MPG Impact of Heater

In my experience and scientific experimental calculations, running the A/C will drop MPG almost as much as running the heater will (when it's hot outside for the A/C) since both will draw electric and mechanical energy from a running ICE.

 

The A/C will draw a lot more electrical power than the heater will. Electrically, for the heater, you're really just looking at the blower. That's on a 50 amp fuse, so not more than 600 watts tops, and usually way less, when it's running at slower speeds.

The A/C runs that blower and also the A/C compressor, and the compressor can be anywhere from 250 to around 3,000 watts depending on the cooling load. 3,000 watts is about 4 HP.

The heater can extract, at maximum, 5,300 watts of heat from the engine coolant. Bit over 7 HP. But remember, gasoline engines are considered awesome if their thermal efficiency hits 40%. So any time your driving calls for more than 4.7 HP from the engine, you're already getting 7 HP of heat whether you want it or not. If you don't, it goes out the radiator, engine compartment and exhaust.

The heater can use a bit more electrical power briefly during engine warmup; there are electric heating elements in there that are only used then, to get a little warmth in the cabin faster. They only total about 700 watts, barely enough to notice, except if the windshield is foggy you can tell it clears faster.

 

Briefly, during warm up...as opposed to over a whole, say..1 hour drive with A/C blasting you will lose more during the latter. Either way, the ICE is still a generator and will net much less MPG using temperature controls than a larger gas power plant in a vehicle.

 

Either way, something is happening, yes, but the numbers also matter, and so does the extent to which they come out of what's otherwise waste.

 

Book science<Field tested make sure the lurkers know the difference in who answers.

 

My receipts are on the table. There's room for yours.

 

I work in the industry every day with real world experience.

 

Yeah..and that's why some Prius drivers prefer to be "cold" in the winter vs. running the engine...especially at stoplights, etc... In winter, when the heat in on, the engine often has to run to keep the heat up. Turning off the heat stops the engine. I have been doing this for years during the depths of winter...and it definitely does have an impact on MPG...at least with Gen3 vehicles ( and Prius C ).

 

Which we know, here on the internet, exactly how? Because you say so? No, on the internet people recognize what you know when you show what you know.

One of the neatest things about PriusChat as an online community is how many people you are among here who are genuinely able to work the numbers and understand what's going on. There may be other regions of the internet where non-quantitative handwaving goes over better (whether or not it has "real-world experience" lettered on it in quick-drying paint).

I don't mean to knock real world experience. There is a kind of it that is just is important and valuable as you make out. Just not the handwaving kind.

What your example shows is how your real-world experience really doesn't contradict how the physics works. You get 7 HP of heat from the engine for free whenever the car needs 4.7 HP or more from the engine. When you are sitting at a stop light and the engine would otherwise be off, that's when the car doesn't need power from it, and in that setting any heat you get from it isn't going to be free. You can put knowing how the physics works together with knowing how your personal driving is split between idle and driving, and see even more clearly what's going on.

 

What I do daily in real time for people looking for solutions and cost effective ways to fix their cars helps more people than someone in their basement regurgitating useless scientific theories and random mathmatical values from books whose likely never lifted a finger on anything but his own car. I know what you do here and don’t owe you any insight to who I am or where I work. If anyone else asks I’d be glad to discuss that though.

 

You're right, you don't, which is why I didn't ask about any of that. In a forum like this, it isn't who you are or where you work that determines how much water your posts hold. It's what you show in your posts that gives evidence of your experience and ability. Not who you say you are, and not what you say you know. Keyboards are cheap.

I guess if I were, like, the only person around PriusChat who got why understanding the science is useful and how working the numbers can help understand things, I might be taking that bit a little more personally. But it turns out this is a place where a pretty good number of people get that, so I guess it'll be ok.

 

Actually, you may only be "impressing" less than a handful of mathematical geeks here who think any of what you post is relevant to their experience or the real world. The rest of the laymen really aren't interested in your ramblings, let alone your disagreements with anyone who challenges you with real world experience. Again, prove you have actually torn down or replaced a Hybrid Battery or a 1.8L engine rather than read things from online articles or books and are simply repeating them here. Your claims, as I already found out previously can easily be debunked from members of the community calling you out and you backing down...mine, all they have to do is find me and dial the right number and have an intelligent and honest conversation and speak to them in real terms about real world Prius issues that they can understand and see work.

