Plus electricity cannot be stored.
FYI:
Electricity can be stored,
1. Batteries
2. Flywheels
3. Gravitational potential energy using a pumped hydroelectric facility.
4. Compressed Air Energy Storage
5. Rail Energy Storage
6. Molten Salt Storage
7. Thermal Energy Storage
Reference: http://discovermagazine.com/2015/july-aug/26-power-stash
It should have been "electricity can not be stored in a profitable way".
None of these ways is what is considered "efficient".
It is more profitable to produce new energy instead of storing it.
Really? Try and tell that to the 1000s of people who are using Elon Musk's Power Wall for load shifting, backup power, and off-the-grid use.
Elon Musk has proven that power storage can be profitable and he invested millions to do just that. Go read more about this project here, https://www.tesla.com/powerwall
We need to start thinking out of the box, like Elon Musk and his team of engineers, to reduce Bitcoin's electricity footprint.