Winter vs Summer MPG

[Maximus]

Here's an interesting chart of how a Prius MPG is affected by the winter vs summer months.  

 

With 6 years of data, the mileage varied from 52 mpg in Summer to 42 mpg in Winter

 

https://sphotos-a.xx.fbcdn.net/hphotos-ash3/523180_4048781410171_629475057_n.jpg

[kechair]

So that's a 23.8% increase over winter MPG. I wonder whether the CMax will show a similar % increase when the weather turns warmer. Only time will tell.

[ptjones]

 

Here's an interesting chart of how a Prius MPG is affected by the winter vs summer months.  

 

With 6 years of data, the mileage varied from 52 mpg in Summer to 42 mpg in Winter

 

https://sphotos-a.xx.fbcdn.net/hphotos-ash3/523180_4048781410171_629475057_n.jpg

From my graph it looks like we are going to have simular numbers change, maybe a little more. I did a little research on Prius and some people had a dip in the middle of summer. I assumed it was for AC use. Nice work Maximus. 

[PWBarrett]

We need a graph good for Texas that goes up to 107 F.

I'm wondering how much of a hit I'll take when I have the AC life-support turned on.

[JohnTrigger]

Yeah, winter gas mix certainly has less BTUs per volume, hence you burn more per mile.  So the summer mix will make a noticable increase in gas mileage, let alone the simple temperature difference similar to what you guys are seeing with your grill covers right now.  Of course, none of us know yet with the late fall release of the CMAX Hybrid, but I bet there won't be as many complaints come late May/early June about as poor of gas mileage (when the summer gas comes back, and temps are moderate).

[dtorres]

Got my C-Max last September when it was still hot and was averaging 42 mpg until it chilled and I started using the heater. Now it's down to 39.5 mpg. We'll see what happens when Spring comes. Currently 5,000 miles on the odometer.

[Generalbeluga]

Here in Southern California, we don't use an E15 or Alcohol winter blend, so I am assuming that any increase in MPG that I might get due to warmer weather will be more than offset by the necessity of using air-conditioning in the summer months?  Thoughts anyone?

[C-MaxJaxon]

Here in Southern California, we don't use an E15 or Alcohol winter blend, so I am assuming that any increase in MPG that I might get due to warmer weather will be more than offset by the necessity of using air-conditioning in the summer months?  Thoughts anyone?

 

Since the A/C is electric and the electric motor only assists the gas engine occasionally at highway speed, I expect the impact to high speed gas mileage to be minimal. We'll have to wait and see how much battery power the A/C draws and how much EV mode is reduced.

 

Since the defroster turns on the A/C to dehumidify the air, we could test the impact to some extent now.

[MikeB]

Here in Southern California, we don't use an E15 or Alcohol winter blend, so I am assuming that any increase in MPG that I might get due to warmer weather will be more than offset by the necessity of using air-conditioning in the summer months?  Thoughts anyone?

This is actually a rather interesting question. In a car, it used to be that heat was essentially free, since the gas engine produced so much waste heat. But that's no longer the case with a hybrid, so making heat now requires energy. The efficiency of making heat is generally pretty close to 100%, meaning that you can convert an energy source directly to heat without any waste (since the wasted energy is in the form of heat, which is what you use).

 

But A/C isn't about making heat, it's about moving it. And A/C can actually be more than 100% thermodynamically efficient, meaning that you can move heat from one location to another using less energy that you are moving. When measuring the efficiency of a heat-pump, the important number is usually the Coefficient of Performance (CoP), which measures how much energy gets moved for a given input energy, and the number is usually higher than 1.

 

So, this is a long-winded way of getting to an interesting conclusion: it may take less energy to remove 10 degrees of heat from the cabin than to add 10 degrees of heat into it, if you're using electricity. A heat-pump is just more efficient in principle than resistance heating.

 

Edit: sorry, this is probably more relevant to those of us with the Energi model, since we have electric heat drawing off the battery. I can't remember which forum I'm in sometimes....

Edited January 14, 2013 by MikeB

[ptjones]

This is actually a rather interesting question. In a car, it used to be that heat was essentially free, since the gas engine produced so much waste heat. But that's no longer the case with a hybrid, so making heat now requires energy. The efficiency of making heat is generally pretty close to 100%, meaning that you can convert an energy source directly to heat without any waste (since the wasted energy is in the form of heat, which is what you use).

 

But A/C isn't about making heat, it's about moving it. And A/C can actually be more than 100% thermodynamically efficient, meaning that you can move heat from one location to another using less energy that you are moving. When measuring the efficiency of a heat-pump, the important number is usually the Coefficient of Performance (CoP), which measures how much energy gets moved for a given input energy, and the number is usually higher than 1.

 

So, this is a long-winded way of getting to an interesting conclusion: it may take less energy to remove 10 degrees of heat from the cabin than to add 10 degrees of heat into it, if you're using electricity. A heat-pump is just more efficient in principle than resistance heating.

 

Edit: sorry, this is probably more relevant to those of us with the Energi model, since we have electric heat drawing off the battery. I can't remember which forum I'm in sometimes....

MikeB I was hoping to see your ENERGI, is there any differences with Hybrid?

[MikeB]

Mostly, it's the same vehicle with a bigger battery and a charging point, but that makes for lots of subtle differences. I do want to get together sometime soon, depending on schedules.

[Generalbeluga]

When measuring the efficiency of a heat-pump, the important number is usually the Coefficient of Performance (CoP), which measures how much energy gets moved for a given input energy, and the number is usually higher than 1.

 

So, this is a long-winded way of getting to an interesting conclusion: it may take less energy to remove 10 degrees of heat from the cabin than to add 10 degrees of heat into it, if you're using electricity. A heat-pump is just more efficient in principle than resistance heating.

 

Edit: sorry, this is probably more relevant to those of us with the Energi model, since we have electric heat drawing off the battery. I can't remember which forum I'm in sometimes....

 

MikeB,

 

From your statement above, can I assume the air conditioning system in the C Max is of the heat pump type and if not, do your conclusions still apply? 

[MikeB]

I don't know what type of A/C we have, other than the fact that it's electrically driven. But in general, an A/C is a special case of a heat pump that runs in only one direction.

[F8L]

There are many reasons why fuel economy will drop in winter weather. The biggest factors are winter blend fuel vs. summer blend, increased aerodynamic drag, increased tire rolling resistance (even when roads are dry), increased warm up times, etc.. Summertime is when you'll start seeing record tanks. This is assuming you can keep the air conditioning to a minimum. ;)

 

In my cars, the difference in fuel economy at 30F vs. 95F can be quite dramatic! I look forward to seeing what you guys get in warmer weather. :)