The electricity is stored in a battery bank from GridPoint that powers everything in the building. Our backup is a Plug Power (plugpower.com) hydrogen fuel cell. I lease it for $375 a month through Government Leasing (government-leasing.com). Our energy bill is only about $70 a month because of our efforts. In all, I've invested about $5,000 to make the office more energy efficient and about $15,000 on renewable energy. I hope to earn back my investment in seven years.