Energy Advocacy for San Francisco and the Bay Area
September 11, 2007
|GET A SOLAR EVALUATION|
Solar For Me?
The most critical requirement for solar electricity is a roof with an unobstructed view of the sun. South facing roofs are best, although east and west facing roofs are good candidates (west facing is preferred due to higher costs of electricity in the afternoon). Your roof (or wherever you intend to mount the panels) should be free of shade, especially during peak production hours between 10am and 2pm. Flat roofs and pitched roofs can both be accommodated - flat roofs are easier for installation and may offer more flexibility on angle adjustment.
As longtime San Francisco residents we just assumed that with our foggy weather, solar electricity simply wouldn't make sense. Most people are surprised to learn San Francisco and the Bay Area are ideal for solar electricity. Fog does reduce the efficiency and output of solar panels, however light colored fog (or "bright" fog) may only cause a 10-15% reduction in efficiency. Dark fog, or heavy clouds, will significantly reduce efficiency, by 75% or more.
In general, Bay Area homes benefit from very high numbers of sunny days, averaging over 300 per year. Also, the relatively temperate climate reduces the stress on the panels - they operate more efficiently at cooler temperatures. And you certainly never have to worry about panels getting covered with snow!
Factors Affecting Solar Output
How Big a System do I Need?
The first thing to assess is what your goals are for solar electricity. Here are some common goals:
Next, take a look at your electricity usage for the past 12 months. Don't worry if you haven't kept all your PG&E bills. You can call (800-743-5000) and request this information, or better yet, get it all online. If you don't already have a PG&E online account, follow these steps:
For guidance, here are
some ballpark estimates of system sizes and costs. In San
Francisco, almost all installations are 2-5 KW, with the
majority in the 2-3 KW range. If you live outside the city
and have a larger home, you might consider something larger
* Cost estimate includes equipment, materials, installation, permits, and is net of rebates.
One last thing to consider is your future expected electricity usage. Future household purchases may be made with solar in mind. For example, you might replace a gas dryer or stove/oven with electric, or buy an plug-in car or electric scooter for transportation. If you know this is likely, you should factor this into how large a solar panel system you need.