Tesla is sending a warning to its Northern California customers: Charge up your vehicle now. If you don't, it's hard to say when you'll next have a chance. That's because Pacific Gas and Electric, the electrical utility for most of Northern and Central California, plans to shut off electrical service to almost a million people as a public safety measure to prevent starting wildfires.

Let's start by giving credit to Tesla for alerting its customers, especially since most drivers only charge their battery to 80 percent to extend overall battery life. Depending on your daily driving and the length of the shutoff, that could make a real difference. But I think the entire episode points out a fatal flaw in Tesla's plan to have everyone buying electric cars.

First, we obviously depend on electricity for just about everything we do every day. I wouldn't be writing this column right now without electricity. You wouldn't be reading it right now without electricity. We're long past the point where electricity is a novelty; it's just something we take for granted.

And, if you drive a Telsa (or a Volt or a Leaf), you need electricity to charge your battery. Most of you probably do that at home or at one of Tesla's Supercharger stations spread across the country. But, in parts of California, you won't be doing either during the shutoff. 

To be fair, Tesla says that it plans to eventually have all of its Supercharger stations equipped with batteries that will allow them to continue to provide charging capacity during blackouts. But, according to Elon Musk this morning on Twitter, the company is still waiting on the go-ahead to install them across the affected areas in California.

I reached out to Tesla for comment, but did not immediately receive a response.

Second, our electrical grid is far more fragile than most of us truly understand. The fact that you can plug in a toaster and make breakfast in the morning is almost luck. It doesn't take much to cause that luck to run out--a storm, a power surge, or a branch falling on a power line. Or, apparently, a utility with such outdated equipment that the only way it can be sure it won't start a wildfire that could burn down most of California is to just shut everything off for a few days.

But, just because it's a little windy in the Bay Area, people still need to go to work, still need to make lunches before sending their kids off to school, and still need to do all of the other things they would normally do. No one is evacuating. Which, I guess is a good thing since they'd only get a few hundred miles before their Teslas all run out of juice. 

Tesla makes great cars--not just great electric cars. Still, without electricity, you're not going anywhere in one.

This means electric cars will never be a truly viable alternative to internal combustion engines until someone figures out how to dramatically increase the reliability of our electrical grid. I'm not suggesting that gasoline is a better long-term strategy (gas stations still require electricity as well), but outside of Tesla's most devoted fans, most people still find it's a far more reliable and convenient option. 

That's bad news for Tesla and for the idea that electric cars are the future. Because, as this power outage makes clear, that future is entirely dependent on a power grid still stuck in the past.