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Cutting carbon

How to lower demand on the grid, the easy way

Illustration of a hoover cleaning up the grid.

In this post, we look at how electricity demand affects CO2 emissions, and how our Community team has used greener electricity by avoiding peak-hour power.

The time of day you use electricity affects how green it is 

At Bulb, we buy green electricity on your behalf. We make sure that for every unit you use, a unit is produced and put on the grid by a renewable generator. But we can't deliver that electricity directly to your house (no energy company can do that). So the energy you use comes from the National Grid.

Once it’s produced, generators add their electricity to the National Grid, which is a melting pot of energy from lots of different sources. It’s not possible to store large amounts of electricity yet, so the grid’s job is to move electricity around the country in real time, to wherever it’s needed, like your home or office. It’s a careful balancing act between supply and demand. 

When everyone boils their kettle during the Bake Off ad break, electricity from the grid is more polluting. That’s because fossil-fuel generators are switched on to meet this higher demand. We can work out exactly how polluting electricity is at any given time by looking at its carbon intensity. That’s a measure of CO2 emissions produced per kilowatt hour of energy used. In fact, we built a Twitter Bot to interpret carbon intensity data and broadcast the greenest times of day to use power.

As our energy system gets smarter, there will be more ways to balance out peak demand

Innovations in the energy industry are helping people to use electricity at different times of the day, when there’s more renewable power available on the grid. Smart meters are already doing this by making live energy usage more visible, and other smart home technologies can make scheduling your usage easier, too. Electric vehicles (EVs) are another big opportunity to shift our typical usage.

Instead of every electric driver charging their car at 6pm, EV tariffs are designed to encourage charging when demand on the grid is low. Our new EV Tariff offers a cheaper rate for electricity used between 2am and 6am, for example. So, by programming your car to charge during the small hours, drivers will be saving money, and there will be more green energy available on the grid to go around. It’s win-win.

Our Social & Community team challenged themselves to avoid peak hours

Here’s Melisa Gooding to tell you more about how they did it.

Our team of 14 has been using Bulb’s Carbon Bot to shift our usage patterns to less carbon intensive hours during the day.

Over a working week, we kept a diary of which electrical appliances we switched on when the Bot told us the grid was greenest - for example washing machines, dishwashers, vacuum cleaners and ovens.

One of our team loading the washing machine at home.
Lou washing responsibly

As we’re working from home it was easy for us to nip to the kitchen and pop things on, and it gave us a chance to talk about being more conscious of our usage. None of us has smart home technology to control our appliances yet, so it was a relatively manual process. If we were in the office, we could have used the timers on some of our appliances, but this would have needed a bit more organisation!

Between us, we accumulated 24 hours using the washing machine, 3 hours using the dishwasher, 1 hour of vacuum cleaning and 30 minutes using an electric oven.

To work out our carbon impact during this challenge, we:

  • created a spreadsheet to capture what time our appliances were on, how long for, and their power rating in watts

  • used National Grid’s half-hourly data to work out the carbon intensity of electricity when our appliances were in use. This is measured in gCO2/kWh (grams of CO2 per kilowatt hour)

  • compared our usage to a ‘high’ carbon intensity measurement (284 gCO2/kWh) to work out our overall CO2 saving

Our team avoided 2.7kg of CO2 by using appliances at low-carbon times over 5 working days

That’s the same as 27 hours of watching Netflix, so around 54 episodes of Peep Show, or driving 9.3 miles in a petrol car.

This may seem like a small difference but:

  • if this were scaled up to Bulb’s UK employees, that would mean 186kg of CO2 saved in a working week. Which is more like 1,863 hours of Netflix or driving 643 miles in a petrol car. That’s the distance from Cornwall to Inverness.

  • if this were scaled up to all of Bulb’s 1.7 million members, it would mean 327.5 tonnes of CO2 avoided every week. That’s the same as 3.3 million hours (377 years!) of Netflix, or driving 1.1 million miles in a petrol car, which is roughly 45 laps around the world.

Encouraging each other and setting manageable tasks can make a tangible difference. The main challenge we found was getting our housemates on board, as we all live in flat shares. But it also gave us a good opportunity to talk about our energy consumption and learn new habits to make our energy usage a little greener.

by Melisa Gooding


Are you following our Carbon Bot yet? Or do you have any other tips for using electricity when the grid is greenest? Let us know over in the Bulb community.