Now Simpliphi, LG Chem, Panasonic and Sonnen are going after the residential energy storage market. I don’t know about the other energy storage system companies, Sonnen is aggressively courting housing tract developers for an entire system, that would be installed on all of the homes in the tract. Arbitrage is just one function of these energy storage systems. The last information I could find on TESLA is they are still using Li, Ni, Co or Li, Mg, Co high density lithium ion batteries. Prone to overheat and cause fires. Simpliphi and Sonnen have adopted the less energy dense but more stable LiFePO4 battery technology. Unfortunately from testing the most stabile lithium ion technology battery is the LTO or lithium titanate battery. The energy density and voltage of this battery type is low compared to the other lithium ion battery chemistries. At 80 to 100Wh/L these LTO batteries would require a 6 foot by 6 foot by 6 foot box to hold a battery pack of about 20kWh. Sonnen is doing that same thing in 6 by 4 by 2 for 20kWh. Sonnen says their product is good for 10 years, the LTO technology depending on once or twice a day charge/discharge cycling, could be online for 25 to 50 years.