Electric Cars and
Expanding the Grid
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There has been some talk recently in the Press about banning diesel and petrol cars by 2014 and replacing them with electric cars.

This has prompted me to spend a few minutes doing a back-of-envelope calculation. By how much would the National Grid's capacity (currently about 40GB) have to be increased to accommodate these vehicles?

In the calculation I have used the Nissan Leaf as representing a typical electric car.

I've shown powers of ten in the following way: 103 appears as 10(3).

This is so that people who wish to quote the text below on Facebook can use it; FB does not support superscripts.


Cars in the UK: approx 32 million
Average annual mileage: 8000
Nissan Leaf: range approx 150 miles
Energy content of charged batteries: 30kWh

Car miles per year
               = 32 x 10(6) x 8 x 10(3)
               = 1.70 x 10(9)

Elec energy transferred to the car batteries per year
(assuming no loss as heat on charging)
               = 1.70 x 10(9) x 30 kWh
               = 51 x 10(9) kWh

Assume this load is spread evenly over 365 days in an 8-hour period, ie overnight.

Total hours of charging
               = 365 x 8
               = 2920h

Extra power requirement from the grid is therefore
                51 x 10(9)kWh / 2920h
               = .0175 x 10(9) kW
               = 17.5 GW

This compares with current demand on the Grid of around 50GW in winter

So increase in Grid capacity needed is 17.5 / 50 or about 33%

    habitat21 adds:

    There are so many black holes in the electric car plan; it is hard to know where to start...

    1.Providing enough city centre and workplace charging points and getting the grid cabling to them is major expenditure.

    2.Charging cables carry very heavy currents. Will the house insurance cover you if there is a fire?

    3.How will people who park on the road charge up their cars? Extension leads across the pavement?

    4.The Grid currently struggles to supply more than 50GW. Where will the extra 17GW for charging cars come from?

    5.The Government gets 37 billion a year from fuel taxes, and spends 3 billion on roads. When all cars are electric, what will replace that 37 billion?

    6.How will the huge upgrades to the National Grid be funded?


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