Sean Cate

Sean Cate

December 12, 2024

Stanford Research Gives Warning About Charging Electric Vehicles at Home Overnight

As electric vehicles (EVs) become more prevalent, their impact on the energy grid is drawing increasing scrutiny. Recent research from Stanford University has shed light on an often-overlooked issue with EV adoption: the common practice of charging vehicles at home overnight could strain the electric grid and hinder decarbonization efforts. Here’s what you need to know about this pivotal study and its implications for the future of EV charging.

The Growth of Electric Vehicles and Charging Challenges

electric vehicle parked at a house gate
Credit: Unsplash

The global transition to electric vehicles is accelerating, with projections indicating that the EV fleet will grow from 7 million vehicles today to over 400 million by 2040. While this is a significant step toward reducing greenhouse gas emissions from transportation, it introduces challenges for electricity grids. Stanford researchers estimate that by 2035, peak electricity demand could surge by up to 25% in the western United States if current charging habits persist.

Most EV owners currently prefer the convenience of home charging, often overnight. However, this trend could necessitate substantial investments in new power generation, storage, and grid upgrades. “We need to rethink how and when we charge our vehicles,” said Ram Rajagopal, co-senior author of the Stanford study.

The Problem With Overnight Home Charging

This figure shows the weekday load profile for 10 thousand samples simulated for residential segments.
Credit: Applied Energy

Overnight electric vehicle charging is convenient but misaligned with the modern energy grid’s dynamics. Historically, electricity pricing encouraged nighttime usage to avoid peak daytime demand. However, with California and other regions generating surplus solar energy during the late morning and early afternoon, daytime charging could be far more sustainable.

Siobhan Powell, the study’s lead author, noted, “Daytime charging uses cheap, abundant solar power instead of relying on fossil fuels at night. If charging habits don’t shift, utilities may have to build natural gas power plants to handle the load.”

Potential Consequences of Unchecked Overnight Charging

This figure shows the weekday load profile for 10 thousand samples simulated for the workplace.
Credit: Applied Energy
  1. Grid Instability: Neighborhood grids could become unstable if a significant number of households charge electric vehicles simultaneously at night.
  2. Higher Carbon Emissions: Relying on nighttime charging could lead to increased use of natural gas for power generation.
  3. Increased Costs: Building additional power plants and storage capacity would come with hefty financial and environmental costs.

The Case for Daytime Charging

The distribution of the data set over counties and types of charging. The inset map in the top panel shows the location of the San Francisco Bay Area in Northern California.
Credit: Applied Energy

Switching EV charging to workplaces and public stations during the day could alleviate many of these issues. Stanford’s analysis found that shifting just a portion of charging to the daytime could reduce the need for grid-scale energy storage by over a gigawatt, equivalent to avoiding the construction of a large nuclear power plant.

California’s abundant solar energy presents a unique opportunity. The state often generates surplus electricity during peak solar hours, which is currently wasted. By aligning electric vehicle charging with this energy surplus, policymakers could maximize renewable energy use and reduce reliance on fossil fuels.

Policy and Infrastructure Recommendations:
1. Revise Electricity Pricing

Generic electric vehicle EV hybrid car is being charged from a wallbox on a contemporary modern residential building house
Credit: Shutterstock

Stanford researchers advocate for restructured electricity rates to incentivize daytime charging. This could include higher nighttime rates and discounts for charging during solar peak hours.

2. Invest in Workplace and Public Charging

public electric vehicle charging spot
Credit: Unsplash

Employers and governments need to expand workplace charging infrastructure. Overcoming disincentives such as high commercial electricity demand charges is crucial. “The price signals need to align with grid needs to encourage more daytime charging,” said Ines Azevedo, co-senior author.

3. Raise Awareness

a woman with a megaphone
Credit: Unsplash

Educating electric vehicle owners about the environmental and economic benefits of daytime charging could foster behavioral changes. Many drivers remain unaware of how their charging habits impact the grid.

Building a Sustainable Future

a growing plant in two hands
Credit: Unsplash

The electrification of transportation is essential for decarbonization, but it requires strategic planning and collective effort. Policymakers, utilities, and consumers all have roles to play in ensuring electric vehicle adoption is both environmentally sustainable and economically feasible.

The Stanford study underscores the importance of transitioning from convenience-driven charging to grid-conscious practices. As Powell emphasized, “This is about making EV adoption sustainable in the long term. Aligning charging habits with renewable energy availability is key.”

By addressing these challenges now, we can ensure that the transition to electric mobility not only reduces emissions but also builds a more resilient and efficient energy system.

Read More: 20 Issues With Electric Vehicles (EVs) That Owners Complain About The Most