I'll simply add a link to my diary about a windmill a farmer friend bought. It's a two-blade, smaller than the Gaia model (7.5kW), but the blades were a major problem and are only fixed now because he bought another windmill for spares and did the job himself. He and his neighbour agree that Aircon is a serious outfit (which doesn't mean Gaia isn't). It's just a cautionary tale about over-hasty buying. (He's now happy with the power he gets from it: roughly covering the needs of house and farm).