JUST below your correspondent's hillside home in southern California, a house is being rebuilt with all the latest thinking in materials technology and construction codes. Much has changed in the eight years since your correspondent did the same. Most strikingly, the house below has a gleaming white roof of fireproof chippings embedded in a mastic undercoating. With summer temperatures in the nineties (32ºC and up), these new reflective coatings are said to reduce air-conditioning bills by 20% or more. Not content with that, the owner has added a five-kilowatt bank of solar panels.
Eighteen months ago, your correspondent ran the numbers to see what it would cost to use photovoltaic solar panels to replace the 8,300 kilowatt-hours of electricity he buys annually from the grid. Economically, solar turned out to be a dud. The 6.4 kilowatts of capacity needed would have cost $48,000 for the panels alone—and half as much again by the time the mounting frames, switching modules, power controller, fault protector, DC-to-AC inverter, service panel and installation charges had been included.
Admittedly, there would have been $14,000 worth of government grants to soften the blow.
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