Households will be paid to cut back their energy use tonight as the National Grid warns supplies will be "tighter than normal".
The National Grid will be activating its Demand Flexibility Service (DFS) which will reward households for reducing their energy consumption.
The scheme was launched in November last year as a way of saving energy supplies when national demand is at its highest and this is the first time it has been activated.
The National Grid says it will run until March 31 of this year, and expects it to be repeated each winter going forward.
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When is it?
The scheme will go live between the hours of 4.30pm until 6pm this evening.
It will be the second night in a row where the scheme is activated, having ran from 5pm and 6pm yesterday.
Around 26 energy firms are signed up to the scheme, including British Gas, EDF, Eon and Octopus Energy.
How do sign up?
You will need to have a smart meter in your home and be signed up through your energy firm.
If you have already signed up, you should have received a notification from your provider informing you about the event tonight.
If you sign up to DFS you will need to authorise your provider to access your smart meter so they can read your data every half-hour for the duration of the event.
Is there a sign-up deadline?
It will depend on how your energy supplier runs its system as some may require you to sign up some time in advance.
However, with some suppliers, you can sign up just before the system launches.
Octopus Energy said that those of its one million customers who are not yet signed up can do so up until the moment the service starts at 5pm on Monday.
Will I be punished if I don’t participate?
The National Grid says there are no penalties for not participating once you have signed up for the scheme or notified your electricity provider that you will take part in a demonstration test or live event.
What appliances should I switch off and how much could I save?
The National Grid ESO has previously said it expects to pay suppliers the equivalent of £3 per unit (kWh) saved, but suppliers are able to choose whether to pass on the full amount or pay more.
Overall, the exact amount you'll get will vary depending on your usage and the number of times you're prompted to cut your usage.
If the National Grid opts for 12 blackout sessions, it says you could earn around £100.
If you significantly cut back your usage you could receive a payment of up to £20.
The National Grid says households could reduce their power consumption during windows by choosing to run power-hungry appliances such as washing machines, clothes dryers, dishwashers, electric showers and immersion heaters before or after the event.
Another option would be to reduce energy usage for example using a microwave instead of the oven during the event window.
Why is it happening?
A National Grid ESO spokesperson said: “Our forecasts show electricity supply margins are expected to be tighter than normal on Monday evening.
"We have instructed coal-fired power units to be available to increase electricity supplies should it be needed.
"We are also activating a Live Demand Flexibility Service event between 5-6pm."
The decision to activate the scheme came after National Grid put three coal-fired power plants on standby over the weekend as the UK is currently engulfed in a cold snap which is seeing temperatures drop to minus 10 degrees.
The National Grid said the move was "precautionary" and if the situation changes then the plants can be warmed up more quickly.
It also said that electricity supplies are not "at risk" and "people should not be worried".
Which energy suppliers are taking part?
- British Gas
- Conrad Energy
- CUB (UK) Ltd
- ENGIE Power Limited
- E.ON Next
- Grid Beyond
- Hugo Energy App
- Labrador (via Perse Technology Ltd)
- myenergyi (via Orange Power)
- Oaktree Power
- Octopus Energy
- OVO Energy
- Pearlstone Energy
- Power Rewaeds App (via Orange Power)
- Shell Energy Retail
- Zenobe Energy Limited