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Can My Electric Car Power My House?

For most drivers, the answer is 'not yet,' but vehicle-to-home charging is coming

Electric vehicles have the potential to power houses when gird electricity is not available. But widespread deployment of the technology is some time off. Photo credit: Portland General Electric / CC BY-ND / Flickr.

As manufacturers introduce new models of electric vehicles, demand for them is growing steadily. New EV sales in the U.S. roughly doubled in 2021 and could double again in 2022, from 600,000 to 1.2 million. Auto industry leaders expect that EVs could account for at least half of all new U.S. car sales by the end of the decade.

EVs appeal to different customers in different ways. Many buyers want to help protect the environment; others want to save money on gasoline or try out the latest, coolest technology.

In areas like California and Texas that have suffered large weather-related power failures in recent years, consumers are starting to consider EVs in a new way: as a potential electricity source when the lights go out. Ford has made backup power a selling point of its electric F-150 Lightning pickup truck, which is due to arrive in showrooms sometime in the spring of 2022. The company says the truck can fully power an average house for three days on a single charge.

So far, though, only a few vehicles can charge a house in this way, and it requires special equipment. Vehicle-to-home charging, or V2H, also poses challenges for utilities. Here are some of the key issues involved in bringing V2H to the mainstream.

 

Gasoline can flow only one way, from pump to car, but with some technical advances, EVs soon will be able to send power back to homes.

The ABCs of V2H

The biggest factors involved in using an EV to power a home are the size of the vehicles’s battery and whether it is set up for “bidirectional charging.” Vehicles with this capacity can use electricity to charge their batteries and can send electricity from a charged battery to a house.

There are two ways to judge how “big” a battery is. The first is the total amount of electric fuel stored in the battery. This is the most widely publicized number from EV manufacturers, because it determines how far the car can drive.

Batteries for electric sedans like the Tesla Model S or the Nissan Leaf might be able to store 80 to 100 kilowatt-hours of electric fuel. For reference, 1 kilowatt-hour is enough energy to power a typical refrigerator for five hours.

A typical U.S. home uses around 30 kilowatt-hours per day, depending on its size and which appliances people use. This means that a typical EV battery can store enough electric fuel to supply the total energy needs of a typical home for a couple of days.

Chart showing number of electric vehicles sold

The other way to assess the capacity of an EV battery is its maximum power output in backup power mode. This represents the largest amount of electric fuel that could be delivered to the grid or a house at any given moment. An EV operating in backup mode will typically have a lower maximum power output than when in driving mode. The backup power capacity is important, because it indicates how many appliances an EV battery could power at once.

This figure is not as widely publicized for all EVs, in part because vehicle-to-home charging hasn’t yet been widely deployed. Ford has advertised that its electric F-150 would have a maximum V2H power output of 2.4 kilowatts, potentially upgradable to 9.6 kilowatts–about the same as a single higher-end Tesla Powerwall home energy storage unit.

On the low end, 2.4 kilowatts is enough power to run eight to 10 refrigerators at the same time and could run much of a typical household continuously for a few days–or much more if the electricity is used sparingly. On the high end, a power level of 9.6 kilowatts could run more appliances or higher-powered ones, but that level of usage would drain the battery faster.

A person lies on the floor of a large meeting room, covered with fleece blankets
People shelter at a church warming center in Houston on Feb. 16, 2021, during a record cold wave that caused widespread power outages in Texas. AP Photo/David J. Phillip

Storing power when it’s cheaper

To draw home power from their cars, EV owners need a bidirectional charger and an electric vehicle that is compatible with V2H. Bidirectional chargers are already commercially available, though some can add several thousand dollars to the price of the car.

A limited number of EVs on the market now are compatible with V2H, including the Ford Lightning, Nissan Leaf and Mitsubishi Outlander. General Motors and Pacific Gas & Electric plan to test V2H charging in California in mid-2022 using multiple GM electric vehicles.

Some homeowners might hope to use their vehicle for what utility planners call “peak shaving”–drawing household power from their EV during the day instead of relying on the grid, thus reducing their electricity purchases during peak demand hours. To do this, they might need to install special metering equipment that can control both the discharging of the vehicle battery and the flow of power from the grid to the home.

Peak shaving makes the most sense in areas where utilities have time-of-use electric pricing, which makes power from the grid much more expensive during the day than at night. A peak-shaving household would use cheap electricity at night to charge the EV battery and then store that electricity to use during the day, avoiding high electricity prices.

