Smart meters are only one part of the equation, another being smart grids.
The argument goes that the near real time data smart meters provide will tell the smart energy system how much energy is being used, when and where across Great Britain. This will help the energy system better manage the supply and demand of energy to reduce waste, and also shift energy usage away from traditional peak times – which are currently reliant on fossil fuel energy – and make better use of the more inconsistent renewables.
https://energysavingtrust.org.uk/blog/balancing-grid-smart-meters