The Skystream Residential Windmill Magnifier Engine The Skystream model has an estimated 400 kilowatts output a month and costs about $8500. It does require a battery bank and it can tie in with the grid system when the winds are less than 8 mph. For optimum performance, wind speed needs to be about 20 miles per hour. One of the requirements for the Skystream residential windmill is that you have one acre of land.The Honeywell Residential Windmill Honeywell also makes a residential windmill that attaches to the top of your house. The system is rated for 166 kilowatts a month and only needs 4 mile per hour winds to operate. The price is about $4500 which includes a grid tie in. This is only designed for low wind areas and not for areas where you have large wind gusts.Windmill electricity is becoming more easier to produce at home thanks to more residential windmill models available. If you are interested in producing free energy, you should check them out.