As of 2011, Photovoltaic systems are used mostly in rural environments where power is expensive, transmission lines require long stretches and people want to live “off the grid” a term meaning that they either have no commercial hookup or sell electricity back to the power company at a rate which gives them a check each month instead of a bill. [1] In urban areas, things are a little trickier because of vegetation, buildings casting shadows, home orientation and general power consumption habits. In cities, where density is high and people tend to live in multi-residence buildings, photovoltaic is almost out of the question.

But let’s say you live in an urban or rural area and you are watching your electric bills climb and want an alternative. Wind is unreliable but the sun shines almost every day. Also, your house is oriented so that from dawn to dusk you get direct sunlight on your roof.

Your house is approximately 2500 feet and you have a family of four. Depending on your individual habits and where you live in the country, you will use between 3KW and 4KW per day. The Energy Information Administration reports that the average house uses approximately 936KW of electricity per month. That means about 3K per day at peak loads and a system that will supply that will virtually erase your electric bill. But this depends on your habits. If you use 100W lights instead of lower power or CFLs, your rates will be different.

For comparison, let’s look at five states: California, New Jersey, Colorado, Arizona and Florida. Each state is a little different. For example, California charges for energy programs even if you don’t use them. But with photovoltaic, these charges can be offset with rebates. Also the federal government has tax incentive programs that are not dependent on state power charges.

Let’s use the average of 936 and plot saving for each state. We are going to use a general purchase cost of $35,000 for a 3K to 4K complete installed system. For monthly averages, we are going to use the EIA, March 11, 2011 report of energy costs by state. The numbers given seem wildly optimistic (A poll of residents locally shows that most bills are around $100 for a standard house.) but these are the numbers the government uses when determining rebate level and tax credits. Luckily, there are plenty of both for each state listed so you may be able to cut the install cost by one-half in tax credits alone. But legislation is always changing and one never knows. The benefit, overall, is that with photovoltaic, you are reducing your contribution towards global warming[2].