In recent days, a new round of misleading headlines say that homes won’t be able to boil a kettle while also charging an electric car. Given the traditional British cuppa holds near-sacred status, this subject was ready-made for attention.
Today, however, the vast majority of home car chargers are rated at or below 7 kilowatts(kW) and can be run alongside kettles, ovens and any other domestic appliances without problems. The source of the headlines, a National Grid “thought piece” published in April, was about problems on home or local electricity circuits, that might arise in future if they are not addressed.
Running 11kW fast chargers at the same time as kettles, on inadequate wiring, is one of these potential problems. But these high capacity units are “vanishingly rare”, says James McKemey, head of the insight team for charge installation firm Pod Point. He tells Carbon Brief:
“When we go to site we have to assess the load there already. If running a kettle would mean blowing your main fuse, we can’t install.”
Major transformation
The media focus on electric cars has grown since environment secretary Michael Gove said on 26 July that the government wanted to ban the sales of “conventional” petrol and diesel cars and vans by 2040.
(It remains unclear if hybrid vehicles would be allowed, as the ban has not been explained in detail.)
This ambition would entail a major transformation of the UK economy. It would pose significant challenges for the electricity grid, the exchequer’s tax take, carmakers and the wider auto sector.
National Grid, which manages the UK power network, has been trying to work out what those challenges look like and what it will need to do to address them. This is an effort to identify potential problems so that they can be avoided, but has been widely misconstrued as a forecast of calamity.
Earlier headlines have suggested the UK will need six, ten or even 20 new nuclear plants to charge electric cars, which would raise peak demand by up to 50%. National Grid published a “myth buster” to explain why these headlines were wrong. It says:
“The government’s recent announcement…has led to lots of speculation in the media regarding the effects on the energy system. Often National Grid’s Future Energy Scenarios (FES), which is our analysis of future energy demands, has been cited incorrectly and sometimes out of context. This article is intended to clear up some of the misconceptions.”
As Carbon Brief had explained in July, the reality is likely to be closer to a 6 gigawatt (GW) or 10% increase in peak demand due to electric cars in 2050, equivalent to two nuclear plants. This assumes smart car charging becomes the norm, extending the current trend in that direction.
Newspapers have also been quick to suggest that electric cars would massively increase annual demand for power. Obviously, electric cars will raise demand for electricity. (A reduction in demand from oil refineries will partly offset this. They use around 1.5% of current UK supply).
However, analysis from Cambridge Econometrics and National Grid suggests electric cars might raise annual demand by just 10% in 2050. Key uncertainties in this outlook include the rate of electric car adoption, the average number of miles driven per person in future – this number peaked a decade ago – and whether autonomous vehicles or car sharing take off.
Cuppa crisis
This week, headlines have found a new electric car problem to worry about – again, based on a piece of National Grid future-gazing. The Financial Times was first to the story on Sunday 20 August under the headline: “Charge electric car but don’t boil kettle, says National Grid”.
It said homes using 11kW, 48 amp fast chargers might not be able to boil kettles at the same time, since most home electricity circuits can only handle 60-80 amps at one time. Kettles are limited to 13 amps, like many other domestic appliances.
The FT article noted that, as of today, only 5% of homes would be able to take an 11kW charger. It added that these homes would be able to handle fast chargers and kettles at the same time, if they fitted a 100 amp main fuse.
This was not enough to prevent the cuppa crisis from spreading, however. In subsequent headlines, the Telegraph (“Don’t boil the kettle while charging your electric car because it will blow the fuse, National Grid warns”), Times (“Charging an electric car while the kettle is on may blow a fuse”) and Mail Online (“Forget that cuppa: Charging an electric car at the same time as boiling your kettle will blow your fuse, National Grid warns”) were among those following the FT’s story.
By this point, caveats were often forgotten and growing certainty took hold. A 22 August Telegraph editorial confidently said: “The National Grid says anyone driving an electric car should not charge it at home while boiling a kettle because the power surge would trip the main fuse.”
In one Daily Mail piece published in print and online, veteran columnist Christopher Booker managed to pull together all the recent misleading headlines about electric cars into a single article.
It’s worth returning to what the National Grid’s thought piece actually says on this question. Note that it was published in April and has only now received widespread coverage. It says, in hypothetical terms:
“The average household is supplied with single phase electricity and is fitted with a main fuse of 60 to 80 amps. Using a 3.5kW battery charger requires 16 amps. If one were to use an above average power charger, say 11kW, this would require 48 amps. When using such a charger it would mean that you could not use other high demand electrical items (such as kettles, oven, and immersion heaters) without tripping the house’s main fuse…
“If your house had fitted the maximum 100 amp main fuse then a more powerful 22kW charger could be used…In reality an 11kW charger, with an above average main fuse, is likely to be a good compromise.”
It’s worth repeating that very few homes are currently able to install an 11kW charger and Pod Point does not believe they are necessary. In any case, only high-end electric car models are able to use three-phase 11kW fast chargers, with most models restricted to 7 or 3.5kW units.
The spread of larger electric car batteries does not mean people will drive further, adds McKemey, so 7kW chargers should remain adequate for almost all homes. Over the past 16 months, 33% of chargers installed by his firm were 3.5kW, another 67% were 7kW and just 0.1% were high capacity fast chargers.
National Grid goes on to identify a second potential “pinch point”, if multiple homes on a local electricity circuit all use car chargers at once. It says some 32% of low voltage circuits might need upgrading once electric car adoption reaches 40-70%, or more quickly if fast chargers are used.
Conclusion
The UK will need widespread adoption of electric cars, coupled to increased supplies of low-carbon electricity, if it is to meet its legally-binding carbon reduction targets. The government wants to ban sales of petrol and diesel vehicles by 2040 and for “almost all” to be zero emission by 2050.
This shift will have wide-ranging effects, many of which will be positive. Roadside air pollution will be eased, motorists are likely to save money on fuelling their vehicles and the UK will become less dependent on imported oil.
Other effects of electric cars will be more challenging. The treasury may need to find a new source of income as fuel duty income evaporates. Carmakers will have to develop new models and new supply chains. Mining for the components of batteries will pose different environmental risks. And electricity grids will need to adapt.
As Pod Point’s McKemey says, however, the idea that no-one is thinking about how to address these challenges “could not be less true”.
Source: Carbon Brief. Reproduced with permission.
