I've subscribed to Xcel Energy's Windsource program for the past year and a half. It covers all of my energy usage (including the cars). How much extra do you pay with Green Mountain Energy? Xcel recently lowered the rate to $1.50 per 100 kWh so really it's not that more per month than "regular" electricity from coal or natural gas.
I'm on the waiting list for a solar farm but the local one has been sold out for the past two years. I would like to put solar on my roof eventually but am waiting to hear what the solar roof will cost. Also I'm somewhat hesitant to make a large investment in solar since my neighbor's property to the south of mine is "up the hill" from my property. If they decided to plant trees, they could easily block my solar panels within a few years. The nice thing about the wind power plans is that they don't require any initial outlay or years of large payments. It costs less than $20 a month to cover all of my usage.
The amount we pay into the program is used to generate 100% renewable energy. While the wind energy isn't running directly to our houses, it directly offsets the actual energy used. It's certified 100% renewable energy:
