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Daox · 10-19-09, 07:34 AM

I just decided to do the calculation for my energy usage for the last month as an example (for me as much as for you).

I used 192 therms of natural gas last January. This is by far the worst month I had. Anyway, 192 therms over 35 days is 5.5 therms per day. My furnace efficiency is around 90%, so 5.5 *.9 = 4.9 therms is roughly my daily usage. Lets convert that to kWh and we get 143.6 kWh.

Now, in my (and your) part of the country, we can harvest 4-5 kWh per square meter per day. So, lets take 143.6 and divide by 4.5. That gives us 31.9 square meters of panel. A square meter is 10.8 square feet, so we need 345 square feet of collector roughly. I still haven't compensated for cloudy days or efficiency loss through the collector. For reference, Gary's solar shed is 240 square feet.

The good news for me is that my house is horribly insulated, so I can likely reduce that 192 therms drastically. Hopefully yours is already lower.

10-19-09, 07:34 AM	#3
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	I just decided to do the calculation for my energy usage for the last month as an example (for me as much as for you). I used 192 therms of natural gas last January. This is by far the worst month I had. Anyway, 192 therms over 35 days is 5.5 therms per day. My furnace efficiency is around 90%, so 5.5 .9 = 4.9 therms is roughly my daily usage. Lets convert that to kWh and we get 143.6 kWh. Now, in my (and your) part of the country, we can harvest 4-5 kWh per square meter per day. So, lets take 143.6 and divide by 4.5. That gives us 31.9 square meters of panel. A square meter is 10.8 square feet, so we need 345 square feet of collector roughly. I still haven't compensated for cloudy days or efficiency loss through the collector. For reference, Gary's solar shed is 240 square feet. The good news for me is that my house is horribly insulated, so I can likely reduce that 192 therms drastically. Hopefully yours is already lower. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.* To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.