Somebody on this board tell me why this would be a bad idea before I waste $700
This would be a better deal if you had a tesla power wall.
Well it seem like the product you are planing to buy is not "free" as in freedom so i don't see the point.
The energy generated with burning wood that you have cut down yourself is more "free" than that made with this product.
Because the cost per watt is higher than it should be. Look for a panel that is about 1 Watt per dollar or better. Get an inverter that can hook up to your house and send power back to the power company to spin the meter backwards and let the power company meter that back to you during the night. Get a large inverter because you can always add more panels to an inverter that is too large but once you grow past the power of the inverter you have to add another.
looks awfully inneficient
I don't know how you can have a reliable solar installation without a shitload of quality equipement from batteries to panels and I'd reckon It'd cost more than 700$
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It depends. If you only have a panel and an inverter you're going to only be able to use the power that reaches your panels so a cloud cover that blocks out 50% of the sun is going to reduce your power by 50%. If you're connected to the grid with a grid tie inverter then all that matters is the average because you sell excess power back to the company. If don't connect to the grid but have deep cycle batteries, how long you can operate above the power your panels provide is dependent on how large of a battery bank you have and how charged it is. Also remember that the process of charging and discharging a battery has an efficiency so some power is lost by storing it.
When using a grid tie operation it is useful to find out the average amount of sunlight that reaches your area. This is measured in kilowatt-hours per day per square meter. You multiply your panel efficiency by that number and then multiply it by the area of your panels. That gives you the kilowatt hours that you'll generate per day before loss during inversion.