Lets start with a 100 watt bulb in the kitchen that is used four hours per day. That’s based on two hours per day in summer and six hours per day in the winter, average 4 hours per day at 100 watts per hour is 400 watt hours which is .4 kilowatt hours per day. Times 365 days a year times ten cents per kilowatt hour is $14.60 per year. Pay PECO $14.60 per year for the electricity to operate a 100 watt bulb 4 hours a day for one year.
How much would a solar panel system cost to provide enough electricity to operate one 100 watt bulb for one year? Quick answer is: $773 if the materials are purchased from Harbor Freight. The payback period is $14.60 per year divided into $773. That’s 53 years. The solar panels only last maximum 25 years. But it’s impossible to generate enough electricity from a $773 solar panel system to light one 100 watt bulb for a year for 53 years. That’s the best case. It’s based on all of the solar power being used by the 100 watt bulb but putting 100 watts into a battery means only about 50 watts are stored in the battery. That’s the efficiency of conversion. Take 100 watts out of a battery means about 60 watts go into the bulb because the battery, the invertor and the bulb are not 100% efficient. Want more details? Here goes.
Harbor freight sells a 45 watt solar panel kit for $139. It needs an invertor and a car sized battery. Three harbor freight kits are needed to generate enough electricity during the sunny days to charge the battery to provide electricity in the evening from the battery and the invertor. That brings the cost to $729 plus 6% sales tax. That’s $773. Over 25 years it’s about $30 a year. The electricity used in 146,000 watts per year, 14.6 kilowatts. PECO charges $0.10 per kilowatt hour. So 14.6 kilowatt hours times $0.10 per kwh is $14.60 per year. Divide the cost from PECO by the cost of the solar system. That’s $773 divided by $14.73. That’s 53 years of tears to get back the $773 cost of the solar materials. Completely Un-Economical. You will never get back the investment because the solar panels will not last even half as long as needed to break even. Another way to prove solar doesn’t pay it to compare the cost per year to buy the system, $30 a year to the cost per year paid to PECO, $14.60.
What about selling solar electricity to PECO? That’s even worse because the savings would be based on PECO paying about $0.06 per KWH. The solar system cannot break even at $0.10 per kwh so it’s impossible to break even at a lower rate of saving. Using solar to save electricity costs is un-economical.
How about using a solar system at a remote camp site? If you used it to light a 100 watt bulb it would cost $773. It would not pay. Use a kerosene lantern. It’s far less expensive. If you want to power an electric stove it’s worse. You will need more watts of electricity. Use a kerosene stove for cooking. Cook over a wood fire. The cost of a wood fire at a camp site is the cost of a match.