Electric Cars Strain the Grid? Think Again

The head of Toronto Hydro, Anthony Haines, was recently quoted in the Star as saying, “If you connect about 10 per cent of the homes on any given street with an electric car, the electricity system fails.” Clearly this would be a concern. But I can’t make this statement jibe with the numbers. We deserve to see where he came up with this. He said that recharging an electric car uses triple the amount of power used by a typical home. Is this true?

I took a look at the specs on one of the leading electric car candidates, the hybrid gas/electric Chevy Volt, due to ship in November. It takes 16 kWh to fully charge, and this will allow the car to travel 40 miles on electric alone. By comparison, a typical Ontario home uses 25-30 kWh per day. The average car travels 12,000 miles per year (GM’s estimate), or 33 miles per day. So that means an average car charge would be only 13 KWh. But if we then assume that some days are more than 40 miles, therefore using gasoline, not electricity, the average electricity consumed drops even further. In other words, the Volt will increase household consumption by less than 50% – lets say 40%.

But households account for only about 1/3 of electricity consumption – industrial and commercial is the other 2/3’s. So that means if every household switched to the Volt, total electricity consumption would rise by about 13%. If electric vehicle penetration is only 10%, then consumption rises by 1.3%. This is enough to crash the electricity grid? We handle these types of variations all the time, just for weather related consumption.

Electric cars offer another potential benefit, if we are smart about it. It is very economical to put simple timers on electric plugs. This allows us to recharge at night, when electric load is much lower. For example today, the demand for power at 6AM was about 14,500 MW. At midday it is forecast to be 21,000 MW. There is infrastructure sitting idle both in generation and transmission assets for about 6 hours/day – the same length of time it takes to fully charge a depleted Volt battery. Of course we can get fancier. Toronto Hydro offers consumers a discount if they permit Hydro to shut off their air conditioning during times of peak load. There is no reason electric car rechargers couldn’t be fitted with the same technology, at minimal cost. Demand for electricity can be shifted to whenever the transmission infrastructure, or generation infrastructure is best able to accomodate it.

What would a wholesale shift to electric cars do to emissions? Would we just burn more fossil fuels to make electricity? The answer is a resounding no. The reason is the efficiency of the electric drive train. With an internal combustion engine, most of the energy consumed is lost as heat out the tailpipe or in the radiator – as much as 80% is lost. Electric cars are much more efficient, converting much more of the energy in electricity into moving the car, with far less waste heat. Even with burning coal, the reduction in emmissions from gasoline would exceed the increase in emissions from burning coal. And of course with electricity, we have many ways to generate power with less emissions than coal.

The Toronto Hydro chief has begun a useful discussion about the impact of plug in vehicles on the electric grid. There are certainly ways to design the system to accomodate plug in vehicles that are better than others. But on the surface, there seems to be very little reason to fear electric vehicles, and many reasons to embrace them, as far as the grid is concerned, and as far as overall emissions, not to mention energy independance. So lets begin the discussion.

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