Rooftop solar panels provide energy over your head


While San Luis Obispo County residents are busy debating whether two large-scale photovoltaic plants should be built on the Carrizo Plain, another much quieter but no less important solar boom is taking place in the county — rooftop solar.

While total numbers are still relatively small, record numbers of homeowners and businesses are installing photovoltaic panels on their roofs in an effort to dramatically reduce electric bills and do their part to minimize the effects of global climate change.

“People are starting to be more aware of their impact on the Earth and are trying to lessen it,” said Mike Emrich, president of Atascadero-based Solarponics, one of about six businesses in the county that sells solar panels.

According to Pacific Gas and Electric Co., 670 homes and 42 businesses in the county have installed solar panels since the beginning of 2007. Together they produce some 7.2 megawatts of power, enough to power about 7,000 average-size homes.

For its entire service area, PG&E has 400 megawatts of rooftop solar, which represents about 35 percent of all rooftop installations in the nation, said Kory Raftery, PG&E spokesman.

Rooftop solar — also called distributed solar — is defined as electrical generation that is intended for on-site consumption and not transmitted elsewhere. It is one of three legs of the platform supporting California’s ambitious goal of getting a third of its electricity from renewable sources by 2020. The others are large-scale commercial renewable energy plants, such as the ones proposed for the Carrizo Plain, and increased electrical efficiency.

A recent report by the nonprofit Local Government Commission predicts that climate change will have severe local impacts on agriculture, human health and infrastructure unless greenhouse gas emissions are significantly reduced.

On Nov. 2, voters endorsed the state’s goal of reducing its emissions by rejecting a ballot measure that would have suspended the goal until the economy recovers and unemployment rates are low.

There is broad agreement that reducing electrical consumption through conservation and efficiency is an essential first step. However, there is less agreement on whether the emphasis going forward should be with rooftop or utility-scale solar.

“You can make good arguments on both sides,” said Matthew Woods, vice president for sales at REC Solar in San Luis Obispo.

The main advantage of putting large commercial projects in the Carrizo Plain and elsewhere is efficiency, Woods said. They would produce massive amounts of power at very low cost per kilowatt-hour during daylight hours, when it is needed most.

However, as much as 30 percent of that power can be lost in transmission, and the plants have significant environmental effects, Woods said. Both of the planned Carrizo Plains projects had to be significantly redesigned to minimize impacts on giant kangaroo rats and San Joaquin kit foxes, both endangered species.

Rooftop solar avoids both of those problems. None of its power is transmitted over any distance, and the panels are installed on already existing buildings.

“A roof can be baking in the sun and heating up the interior, or it can be producing power,” Woods said.

On the downside, the upfront cost of installing solar panels can be a bigger expense than many homeowners and businesses can afford to pay, particularly in a struggling economy. It is common for homeowners to pay more than $10,000 for a solar installation after rebates. Also, not every building is suitable for rooftop solar because of poor orientation to the sun or shading from trees and other buildings.

For most renewable energy advocates, however, these debates are academic. They argue that California should be moving full speed ahead with both rooftop and utility-scale solar if the state is going to get serious about reducing its dependency on foreign oil and confronting the growing threat of climate change.

“We need to do it all — rooftop, ground, commercial, residential and utility-scale solar,” said John Ewan, owner of Pacific Energy Co. in San Luis Obispo.

“That said, the first dollar any person or business spends should be on conservation and efficiency,” he added. “The road to reducing greenhouse gases is wide and varied, requiring ingenuity and commitment from many people in many different ways.”