I receive many calls for people who want to generate all of their electricity with solar power. They are usually shocked when I tell them what it will cost. Perhaps I can explain why …

Let us start with electricity. You buy electricity from the power company.The power company charges you a “delivery” charge and “usage” charge. The delivery charge is usually small. The usage charge, however, varies from home to home based on how much electricity you use.

Electricity usage is measured in kilowatt-hours (kWh for short) and the bulk of your electricity bill is your usage in kWh times the price of a kWh. The typical American home uses about 10,000 kWh per year. (In Europe, the average home uses about 3,300 kWh per year).While 10,000 kWh does not seem like a lot, for a solar electric system it is.

*Sizing a Solar PV System*

We speak of solar systems in terms of their rated peak power output. For example, a system of five 200-watt panels has a rated peak output of 1,000 watts. Using the rated power, we estimate the total electricity production of the system based on the sun and shade conditions for your location. (Average sun hours per day x Rated power x System efficiency x 365 = kWh per year)

In my area, in unshaded conditions, a 1,000-watt solar electric system with the panels facing polar south and mounted at 45 degrees will generate about 1,200 kWh in a typical year and offset 0.7 tons of carbon dioxide per year. The panels will cover 65 to 85 square feet and cost around $8,000 to $10,000** installed.

Now imagine that a homeowner uses 10,000 kWh per year and wants to offset half of that power    consumption, 5,000 kWh per year, with a solar electric system. To do that, they would need a system just over four times larger than the 1,000-watt system used in the example above. Here is the math: 5,000 kWh per year / 1,200 kWh per year = 4.2, 4.2 x 1,000 = 4,200 watt
system.

Therefore, a system big enough to generate 5,000 kilowatt-hours per year would need to be about 4,200 watts. It will offset about 2.5 tons of carbon dioxide, cover 275 to 360 square feet, and cost $34,000 to $42,000** installed.

*Ouch! For most of us, those are big numbers.*

**Grants and Tax credits not included in the cost estimates.

*Making the Numbers Smaller*

While solar electric systems are expensive in the short term, they are quite reliable, can be expected to last well beyond the 25 year warranty provided by most panel manufacturers, and they will eventually pay for themselves by offsetting electricity you buy from the power company.

So how do you make the cost of the solar electric system smaller? Use less electricity. This turns out to be both economically sensible and environmentally smart.

If, for example, you cut your usage from 10,000 to 5,000 kWh per year, your home’s carbon footprint (the amount of carbon dioxide your home is responsible for putting into the atmosphere) goes down by about 2.5 tons per year.

Also, by cutting your usage in half, to 5,000 kWh per year and putting in a 2,100-watt solar system, you can realize three savings. Your electric bill goes down by half because you have reduced your usage, it goes down another 25% per year because your solar system is making half of your electricity, and your only need to put up  a 2,100 watt solar system at half the cost of a 4,200 watt system.

Read More By Mark at www.newenglandbreeze.com/tem.html

Thanks,
Mark Durrenberger