The market for wind power seems to be split in a low-end (500W - 5kW) for point solutions and a commercial high-end (150kW and above). The middle segment that will be required for sustainable living after the pole shift does not seem to be very large yet. I have only found a few vendors with such windmills yet. Probably due to the price level, I don't think most people would want to invest for a mere 20kW unless they have a very good reason (like the pole shift), and they are too small for the commercial market. I have finally found a windmill in the right size, 20kW and available in my area.
Offered by Jan.
Any manufacturer that you talk with will say theirs is the best. The 20kW and higher
windmills will always be more efficient, but there are other considerations you may
want to keep in mind. First off, you need some pretty significant equipment to mount
(raise) and/or unmount such a heavy load. It's no small undertaking. If the cost doesn't
scare you, the maintenance might. You may or may not be worried about the visibility of
a larger tower needed for these larger beasts.
Using the 500w - 5kW ones, you can install multiple ones for redundancy and spare parts. They won't be as efficient and can cost more per watt, but on the practical side would allow you reduce your losses in case of failure with no backup. Regardless of size, another consideration would be to find ones with a permanent magnet motor, instead of the usual copper winding motor. In the event of a strong electromagnetic pulse, such as a strong solar flare or pole shift, anything with an inductive load would be the first to go. A permanent magnet motor would be least affected. I don't mean to scare you off the larger ones, you will have to weigh the strengths and weaknesses of either choice for yourself. I am only trying to give you some other ideas to consider when you make your decision.
Offered by Steve.
I am fully aware of the backup requirement, so I plan to have two windmills and store spare parts for maintenance. I do however agree with you that the size may be a problem. I must be assured that it is in fact possible to de-mount the windmill manually before the pole shift, and mount it again afterwards. One major reason for wanting to use the 20kW windmills is in fact their height above the ground, so they will stand above the forest and catch the wind.
Offered by Jan.