Key phrase, surplus electricity assumes you have "Off Peak" electricity to spare. With an increasingly 24/7 economy, digital server farms, and electric vehicles being charged overnight, that "surplus" electricity looks more like unicorn farts than a solution to avoid building more generating capacity.
Perhaps not as true as it once was, peak demand is often met with high temperatures from daytime heating, especially in the summer months when pretty much everything is using the HVAC to full capacity.
What is often neglected to be considered, is that electrical energy is largely used instantaneously, as the amount of grid storage is negligible. This is changing with Solar roofs equipped with a Tesla (or competitor) Wall or Vault system. The user can program (at their discretion) to sell unused power to the grid during any time they choose (rates vary during times and seasons). The grid is also intelligent and will review weather forecasts, for example if the forecast is for a storm in the next 24 hours and your Wall units are at 50% charge, they make take power from the grid and fully charge preemptively to if there is an outage; you are secure.
The other consideration is that batteries that do not make qualification standards for the Tesla EV line; may be very good candidates for a Wall or Vault type utility storage device. Even batteries that have exhausted their useful life as a vehicle battery (down to 80% of full charge), may be useful for utility storage.
Consider all the energy that is generated, and lost due to demand exceeding supply - energy storage is a huge market segment that needs to be developed.