There are 365 days in a year. A battery that you charge and discharge every day will make money daily for you. A battery that you charge and discharge once a ye

There are 365 days in a year. A battery that you charge and discharge every day will make money daily for you. A battery that you charge and discharge once a year, will only make money once a year for you. Plus, it will also lose quite a lot of energy due to self-discharge. That's it, in a nutshell. To make it concrete, a Tesla Megapack has about 20 MWh of energy, costs about $7 MM (including maintenance) and has a lifetime of 10 years [1]. At the end of its lifetime the energy drops to about 70% of the initial charge, but I'll ignore that. So, the price per kWh comes down to 7000000 / (365 x 10 x 20000) = 10 cents. That's somewhat steep, but acceptable. The average price of 1kWh in the US last year was about 14 cents and in the state of New York about 20 cents [2]. If you manage to generate electricity with solar panels for less than 10 cents/kWh, then solar+short term batteries are competitive. If you can only sell energy once a year, then the cost comes down to 365 times higher, or about $35/kWh. [1] https://www.tesla.com/megapack/design https://www.tesla.com/megapack/design [2] https://www.bls.gov/regions/new-york-new-jersey/news-release/averageenergyprices_newyorkarea.htm https://www.bls.gov/regions/new-york-new-jersey/news-release...