A/c On Or Off?

[FourFourTwo]

My apologies if this has been covered before.

Since we are now all driving around with our heaters on, I was wondering what you more experienced hybrid drivers do regarding the A/C.

So far, I have been driving with the temp set to about 21C and the A/C off, as in my previous cars A/C put an extra load on the engine and reduced fuel economy.

Is it the same in the Auris HSD/Prius, or what effect, if any, does activating the A/C have on fuel figures?

[Janine1]

I am sure that turning the A/C on has a negative effect on the fuel economy.

However, it is recommended (at least in the Yaris manual) that when defrosting, turn the A/C on. This is used to suck moisture out of the car.

[Jan&tone]

Set temp at 19/20 and put a/c on with air coming in from outside, NOT recirculate.

Comfortable, dry journey with no misting.

Fuel economy will suffer slightly but not as much as conventional cars, you will make up the differwnce in Spring/Aurumn...

[Terry953]

My apologies if this has been covered before.

Since we are now all driving around with our heaters on, I was wondering what you more experienced hybrid drivers do regarding the A/C.

So far, I have been driving with the temp set to about 21C and the A/C off, as in my previous cars A/C put an extra load on the engine and reduced fuel economy.

Is it the same in the Auris HSD/Prius, or what effect, if any, does activating the A/C have on fuel figures?

On these cold frosty mornings I switch everything on - Temp up to 'HI' - Rearscreen [and mirrors] to defrost On - Windscreen demist On - Fan speed to Max - The A/C comes on automatically so I leave it to dispel any moisture - Set air flow to outside, Before I get out to scrape the side windows the engine has started to help.

Your consumption score will depend on how long / traffic infested your journey is.

I recently got 60.1mpg over a 130 mile trip after performing the above procedure, then the next day did a 20 mile journey and got only 48mpg. But in both cases had good visibility and was nice and warm, I consider comfort is my No.1 priority not MPG.

[Mooly]

It's essential to run AC regularly as car systems are not "hermetically sealed" like a fridge or freezer. Using ensures the refrigidgerant and oil circulates thus keeping seals and joints "gas tight". Lack of use is number 1 reason for needing the system to be recharged in summer. The loading on the engine is minimal, particularly in cold weather as the compressor runs very infrequently.

Now you mention the Prius/Aris hybrid... and doesn't that have an AC system that runs even when the engine is off ? It would be interesting to see how that is driven and where the potential for leakage is. The main area is usually the compressor front seal that drys out when left unused.

[Ancient Nerd]

For the Prius, you should leave the aircon on. It is electrical, not driven by the engine. Unlike most cars, there is negligible impact on fuel consumption. I think there are even one or two stories around of it improving the mpg figures (both here and on PriusChat).

IIRC, there was a suggestion that keeping the cabin air cooler, in turn keeps the Battery cooler, which improves the performance of the Battery, which improves fuel consumption.

Anyway, I always leave mine on. I assume the Auris has taken the same aircon along with the HSD from the Prius, so I suggest you do the same.

[RobMagpie]

On other vehicles with A/C I have had (not toyota) it stated not to use it below 4c. I think it may have not come on even though the switch was on. Not sure of the reason, possibly freezing up. Is it the same with the prius?

[Doesn'tExist]

I just leave it on all year round, that's why it is climate control. The compressor comes on when it needs to cool and stays off when not.

[capnbirdesye]

It sounds like swings and roundabouts to me, doesn't the aircon pump take power from the Battery which would otherwise be stored to help power the car and thus lowers your mpg in this way rather than conventional belt drive adding extra load to the engine

[kithmo]

On other vehicles with A/C I have had (not toyota) it stated not to use it below 4c. I think it may have not come on even though the switch was on. Not sure of the reason, possibly freezing up. Is it the same with the prius?

Correct, The AC does not come on at low temperature so you may as well leave it on.

[Grumpy Cabbie]

It sounds like swings and roundabouts to me, doesn't the aircon pump take power from the battery which would otherwise be stored to help power the car and thus lowers your mpg in this way rather than conventional belt drive adding extra load to the engine

The ac on a Prius or Auris HSD is driven by the traction Battery. The Battery is powerful and running the ac on low such as in winter will take a super small amount of power, esp compared to moving a car even 10 feet.

I would add that the ac can draw upto 4kw when on full on a hot day in summer. This will drain your HV Battery rather quickly and will make a rather alarming electrical humming noise. Still better than sitting in an oven (esp those of us with black cars!).

[johalareewi]

With the Prius, the A/C switch doesn't actually switch the A/C on and off. It just lets the climate control system know if it is OK to use the A/C if it becomes necessary.

[Grumpy Cabbie]

With the Prius, the A/C switch doesn't actually switch the A/C on and off. It just lets the climate control system know if it is OK to use the A/C if it becomes necessary.

