Ours is 9.6kW. We averaged about $80/month or 750 kwh usage for what they based their calculation on. We would've been closer to $75/700kwh, but my wife left the xmas lights on 24/7 during the month of Dec, so our Jan bill was $135/1340kwh which bumped it up. Solar City said Xcel would approve a system that would provide up to 115% of average usage.