Photovoltaic systems have a key role in energy-efficiency strategies. Home photovoltaic systems are no more an unaffordable dream.
Photovoltaic systems only make sense in energy-efficient homes. Only in such homes PV systems can meet most or all the household's electricity needs.
Unfortunately their use can also be misleading, and a mere piece of the marketing strategies of developers and builders.
Average American households consume too much electricity: about 12.000 Kw-hour of electricity per year; a 2 kW photovoltaic system output will meet less than 1/6 of that consumption, even in the South, where solar resources are better. And that's too little, and not much helpful.
When installed in homes with low or moderate levels of insulation and with inefficient appliances and equipment, photovoltaics systems are not much helpful. They will provide too little electricity (see box).
They should be designed and sized to meet all the home's electrical needs: to operate all the light bulbs, appliances, electronics, heating and cooling equipment and other needs.
Solar PV systems are now competitive with fuel generation in many regions, worldwide.
A 5 kW installed PV system, in North Ameica, may cost about $20.000, and it can be a good investment - as long as you have reasonable or good solar resources and meet some basics. Such a system cannot meet the average consumption of most American homes, but can meet most or all the needs of a very energy efficient home. The key to it is energy efficiency. First, you have to reduce the home's energy requirements significantly. And that's possible, in new construction.
Obviously, there are also situations where buying green power - from large wind systems, or other renewable source - is more advantageous than producing green electricity on-site.
See: Photovoltaics Guide