Cars - For Car Enthusiasts @lemmy.world dragontamer @lemmy.world 3 wk. ago

Efficiency test of my 2024 Prius Prime: Gasoline vs Electricity in my first week.

The Prius Prime is a dual fuel vehicle, able to run 100% on Electric, or 100% on gasoline, or a computerized blend in-between. This presents me a great opportunity to be able to do a direct comparison with the same car of an EV engine vs an ICE engine.

Toyota computer claims 3.2mi-per-kwhr.
Kill-a-watt (https://en.wikipedia.org/wiki/Kill_A_Watt) claims 2.2mi-per-kwhr.
Additional 1.5% losses should be assumed in the wires if you wish. (120V drops down to 118V during charging, meaning 2V of the energy was lost due to the resistance of my home's wires).
Level 1 charger at home (known to be less efficient).
Toyota computer claims 53miles-per-gallon (American Gallon).
I have not independently verified the gallon usage of my car.
295 miles driven total, sometimes EV, sometimes Gasoline, sometimes both.
30F to 40F (-1C to 4.5C) in my area this past week.
Winter-blend fuel.
12.5miles per $electricity-dollar (17.1c / kw-hr home charging costs)
17.1 miles per $gasoline-dollar ($3.10 per gallon last fillup).

If anyone has questions about my tests. The main takeaway is that L1 charging is so low in efficiency that gasoline in my area is cheaper than electricity. Obviously the price of gasoline and electricity varies significantly area-to-area, so feel free to use my numbers to calculate / simulate the costs in your area.

There is also substantial losses of efficiency due to cold weather, that is well acknowledged by the EV community. The Prius Prime (and most other EVs) will turn on a heater to keep the battery conditioned in the winter, spending precious electricity on battery-conditioning rather than miles. Gasoline engines do not have this problem and remain as efficient in the winter.

27 comments

So gas costs about $4.90/gal local currency where I live, and electricity costs about $0.096. Assuming everything you calculated is correct, and we ignore environmental impact differences (which is substantial here since electricity where I live is almost completely renewable), your setup would cost a quarter as much while electric vs. gas here.

Based on local prices, your two numbers for comparison are 31.7 miles per electricity dollar vs. 7.6 miles per local gasoline dollar.

I will certainly get dinged for cold weather which, based on the commonly accepted metric for older electric vehicles, is about half the range, so it will only be twice as cost-effective during those periods.
- Based on local prices, your two numbers for comparison are 31.7 miles per electricity dollar vs. 7.6 miles per local gasoline dollar.
  
  53mpg / $4.90 == 10.8 miles / $gasoline dollar.
  
  2.2mi/kwhr / $0.096 == 22.9mi / $electric-dollar.
  
  Are these Canadian dollars btw? And is this some kind of time-of-use / nighttime energy setup for lower costs?
  
  If I switch to on-peak / off-peak plan for my local electricity, its 28c/kwh onpeak and 12c/kwh offpeak. So I get much cheaper electricity off-peak but my daytime energy (air-conditioning, computers, refrigerators, etc. etc.) all get much more expensive (17c to 28c is a HUGE jump).
  
  Canadian dollar, and no variable rate for residential electricity. Pick a time, it will be $0.096.
  
  My math may be off, I'm definitely not at my best right now.
I have a 2021 prime and also concluded that gasoline is cheaper than running on electricity. I actually only charge up when charging is free. I don’t live in extreme cold, but most of the issue is electricity is so expensive near me that it actually negates any savings.

You have a lot better math than I did though, so Kudos.
- With a 32% loss between wall and miles-driven, (assuming Toyota's battery meters in the car are accurate) there's clearly something going on here. I'm thinking L1 chargers are extremely inefficient. It is well known to anyone charging their car that the battery fans + heater turns on when you plug it in the winter. You can literally hear the battery conditioning turn on.
  
  L2 chargers are faster, meaning battery conditioning (be it fans for cooling, or heat for the winter) will be run less. Ex: If you charge 3.5x faster on L2 there will be 3.5x less battery conditioning, leading to more efficiency.
  
