EV Battery For Home Solar Backup – Reality Check

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EVs Have The Promise To Transform Home Backup

There has been a lot of buzz about Electric Vehicle batteries being able to power your home. This technology is definitely exciting and has a ton of promise. After all, why have a home battery for backup if your new car already has a battery in it?

As it turns out, there are a lot of reasons, especially in Southwest Florida. Some of the reasons are just practical, and some are due to technical challenges. But it’s also important to have perspective on what a battery can and can’t do. Batteries don’t create electricity. They just store it. You need a source to recharge them. And the capacity of batteries – or lack thereof – may surprise you.

We believe that a technological revolution is on the horizon where EVs and homes will play nice together. But the breakthroughs and practical applications are probably not coming until the late 2020’s at least. One of the big reasons is the lack of standardization. One of the first and most promising vehicles to promise home integration is the Ford F150 Lightning. To integrate this truck with your home for backup, you will need an inverter, transfer switch, monitoring gear, and modifications to your existing electrical system most likely in the form of a carved-out critical load backup panel. This will all be expensive and proprietary to Ford. You will buy the integration hardware from the dealer and it will be installed by licensed electricians who contact with them.

This locks you into the Ford ecosystem, which the manufacturers love. What happens when you sell that truck in 5 years? Well, you have to buy another compatible Ford vehicle if you want it to work with your expensive home integration gear. And in 5 years, will new models even be backward compatible? Who knows.

And how does solar power integrate into these proprietary “smart switches” that will be necessary for home integration? Will existing solar panels be compatible? Maybe.

Before going this route, we should also be asking ourselves if this is a practical solution to home backup in the first place. As a Southwest Florida resident, ask yourself what is one of the first things you do when a storm approaches. You fill your car up with gas, right? That’s so you can move around after the storm and bug out if you need to do so urgently. Think about what will happen if you use your vehicle as a power source for your home. You’re going to wake up to a depleted battery the morning after the storm passes. Is that a good idea?

And how long can your EV power your home? The media would make you think that it’s a magical well of electricity, especially when articles claim the average household uses 20 kWh per day in electricity. That is completely false for Southwest Florida homes. It is not uncommon for us to use over 100 kWh of electricity in the summer months, and that is precisely when we need backup power the most. So, at best, you will have enough juice to power critical loads and get you through the night, but you will need to recharge the battery the next day, presumably with solar power.

Note that this is no different for a stationary home battery, where capacity can be even more limited, but a stationary battery is not dual-use and doesn’t need to also get you around town. It can stay “plugged in” to the sun all day and absorb maximum charge, whereas your EV will cease to charge if you need to run out for supplies.

And then the building code comes into play. The rules are not keeping up with the technology, and the rule-making authorities move very slowly. And for good reason perhaps. EV fires are not uncommon, as we learned after Hurricane Ian. Submerged vehicles later burned down some homes. There are significant barriers to integrating a mobile battery with a home’s electrical system. The manufacturers will surely address these issues with their smart switch integration hardware, but each will have its own approach and there will be complexities that make some homes incompatible or unsuitable. And then you get to the Fire Code. There are limitations on the capacity of a battery that can be connected to a home. Only time will tell if exceptions are carved out for some of the larger batteries like those found in the Ford F150 and Teslas.

Does this new technology have promise? Absolutely. We are excited to be part of it and integrate solar energy into any backup source. But right now we are in the early adopter phase. The solutions are few and far between and very expensive. At this time, we are recommending people who want backup power stick with stationary home batteries. In 10 years when it is time to replace them, perhaps it will be a good time to switch to whatever EV technology has come along.



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