Solar photovoltaic (PV) residential systems can operate for 25 years or more; and they should be designed to meet most or all of the home's electricity consumption.
Reducing electricity consumption in existing homes may not be easy. But that’s not impossible. And you should try hard to achieve it before installing a PV system in your home.
Using a photovoltaic system to meet 20% or 30% or the electricity needs of a building is not really interesting. And it doesn't make sense to install a very big solar PV system. It would be too expensive.
What to do then?
We should reduce the energy consumption of our homes, schools and other buildings - by making them more energy efficient - before installing a PV system.
Many American homes consume 10.000 kilowatt hours/year (kWh) or more (around 12.000 kWh/year on average). But it is possible – even in cold climates – to reduce such consumption to half or less, and meet the remaining electricity consumption with 4 kW-6 kW photovoltaic systems.
A 4 kW or a 5 kW photovoltaic system can meet all the needs of modest-sized-energy-efficient single-family home in southern US, while a 6 or a 7 kW PV system can do the same in many colder North American climate zones.
To reduce your electricity needs, consider...
- Low-energy lighting, appliances and electronics; energy efficient lights, refrigerators, dishwashers and other energy-efficient domestic appliances and electronics will reduce your energy consumption by 30% or more, compared to conventional lighting, appliances and electronics. Do not undervalue these improvements. They are important (see: Home Appliances Guide).
- Alternatives to air conditioners (space cooling accounts for 22% of the electricity consumption of the average American home).
- Consider very high levels of insulation and air sealing, and also high-performance windows and doors. In new homes, energy conservation techniques (using high levels of insulation or energy efficient windows) will reduce space heating needs to low levels, making possible a smaller and cheaper PV system.