Sodium Nickel battery (new technology)

[Skvez]

LS,

Yes even with thermal insulation there will be some heat loss meaning the battery has to use some of its power to keep itself hot so they wouldn't be efficient for long term power storage.
However I see it as being very useful for storing the solar power produced in the day and the wind produced in the night for use as required throughout the day (typically lighting in the evenings). With short charge/discharge cycles like this I see the technology being very useful to preppers.