I have a green house that I want to go 100 % solar and wind over the next year or two. Right now with everything running I need power for lights, air pumps and water pumps. The lights 1200 watts run 12-14 hours a day. The air pumps 50 watts total run all a day. The water pumps run 15 minutes every 3 hours 300 watts total. I run the lights at night to help heat during the coldest part of the day. What I would like to do is have enough batteries to run my greenhouse a day, when they are charged. If it takes one day or several days to charge the batteries. I would like to use the power harvested for a day. I'll add more solar panels as money permits. I live in a crappy wind area and have to depend on surface winds, So I'm building several 200 watt wind turbines. they'll only be supplement watts hopefully on cloudy days.. So here is several questions

1 Harbor Freight has these 45 watt kits on sale for $4.44 per watt I'm thinking about buying 3 of them. I've not found anything for a better price per watt. Would this be a good buy?

- Harbor Freight Tools - Quality Tools at the Lowest Prices

2 Can I use a larger inverter than I have power for. If I want 2000 watt Inverter but I only have enough power for 500 watts. will it work? So not to have to buy more than one inverter.

3 Can I use a 3-way switch, have grid on one pole and solar on the other pole? Just wondering grid common to battery / inverter common.

4 Any good links to calculating batteries needed? Plan to buy golf cart batteries from Sam's club. Like to know how many batteries I need for the above description.

Wow, that is a lot of power. 14 hours times 1,200 watts = 16,800 watt hours. Then 50 watts times 24 hours = 1,200 watt hours. Last is the water pump @ 2 hours per day, which equals 600 watt hours. That's a grand total of 18,600 watt hours per day @ 120V AC, which is 155 ampere hours. Since you can't use more than 50% of a deep cycle battery's rated output, you'll need to have a minimum of 400-440 ampere hours @ 24V worth of batteries per day, which is a total of four average sized golf cart batteries. So to have two nights worth of battery power, you would need 8 golf cart batteries total.

To charge these batteries, you'll need at least 2,600 watts of solar panels, since A) you're planning on using a portion of this energy 24 hours per day (and what is being used obviously can't be put into your batteries) and B) depending on your location, you'll only produce 50-60% of each panel's rated output during the winter months. This means you'll need a bare minimum of 2,600 watts of solar panels, although more definitely wouldn't hurt, because of inverter inefficiency and battery losses.

As far as your questions, I do have answers:

1) That's not at all a good deal if you need more than 45 watts, or a warranty longer than 365 days. For good prices on good panels, this site and this site are the places to shop. Note, stay away from both Sun and Suntech brand panels. Kyocera and Evergreen are the best price per watt panels on the planet that are worth owning.

2) Yes. As a matter of fact, it's necessary. If you happen to need exactly 300 watts, and you buy a 300 watt inverter, it won't last nearly as long as a 600 watt inverter would have lasted.

3) No you can't, but you can use one of these switches, although you'll need one of these switches, if it will be mounted outside.

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On this site, 99.999% of all underlined words are links.

A watt saved is better than a watt generated, since it always costs less than 10% as much, and can cost as little as 1%.

V=volt, A=ampere, Ah=ampere hour, Wh= watt hour, VOC=open circuit voltage, ISC=short circuit current, VMPP=voltage @ max power, IMPP=current @ max power, BTW=by the way, your=belongs to you, you're=you are, too=in addition to, two=1+1, to=towards

Thanks for answers me and my wife appreciate it. My wife says go for it. Shes not happy with power supplier advertising how wonderful they are and then complaining they didn't make enough money for their stock holders.

I'm going to set a goal for 25,000 watt hours per day spread out over the next couple years. Think I'll need to learn a few sailor's prayers for good winds, to pick up some of it.

Thanks again
kevin and mary