As manufacturers introduce new models of electric vehicles, the demand for them continues to grow. Sales of new electric vehicles in the United States roughly doubled in 2021 and could double again in 2022, from 600,000 to 1.2 million. Automotive industry leaders expect electric vehicles to represent at least half of all new car sales in the United States by the end of the decade.
In areas like California and Texas who have suffered significant weather-related power outages in recent years, consumers are beginning to view electric vehicles in a new way: as a potential source of electricity when the lights go out. Ford has made backup power a selling point of its F-150 Lightning electric pickup truck, which is expected to hit showrooms in the spring of 2022. The company says the truck can fully power an average home for three days on a single charge.
So far, however, only a few vehicles can charge a house this way, and it requires special equipment. Vehicle-to-home charging, or V2H, also poses challenges for utilities. Here are some of the main problems with the generalization of V2H.
The ABCs of V2H
The most important factors involved in using an electric vehicle to power a home are the size of the vehicle’s battery and its configuration for “two-way charging”. Vehicles of this capacity can use electricity to recharge their batteries and send electricity from a charged battery to a home.
There are two ways to judge how “fat” a battery is. The first is the total amount of electric fuel stored in the battery. This is the figure most widely publicized by EV manufacturers, as it determines how far the car can travel.
The batteries of electric sedans like the Tesla Model S or the Nissan Leaf could store 80 to 100 kilowatt hours of electric fuel. For reference, 1 kilowatt hour is enough to power a typical refrigerator for five hours.
A typical American home uses about 30 kilowatt hours per day, depending on its size and the devices people use. This means that a typical EV battery can store enough electric fuel to meet the total energy needs of a typical home for a few days.
The other way to gauge the capacity of an EV battery is its maximum power output in standby power mode. This represents the largest amount of electrical fuel that can be delivered to the grid or to a home at any given time. An electric vehicle operating in emergency mode will generally have a lower maximum power output than in driving mode. Standby power capacity is important because it indicates how many devices an EV battery can power at the same time.
This figure is not as widely publicized for all electric vehicles, in part because in-home vehicle charging has not yet been widely rolled out. Ford has announced that its electric F-150 will have a maximum V2H power of 2.4 kilowatts, potentially expandable to 9.6 kilowatts – about the same as a high-end single Tesla Power Wall home energy storage unit.
At the lower end, 2.4 kilowatts is enough to run eight to ten refrigerators at the same time and could run much of a typical household continuously for a few days – or much more if electricity is used sparingly. . On the high end, a power level of 9.6 kilowatts could run more devices or more powerful devices, but that level of usage would drain the battery faster.
Storing energy when it’s cheaper
To draw electricity from their car to the house, EV owners need a two-way charger and a V2H-enabled electric vehicle. Two-way chargers are already commercially available, although some can add several thousand dollars to the price of the car.
A limited number of electric vehicles on the market are now 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 owners might hope to use their vehicle for what utility planners call “clipping– draw household electricity from their EVs during the day instead of relying on the grid, thereby reducing their electricity purchases during peak hours. To do this, they may need to install special metering equipment that can monitor both the discharge of the vehicle’s battery and the flow of electricity from the grid to the home.
Peak shaving makes the most sense in areas where utilities have time-of-use electricity pricing, which makes grid electricity much more expensive during the day than at night. . A peak household would use cheap electricity at night to charge the EV battery, then store that electricity for use during the day, avoiding high electricity prices.
Public services and the future of V2H
Although V2H capabilities exist now, it will likely take some time before they are widely adopted. The market for V2H-capable 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 is likely to be homeowners who want backup power in the event of a grid outage but don’t want to invest in a special generator just for that purpose.
Allowing owners to use their vehicle in the event of a power outage would reduce the social impacts of large-scale blackouts. It would also give utilities more time to restore service – especially when utility poles and wires are badly damaged, as has happened during Hurricane Ida in Louisiana in August 2021.
Power companies will still have to spend money to build and maintain the network to provide reliable service. In some regions, these network maintenance costs are passed on to customers through peak charges, which means that people without V2H – who will be more likely to have lower incomes – may well bear a greater share of these costs than those with V2H, which avoid buying peak electricity on the network. This is especially true if many electric vehicle owners use solar panels on the roof to recharge their car batteries and use these vehicles to reduce consumption peaks.
Yet even with V2H, electric vehicles are a huge potential market for electric utilities. Two-way charging is also an integral part of a larger vision of a next-generation power grid in which millions of electric vehicles constantly draw power from the grid and return it – a key part of an electrified future. However, energy planners will first need to understand how their customers use V2H and how this may affect their strategies for maintaining network reliability.
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