down on the solar panels) and take advantage of net metering.

BUILT-IN EFFICIENCY:Solar electric or photovoltaic (PV) systems convert the sun's heat energy into electricity. A system of wires behind the roof-mounted panels carries direct current (DC) power to an inverter, which converts it to alternating current (AC), which is then run through the service panel (and ideally tied to the meter) to serve the home's electrical needs. Where allowed or offered, surplus energy can be sold or credited back to the utility, a process called net metering. Advanced technology has enabled so-called “built-in photovoltaics,” a strategy that better integrates the panels or tiles into the roof finish (shown), and may be accomplished as the roofing material is being made. Installing the system then occurs as the rest of the roof is being placed by the roofing sub and connected by the electrician, saving labor costs and cycle time. Today's latest PV arrays require about 100 square feet of roof area per kilowatt, and a 2kw to 3kw system typically provides an adequate hedge against peak-rate electricity, if not offsetting the power grid entirely.

Which means remaining on the grid, a far cry from the goal in the 1970s. Simply, net metering allows surplus electricity generated by a PV array to be “sold” or credited and sent back to the utility, in essence spinning the meter backward, usually during peak hours, when rates are at their highest and the panels are collecting and converting the most energy.

When grid power is required (such as at night, when use and rates are at their lowest), those energy credits kick in. The home owners are only charged for electricity when their use of grid power exceeds what their solar system can generate. To date, 42 states offer net metering.

While a “net zero” electricity goal—in which credits and grid-power use balance over the course of a year, resulting in a zeroed-out electric bill—has been achieved, it can be a difficult and delicate calculation. “You can strive for it, but the homeowners' lifestyle is a wild card,” says Kelly. “We recommend sizing a system to save 40 percent to 60 percent of the owner's electric bill, rather than oversizing for net zero.”

LIGHT FANTASTIC:As any architect will tell you, daylight is essential to indoor comfort. The more surfaces drawing natural light, the better. Thankfully, today's high-performance windows and skylights, as well as translucent panels, glass blocks, and solar tubes for more private or internal areas, can be specified to block unwanted solar heat gain, reduce thermal transfer to R-values approaching those of a solid wall, and cut glare (the latter also helped by placing glass on multiple surfaces in a given room). Thus, windows, glass doors, and skylights can actually contribute to the home's overall energy efficiency while partially offsetting energy consumption for artificial light. These features, of course, should be Energy Star–qualified, and appliances should employ efficient compact fluorescent lightbulbs to reduce their energy use.

Further offsetting up-front costs, or at least making them more palatable to builders and home buyers, is the fact that solar thermal and PV have few, if any, moving parts to break. While they may require a trained installer (a network of which is evolving), they are almost self-contained systems bolted to the roof frame and fed into the subpanel or water heater. To further assuage homeowner fears of and responsibility for maintaining a system, suppliers, including SunPower, offer remote monitoring and troubleshooting services. By all accounts, though, solar thermal and, especially, PV systems have proven to be low maintenance and reliable, with warranties ranging from 10 to 25 years.

But we've been here before, to some degree. What's to keep solar from again being a flash in the panel, as it has shown to ebb and flow in consumer and housing industry consciousness since the 1970s? “This time, it's an economic driver instead of a regulatory or social driver,” says Reedy. “In the end, it's all about money, and now we can show it's a good investment.”

Solar energy solutions don't operate in a vacuum. To be truly effective, they must be part of a comprehensive commitment to reducing a home's energy needs. “The goal is not to replicate or replace the utility, but to conserve energy in a responsible manner,” says HUD's Dana Bres. That means designing and building a high-performance house first, one that lowers its energy demand as far as possible—including passive solar techniques (see “Passive Aggressive,” above), before adding solar thermal or PV to the mix. “At that point, you're talking about a 1kw to 3kw system to offset a total load of 5kw to 7kw,” Bres says. “That's achievable and reasonable.”

Active solar technology is continually evolving to further dig its heels into the building industry, make the most out of the sun, and improve its aesthetics. One such advancement is the Heliotube from Soliant Energy in Pasadena, Calif., which employs concentrator design for its PV panels. Each panel (similar in size and shape to a conventional flat-panel PV) features an array of self-powered tubes and lenses that turn to track the sun's path across the sky, optimizing sunlight to the solar cells. To reduce its premium cost compared even with PV, much less retail utility rates, Soliant eschews expensive silicon for a triple-junction, high-efficiency mirror material, which also boosts the system's efficiency. The downside? Chiefly that concentrator technology is bulkier than flat-panel PV. As a result, Soliant plans to launch its product in the commercial building sector first, likely in 2009, where rooftops are either flat or relatively unseen. A move into residential may follow a year or more later, depending on Soliant's success and continued consumer acceptance of and demand for solar solutions.

PV PATH:You can't walk through a Home Depot without tripping over a section's worth of photovoltaic-powered landscape lights and matching lampposts, so feed the consumer consciousness they've instilled by installing them in a spec home. Not only are they relatively inexpensive to buy and install (no wires required), but they resonate with buyers—and save energy by not only going off the grid to mark a path, illuminate a driveway, or uplight a shrub, but also by operating automatically and efficiently instead of relying on the owners to switch them off at bedtime.