Sorry trees i don't have the detail on discharge but i would think it would be competitive with other battery options, whilst this product is available in limited supply in the USA it is still under development, however eliiy power in Japan who are developing the battery for Enphase already produce storage batteries for solar, there current home battery is the ie6 2.5 Kwh lithium ion battery is guaranteed for 10 years or 3600 cycles with an efficiency of 95% it's hard to work out all the detail as the pdf's are in Japanese, see below site http://eliiypower.co.jp/english/products/index.html
