EnergySage reviews panel offerings from two manufacturers: Tesla and CertainTeed. Tesla panel efficiency range is from 19.3% – 20.6%, and cost is $3.03 to $3.35/W, bringing it to $29,088 to $32,160 for a 9.6 kW system before the ITC. They offer 4 pre-set sizes: 4.8 kilowatts (kW), 9.6 kW, 14.4 kW, and 19.2 kW. CertainTeed panel efficiency ranges from 16% – 20.21% with cost at $2.54 to $3.28/W.