How did I go about doing it?
1) I chose a specific house, with one half of the roof that is facing south. I got floor plan of the house to know how big the house is square-footage-wise, and found that eight people occupy it.
2) Formula to calculate average annual solar panel installation output:
(PV array wattage) x (average hours of sun) x 75% x 365 days
- PV array wattage=1 panel wattage x # of panels
- Average hours of sun=4.2 hours/day (1)
- 75 % decreases overall output to account for inefficiencies and other factors that could reduce the output of the solar panel installation.
- 365 days = 1 year
3) I looked through comparisons of solar panels efficiencies here plus costs of the panels in relation to their output and chose Kyocera KD240GX-LPB Polycrystalline Silicon Solar Panel as one of the cheapest and quite efficient panel. Costs are here.
Characteristics of one panel:
- gives 240 watts
- weighs 21 kg
- dimensions: 1662x990x46 mm
I approximated the surface area of the roof and compared to the dimensions of the panels, and found that 30 panels could be installed on the roof.
4) Calculations:
21 kg x 30 panels = 630 kg on the roof... (will it be able to handle the weight - I need advice of knowledgable people)
240 watts x 30 panels = 7,200 watts = 7.2 kWh
7.2 kWh x 4.2 hours/day x 0.75 = 22.68 kWh/day x 365 = 8,278.2 kWh/year
Cost of panels = $12,370. I am not sure what the cost of installation is though. There is a federal rebate that reduces the cost of solar panels+installation by 30 % from the original total price. Some states have additional rebates and other incentives. Indiana does not have a state rebate.
Is 8,278.2 kWh/year enough for a duplex with 8 people?
By looking at average residential uses of electricity in Indiana per capita (about 5,000 kWh/year), I am assuming that 8 people in a the house i am modeling would need more electricity than 8,278.2 kWh/year. Also, considering that peak of panels efficiency will be during the summer when students don’t use it, solar panels may seem to be redundant for their use. However, solar panels could charge other campus buildings in the summer reducing college's electricity bill in general. If many buildings around campus with roofs facing south had solar panels installed, they could produce a certain percentage of campus’s electricity decreasing its carbon and emissions footprint. Federal and state rebates can make it less costly, but maybe not economically feasible yet.
By looking at average residential uses of electricity in Indiana per capita (about 5,000 kWh/year), I am assuming that 8 people in a the house i am modeling would need more electricity than 8,278.2 kWh/year. Also, considering that peak of panels efficiency will be during the summer when students don’t use it, solar panels may seem to be redundant for their use. However, solar panels could charge other campus buildings in the summer reducing college's electricity bill in general. If many buildings around campus with roofs facing south had solar panels installed, they could produce a certain percentage of campus’s electricity decreasing its carbon and emissions footprint. Federal and state rebates can make it less costly, but maybe not economically feasible yet.
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