By day electric vehicles are taking the world by storm: their sales are doubling every year, their fuel efficiency is off the charts, and some of them can even accelerate from 0-60 mph about as fast as you can say Elon Musk.
By night the electric vehicle (EV) community continues to make waves. While you are in bed dreaming about how some day you too might own an electric car, many EV owners are doing something dramatic; something unusual; something that is reshaping the energy landscape.
They are using gobs of electricity.
Today we once again crack open Opower’s energy data storehouse (the world’s largest, spanning more than 50 million households worldwide) – this time to examine the energy usage behavior of an increasingly important segment of utility customers: electric car owners who charge their car in the wee hours of the night.
To fuel our analysis, we evaluated anonymous data from about 2,000 night-charging EV owners in the western U.S. (see Methodology below) — a region where Teslas, Nissan Leafs, and other plug-in electric cars abound.
Our statistical findings suggest how vastly EV owners’ energy profiles can deviate from normal; why the timing of EV charging is so important; how solar panels fit into the picture; and what it all means for utilities, their customers, and the future of the electric grid.
After a Long Day, It’s Time for a Good Night’s Charge
The wee hours have in recent years gained traction as a popular time for EV owners to recharge their vehicles.
In the hourly usage curves below, you can see that the EV owners in our dataset (light blue) exhibit a massive spike in electricity use beginning at midnight, shooting up to around 4 times the average level.
Why the huge usage bump at midnight sharp? The answer hinges on incentives and utilities’ ability to shape consumer behavior.
Specifically, many EV owners in the western region (upwards of 60 percent, according to one California study) — and all the EV owners considered in our analysis — have signed up with their utility to get highly discounted electricity between midnight and 7am, in exchange for a daytime price hike. The sudden surge on the right side of the graph above suggests the behavioral effectiveness of this framework: when EV owners enroll in a time-of-use rate plan, they operate in alignment with it.
Offering an off-peak rate plan tends to be a savvy move by utilities: it helps them prevent power-hungry electric cars from overtaxing the electric grid during the day, when system-wide demand is already on the high side. As we’ve previously examined on this blog, high electric demand in the afternoon hours is notorious for destabilizing the power grid.
That’s why utilities in numerous states — ranging from California to Texas to Georgia — have been quick to introduce targeted customer engagement programs and off-peak charging incentives that help smooth the integration of EV’s into their territory. Last month, Minnesota became the first state to roll out a statewide approach for promoting night-time EV charging.
We’ve seen above that EV owners who have an incentive to charge their car at night understandably exhibit abnormal electricity usage during those hours. What may be more surprising is what happens after the sun rises…
After the Sun Rises, Electric Car Owners Are Still Different
It’s morning, around 7:00 a.m. Teslas have been charged, the time-of-use electricity price for participating EV households has cranked up, and the hourly electric usage from those households has diminished.
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