California architects Arkin and Tilt used California Energy Commission rebates and a now-defunct grant program to lower the cost of their $15,000 system to $6,000, and solar supporters agree that incentives are the most important catalyst for growth because they attract users and lower system costs. Not every state offers incentives, but many of those that do are at the forefront of efforts to drive widespread adoption of solar technologies. California, for example, is eyeing another bill to put solar power in half of all new homes within 13 years, and Oregon recently raised its income tax credit to $6,000 per installation. A federal energy bill signed by President Bush offers a $2,000 credit to homeowners with installed systems.

Solar panels' increased efficiency and output are also driving installation growth. Today, a single panel carries a rating of 5 watts to 200 watts; the rating indicates the amount of power the panel can be expected to produce in full sunlight. Generally, the bigger the panel, the more watts it produces.

Solar-panel manufacturers aren't done yet. SunPower will soon launch a 220-watt silicon-based panel with the same dimensions as its older products. And d.Blue, the newest photovoltaic module from Scottsdale, Ariz.-based Kyocera Solar, reportedly offers a breakthrough in energy-conversion efficiency that maximizes the amount of sunlight a cell can absorb. It's rated at 167 watts.

Other companies are looking to the future as well, developing new processes and technologies that could change the way electricity is produced and consumed. STMicroelectronics, a Geneva, Switzerland-based semiconductor manufacturer, recently discovered new ways to produce solar cells that will generate electricity at costs 20 times lower than those produced by current products. Meanwhile, Matsushita Electric Industrial Co. of Osaka, Japan, has teamed with Nanosys, a Palo Alto, Calif.-based nanotechnology company, to develop solar coatings that could be painted on roofs and walls. Related products are not expected to hit the market for several years, however.

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Scarpa, a solar-panel user for more than 10 years, says some architects avoid solar technology because it seems too complicated. “The truth is that it's very easy,” he insists. “Don't be turned away by the perceived difficulty.” He also advises architects to design a house and its solar system as one unit. “If you treat it as part of the architecture, it will blend in much nicer,” he says.

Other architects who have worked with solar systems warn that it's cheaper and easier to install panels when the house is being built. “If I tried to retrofit my roof with a solar panel now, it would require demolition,” says Chicago architect Zoka Zola, AIA. “It costs five times more to retrofit, but a fraction if you do it at the beginning.” She adds that architects working with limited budgets that won't permit installation during construction should design so the client may easily install panels later.

Solar-savvy architects also say that the best type of installation is tied to the homeowner's utility grid. “A large system turns the meter backwards so that during the day, excess power is sold back to the utility,” Macdonald explains. Scarpa says architects also may choose a grid-independent system and store power in a battery, but he cautions that the battery “takes up a lot of space and costs a lot.”

Arkin encourages architects new to solar to visit solar projects in their area and to contact their local utility companies for information about tax breaks and incentive programs. Even better, “try the panels on your [own] home,” he says. “Study them and learn from them.”