How Much Power Can A Home Solar System Produce?

One of the reasons an individualized site assessment for a home solar power is so critical is to offset the homeowner's expectations with realistic projections. The following statements are true:

- According to the U.S. Department of Energy, enough solar energy reaches the earth every hour to power the planet's needs for a year.

- If 100 square miles of photovoltaic panels were to be placed in the American southwest at optimum sites, they could supply the entire country.

- Estimates suggest that a 3.6 kW photovoltaic solar array can supply 50% of the energy needed by the average American home. (Annual consumption in American homes is roughly 10,000 kWh a year.)


However, the amount of solar radiation reaching the earth at any given location is affected by:

- the geographic position of that location on the globe,
- the time of day,
- the season of the year,
- the landscape of the site,
- and local weather at any given moment.

All kinds of things cause sunlight to be diffused, from the molecules in the air itself to water vapor, dust, clouds, pollutants, and major environmental events like forest fires and volcanic eruptions.

On even the clearest day, some degree of atmospheric interference will reduce direct beam radiation by at least 10%; on a cloudy day, as much as 100%.

This does not mean there is not sufficient light, but it can mean there is not enough direct solar radiation for a photovoltaic panel to convert photons into electricity.

Any reputable solar installation company will conduct a specific site assessment at your home and will be able to supply you with real-world figures from other home solar power systems in your area.

You can also use data for peak solar hours by region to make power production estimates. (For this purpose, solar4power.com has a good set of peak sun maps in their "Basics" section. Map links are at the bottom of the page.)

These figures will give you a working estimate to project the amount of electricity your system will produce, but the only way you will know specifically is to monitor the array during the first year of use. All systems have separate power meters for this purpose, which also serve a function in maintenance of your solar array.

A severe drop-off in power production that does not correlate with current weather conditions generally indicates a mechanical problem. If the company with which you are working does not include such a meter in the bid you receive, ask for it. For one thing, if you sell your home, specific data on the array's operation will help you to prove its value in the sale process.

So, even in the best case scenario, a homeowner is moving forward on projected data alone until hard data has been accumulated; that is simply part of the "leap of faith" required to make the move to a home alternative energy system.

The greatest "leap of faith," however, comes when homeowners start looking at the cost of the solar array they are contemplating.

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