Electric Vehicles and the Grid

September 13, 2022

I wrote back in March about electric vehicles (EVs) and how I thought we would be up to the challenge of generating enough electricity to meet this new demand https://www.notlhydro.com/electric-vehicles-and-electricity-demand/. I would first like to discuss a bit of analysis that reinforces my optimism that we can meet the generational demands of electrifying the transportation sector.

In my March blog I reported that, according to the Environmental Commissioner of Ontario, transportation comprises about 39% of energy use in Ontario while electricity is 23%. In 2020, the load on the electricity grid was 132 TWh. This would imply that electrifying the transportation sector would need 224 TWh. In fact, the requirement will be much less than that. The reason for this is that EVs are much more energy efficient than internal combustion engine (ICE) vehicles. In fact, depending on how you measure it they are 2-4 times more efficient. ICE vehicles generate a lot of heat that is wasted.

I did the following calculation of how many TWh would be needed if every car became an EV.

Number of residential customers in Ontario (2020)4,800,000
Number of vehicles per residence (Canada average)1.5
Number of consumer vehicles7,200,000
Annual mileage per vehicle (Canada average)16,000 km
kWh required per km0.2
Total kwh annual requirement23,040,000,000 kWh
Annual terawatt hour requirement23 TWh

The transportation sector includes buses, trucks, trains and planes so is more than just consumer vehicles. Even so, at around 10% of the total energy requirement for the sector this 23 TWh estimate seemed too low. The reason for that is the more efficient use of energy by electric vehicles. Much less than 224 TWh will be needed as the transportation electrifies.

Electrification is not the only option for decarbonizing the transportation sector. Non-carbon based fuels are being tested with airplanes and hydrogen could be a better replacement for the trucking and bus sectors. There are multiple solutions and a mix of the best technologies and the lowest overall cost will determine the eventual solutions.

I would now like to discuss the impact of EV growth on the transmission and distribution grids. The following chart shows the hourly demand of a customer with a Tesla. As can be seen, the charging of the Tesla has a huge impact on the demand for electricity: an increase of 12-13 kW and a quadrupling of demand. If 7.2 million electric vehicles all had Tesla-like demand and all charged at the same time the total demand in Ontario would be 86.4 MW or three times the current peak. The transmission and distribution grids will therefore need to deal with the increase in overall load from electrification and an increase in demand at key times.

For both transmission and distribution systems the real issue is the level of demand. The systems have maximum amounts of electricity they can handle at any point in time. The calculation of the demand if all 7.2 million cars were charging at one time is obviously unrealistic. Reasons for this include the following:

  • EVs do not need to be charged every day. Our Tesla customer charged the EV 71 out of 222 days or every third day on average.
  • The incremental demand was also lower on many of the charge days as the car was likely only partially discharged.
  • Not every charger has the same level of demand as this one. Most level 2 chargers have 6-7 kW of demand. Tesla chargers have a higher demand.
  • Customers will charge at different times in the day depending on their needs and the cost of charging.
  • The Government of Ontario is introducing a new rate structure in 2023 that will have very low night time rates and higher peak time rates. This is being structured to appeal to EV charging.
  • We anticipate that as EVs become more widespread, the Government will introduce programs to encourage EV owners to allow LDCs to have some control over the charging so as to manage the level of demand either provincially or locally.
  • NOTL Hydro’s current peak is between 4:00 pm – 6:00 PM. This charging is mostly after 6:00 PM so the incremental charge is not on top of peak demand.

Distribution Grid Impacts

However, even taking into account the above, the incremental demand from EVs is likely to be an issue for distributors as EVs become more popular. This will manifest itself in three separate areas:

  1. Local transformers – As more customers who are serviced by the same local transformer get EVs the risk of that transformer overloading rises. This will particularly be the case for smaller transformers. This will require distributors to monitor their local transformer loads more carefully. For pole-top transformers the solution is simpler as more pole-top transformers can be added to the system with fewer customers on each. For pad-mounted transformers the simplest solution will be to replace the transformer with a larger one. We have already done this in a few cases and are also moving to a larger transformer as the standard for new installations.
  2. Primary Wiring – Some of the primary wiring may not be large enough for the higher local demand if it was sized based on standard household demands. These will not be easy to upgrade as the wiring is connected to all the local transformers and can be buried.
  3. System transformers – If the load on the distributor system gets too high then the transformers feeding it will need to be upgraded. These are expensive pieces of equipment with a total replacement cost of several million.

Transmission Grid Impacts

The potential impact of EV growth on the transmission system will depend on where the incremental generation required to supply this demand is located. If the increased demand is offset by generation on the local grid (likely a combination of solar power and storage) then the impact on the transmission grid could be minimal. If the increased generation is larger transmission connected generation, such as solar farms, wind farms, hydro dams and small modular nuclear reactors, then the transmission grid will need to grow. This will be a challenge for a number of reasons:

  • Many transmission lines have been hemmed in by urban developments. There is little room for expansion making upgrades both more challenging and more costly.
  • There has been a deliberate effort to control the cost of transmission over the past 20 years by limiting its growth. The decline in grid demand since 2007 has added to this necessity. Moving to a strategy of expansion will take an adjustment for Hydro One, the government, the regulators and the public.
  • There has been opposition to growth in the transmission grid from those that do not want transmission lines near where they live. Approaches will need to be developed to meet these concerns while still allowing for the needed growth.
  • Transmission lines need to operate with more redundant capability than distribution lines due to how vital they are and to the challenges of performing maintenance. This means growth in demand will have a bigger impact on the need for new and upgraded lines. It also means that performing these upgrades will be more difficult as the lines cannot be out of service while the upgrades are happening except in a very controlled and planned manner.
  • Any upgrades in the voltages of transmission lines would require all the transformers connected to those lines also be replaced. This is not simple or cheap.
  • Hydro One has the capability to design and build the needed lines. The approval processes are very long with considerable uncertainty. These processes may need to be accelerated or the risk of demand growing faster than supply can manage becomes very real.

The actual result will likely be a mix of the two. Larger scale generation is still cheaper on a cost per kWh basis. However, once you factor in the transmission costs the local generation starts to become viable. The challenge then comes the ability of the local distribution grid to handle the additional generation or to enhance this capability in a cost-efficient fashion. This is all very doable, just not easy or cheap. The good news is that all this growth means lots of additional revenue to pay for these investments.

1 thought on “Electric Vehicles and the Grid

  1. Yes – the one assumption we cannot make is that all vehicles will be charging at the same time! The odds of this happening are very low. Also EV transition will take time and not happen overnight giving time plan and do upgrades where needed.
    The grid will be fine – it comes down to good management and monitoring the local demand.

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