Utilities and the future of V2H

While V2H capabilities exist now, it will likely be a little while before they see widespread adoption. The market for V2H-compatible electric vehicles will need to grow, and the costs of V2H chargers and other equipment will need to come down. As with Tesla’s Powerwall, the biggest market for V2H will probably be homeowners who want backup power for when the grid fails but don’t want to invest in a special generator just for that purpose.

Enabling homeowners to use their vehicles as backup when the power goes down would reduce the social impacts of large-scale blackouts. It also would give utilities more time to restore service–especially when there is substantial damage to power poles and wires, as occurred during Hurricane Ida in Louisiana in August 2021.

Power companies will still have to spend money building and maintaining the grid to provide reliable service. In some areas, those grid maintenance costs are passed on to customers through peak demand charges, meaning that people without V2H–who will be more likely to have lower incomes–may well bear a greater share of those costs than those with V2H, who will avoid purchasing peak power from the grid. This is especially true if lots of EV owners use rooftop solar panels to charge their car batteries and use those vehicles for peak shaving.

Still, even with V2H, electric vehicles are a huge potential market for electric utilities. Bidirectional charging is also an integral part of a broader vision for a next-generation electric grid in which millions of EVs are constantly taking power from the grid and giving it back–a key element of an electrified future. First, though, energy planners will need to understand how their customers use V2H and how it may affect their strategies for keeping the grid reliable.


Seth Blumsack is a professor of energy and environmental economics and international affairs at Penn State. This article was originally published at The Conversation.

6 Comments

  1. Charlie Sullivan | | #1

    The possible functions lumped together here under V2H are sometimes distinguished as V2H (vehicle to home) and V2G (vehicle to grid). V2H is primarily backup power, for when the grid goes down. V2G allows delivering some power from the vehicle while the house remains connected to the grid, as with grid-tied solar.

    Not mentioned, but important to this audience is V2L (vehicle to load), which is what you'd use to provide job-site power from your F-150 Lightening, plugging tools or battery chargers into outlets on the truck.

    It's worth distinguishing between these three because the hardware and control systems required are different--you might buy a system capable of one and end up disappointed when it can't do all three.

    We are in the early stages of this--manufacturers of charging equipment and vehicles aren't sure what standards will be used and which features will be popular. Some vehicles have bi-directional on-board chargers that can feed AC power back out of the vehicle for V2G. Others have provisions to feed DC power out of the DC fast charge connector, to an inverter that creates the AC power on the building side of the charging connection, for V2H or V2G. While others have a separate inverter on board intended for V2L at a job site, but can also be used for V2H with a separate, manually connected cord, like you'd use with a portable generator, or used with extension cords run to individual appliances during a power outage.

  2. David Leffingwell | | #2

    Hyundai/Kia's latest EVs (Ioniq5 and EV6) support V2L. Kia's gives up to 1.9kw of power (US model).

  3. Vince Caruso | | #3

    Hybrid or plug-in-hybrid are a good option for backup. Need a 12v to 120v sine wave inverter (~$100) to connect to the 12v car battery. Move the car outside, away from house, put the car in Ready Mode which will monitor the large traction battery and run the engine for a short time to charge it up when it gets low, then shut off till it runs low again. The traction battery will keep the 12v battery charged providing power to the inverter. You will want a fuse to limit the draw from the 12v battery so the auto charging system is not stressed.
    The NYT did an article some years ago of a man who used his Prius Hybrid to run his house during a major ice storm. A tank of gas could last you a week or more. Only issue is your home heating system may need more power to start up or even run then you can provide with this option.
    Prius in Japan has an Toyota factory option ($250 or so) to get power out of the Prius charging port with a built in inverter and an adapter you plug a extension cord into to get 100v (Japan standard). Not available outside Japan.
    Lots of YouTube videos and web pages on using an inverter with a PHEV or EVs.

    !! Note: !!
    Keep a car that uses gas well away from the house to prevent Carbon Monoxide Poisoning, common in power failures with gas generators placed in the garage or outside to close to the home! Many, many, many deaths each year due to this!!

    1. Nick Defabrizio | | #4

      Vince, I just saw this. I have a Honda Clarity plug in hybrid. I live in an area where the grid goes down a lot. Your comments inspires me to look into this. The Honda has a fairly large battery for a plug in and a 6 gallon tank

      Your warning about carbon monoxide poisoning is well said and sadly very much true

      1. Charlie Sullivan | | #5

        Yes, keep it away from the house and make sure you have a good CO monitor working.

        1. Nick Defabrizio | | #6

          agreed

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