A 2,100-sq-ft home requires a two-ton AC unit with a rated power consumption of 3,500 watts. Running the AC unit eight hours per day uses 868 kilowatt-hours per month of electricity. The cost of electricity from the grid per year at $0.10 per kilowatt-hour is $1,044.00.
A 900-kilowatt-hour-per-month solar harvesting array installed costs $67,500.00 and covers 20 x 43 ft. This is the true retail cost without the rebates and incentives.
Solar energy efficiency with current technology is about 33% overall, taking into consideration the angle of the sun during the day, time of year, clarity of sky, rotation of the earth, etc.
The lifespan of the solar array has to be 21 years, because that is the amount of time needed to make the environmentalist crowd's amortization of the debt with government subsidies break even for the homeowner to foot the cost.
Cost of energy to run your AC unit for 21 years is $21,924.00. Cash return provided by a solar array at 33% efficiency is $7,307.26. Initial investment in Solar Array of $67,500.00 was amortized over 21 years at 0% interest with no upkeep or maintenance costs. Your return on investment: spend one dollar and get $0.12 back. Net loss: 88% of investment principle.
Passive shading is the low-tech solution to solar heat gain. Heat gain is the effect of solar radiation on your home during the day -- i.e., raising the ambient temperature your air conditioner is removing. By shading the two largest heat-producers in your home -- windows and roofing -- this shading method, based on all available research, will effectively reduce air conditioning costs by between 35% and 50%.
Initial investment in heavy-duty white vinyl tarp, bungee cords, white vinyl pipe connectors, glue, and screws to build simple awning shades and cover the roof with a tarp is $350.00. Expect to replace the tarp every three years (total of $2,450.00 over 21 years). The tarp is readily recyclable or can be used for moisture retention in farming. The savings provided by passive shading are represented by a reduction in AC costs by 33% over 21 years, totaling $7,307.26. Your return on investment: for every dollar spent $1.00, you get $3.00 back in your pocket. Net return on investment: 300%
- "The Real Cost of Solar Energy", Alan M. Aszkler