Buy the lowest cost 40kW solar kit priced from $1. This high-power, low cost solar energy system generates 40,120 watts (40 kW) of grid-tied electricity with (68) 590 watt Axitec XXL bi-facial model PS590M8GF-24/TNH, GoodWe single-phase string inverters, 24/7 monitoring, disconnect box, rooftop mounting,. Compare price and performance of the Top. Refer to your electric utility bill to find the actual kWh used per month and compare it to how much power these low cost 8kW PV systems can generate. The average American uses 920kWh per month. Based on that average this system could reduce your bill to ZERO. Optional solar mounting support, PV combiner boxes, and cables. This article explores the factors influencing the cost, typical price ranges, and features associated with different price points. According to the most recent Residential Energy Consumption Survey (RECS), the average American household has a square footage of 1,818 and consumes 10,566kWh of electricity annually at a cost of $1,380. Obviously, electricity consumption and cost vary widely based on numerous factors — as does the.