Two more power companies, Scottish Power and EDF, have joined Octopus Energy in trialling "surge pricing", where new tariffs will charge customers more for using energy during peak periods, and less in quieter ones.
Together the trio have a combined 11mln customers, whose smart meters will automatically send updates every half hour back to the companies about how much energy households are using.
Partly it is designed to encourage people to use less energy during peak hours to reduce stress on the electricity grid, with peak times generally being the morning and evenings.
Earlier in the week Octopus said it starting a two-month trial with National Grid Electricity System Operator (ESO) this week, which will pay households if they reduce their power consumption below their usual levels for specific periods when demand is high, for example between 9am-11am and 4.30pm-6.30pm.
All three energy suppliers already provide these tariffs based on energy use at different times of day to a small number of customers.
A Scottish Power spokesman said: “Time of use tariffs that are updated on a half-hourly basis will give consumers a real opportunity to save money on their energy bills, particularly for EV drivers charging from home."
They said half-hourly updates will provide the companies an accurate profile of local electricity demand, which will be more useful as electricity use increases due to electric cars and other net zero plans.
“This will allow network companies to get more out of existing grid infrastructure and target upgrades to the grid for increased demand more efficiently,” the spokesman said.
EDF said: “Half-hourly market settlement will play a key part in our transition towards a net zero future, as well as benefiting customers.
EDF said its existing time-of-use tariffs enable customers to enjoy lower prices at night-time, when demand for energy is lower and therefore cheaper, including a tariff designed to allow electric vehicles to be charged at a cheaper rate.
Octopus said participating homes in its trial could reduce power demand by 150MW during each two-hour trial event and if they meet their targets they would get free electricity during the trial event, earning up to 35p for every kilowatt-hour of electricity saved.
National Grid said the pilot scheme will help inform its plans to run a zero-carbon grid for certain periods by 2025 and a fully decarbonised grid by 2035 and build understanding of how households can support this goal.