Green Jobs
[ PV panels being installed on the Salveo townhouses in Magnolia; image: Parsons Public Relations ]
It’s an inspiring scene, and one we’ll no doubt be seeing played out more and more. Though at the same time, I can’t keep myself from wringing my hands over how long it has taken us, and how much further we have to go. We lose an valuable opportunity every time we put up a new building without rooftop photovoltaic (PV) and solar hot water systems like those those being installed in the photo above.
The twelve panels that make up the PV system — provided by Puget Sound Solar — cover about 150 square feet of the roof. Rated at 2.4 kW total, the panels are expected to produce about 2,800 kWh of AC electrical energy per year. The solar hot water system is estimated to produce about 2/3 of the hot water needs for a typical two-person household.
As of 2005, the average household located in the pacific division of the western census region consumed 21,000 kWh/ per year total energy, of which 8,500 kWh was electricity. So matching annual household electricity use would require three of the above-described PV systems, and 450 square feet of roof. For comparison, a typical townhouse footprint is about 800 square feet. Offsetting the entire household demand to achieve net-zero energy use would take 7.5 of the PV systems and 1125 square feet — too large an area to fit on a townhouse roof.
The point is that rooftop PV has the potential to produce a big chunk of household energy use in low-rise buildings, even with Seattle’s less than ideal solar input. But of course the catch is PV has high up front cost, and relatively long pay back periods. A 2.4 kW PV system like the one noted above costs in the neighborhood of $20,000. Washington State law mandates authorizes utilities pay up to 15 cents per kWh generated by PV, and there is a 30 percent federal tax credit available for the purchase of PV systems. Applying those two factors yields a 33 year payback.
We need better incentives. Can anyone out there tell us if the new stimulus package will help?