The best solar panels currently available are about 13% efficient in converting sunlight to electricity. A typical home will use about 40. kWh of electricity a day (1 kWh = 1 killowatt hour; 1 kW = 1000 J/s). Assuming 8.0 hours of useful sunlight per day, calculate the minimum solar panel surface area necessary to provide all of a typical home’s electricity (The sun supplies energy at the rate of about 1.0 kilowatts per square meter of earth )
It costs approximately ,000 to install a solar panel and battery kit this size with a 20 year warranty. If electricity costs continue to average {content}.10 per kilowatt hour for the next 20 years, how many years will it take for such a system to pay for itself?
6,000 days = Just under 16 and a half years
Which is exactly why you don’t see millions of these installed all over the place – too expensive to be cost effective and that is without any maintenance costs.
The technology is still in its infancy. It seems that every time I look, there is something new. Consider that the best commercial solar panels are about forty percent efficient, but the link goes to a promise of a solar panel design that doubles the current best. Also the mass production of designs should bring the manufacturing costs down.
In my area, solar panels are mostly used where there are no power lines. Your usage will depend upon what you need to power and when.
The use of lead acid batteries has an overhead of about fifty percent and a useful life of from three to five years depending upon quality, use, and environmental conditions.
Inverters to convert the direct current into alternating current will also have an overhead that varies according to the amount of power being used at the time. The quality of the equipment will determine if you are getting a square wave, modified square wave, or sine wave output and at what power levels. You will need to determine if multiple inverters or a single high current inverter is best for your application.
The panels themselves have different design criteria and you need to choose that which best fits your needs. Does your roof have any shade? Do you get the roof tile solar panels? Fixed panels mounted on the roof? Panels that will track the sun? Do you have an area that gets sun all day? Do you get fixed arrays of solar panels? Do you get arrays that track the sun? Do you get a lot of cheap low efficiency solar panels or a few high efficiency solar panels? How much area can you dedicate to solar panels?
Do you live in an area with power lines? Do you interface your solar system with the grid? Do you want your solar system to remain isolated from the grid but still have the option of using the grid? Do you use your solar panels to supplement the grid? Does your electric utility company purchase your excess power at a lower rate and sell it back to you at a higher rate? Does your electric utility company allow you to run your electric meter backwards, using the grid for electric storage? Does your electric utility company charge to have your solar system interfaced with their power?
You may come up with other requirements, regulations, options, or problems. But the bottom line is that you need to answer many questions before you can even begin to calculate your return on investment. There are just too many variables.