Bitcoin itself is energy or can be converted into energy. If I can buy wood to burn for energy with Bitcoin, I am converting mined Bitcoin into energy.
Perhaps an equally good "battery", this is the principal of fungibility as a currency. Given the built-in halving structure of bitcoin, in the long run bitcoin may "store" or buy more electricity relative to the dollar that has inflationary pressure (USD tends to lose 3%/yr in real value due to inflation).
Then Bitcoin stores no energy whatsoever. If I purchase the same amount of electricity with $, or with gold, or with seashells instead of Bitcoin, there will be no difference on the side of the electricity supplier. Aside from, of course, Bitcoin potentially affecting electricity prices.
