February 02, 2006

Ontario Solar Power Plan: Some Numbers

I thought it would be useful to provide some figures about costs and production in regards to using solar panels in a household. Most of the numbers I'm posting are from Wikipedia (here and here). I've provided a quick reference first for those who don't want to read my poor technical explanations below. However, I would encourage people to check them out and make sure I'm accurate, or close enough.

Quick Reference
  • aproximate average cost of solar panels(SP) = $5.71CDN/watt
  • average amount of watt power produced by SP = 21W/square metre
  • avg. watt-hours produced in 1 day (12 sunlight hours) = 252 Wh/square metre
  • avg. watt-hours used to heat residential home = 8600Wh (8.6kWh)
  • approx. number of panels needed to cover winter heating needs = 33 square metres
  • approx. cost to install system to cover heating power consumption = $4000CDN



The approximate cost of purchasing and installing solar panels is $3-$7 (US figures) per watt. Based on today's currency exchange rate of $0.87, the approximate cost would be $3.43 - $8.01 per watt. At middle-northern latitudes, at their most efficient, the amount of energy solar panels can produce on average is somewhere between (in watt hours) 12W - 30W/square metre (depending mainly on season). If Ontarians could generate these averages (average of 21W) it would take too many to be reasonably done with a residential home. According to a 1997 survey done by Natural Resources Canada, a household that heats through an electricity/natural gas combination (the majority of houses in Canada) uses approxiamtely 8.6kWh of electricity for heat in the winter. At this rate it would take 409 square metres to heat your house... or would it? Households' energy consumption is based on kilowatt hours (kWh). This is related to, but not the same as kilowatts. This figure is based on the number of items being used x their energy rating x the number of hours used for. For example, if I were to use three 20W lightbulbs for three hours, the amount of energy being consumed is actually 180 watt hours (180Wh). * 3 (bulbs) x 20W x 3 hours = 180Wh If a household were to have three square metres of solar panels capable of producing 21W/square metre, then over a period of 12 sunlight hours they could produce roughly 756Wh. * 3 (panels) x 21W x 12 hours = 756Wh With these figures in mind, to heat an average Canadian house in the winter it would take approxiamtely 33 square metres of panels, not 406. The cost to put such a system in place would be approximately $4000CDN. * $5.72 (3.43+8.01/2) x 21W/square metre x 33 square metres = $3963.96 It's hard to say how long it would take a person to recoup this cost because these numbers are based on averages and estimates, not actuals. As well, the $4000 figure is also just for heating your home int he winter, not running any lights or using utilities. Some numbers floating around the net put the actual cost, of installing a system that covers all your electricity needs and provide you with excess, closer to $10000+. However this figure may be very liberal.

1 comment:

bruce said...

This seems like a silly post, as you would NEVER use solar PV to HEAT a house! If you want to heat a house with solar, you would use solar THERMAL. Solar thermal is approx. 95% efficient in converting sunlight to heat whereas solar PV is closer to 17%. In addition, the number of hours of sunlight in the WINTER which is when you need the heat, is closer to 2 hours per day...not 12 hours per day as in the summer.

Both solar PV and Solar Thermal have a place in your house, but use them correctly.


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