John Langdon, with a company called HelioVolt, points out that solar power is in a state similar to the situation of air conditioning in 1950: not yet considered standard equipment in new construction. Back then, window units were the prescribed retrofit for buildings without central air — and 6-inch deep solar panels are the corresponding retrofit for non-solar buildings now.

In 2007, solar installations soared 45 percent, but with solar power still less than 1 percent of the U.S. total, that's a drop in the bucket. Steep energy prices and subsidies help sales; however, at about $40,000 for a typical installation (before subsidies) price is the obstacle to buyers.

Solar companies can't lower the price, but they are addressing another objection: the ugly appearance. Thick panels and add-on brackets for roofs are giving way to thin-film construction and roof tiles that are attractively integrated.

Central air conditioning caught on nicely, thank you; it won't be long that solar power — with better aesthetics — will catch on too.

Questions can be sent to Jim Parks at [email protected]. To find out more about Jim Parks and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.