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Guest blog: Greener and cheaper: top tips for home charging your electric car

Consumer Posted: 5 March, 2021. Written by Laura Thomson, Co-founder of Power My EV

If you are able to plug in at home, you’ll know that home charging is one of the best things about switching to an electric car.  No more queuing at petrol or diesel pumps, and no need to defrost your car on a cold morning.

Home charging doesn’t just reward the driver either. Charging an electric vehicle using the greenest energy can make your driving much less carbon intensive and ‘pay back’ the carbon emitted in its manufacture so much faster. Polestar, an electric car maker owned by Volvo, recently calculated that, in terms of carbon (so not thinking about petrol and diesel’s methane and nitrous oxide emissions) a Polestar 2 would have to travel 50,000 miles on average grid energy, compared to only 31,000 miles before payback if powered from renewable sources only. You could expect a smaller EV to pay back much quicker. The Renault Zoe weighs 30% less than the luxury Polestar 2.

Green energy is also cheap energy, so the price you pay for each mile will lower along with the carbon. Add in free road tax and lower servicing costs and there is no question that electric cars lower the monthly cost of motoring. 

So, how do you get these cheap, clean electrons into your car? Many suppliers are now marketing targeted electric vehicle tariffs (called EV tariffs), to make it cheaper to top up your battery. There are also innovators like Octopus Energy that are trialling dynamic tariffs that follow the cost of energy in real time. The good news is that, on the whole, the biggest savings come from charging with the greenest energy.

Why is overnight charging cheaper?

Because demand is low overnight, the energy on the grid becomes cheaper overnight. It’s greener energy not because the wind blows more overnight (the top time for wind in the UK is actually the afternoon), but because the low levels of demand means we generally don’t have to switch to the more carbon-intensive electricity, like gas or even coal. 


In the UK we pay an average 16.6p per unit of electricity. This fixed price reflects how energy at market rates will be used by a standard home profile. The profile is what we are expected to use over the course of each day and over an entire year. Utilities calculate that our use will peak around 5pm, with the winter being our highest use months.


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But EVs mean our patterns can be very different from these profiles - and crucially our charging can be shifted into the small hours. At the same time, renewable sources, like wind and sun, have grown in the last decade to nearly 50% of the annual grid supply. Future growth will need to be supported by a variety of ‘flexible’ demand schemes - of which EVs sitting on our driveways are one.


The result is that utilities can offer EV tariffs today with cheaper energy overnight to encourage us to flatten the demand through the day. In the future the energy market will probably respond with more dynamic ‘time-of-use’ tariffs, like Agile from Octopus Energy, that pass on the wholesale price of energy as a signal for us to switch on or off. There will also be ‘type of use’ tariffs that offer a low-flat rate for EV charging 24/7 in return for allowing the utility company to micro-manage the charging of your car within your own schedule.


Before we skip ahead into future energy scenarios, let’s take you through our top tips for choosing the best EV energy tariffs available right now, plus throw in a few other ways to save money on charging your car. 

How to pick the best EV tariff 

  • Don’t just look at the overnight rate - the standing charge and day rates for EV tariffs are often higher than you’d normally expect to pay. Energy companies calculate that you’ll shift so 66% will be in an off-peak, and that leaves 34% of your use in the pricey day rates.
  • Think about splitting your gas and electricity supply (Check first that your chosen utility will allow this, some will only put you on an EV tariff if you take your gas there too).
  • Find the time delay button on your washing machine and dishwasher. Almost all modern machines have a delay function. If you press the button repeatedly you will increase the time your machines will wait before they start. 
  • You might be better off without an EV tariff. Some retailers, like Symbio offer very cheap Economy 7 rates that might work better, especially if you need more than 5 hours to charge overnight. 
  • How green is the supplier? Although EV tariffs tend to be backed by 100% green energy promises, there is a big difference to what this means in practice. Is your provider buying green power or just green power certificates? These REGO certificates don’t provide much support for generators of green energy. If you want to know more, green supplier Good Energy has published research on greenwashing in the energy industry
  • If you are thinking about a dynamic tariff like Agile, look into car chargers that can time your charging for the cheapest and greenest times. Inside your home, you can download the Octopus Watch app. This will help you keep an eye on the prices and tell you the cheapest times to use electricity in your house the next 24 hours.
  • Relax, because most of the EV tariffs don’t have exit fees, so you can switch tariff again if your use changes.


Other ways to keep your EV charging costs down


Once you have got your EV tariff sorted, you might be wondering what else you can do to lower your charging costs, and make your driving even greener. Here are our five top tips on how to charge cost efficiently:

  • Keep your battery cool: Fully electric vehicles have a lithium-ion battery, which can be damaged if it is allowed to overheat. Avoid charging in direct sunlight if you can, and store your electric car in a carport or garage if you can.
  • Avoid the last 20%: The first 20% and last 20% take the most energy to fill. Avoiding running your battery down past the last 20% or charging it beyond 80% full keeps costs down. 
  • Top up using free charging points: Some supermarkets and car parks offer free charging for the duration of your stay. Your workplace might also offer low-cost charging.
  • Consider solar. Sun power can drive down your EV charging bills considerably if you’re at home during the day. Prices have fallen dramatically in the last decade. With an electric car to charge, the payback on the entire system can be as little as 7 or 8 years, leaving you with free electricity for years.
  • Maintain your vehicle: Check your tyres to ensure you get the most from your battery. Stick to the manufacturer's recommended servicing intervals to maintain maximum efficiency.


Laura Thomson, Co-founder of Power My EV


Find your best energy tariff using Power My EV’s free online EV tariff comparison. A quick assessment will let you calculate the cheapest tariff for your car charging and home. It works even if you have solar on your roof or a home battery on your wall.


About Power My EV


We set up Power My EV after we as a family switched to an EV. We realised that our home energy was the key to making our switch to electric matter. The energy we put in not only lowers the total cost of ownership, but also boosts the green credentials of both home and car. We created two tools - one to help people pick an electric car based on their needs and journeys, the other to find the best green energy to power it.