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Old 08-12-2019, 03:13 PM   #21 (permalink)
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Quote:
Originally Posted by JSH View Post
According to my Spark EV A/C uses 5% of the total energy consumed on my commute. Heat consumes about 33% but the Spark EV has an inefficient resistance heater.
I wonder why they do not use the AC in reverse like some home AC units.


Should have a similar COP.

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Old 08-12-2019, 07:32 PM   #22 (permalink)
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Quote:
Originally Posted by teoman View Post
I wonder why they do not use the AC in reverse like some home AC units.


Should have a similar COP.
Some newer units use a heat pump. My Spark is a compliance car so it was all about selling the required 2,000 EVs per year for the minimum cost.
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Old 08-14-2019, 04:50 PM   #23 (permalink)
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Quote:
Originally Posted by MeteorGray View Post
I can't tell the difference in fuel mileage with and without the air conditioner. I try to see evidence of it on the Scangauge via its instantaneous mileage readout, but the variations of highway, wind, etc tend to mask any contrast between "on" and "off" mileage differences for me.

I measured a 6% hit, based on steady speed testing I did with a Canadian market Nissan Micra (same 1.6L, 109 hp engine & AC components as the 2012-2019 Versa Note & sedan).

Thread: AC vs. MPG: impact of air conditioning on fuel economy tested
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Old 08-16-2019, 05:38 PM   #24 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
I measured a 6% hit, based on steady speed testing I did with a Canadian market Nissan Micra (same 1.6L, 109 hp engine & AC components as the 2012-2019 Versa Note & sedan).

Thread: AC vs. MPG: impact of air conditioning on fuel economy tested
That 6% hit due to an air conditioner sounds reasonable to me.

I just got off a 400-mile trip in typical-for-around-here 95F weather with the air conditioner keeping me cool in my Mazda3. As I noted above, it always seemed the variables on the highway kept me from seeing a difference on the Scangauge comparing the mileage with the compressor on vs off. However, today the conditions on a very flat section of road let me see that difference for the first time on the gauge. I cycled the AC compressor on/off, and indeed the instantaneous mileage screen showed a several MPG hit with the compressor on vs off.

Usually, variations in the road or traffic or wind made too much "noise" for me reliably to see it on the gauge. Not so today. The differential showed up there.

Today, without the intervening effects of any noticeable wind, with the AC running I got some of the best mileage for my car, 49.2mpg. The only "hypermiling" I do on the highway is speed control, and today I benefited from being able to find a truck that was running about 55mph on a 70mph Interstate over a 50-mile stretch. So, I stuck behind that truck at about a four- or five-second elapsed-time distance for about 50 miles, which let me benefit from the bit of extra mileage without attracting the hatred of those who were passing us at a 70 - 80 MPH clip. Without the truck for them to blame, I would have been running much faster for sure.

So, I know the air conditioner cost me some MPGs, and the Scangauge confirmed that today. I just don't know how many MPGs I lose, as asked by the OP. Because I live in a tropicalesque climate, the air conditioner runs the vast majority of time, and my Fuelly records don't show much difference in mileage winter-or-summer that could be attributed to the air conditioner; at least as far as I can tell.
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Old 08-17-2019, 08:43 AM   #25 (permalink)
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I have had people furiously insist that air conditioning does not decrease fuel economy. Really? Electricity bills are ridiculous during the summer specifically because of the air conditioning, except you are relying on a gas-powered generator?

It is amazing how people use wishful thinking to justify their decisions.
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Old 08-18-2019, 11:29 AM   #26 (permalink)
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I think the reason some people say that the AC does not decrease their fuel mileage is the standard comparison between a car on the highway with the windows rolled up with the AC "on" vs that same car with the windows rolled down with the AC "off."

Yes, it costs to run the AC compressor, but the aerodynamic hit that results with the windows rolled down costs too. It is often said to be a wash. So why not stay cool.

Of course, a die-hard hypermiler can make the point that one should drive with the windows up and the AC off for maximum fuel economy. That might work for the hardiest of us, but you could be arrested for doing that with children on board. :-)
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Old 08-18-2019, 03:18 PM   #27 (permalink)
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I only use AC with passengers. I was in Phoenix yesterday and had my windows down when I was not on the highway.

For some reason I drank a quart of something I picked up from the dollar store and a gallon of water in one day.

You could argue I ran off refrigerated water. I do not know how much gas I saved, but refrigerated water is cheap!
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Old 08-18-2019, 03:25 PM   #28 (permalink)
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Quote:
Originally Posted by Xist View Post
I have had people furiously insist that air conditioning does not decrease fuel economy. Really? Electricity bills are ridiculous during the summer specifically because of the air conditioning, except you are relying on a gas-powered generator?

It is amazing how people use wishful thinking to justify their decisions.
The gas-powered generator is already running. Adding A/C what with todayís efficient systems isnít much of a burden. I think you need to revisit that one.

Fire off a 7-liter Chrysler with an RV-2 compressor and IT IS 10% or better at speed. (It required matched drive belts. Literally cut from same roll and next to each other). Up to 20% around town. The competitors werenít really any better in the 1960s - Ď70ís.

But one could open vent windows, and floor vents to modify airflow at speed. Windows opened about 1-2Ē. Fall & Spring. Not forced to use HVAC like today.

Itís the same problem as today, though, where folks DONT account for slow speeds & idle time. That 70-mph trip is more like an average 57-mph. Failure to understand their own driving. And those slow or stopped moments can cook you.

An EM driver counting pennies would start up the air conditioner as he exits the highway. The small on-highway savings would underwrite a fair amount given a great distance covered (were fatigue not a factor).

.

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