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« The amazing story of the Austria House in Whistler | Main | Solar panels on the roof of Poulsbo Middle School »

February 02, 2011


Thomas Weber

Dear blogger (I cannot find your name on this blog page).

I've read your posts with interest over the last three years and am interested in emailing you directly about the library issue. How might I be able to contact you?

Thomas Weber


First, I am not sure you would be better off being off the grid. If your state has net metierng, you can bank power when making more than you are using. You can get it back when you use more than you are making. Batteries are an unnecessary, costly accessory. Unless you have critical need for power when the utility has an outage, you can do without them. In any event, buying and maintaining a small generator would be less costly.Using one manufacturer's panels (they call them modules), you could get a 7.5 Kw system on your 900 sq ft. This means something around 5 kW effective.Look up INSOLATION TABLESon the Internet to find the average annual sun energy where you live.In my area it is 5 hours. 5 x 5 is 25, so you would get an average of 25 killowatt hours per day. Look at your utility bill, and see how much you now use. This will put you in the ballpark. It is likely, though, you won't get a full 900 sq ft of modules. And, the angle from north-south your latitude and the pitch of the roof will all contribute to the efficiency of the system.My 6 kW system gives me 20kWh per day. Living alone, this is much more than I use for the items you mentioned. I keep track of daily electric meter readings. From a four-year record, I know roughly how much surplus I would have, and use that to augment heat from the gas furnace. Actually I used no gas last winter, except for heating water.Read all you can on the Internet, and in the green search box at the top of the page.Certainly you want to reroof prior to mounting the modules. Solar contractors like to say the modules protect the roof, but really it is only partial protection.Brain

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