Re: green lunacy
No, the efficiency is much higher than 30%. You also have to factor in that the National Grid has to switch off a lot of wind power at night due to over supply. Coal and Nuke plants don't like to be turned on and off frequently. If the excess power can be stored even partially, it's a good investment. The 12 second turn on time is very handy for accommodating peak loads. There isn't any other system that can do that.
Eventually, it may be possible to supplement and then replace pumped storage with electric cars that can move power in both directions as needed. The business model will need to be worked out and there will be a need for people to be able to opt-out from time to time if they are planning on a long trip and need a full charge in their cars.