re: Sweden - Saving Money by Using Electric Vehicles to Power Homes

In the overall scheme of things, the batteries help level out the demand from the power plants and that alone as much as doubles the effective output of power generation if enough batteries are involved.

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What’s the ROI on your car?

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I paid $25,000 for it in 2015. If I had relied on rideshare at a $100 a week budget, it's 4.8 years. Then if we add in maintenance, repairs, insurance, gas, it's more like 10 years. So as of 2026, I'm just now about to roll over to 160k miles, I am in the green.

Also, it does have 120V outlet so I can use it as a generator in emergencies, burning sweet beautiful crude which is widely available. I wonder if I idled in the driveway and plugged that back into my grid what the cost savings would be on my electric bill vs what I burn in gas. Hard to compare apples to oranges though, I'm not metered with peak hours vs non-peak.

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I'm gonna go ahead and say that saving $100/m on your electric bill by using a $70k car has an ROI of 58 years. That's if the car and battery last 58 years.

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This is nonsensical. You didn't buy a $70k generator, you bought a car. Using it for backup power and saving a few bucks in the process are bonuses.

I paid $10k for a generator, what's my ROI on that? There is no return. The return is negative because it costs 10 times more to use it vs. grid power.

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I’m gonna go ahead and say those batteries are not set up for that with pulling a much higher amount of energy.

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Their batteries are supposedly capable of up to 200kW while driving, so that shouldn't be an issue. The limiting factor will be the charger/breaker. The Tesla home chargers have adjustable settings, and will use Wifi to tell the car how many amps it can draw based on those settings. So if the charger is connected to a 40A, 2 pole breaker, it tells the car to draw 32A max (80% of the breaker rating to avoid overheating issues). 32A at 240V is 7.6kW. I'd assume that the same communication can occur if the car is charging the house, and 7.6kW is a decent amount of power.

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I’m betting the batteries don’t last long and have to be replaced

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I was thinking the same thing, but someone smarter than us has probably done the math on this and figured that it was worth it. To handle it efficiently, the system probably needs to monitor how much power the entire home is drawing. That way the car can provide power when the home's load is fairly high (cooling/electric heat is on), then does nothing (or charges) when it cycles off. That would help limit battery degradation.

The simpler solution is already available in Teslas. You can plug it in whenever you get home, but tell it to only charge during off-peak hours. I haven't played around with the setting as I have no interest in using it, so I'm not sure if it's easy to have those charging hours automatically adjust based on time of year.

I'll dig into it when I'm off the clock, but I'm curious to see how the Tesla charger is able to sync the voltage that it supplies with the electrical utility's. It can be dangerous if the waves of both sources aren't at the same phase, as the panelboard can potentially see much higher voltages than 240V.