Can an EV power a house?

04 Apr.,2024

 

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Looks like I stirred up a hornet’s nest. After a post appeared in my news feed about powering your house from your electric vehicle using “vehicle to load” (V2L), I thought I would ask my various Facebook groups what has actually been done.

This is what I sent out: Hi all, I would like to write an article for cleantechnica.com about using the power take off on EV’s like the Atto 3 and the Ioniq 5. I am looking for people who are willing to share photos and real life experiences. Is it possible to power your house with your EV in an emergency? How? Unfortunately, I have a Tesla so cannot do this experiment myself.

This is the story that stirred up my enquiry — I didn’t think it was real: Katie Pie told me that she was able power her “basics” for the 4 days her power was off. The car supplied power for lights, fridge, freezer, wifi, coffee machine, kettle, washing machine and dryer. She used an extension cord and a multibox. The family had to manually manage the load (e.g., unplug the freezer while the washing machine was running, etc.).

Using a BYD Atto 3 and lots of extension cords, Katie was able to keep her house running during the blackout caused by Cyclone Gabriel. It is no longer a case of asking what do you do in an emergency if you have an electric car; it is proving to be a case of, what do you do if you don’t!

Here is her original post: “4 days and 4 nights no power and the car ended on 70% from 100%. Basics + 1 load of washing. Keeping in mind V2L will only work to 15% SoC, my new estimate is more like 7-10 days of usage in a power cut (half what I had guessed before lol). We didn’t turn the car on during the 4 days and had no 12v batt issue on restarting once our power came back. We used extension cords for everything but currently figuring out a system to plug into the house. Hope this is helpful. All the best to those still dealing with the cyclone aftermath xx.”

“Edit: hubby came home (electrician) and said it would be more like 14 days as we didn’t have the deep freezer or fridge on continuously to begin with. Yet to test if it will handle the water pump up to the top tank as we are gravity fed from there and haven’t run it dry yet. Our V2L cable arrived literally the day before the storm! So lucky.”

Wikipedia tells us that Severe Tropical Cyclone Gabrielle devastated parts of the North Island of New Zealand in February 2023. It is the costliest tropical cyclone on record in the Southern Hemisphere, with total damages estimated to be at least NZ$13.5 billion (US$8.4 billion), of which the provisional cost of insured damage is at least NZ$1.5 billion (US$920 million).

Ecotricity NZ deployed EVs on loan from BYD, Hyundai, and MG as mobile power stations to its customers. Watch (it’s only 6 minutes) them navigate severely damaged roads to get power to those afflicted by the blackout. It is no wonder BYD is on the rise in Australia and New Zealand. The BYD is currently the second best selling EV in Australia and Zealand, behind the Tesla Model Y.

Another story of V2L helping out in a crisis from New Zealand: “I have a 4 kW solar panel system connected to an 8 kW battery backup for my house. The battery backup can discharge at a rate of 2.5-3 kW per hour. When cycling, I used up the house battery in approximately 5 hours while powering three circuits: the TV, fridge, microwave, and internet. After that, I had to plug in my BYD battery. With the BYD battery, I was able to power the TV, internet, two lights, and occasionally use the kettle as needed. The fridge also remained operational. Surprisingly, the BYD battery lasted for a day and a half, and I only used around 10% of its capacity. The BYD battery can discharge at a similar rate as the house battery, around 2.5-3 kW. Overall, it worked really well.”

Numerous people shared stories of using their V2L capacity for camping and other outdoor needs:

“At a local park and the public bbq was broken, meaning we couldn’t cook our snags. Atto to the rescue with the help of an air fryer!”

“Earlier this year my grandson and I were asked to play a gig at a function here in Gayndah. We turned up to find the power could not be turned on so we plugged into our Atto3 and got the job done.”

“We did that. We have an Atto 3. We had a power outage for 6 hours in the middle of winter. We ran a heater and the kettle off the car. Brilliant!”

During last year’s floods in Brisbane, a friend was able to help his neighbours by powering a high-pressure cleaner from his Ioniq 5. He tells me he bought the Ioniq over the Tesla specifically for this feature. He and his friends frequently go rogaining (similar to orienteering) in the Australian bush. With his Ioniq 5, he can power the entire campsite.

Getting back to my Facebook request: most people understood what I meant, but others had a little fun with the phrase “power take off,” explaining the PTO on tractors and land rovers or telling me that you just put your foot down and get plenty of power to take off.

So, your electric car is great for emergencies, and for convenience when you’re away from home and need some power — but can you plug your car into your house? If you can, is it legal? Would it be convenient? “Honey — I just have to pop out for a few hours — I’m unplugging the house.” I guess you would need some backup anyway, like a home battery or grid access. Stay tuned for the next article on this topic when we look at what people have done to power their homes using their EV batteries.

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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.

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.

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.

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.

[The Conversation’s science, health and technology editors pick their favorite stories. Weekly on Wednesdays.]

Can an EV power a house?

Can my electric car power my house? Not yet for most drivers, but vehicle-to-home charging is coming

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