Perhaps the most cost efficient means of generating your own power lies in the windmill. It’s a very simple design and doesn’t cost a whole lot, but just like solar power there are a few drawbacks one must take into consideration before purchasing a windmill thinking they will eliminate their electric bill.
The first and most important thing you need is wind and for most this is a showstopper. Most places just don’t have enough consistent wind to spin a windmill. The other problem if you do have wind is that it is totally unreliable. It will almost never provide a consistent power source for a house, so as a result it is more of a supplement to a solar powered or a grid tied system. Most of the time they are used to charge batteries in remote locations that do not have a dedicated power source provided by the power grid. But, if you think you live in an area that has a lot of consistent wind and you are interested in protecting the environment, a windmill is about as clean a power source as you can get (both in manufacturing and operating) and the start-up costs are much cheaper than solar.
The other thing you need besides wind is land. I have yet to find any descent sized windmill that is designed to operate on a lot less than 1/2 acre in size. The more land you have, the more options there are, from 3 foot diameter blades all the way up to 20 foot. As you might expect, the larger the windmill, the more power it can generate, but the more land you will need.
Every manufacturer will highly encourage you to raise the windmill off the ground at least 30 feet. This puts the windmill in a less turbulent flow of air that blows stronger and more consistently. But before you go out and purchase a 20 foot diameter windmill that sits atop a 60 foot tower, make sure you don’t have any restrictions in your home owners association, covenants or insurance company that will prevent you from installing the windmill on your property. The covenants and association memberships can make you take the windmill down if they are not allowed and if your insurance company doesn’t cover it, your policy could be void in the event of an accident.
As mentioned above, windmills come in all sizes. Some large with 20 foot diameters and some small with 3 foot diameters. The smaller windmills will produce about 400-watts of power in a 24 mph wind while the giant windmills can produce over 12,000-watts in the same wind. Each windmill has its own set of specifications and perhaps one of the more important features is the start-up speed, which is the minimum wind speed needed for the windmill to start producing power. Most windmills have a minimum start-up wind speed around 10 mph. If you have a lot of wind, but it falls below the minimum start-up speed, you’re not going to get any power out of the windmill.
The windmill that looks promising for home owners with the above requirements is this unit here. It has a 12 foot diameter and can produce about 1200 watts/hour. That’s not too bad if you’ve got the space.
If you’ve got the wind, the land, and you are permitted to install a windmill then you will need to buy the remaining components in order to start utilizing the power of the wind. You will need a grid-tie inverter if you want to remain connected to the utility grid. The inverter converts the DC voltage from the windmill and turns it into a pure AC sine-wave. When the windmill produces more electricity than you use, the inverter allows the electricity to be pushed back onto the power grid, at which point you start receiving credit from your electric company.
From what I’ve read, most electric companies will not pay you for any excess electricity you create. That is to say, the best case scenario is you will have a $0 balance on your electric bill, but that is completely dependent upon your area and who provides your electricity. The grid-tie inverters cost anywhere from $2000 an up depending on how much power your windmill(s) will generate. You will also need a DC disconnect switch and a utility disconnect switch, both cost around $100. A 1.2 KW windmill will cost about $5000. So just the parts are going to run you about $8000.
You might be able to erect the tower and windmill yourself depending on its size, but this would certainly be at least a 3-man job. However, the inverter and DC disconnect switch must be installed by a licensed professional. It would be wise to have a professional do the entire project for you to ensure everything was installed correctly. They may even offer warranties on their installations or discounts if you buy all the parts from them.
UPDATE: Solar PV panel prices have dropped considerably in the past year or so. It would appear that a windmill solution costs about as much as a solar PV solution.