How do I work out how much solar power I need!

Would like to charge my i3 by solar panels at least part of the time. Looking at buying 10 sunpower x series 345 w panels. I am home a lot of the time during the day so should be able to make use of the sun. Anybody any experience of such an arrangement??

gaz26 said:

Would like to charge my i3 by solar panels at least part of the time. Looking at buying 10 sunpower x series 345 w panels. I am home a lot of the time during the day so should be able to make use of the sun. Anybody any experience of such an arrangement??

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The i3 will be a very efficient EV, probably the most efficient on the market when it is released. The car will have an EPA rating on the window sticker that tells you how many kWh's the car needs to drive 100 miles. A 60kWh Tesla Model S for example needs 36kWh's and a Nissan LEAF needs only 29kWh's. I Expect the i3 to be rated at about 24-25kWh's so lets say it needs 25kWh's to drive 100 miles for arguments sake.

How many miles do you need to drive in a year? If you drive 15,000 miles than you need 3,750kWh's, if you only drive 10,000/yr then you only need 2,500kWh's. You'll then need to calculate how many kWh's your array will make annually. You can't arrive at that figure simply by knowing the panels you are using. You need to know the orientation they will be installed, factor in any shading issues you may have, where you live, etc. My array is 39 Sunpower SP225 panels and It generated 10,000kWh's per year. You may live in an area that has better or worse production than I do in NJ and you may not be ale to install them in optimum orientation either so without knowing all the facts, it's not possible to know the system output. If I had the panels you propose and only 10 of them on my roof, I would probably generate about 2,800kWh's per year if that helps.

So how many solar panels do you have Tom to get 10,000, and what's their energy output? When a solar panel says 247 watt.. is that per hour, day? how do you calculate that?

Thanks that's really helpful Tom. The system should produce 3000 kwh per annum. Summer produces more than winter. I can be at home during the day so that helps to make use of the generation for charging. I recall reading BMW will provide a home charging unit that can charge the I3 in 3 hours??