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Efficiency test of my 2024 Prius Prime: Gasoline vs Electricity in my first week. (self.cars)
submitted 3 days ago* (last edited 3 days ago) by dragontamer to c/cars
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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.

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[–] [email protected] 7 points 3 days ago (1 children)

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.

[–] dragontamer 2 points 3 days ago* (last edited 3 days ago) (1 children)

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).

[–] [email protected] 1 points 3 days ago (1 children)

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.

[–] dragontamer 2 points 3 days ago* (last edited 3 days ago)

NP, thanks for responding and clarifying.

I'm guessing you live somewhere in the territory of Quebec or Manitoba then? Google seems to suggest that your numbers are realistic for a couple of provinces/territories with lots of spare electricity.

[–] surewhynotlem 5 points 3 days ago (1 children)

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.

[–] dragontamer -1 points 3 days ago* (last edited 3 days ago) (1 children)

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.

[–] surewhynotlem 8 points 3 days ago (2 children)

Hey man, I'm just trying to make you more accurate. No need to get all fussy about it.

[–] davidagain 2 points 2 days ago

Dude genuinely sees flying off the handle as the right way of responding to disagreement. He explains that people who criticise him are iredeemably dishonest so debating them is a waste of time and he finds it ends the discussion much quicker if he puts a lot of anger and insults in.

Straight up!

https://lemmy.world/comment/13878703

I'll paste it on case he deletes it.

You want them to take it back. Do so.e research, and prove them wrong. Otherwise, stop shouting.

BTW: Seriously, you seem naive to me so let me give you a serious protip.

If someone thinks you are biased on the internet, and you owe them nothing (not like a close friend or a family or something), you STOP TALKING WITH THEM BECAUSE ITS A WASTE OF TIME. And I’ve found that shouting, and direct insults, is the fastest way to make it clear that I’m ending the discussion.

Again: don’t waste your time trying to prove yourself against baseless accusations on internet. Its not worth the hassle. If you find yourself doing that, you are the one who will get stressed out in the long term.

So I reject your advice and instead replace it with the exact opposite. Get angry. Shout, end the discussion. Then move on with your life. The discussion has been blown up, so its easier to move on. Don’t lol “do research” on behalf of other people who don’t give two shits about you and drag on the unnecessary discussion for days. They never were going to believe you anyway, because they thought you were biased from the start.

He lives by the anger and insults advice, I can attest, but in terms of ending the discussion, and moving on with his life, he's not so good at that part. I believe him when he claims to refuse to do any balancing tests, but not for the reasons he claims, he just doesn't want to know about data that paints a different picture.

[–] dragontamer -5 points 2 days ago* (last edited 2 days ago)

I'm just trying to point out that you made an irrelevant comment. No need to get fussy about it. Maybe think a bit before posting next time, lol.

Not all factoids are relevant to a discussion. Especially the things that are only fractions of a percent difference.

[–] phoneymouse 6 points 3 days ago* (last edited 3 days ago) (1 children)

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.

[–] dragontamer 8 points 3 days ago (3 children)

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.

[–] phoneymouse 5 points 3 days ago* (last edited 3 days ago)

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.

[–] [email protected] 7 points 3 days ago (1 children)

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.

[–] dragontamer 2 points 3 days ago* (last edited 3 days ago) (2 children)

How far did the electrician have to run the new line for you?

My case will be cheap. But I have coworkers who needed like $1500 in labor costs to run a wire like 40 feet through 4 different rooms on different floors.

Garage vs basement circuit breaker on the other side of the house... Lol.

[–] phoneymouse 3 points 3 days ago (1 children)

Really depends on your location. Around me, it’s hard to get an electrician to do any job that doesn’t at least cost $1500. $500 would get you an unlicensed guy to do it under the table, unpermitted.

[–] [email protected] 1 points 2 days ago

I live in a large city suburb. It was a licensed electrician. Still $300ish.

[–] [email protected] 2 points 3 days ago

External conduit in the garage, about 12ft, so not terrible.

[–] credo 2 points 3 days ago (1 children)

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.

[–] dragontamer 2 points 3 days ago* (last edited 3 days ago) (1 children)

It's partially subtraction.

The 100W heater (or whatever it is....) to condition the battery in the winter is a subtraction problem, not a multiplication problem. The heater needs to run during the winter when charging or when driving.

1100W L1 charger - 100W heater is less efficient than 3500W to 10,000W L2 charger - 100W heater.

Now there is another component of multiplicative losses (the inductor and/or voltage conversion coil + MOSFET switch resistance). So it's partially subtraction and partially multiplicative losses. Ultimately I'll need to just test the damn thing to find reality, we can't math this out on paper. (100W losses I assumed earlier was just that, an assumption. I have no idea how much the battery conditioning circuits / pumps / etc. uses up in practice)

The real problem is that I'm not aware of any Kill-a-watt model for 240V circuits. I'll have to rely upon the charger to give me accurate readouts. But all the theory (and apparently some internet testing) suggests that the

[–] Passerby6497 1 points 3 days ago (1 children)

You can look into a current clamp meter as a stand in for the kill-a-watt. If you're willing to tinker a bit and like automation, you can use one of those and an esp32 board to make a remote power monitoring system for your 240v circuit.

If you're less willing to tinker you can get some off the shelf stuff that you run the wires through or a clamp style variant to do something similar.

(Note: I can't provide any recommendations on off the shelf products, I just bought the clamps and am working on tinkering it together).

[–] dragontamer 2 points 3 days ago* (last edited 3 days ago)

Hmmm, current is the bulk of it. But voltage drop is also important as that'd measure wire losses. (All wires have resistance and it adds up the longer the wire runs get).

But yeah, good idea. I'm actually into electrical engineering so ESP32 is right up my alley. I mean, I prefer AVR but any uC can be used in that circumstance.

[–] [email protected] 1 points 2 days ago

Can you do the same with L2 charging now pls?

[–] [email protected] 1 points 3 days ago (1 children)

I don't expect gas to be so much cheaper than electricity

[–] halcyoncmdr 5 points 3 days ago* (last edited 3 days ago) (1 children)

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.

[–] dragontamer 1 points 3 days ago

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.

[–] [email protected] -3 points 3 days ago

Very interesting and great work. I'll stick with older cars that don't spy on me however. I suggest everyone do the same