  Its a fools errand to "try to save money" through this however, as buying new L2 chargers will likely cost you $thousands, and the Prius Prime already cost $thousands more than a regular Prius. So do this because you're a believer in electricity (ex: lower emissions, nuclear/solar power use, reduction in oil and/or geopolitical issues with the Middle East, yadda yadda). But DON'T necessarily do any of this to save money, the math just isn't adding up for me yet.
  
  My level 2 charger cost $600 and I paid an electrician to install a 240V plug for 2 hours and parts (~300 IIRC). I wouldn't say "thousands". Maybe a thousand plus some if you want a fancier charger.
  
  Yeah — I mean, it’s really just a feature of the PHEV that we get to compare gas vs electric. And, the Prius is THE most efficient hybrid. So it’s a tight comparison. If you’re going from a gas guzzling truck or SUV to an EV in the same class, you’ll probably save money. And, if you don’t, you’ll definitely be doing the right thing anyway and probably end up with better overall features and tech than you currently have.
  
  I just did some napkin math using Google research numbers. On average L2 charging appears to be 7.3% more efficient than L1. (83.8% efficient for L1, 89.4 for 2.. and the percentage increase is not subtraction problem for anyone wanting to poke at my math).
  
  So using your electricity-only efficiency numbers, you would still only get: 12.5 * 1.073 = 13.41 miles/dollar.
If you're going to add transmission loses, you should reduce the miles spent driving to the gas station from your driving distance to be fair. That's just overhead and not part of your use of the car.

You should also charge for your time going to the gas station and spent there.
- Okay, so you want me to remove 0.25 miles from my 530 mile tank?
  
  And you think that meaningfully changes the calculations... why? But sure, its a 529.75 mile gas tank (1/4th a mile out of my way between my work and house), for a difference of 0.05% less efficiency on the gasoline engine.
  
  Any other effects you want me to throw on here? Or are you splitting hairs? But I think ~30% losses from the advertised ranges in the 30F / -1C temperatures for EVs is the main problem here that people probably should know about. And honestly, I'm not sure if 0.05% losses due to trips to the gas station are... relevant.
  
  I've ignored the wire-loss (1.5% losses) in my house btw for the above calculations. But I have the ability to measure the 120V to 118V loss thanks to Kill-a-Watt. I bring this up because my coworker was getting 8V of loss (aka: 6% losses) when he was charging his Tesla. So wire losses might be substantial and the reader should be aware of how to actually measure wire losses.
  
  Hey man, I'm just trying to make you more accurate. No need to get all fussy about it.
I don't expect gas to be so much cheaper than electricity
- This will vary fairly widely based on electricity pricing in your area, and ambient temperatures. Batteries are less efficient in cold weather, and have to maintain minimum temperatures.
  
  Here in AZ for instance, we pay about 13 cents, and temperatures are usually warmer than in OP's use case. If you're in an area that tends to have higher gas prices or prices that swing up and down a lot that will also have a fairly large effect on the comparison for you.
  
  Pricing should be more stable than gas overall though either way since electricity pricing is usually pretty stable for the consumer, outside of Texas that is.
  
  The /c/technology discussion also brought up many examples of nighttime charge / time of use electric plans.
  
  Depending on your country or other locations, you might have substantial savings for night time off peak savings.
  
  I can drop from 17.1c to 12c night time / off-peak charging for example. But my on peak / daytime charge skyrockets to 28c.
Can you do the same with L2 charging now pls?
- I found a L2 charger at work. At 50F driving and 50F charging. Odometer reports 18.5mi drive and charger reports 5.38kwhr.
  
  Or a total of 3.4mi/kwhr, the most efficient reading I've ever gotten.
  
  Looks like L2 chargers up the efficiency by significant margins. I'll do additional tests later of course. But it sounds like you are interested in the first test results.
Very interesting and great work. I'll stick with older cars that don't spy on me however. I suggest everyone do the same

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