EVs may eventually be a major contributor to keeping our grid robust, despite what you may have heard.
There have been quite a few doom and gloom scenarios about AI and EVs putting too much stress on the grid. But here’s a fact that Toyota recently shared that may surprise you. There are already more than four million EVs on U.S. roads. If they were all equipped with bidirectional charging, they could collectively send back as much power to the grid as approximately 40 nuclear reactors, according to Toyota.
EV Rider has reported on what’s known as Vehicle to Grid or V2G before. That’s a process where electric vehicles can feed power back into utility grids when they’re plugged in and parked at home.
Toyota’s V2G Pilot Program
I’m revisiting the topic because it’s gaining momentum, with one example being Toyota. Toyota has teamed up with Texas-based Oncor Energy, which is one of the nation’s largest utilities.
They’re in the midst of rolling out the next phase of their vehicle-to-grid pilot program.
The beauty of V2G is it helps utilities manage power spikes. For example, if a heat wave hits, participating EVs that are sitting plugged in at home or in a garage can send power to the utility as needed to lessen the possibility of a brownout – or worse.
Toyota isn’t the only company doing this. EV Rider has also done stories about Tesla working with California’s PG&E utility and a California school district with EV buses doing the same thing.
Toyota has been working on its program since late 2022 at its test facility in South Dallas.
Many EVs, including vehicles like the Chevy Silverado, Tesla Cybertruck and Ford F-150 Lightning can also serve as full backup power supplies for homes during power outages. For homes with rooftop solar, EVs can store excess energy produced during the day to power some or all of the home at night – or even charge another EV when it arrives home for the night.
Given how big EV batteries are, even most home central air conditioning systems can be run for days at a time during a blackout.
Here’s where it really gets interesting. There are roughly 295 million vehicles in the U.S. If we all switched to V2G EVs and all utilities and automakers participated, we would have enough power to cover about 175 million U.S. homes for about 1.3 days during power outages. That’s according to an EV Rider prompt requesting an analysis by Microsoft CoPilot, which is an AI provider.
Whether we as a society have the will to make such a dream come true on a large scale is a different question entirely.
For anyone interested in the details, here are the assumptions and math CoPilot used to come up with that estimate. If you find any
errors with CoPilot’s assumptions, please let me know in the comments.
Cartoon Short: EV Rider & Zappy Promote V2G
Assumptions Used For V2G theoretical Estimate (source: CoPilot AI)
Estimate of how many cars/vehicles are in the U.S.
- All registered motor vehicles (cars, pickups, SUVs, vans, trucks, buses, motorcycles): estimated to between 285 to 296 million by CoPilot looking at available public data.
For the calculations below CoPilot used a round estimate:
- Total EVs in a 100% electric fleet: 285 million vehicles
2. Assumptions for the V2G scenario
Assumption 1 – Number of EVs
- N_EV = 285,000,000 vehicles
Assumption 2 – Average battery size per EV
Assume a mix of sedans, SUVs, and pickups, with an average battery of:
- E_bat = 70 kWh per vehicle
Assumption 3 – Total theoretical storage in the fleet
Total battery energy if you could use 100% of every battery:
- E_total = N_EV * E_bat
- E_total = 285,000,000 * 70 kWh
- E_total = 19,950,000,000 kWh
- That is about 20 terawatt‑hours (TWh)
Assumption 4 – Average U.S. household electricity use
Average U.S. home uses about 10,500 kWh per year.
Convert that to daily usage:
- E_home_year = 10,500 kWh per home per year
- E_home_day = 10,500 kWh / 365 days
- E_home_day ≈ 28.8 kWh per home per day
Assumption 5 – Number of U.S. households
Use a round estimate:
- N_homes ≈ 132,000,000 households
Assumption 6 – Realistic usable portion of EV battery for V2G
Since all vehicles can not be drained to zero, and they are not all plugged in at the same time, CoPilot made the following assumptions:
- 50% of vehicles are plugged in and available at any given time
- 50% of each battery’s capacity is allowed to be used for V2G (to preserve driving range and battery health)
Combined usable fraction:
- f_usable = 0.5 (plugged in) * 0.5 (allowed depth of use)
- f_usable = 0.25
3. Usable grid energy from the EV fleet
Start from the total theoretical storage:
- E_total ≈ 20 TWh = 20,000,000,000 kWh
Apply the usable fraction:
- E_usable = f_usable * E_total
- E_usable = 0.25 * 20,000,000,000 kWh
- E_usable = 5,000,000,000 kWh
So the usable V2G energy at any given time (under these assumptions) is about:
- 5 TWh, or
- 5,000,000,000 kWh
4. How many homes could that power?
4.1 Number of homes for one day
Energy needed to power one average home for one day:
- E_home_day ≈ 28.8 kWh per home per day
Number of homes that can be powered for one day by the usable fleet energy:
- N_homes_1day = E_usable / E_home_day
- N_homes_1day = 5,000,000,000 kWh / 28.8 kWh per home per day
- N_homes_1day ≈ 173,611,111 homes
Round that:
- About 170 to 180 million homes for one full day
Since the U.S. only has about 132 million households, that means:
- The usable EV storage could power more than all U.S. homes for one day.
4.2 How many days of power for all U.S. homes?
First, total daily electricity usage of all U.S. homes:
- E_US_homes_day = N_homes * E_home_day
- E_US_homes_day = 132,000,000 homes * 28.8 kWh per home per day
- E_US_homes_day = 3,801,600,000 kWh
- That is about 3.8 TWh per day
Now divide usable storage by that daily need:
- D_days = E_usable / E_US_homes_day
- D_days = 5,000,000,000 kWh / 3,801,600,000 kWh per day
- D_days ≈ 1.315 days
So the usable EV fleet storage could power all U.S. homes for about 1.3 days under these assumptions.
5. CoPilot’s Final summary
- Number of vehicles: about 285 million total motor vehicles in the U.S. (not just passenger cars).
- Battery assumption: average 70 kWh per EV.
- Total theoretical storage: about 20 TWh of energy in the full EV fleet.
- Realistically usable for V2G at any given time: assuming 50% of vehicles are plugged in and 50% of each battery is allowed for grid use, about 5 TWh (5,000,000,000 kWh).
- Impact on homes:
- That can power about 170–180 million homes for one full day, or
- Power all ~132 million U.S. homes for roughly 1.3 days of typical electricity usage.