Steam....someone said "If you build a steam pressure boiler, you will have a very interesting talk with a very specialized insurance agent".
$20,000 will not come close to buying enough wind or solar to completely pay your bill...unless you use 35 KWH a month, but most of us use 500 or more. I know a person that has $55,000 in solar panels and gets 275 to 325 KWH per month. IF you have wind (and you do not know unless you put an anemometer at the height of the proposed tower and watch it for a year), then you might do OK with a windmill in the $30,000 range. Build it yourself and save! I have a 5.5 K wind turbine that I build for less than 10 grand, but, I trusted a fellow that did a wind study for me. He was wrong, ohhh, so wrong. Part of me wants to play with it and make it better, but part of me says if someone wanted to buy it, I should sell it. My record days are 28 & 30 KWH. IF (capital IF) I had wind to do that every day it would pay my entire bill with some left over. I am not disappointed with the device, but do not have proper wind to drive it.