Good News Part II: More EVs Don’t Crash the Grid

Pacific Gas and Electric, Southern California Edison, and San Diego Gas and Electric are California's three investor-owned utilities (IOUs).
Credit: Synapse Energy Economics, Inc.

This blog is an update to a previous blog, “Good News: EVs Are Not Crashing the Grid

Will electric vehicles (EVs) cause blackouts? The evidence suggests otherwise. Despite what the naysayers may tell you, new data from California shows that utility grids have the capacity to support a surge in electric vehicles.

That’s extremely important for other states, as well.

For example, New York just announced a landmark initiative to determine how the state’s electric utilities can best help accelerate transportation electrification while cost-effectively maintaining grid reliability. This effort coincides with a parallel New York initiative to establish new residential EV electric rates that could potentially defer utilities’ costly electrical system upgrades and save EV drivers even more on fuel costs.

Since 2012, California regulators have required the state’s three investor-owned utilities (IOUs)—which serve three-quarters of the state’s electric demand—to file reports that primarily look at how EVs affect the local grid and drivers’ charging behavior. In my last blog, I presented on findings from 2016.

Now, the results are in for 2017, and the news is still good:

  • The grid can still accommodate hundreds of thousands of EVs at minimal cost; and
  • Time of use (TOU) are simple and useful tools for shifting EV charging load to periods that are beneficial for the grid.

In 2016, the fraction of EVs that necessitated distribution system or service line upgrades was a mere 0.19 percent. (Upgrades occur when the electric infrastructure at or near the home is unable to accommodate additional EV charging.) Even though the number of EVs in the utilities’ service areas jumped by more than 60,000 last year to more than 270,000 EVs, the number that required upgrades dropped to 0.17 percent in 2017. And while the three IOUs spent approximately $610,000 on those upgrades in 2016, they spent only $500,000 in 2017. Considering the $5 billion that the utilities spend annually to maintain their systems, these EV upgrade cost figures are a drop in the bucket: about 100th of 1 percent.

Average upgrade requirement was 0.17 percent across the IOUs
Credit: Synapse Energy Economics, Inc.

That is not to say that we should not be looking for ways to better manage EV charging. The amount of power an EV can instantaneously draw from the grid to recharge is comparable to that of a single-family home. Using price signals to shift this large, yet flexible, demand to off-peak periods when the system has spare capacity can ease the stress on the grid (and on your wallet). Charging off-peak in some areas may also occur at times when renewable sources, such as wind and solar, are generating more energy—meaning more EVs are powered with emissions-free “fuel.” (See NRDC's Driving Out Pollution report for more.)

Each of the three utilities in the report offers time-of-use (TOU) rates to their residential customers, and contrary to standard rates, these TOU rates vary predictably depending on when the energy is used. For example, a kilowatt-hour used at midnight may be two times cheaper than one used at 4 p.m. We now know in theory and in practice that these rates are more effective than conventional residential rates at prompting EV drivers to charge up when its most beneficial to the entire electric system: similar to the results from 2016, the 2017 figure below demonstrates that EV drivers on TOU rates do more charging off-peak and contribute less to costly distribution system peaks than drivers on flat rates. A distribution peak is generally the period when electricity demand on the grid is greatest over the course of a day, month, or year. The greater the peak, the more expensive the grid infrastructure and electric generation needed to meet the demand—if left unchecked.

Credit: Synapse Energy Economics, Inc.

The data also reveal that the length of the off-peak periods affects the diversity of EV peaks: The greater the window of time to take advantage of low-cost electricity, the greater the diversity in individual EV charging times. That’s a good thing. Think about a brick-and-mortar department store planning its sales strategy for the holiday rush. If the store offers a discount on all items for only 24 hours, it might be much more crowded and chaotic during that period than if it extended the sale for a week and allowed customers more flexibility to come in at convenient times.

The same principle holds true for EV charging. Generally, the greater the off-peak window (sale period), the less likely individual peaks (when customers come to shop) will hurt system reliability (overcrowd the store to the point of compromising customer service). And with the “smarts” embedded in most EVs today, it’s easy to “set and forget”: drivers can program when they want their EV to charge and take advantage of the lower off-peak pricing available through TOU rates.

In short, California brings welcome news for all states experiencing and accelerating EV growth—including Pennsylvania, Maryland, and New York. Rather than crashing the grid, EVs in the country’s largest EV market have only had a marginal impact on it. Moreover, TOU rates are transparent, effective tools for making the grid more reliable and flexible while driving greater fuel cost savings for EV drivers.

The data make it clear that states, utilities, and grid planners need not fear transportation electrification; they should embrace it.