 

I can't help wondering who you're quoting at "impressing"; seems to be the first use of the word in this thread. Has me wondering a little about your age (no, you don't have to say). With a certain amount of time kicking around, people often find more interesting goals to pursue than "impressing" anybody.

What's really enjoyable about a community with enough 'geeks' in it is not so much some kind of mutual-admiration-society vibe, it's the ability to have quick tight conversations that don't get bogged down in muddle, and stay focused on the same reality the car inhabits, the one where the reasons it works or doesn't work are going to be found. Some sort of dreary quest to "impress" wouldn't be nearly as interesting, or fun.

Curious that in your first post to this thread, it was your "scientific experimental calculations" you were embracing, before coming to your disdain for "useless scientific theories and random mathmatical values"; quite the change in tune to have set in between your fifth-ever post on PriusChat and your eleventh.

It wouldn't have been nearly as much fun participating here all this time if there weren't as many people driving working cars because I was able to help them, so I guess enough people are "interested" to keep it worthwhile. But to your point about "backing down":

I don't know how much time you've been able to spend poring over 15 years of PriusChat history since Friday when you signed up (or what kind of bee in your bonnet made you want to), but as you get a sense for who's who around here and go back and look, you're likely to find that often the members of the community calling me out (if that's your favorite phrase for that) are members I respect, and who respect me, genuinely catching me on some mistake or oversimplification, and me thanking them for the catch. That's more the way things go among "geeks" (if that's the word you wanna use); we generally do not find it shameful either to make a mistake, or to say "thanks for the catch" when one is pointed out. We're more likely to find it shameful not to.

 

Yeah it's called Trip A and MPG. Not useless arbitrary numbers conjured out of thin air like some people do here.

I'll be waiting for the Thank You letter in my inbox depending on how ethical you are. Don't worry, I didn't JUST sign up..I've been here the whole time watching.

 

Oh. Um, what catch am I thanking you for, exactly?

My thanks to other people, as you've seen, haven't been in their email inboxes; they've been public. (Have to wonder where you'd have seen them, otherwise. ) You can surely expect the same, when merited.

By a funny coincidence, very recently in another thread someone asked about the history of a bogus idea that was floating around PriusChat for a while, and it goes back to somebody in 2019 saying he "tested the wires with a multimeter" and decided whatever he saw meant some wires had to be swapped. Only no one had thought to ask just what he probed with the multimeter, or what the meter showed him, or how he decided what it showed him meant what he thought. He mentioned the meter and people thought "oo, he mentioned a meter, must be something to it" and the rest was history, and for a couple years put people through needless headaches.

Replicability, it turns out, doesn't come from just saying you used a multimeter, or used Trip A, or used an MPG display. It comes from showing the work: how you used it, under what conditions, what it showed you, and how you got from there to what you thought it meant. Which lets other people, maybe some less disdainful of math, see for themselves whether what you saw means what you thought it meant.

As a funny side effect of that process, people also start to see how the math that's involved really isn't just arbitrary or conjured out of thin air.

 

Daily trips, same conditions, everything equal over a period of several months or years closely watching simply the available stats the car gives you is more accurate than arbitrary math from your head conjured up from a book or YouTube video. You just can’t handle Truth when it upsets your world view of how you thought things should work and it was ACTUALLY that simple the whole time and it took someone with 20 posts (on this account) to point that out.

 

So which was it? And what were the data? And what did you think the data told you?

You phrased all that in the classic way you always see when somebody kinda wants to sound like they did some kind of "scientific experimental calculations", but also wants to make sure nobody reading is able to check.

 

I can keep the insults rolling if you can, I get enjoyment watching people squirm under pressure. But since you asked, 11 miles each way to work and back 6 days per week, no extra trips, same throttle and traffic patterns everyday, mostly the same weather conditions, 42 psi in tires constantly throughout the testing, same gas station, same exact pump number filled up at, ultra gauge on dash with OBDII readout of gallons used per start/trip compared to Trip A and car info on dash. I'm psychopathically vigilant about real world data and completely discredit by default anyone who armchair quarterbacks from his home office what he thinks he knows that hasn't wrenched before. I have the screenshot of you saying it and backing down from months ago.

 

Please, post! If I couldn't laugh at myself, I wouldn't wanna be around me.

And then I'd have a better idea what you're going on about.

 

It was regarding a technical question about a Gen 4, and someone asked you if you ever worked on one after you posted an absolute answer on something (and were wrong about it, like bigly), and you went off into the bushes with your tail tucked. I'd have to go back 6 months or so but it's there and I know you remember it.