My Tesla Energy Costs Versus Gasoline

The Caveat

I'll state right off, that this whole post is based on very limited data. Sixteen days worth, to be precise, and my driving during this time involved mainly just my work commute and driving about on the weekend here and there. No long trips. I'll revisit this subject in the months to come, but because the Tesla is a new toy, I wanted to look into energy price comparisons now.

I thought I'd take a look at how much money, if any, I am saving by driving an electric car instead of a gas car.

Crunching The Numbers

Luckily, I have good data on how much I have spent on gasoline over the past year. Because I track all my spending in an app and on Mint.com, I can easily pull close to a year's worth of data. For this study, I'm using data from November 2017 (the first full month we lived in our house in Washington) through August 2018. (I got my Telsa midway through September 2018, so I'm excluding that month from my calculations.) My gasoline costs include all taxes.

To calculate electricity costs, I need to be a bit more careful. Unlike some areas, my electricity costs are comprised of only two components: costs for electricity used and taxes. My power company does not assess a delivery fee or a base monthly service fee like they do in other parts of the country. Here's a copy of my bill. As you can see, no extraneous charges. Just energy costs and city tax. (State tax is included in the electricity price.)

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Based on this information, I have what I need to create a basic spreadsheet to compare my monthly average gas costs with the average electricity costs for my Tesla. Last week, I posted some efficiency numbers for the car, but here's a slightly updated version (2 more days of data). My efficiency dropped by 1 Wh/mi. (Technically, it rose, but that means it got worse because lower is better for this metric.)

Here's my spreadsheet. Formulas are pretty simple. I extrapolate the electricity costs to a monthly value based on a 30 day month. Electricity costs and taxes are taken directly from my electric bill.

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Note that my electric company does not offer a Time Of Use plan to residential customers, where electricity rates are lower during non-peak hours. They tried it once in 2001 / 2002 but most customers ended up paying more, so they cancelled the program.

"Oops. My bad!"

Given that 16 years have passed and electric cars are becoming more popular, I hope they may reconsider this decision and try the program again. If they did, I could program the Tesla to charge when rates are lowest and possibly save even more.

The Verdict

Based on this, I am saving an average of $51.56 each month by driving an electric car instead of my Prius.

Last month, I adjusted my budget by lowering my gas budget from $100 a month to zero and increasing my electricity budget by $50. I picked that number simply because it was half of my gas budget, but it looks like that was a good guess.

Some Final Thoughts

The car is not going to pay for itself via gas savings. I never thought it would and I've never heard anyone claim it would. But in addition to gas savings, there are a lot of other savings an electric car offers: No oil or oil filter changes. No radiator fluid or transmission fluid changes. No tune ups needed. No spark plugs. No timing belts. No air filter changes. No emission test fees. These savings will add up over time.

My old car was a Prius that got between 48 and 53 miles per gallon. If I drove a non-hybrid car, my savings could easily be twice what they are.

My initial thought is that living in a mountainous area might result in better energy usage numbers. Sure, I have to use more energy going up hills, but I regain a lot of it going back down. Compare this to a place like Arizona, where I used to live. There, the terrain is pretty much flat, which means there are next to no opportunities to charge via gravity. Of course, you still regain some charge from just slowing the car via regenerative braking. I wonder if anyone has compared energy efficiency on the two types of terrain...

Electricity is a price-regulated commodity (at least in most states, including my home state of Washington). This means wild swings in prices are rare. Gasoline, on the other hand, is not regulated and wild pricing swings are common and subject to various geopolitical forces.

A Time Of Use plan could be critical in some areas. In Arizona, the electric company charges three different rates during the year. Lowest rates are in the spring and winter. Rates are higher in June, July, September and October, and rates are the highest in August - peak air conditioning season. Charging your car in such an environment would necessitate being on a Time Of Use plan to charge at the cheapest rates possible.

Installing solar power at your home would increase your savings, although maybe not enough to pay for itself.

Where'd his glasses go in panel 7?