What is the WhenToPlugIn app?

Our WhenToPlugIn app is a handy tool for your mobile phone that helps you make smarter energy choices at home. It's powered by carbonintensity.org.uk, the same carbon intensity forecasting tool built by National Grid ESO, The Environmental Defense Fund Europe, The University of Oxford and WWF that powers the Green Light Signal.

The WhenToPlugIn app shows you the live carbon intensity forecast and lets you know when the electricity in your home will be cleanest over the next 48 hours to help you plan your electricity usage. The app also offers a full breakdown of the energy sources powering the electricity in your region and provides live updates as new clean energy records are broken too!

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The WhenToPlugIn app is optimised for iOS 14+ and Android 11+ systems, on models from iPhone X+ (iOS) and Google Pixel 4+ (Android).

What is carbon intensity?

Carbon intensity is a measure of CO2 emissions per unit of electricity consumed. When it's low or very low it suggests that renewable and/or nuclear energy is playing a key role in the energy mix that powers your home. This is happening more as the electricity system is transformed: In the last seven years we have decarbonised Great Britain’s electricity system by 66%, connecting people to more green and clean energy sources. 

The WhenToPlugIn app uses carbon intensity to determine the best times to use energy, based on your location – meaning the power coming into your home is predicted to be cleaner at that time compared to other times.

How do I download the WhenToPlugIn app to my mobile phone?

Simply head to your app store of choice and search for the WhenToPlugIn app. Then follow the prompts to download the app on to your phone. Once downloaded, head into the app to get started and follow the steps below.

  • On your mobile phone, head to your app store of choice to download the app and follow the prompts to install (The WhenToPlugIn app is optimised for iOS 14+ and Android 11+ systems, on models from iPhone X+ (iOS) and Google Pixel 4+ (Android).
  • Once in the app, read through the on-boarding information, then enter either your postcode or region to access the carbon intensity data where you are.
  • Once set up, the app will be able to provide you with lots of useful information including the carbon emission intensity in your area and also your next best window of opportunity to use low-carbon energy sources.
  • If the current carbon intensity is high, you can set a reminder in the app to alert you to a time where the carbon intensity rating will be lower - meaning you can use electricity from power sources that emits less carbon dioxide which is better for the planet.

High energy inspiration

Want to feel positive about the energy you’re using? Here are some fun ideas about what you can do when your app tells you that you have the green light to plug in. How about...

  • Stream: Stream a film or play a game online.

  • Cook: Turn up the heat on your electric hob and cook up a storm.

  • Heat: Feel good that your kettle or electric boiler is heating up with clean energy.

  • Clean: Can you get all your laundry, tumble drying and vacuuming done before the carbon intensity changes?

  • Create: Make music, movies, social filters, or digital art whilst the carbon intensity is low.

  • Charge: Plug in your electric vehicle.

Because together we can reach net zero.

#PowerOfAll #WhenToPlugIn

Get the National Grid digital voice assistant skill

Our smart skill for your favourite digital voice assistant tells you the best times of day to ‘plug in’, and provides live updates about your local electricity mix so you can make smarter energy choices at home.

Discover the voice assistant skill

Frequently Asked Questions

What will the app tell me?

The WhenToPlugIn app has been developed to help everyone take advantage of zero carbon energy. It will tell you the best time to use electricity by searching for the lowest possible carbon intensity time periods in your region. It will also show you the regional carbon intensity forecast across Great Britain and tell you about the new energy records being broken.

What is zero carbon energy?

Zero carbon energy produces no carbon dioxide or other greenhouse gases. It's generated from renewable sources, including onshore wind, offshore wind, solar and water, as well as from nuclear power stations. While it's not a renewable energy source, nuclear is a ‘clean’ source of energy as it produces no carbon dioxide emissions or greenhouse gases of any kind and so produces electricity with a low carbon intensity. Our WhenToPlugIn app will encourage you to take advantage of this.

How does the carbon intensity forecast work?

The 'When To Plug In' app is powered by carbonintensity.org.uk, a carbon intensity forecasting tool built by National Grid ESO, The Environmental Defense Fund Europe, The University of Oxford and WWF.

The API uses machine learning and sophisticated power system modelling to forecast the carbon intensity and electricity generation mix for Great Britain.

It pulls data from large power stations, wind and solar generation, and the electricity we bring in from Europe via interconnectors that run under the sea, and balances that with electricity demand from consumers, businesses, and industries.

What are the factors that impact carbon intensity and the amount of zero carbon energy sources in my local or national mix?

Carbon intensity varies by hour, day, and season due to changes in both electricity supply and demand. The forecast is based on an AI that predicts weather patterns to make sure energy providers can manage where we are getting our energy from and how much is needed.

It isn’t only the weather in Great Britain that can affect the forecast, but also the weather in countries across Europe such as France where we share electricity via interconnectors. The amount we can bring in from these areas depends on the conditions that drive up energy demand in those places, e.g. cold and wet weather.

Won’t the app just tell me to plug in in the middle of the night and use off peak electricity hours?

Great Britain continues to draw more and more power from zero carbon sources, meaning that there are ever-increasing opportunities during the day for people to use electricity with a low carbon intensity – not just at night.

Will it make a difference if I plug in when the app tells me to?

In short, yes! Every green action helps and net zero won’t be possible without everyone’s input, but the biggest impact of all comes from system transformation. The energy sector has undergone huge change over the last decade or so. There has been a massive shift from using coal to generate electricity – which resulted in lots of carbon dioxide emissions as the coal was burned – to using ‘clean’ forms of generation such as renewable wind and solar power.

However, there is much more that needs to be done, because transforming Great Britain’s energy system will enable other sectors such as transport and construction to reduce their emissions also. Here are some examples of significant changes needed over the next decade:

  • Increase capacity for clean electricity generation by quadrupling offshore wind generation by 2030, to ensure we can meet growing demand from homes, businesses and transport with low-carbon supply.

  • Reinforce the electricity network so it is ready for the predicted rapid growth in electric vehicles and in low carbon heating systems, such as heat pumps.

  • Develop supply and demand of hydrogen gas, which is a cleaner fuel type, especially with industrial users.

  • Develop and implement technology to capture carbon emissions, particularly from gas powered electricity generation and industrial processes.

  • Increase energy efficiency measures to make homes more insulated and to reduce wasted energy.

As a nation, we are making excellent progress and we have the technology and know-how to deliver what needs to be done. Everyone – from Government, to the energy regulator Ofgem, to businesses and individuals – has an important role to play in making it happen.

If everyone used electricity when the National Grid app said to plug in, what impact could that have?

Our calculations show that if one million Brits used the app and switched to using their washing machine when the electricity in their area was produced by cleaner energy sources, we could collectively help save 76,650 tonnes of CO2 each year: equivalent of taking a whopping 36,500 cars off the road. By using tumble dryers at cleaner times, we could see a huge 164,250 tonnes of carbon saved, which is the equivalent to taking more than 78,000 cars off the road.

These statistics are calculated per number of people using the appliances, the frequency of use and the average power rating to work out the potential amount of CO2 emissions reduced if moving to the lowest emissions hours (100g/kWh CO2).