Nitpick - I make it closer to 1 hours electricity but I agree it's way too low from a fixing global warming point of view. The figure 2,850GWh by 2040 works out about 280 Wh a head if you guess a 10bn population. For comparison a Tesla Powerwall is 13.5 kWh. Something like 100x that storage would be good if we are running on renewables.

With something like the nantenergy battery they are already talking $100/kWh and have cheap materials so it would seem quite plausible to get down to say $25/kWh by 2040 meaning you could get 40kWh for $1000 or so which I think may be a better target. (https://www.engineering.com/ElectronicsDesign/ElectronicsDes...)