The US average wind speed is 12.5 mph.
If you double the wind speed you increase power potential by times 8.
If you double the diameter of your blades increase power potential by times 4.
 Last check on current average market prices I'd put solar at $10 (USD) per watt, wind at $1 per watt (if you buy rather than build, this is about why you should build).
 Those are some of the standard basics of wind electric generation.
 If I felt photovoltaic (aside from just assembly) was something I could build at home I'd likely write about that.Some background to the author of this blog:

 I've been making my own power from wind, sun, and petroleum for around 35 years, using gas powered generators (typically, lawn mowers hooked up to car alternators) as backups to keep my batteries from staying at a discharged state, though if I lived 'on the grid' I'd likely have had a 12 volt battery charger to do that with.
 My father taught flight school, I'm built around 400 RC (radio controlled) airplanes, basically I've got some experience with airfoils, designing them, building them, and putting them to the test.
 It was not hard for me to 'change gears' here from building RC planes to do the same with wind generators as a 'hobby'. But if you want a 25 Kilowatt turbine, I'm not the guy you want to talk to.
 For the past 1.5 years, 90% of my power has come from 2 wind generators (the other 10% is solar) one wind generator with around a 5 foot blade diameter, the other is around 4 foot diameter. I have 3 others I took down and am still making modifications to before I put back up into the air. And even without those running, I have not had to start my gas backup generator in 1.5 years.
 Some warnings:
 Even a AA size flashlight battery, if short circuited, can cause a fire (study and LEARN about what your doing before you make even your first attempt at wind/electric power).
 Blade tip speed can be quite fast, nice to look at in the air, but if you break a blade in high winds, it is like having a razor sharp sword, flying at you at that same speed. One warning on that is if you see any vibration going on, shut it down, and at a minimum, rebalanced your blades again.
 The above is one of the reasons why I recommend smaller wind turbines, the greater your diameter, the greater the force if your blades loose balance.
 Another reason, is if you have many small ones instead of one monster size one, if you do have a problem, if you only have one wind generator your out of power until you get it fixed.
 Smaller ones are also less expensive, take less time and I've never had a bird fly into the spinning blades (not once, that I know of, in around 35 years, not just easier on the birds, but on the blades too!).
 Now, why would I want to promote this?
 If 100 people were to design and build their own wind generators, we will have the potential for innovation to result. If 1000 people design and build their own wind generators, we increase the rate these new innovations may be discovered.
 Another reason for self reliance (instead of buying power from someone with a huge wind generator?)
 In my area we have some of (if not 'the') highest electric rates in the nation, I lived in town for a couple of years, my electric bill around $400 a month.
 $400 times 12 months, times 35 years = $168,000.00 USD. (a more detailed analysis provided me with closer to $148,000 for my actual savings).
 This $ was not spent sending it every month to a large corporation. Instead, it was spent in my local community buying 'things' and 'goods' and 'services' made or grown or done, by 'people' = more jobs improving my local economy.
 Some basics:
If you pass a magnet close and fast, over a coil of insulated wire, with both ends of that wire connected to a volt meter, you can see the needle (if the kind that uses one) move, going both in the + and - direction (alternating current).
 A diode, is something that acts like a trap, by only letting the flow go in one direction, this then provides direct current. For more information on how this works
 There are plenty of places also you can go to see others who have built their own wind electric generation system (try and start out with toy or very small and simple examples first) and I've found to be a good place with many different examples of DIY (Do It Yourself) wind generators.
 One item I would like to stress, is to try to get into this with as little if not $0.00 money invested.
We have an abundance of materials already on the surface of planet earth, so to minimize impact a good place to start looking for materials could be as close as your own trash can.
 As an example, parts I've gotten from the local town dump:
a 3 foot pvc pipe 6 inches in diameter, cut lengthwise in half, then quartered then cut those sections to make turbine blades, mounted to a circular saw blade, mounted to a car alternator with the electro magnet removed and replaced with magnets from a microwave oven = free power.

 Another item I'd like to stress due to experience. Rather than trying to get a ton of power from a small wind generator consider the advantage of NOT going after that.
 If the US average wind speed is 12.5 mph, then to target building a wind generator for 7 mph, while it may not give much power output, that would be power your NOT getting, if your turbine only starts producing 12+ volts at 28 mph. Basically, the greater your power input, the higher wind speed your going to need before you get it (for the same size blades) or, the more 'force' is require to get it spinning, to much force required to produce high power and your blades will need more force against them to reach that objective.
 There can be a lot of "hours" of incoming power that you would not otherwise get. And when you have an extended time of low wind, no sun, that can make a huge difference at being "able" to put power back into your batteries, rather that staying at a low state of charge (not good for them!).
 If I only get 1 amp of power from a small wind generator at low wind speeds, fine, what happens when I have 10 or more of these in the air?
 Some more math, you can increase your voltage at a set rpm (how fast the magnets pass over the coils) if you increase the number of turns of wire in each coil, but you also then increase the distance of the outer part of the coil, from the magnet. The closer your magnet to the coil the greater the power output. You can also increase your power by increasing the strength of your magnets used.
 But again, increase it to much, and your going to need higher wind speeds.
 Also, keep in mind while you build, what is going to happen if the winds exceed 50 mph.
 The time to take that into consideration, is not when the wind is that speed. Working on a wind generator while it is up, and the wind is blowing, is a recipe for disaster (the kind body parts are severed).

 Even driving a car is dangerous, if you don't first know what your doing, and what to do, and not to do, so before even making your first attempt, read up on it!
 The scientific community tends to be one that shares what we have learned, utilize that!
But dont just build you wind generators for power or $ reasons, try getting into it just for the FUN of it!
 Some people build their own telescopes, their own RC airplanes, try considering this as a hobby, where even a 1 foot diameter turbine could power an outside LED lighting system.
 The main reason for encouraging this hobby, is innovation.
 The more of us doing this, the faster we are going to come up with new innovative ideas that we can then share with others.
 You never know, if you could be the one that comes up with something, the whole world could benefit from, until you give it a try.
 Start small, but start.

 Another item:
 When the wind is howling here in Alaska in the winter, and my batteries are topped off, and all my lights are on?
 I disconnect one or more of my wind generators from the battery, and directly wire it to a heater element! (I turn the bitter winter winds, into HEAT).
 You don't need fancy equipment, to experiment and have fun, but I highly advise you investigate this first before you even start, so you have a good understanding of not just how to build one, but why it is working, what it is doing, and how to do so, practicing good safety.
 So while there are many reasons to get into wind power, like reducing carbon emissions, saving some $, there is also the part about this that is learning the science and having some FUN!
 Though I do have to admit, when there are power outages in my area (often related to storms), having my lights ON (selfreliance and independance) while every one else is without power, is kind of fun too (not that I dont feel bad for them).
 And I hope I've been able to provide some good thought provoking insight into the science that is blowing in the wind.