or, When Is Your Electric Car Really Green?
Plugging in your electric car feels like the clean, modern choice — and it usually is. But the environmental impact of charging your EV depends less on which tariff you’re on and far more on when you charge. The electricity system has to keep supply and demand in balance every second of the day. Renewables like wind and solar are always used first because they’re the cheapest and cleanest sources available. However, they can’t be turned up or down instantly, so when demand changes — for instance, when millions of cars start charging — flexible gas turbines step in to fill the gap.
That means the extra electricity your car draws often comes from gas-fired generation, regardless of your “green” or “off-peak” tariff. Your supplier may match your usage with renewable certificates over the year, but in real time, your car might still be indirectly using gas power.
So how can you make your charging genuinely greener? The key is timing. Midday on sunny or windy days is often the cleanest time to charge, when renewable output is high and demand moderate. Overnight, especially on windy nights, can also be a good option: wind farms tend to keep running when demand is low, helping to cut the need for gas. Early evening (around 4–8 p.m.) is usually the dirtiest time to plug in, as demand peaks and gas plants ramp up to meet it.
If your charger or energy supplier offers “smart charging,” take advantage of it. Apps such as Octopus Intelligent, ev.energy, and Tesla’s scheduled charging can automatically choose the lowest-carbon and cheapest hours to charge your battery, saving you money while reducing your footprint. You can also check the live carbon intensity of the UK grid using the National Grid ESO “Carbon Intensity” app or website, which shows the best times of day to use electricity with the smallest environmental impact.
Finally, if you have solar panels at home, charging your EV in the middle of the day can make it genuinely zero-carbon. Even without solar, a little attention to timing goes a long way.
Your tariff sets the price, but the time you charge determines the carbon. Choose your hours wisely and your electric car will run on a much greater proportion of renewable power than gas.