The above is correct when using the 'Auto' setting. But you're right, the a/c isn't always used and in cold weather very rarely when using Auto but it will switch the ac on when the windows start to steam up so must have some moisture detection.

[capnbirdseye]

The ac on a Prius or Auris HSD is driven by the traction battery. The battery is powerful and running the ac on low such as in winter will take a super small amount of power, esp compared to moving a car even 10 feet.

I would add that the ac can draw upto 4kw when on full on a hot day in summer. This will drain your HV battery rather quickly and will make a rather alarming electrical humming noise. Still better than sitting in an oven (esp those of us with black cars!).

Seems odd that the traction Battery also powers other stuff such as the aircon, seems to defeat the object and in hot areas like California/Florida would mean they would need aircon on high most of the year and thus continually lowering the MPG more than maybe a belt driven pump would.

[Grumpy Cabbie]

The ac on a Prius or Auris HSD is driven by the traction battery. The battery is powerful and running the ac on low such as in winter will take a super small amount of power, esp compared to moving a car even 10 feet.

I would add that the ac can draw upto 4kw when on full on a hot day in summer. This will drain your HV battery rather quickly and will make a rather alarming electrical humming noise. Still better than sitting in an oven (esp those of us with black cars!).

Seems odd that the traction Battery also powers other stuff such as the aircon, seems to defeat the object and in hot areas like California/Florida would mean they would need aircon on high most of the year and thus continually lowering the MPG more than maybe a belt driven pump would.

Actually it's a very good system. Wait until summer when you need your ac on. It'll only run on full for about a min or so at most when you first get in after parking up in the sun. There are many Prius owners from Florida and California on the US forums and they don't have a problem with the ac not being upto scratch.

One thing you'll find is that the mpgs on the Prius go up significantly in summer as contrary to normal cars, its the heater on the Prius that really hammers fuel economy.

[twohats]

The ac on a Prius or Auris HSD is driven by the traction battery. The battery is powerful and running the ac on low such as in winter will take a super small amount of power, esp compared to moving a car even 10 feet.

I would add that the ac can draw upto 4kw when on full on a hot day in summer. This will drain your HV battery rather quickly and will make a rather alarming electrical humming noise. Still better than sitting in an oven (esp those of us with black cars!).

Seems odd that the traction Battery also powers other stuff such as the aircon, seems to defeat the object and in hot areas like California/Florida would mean they would need aircon on high most of the year and thus continually lowering the MPG more than maybe a belt driven pump would.

Actually it's a very good system. Wait until summer when you need your ac on. It'll only run on full for about a min or so at most when you first get in after parking up in the sun. There are many Prius owners from Florida and California on the US forums and they don't have a problem with the ac not being upto scratch.

One thing you'll find is that the mpgs on the Prius go up significantly in summer as contrary to normal cars, its the heater on the Prius that really hammers fuel economy.

And it means that the ac still works while you are stopped or stooging around in ev mode!

[Aeneas]

I've read here and on other posts that MPG on the Prius is reduced greatly in winter, and in fact this is what I am finding in the current cold spell. Could someone explain the elements that go into the reduced MPG and why; eg why does the heater reduce MPG but not the air conditioning?

[Doesn'tExist]

Well in the winter the engine needs to run to run the heater, but you hardly need the aircon condenser to cool temperature down so you just don't use that as much. Short and simple version.

[timberwolf]

The air conditioning does reduce the MPG, but when you compare it to all the factors that cause the petrol engine to run in winter they are insignificant to most owners.

There are some Prius owners, who are very keen to gain every MPG that they can, and they will no doubt have spent a lot of time figuring out how to use the air conditioner for least amount to gain the most MPG. The rest of us just use Auto A/C all year round, and our MPG figures reflect that.

[Grumpy Cabbie]

I've read here and on other posts that MPG on the Prius is reduced greatly in winter, and in fact this is what I am finding in the current cold spell. Could someone explain the elements that go into the reduced MPG and why; eg why does the heater reduce MPG but not the air conditioning?

The a/c runs off the HV Battery and under normal load it hardly uses much juice. As such the petrol engine doesn't have to run much to put that charge back into the HV Battery and when the engine isn't running fuel isn't used and the mpg's remain high. In a normal car the a/c runs off a belt connected to the engine and the drag it causes means the engine has to work harder to power the a/c (esp in start stop town traffic) and hence uses more fuel.

However, to get heat the petrol engine must run to warm up the coolant (the water in the radiator) which is then pumped around the engine but also into the heater inside the cabin which then has a fan to blow it onto you keeping you warm. This system is the same in the Prius as well as normal cars and all that happens is that the Prius has to run its engine more often than it would normally do to heat this water (whereas a normal car will have the engine running all the time) and running the engine uses fuel.

When the car is warming up in a morning and when stationary at the traffic lights try turning the heater on and off and you will find that the engine will cut out when you turn the heating off and then fire up again when you turn the heater on again. The Prius isn't worse than a normal car in winter, all it is doing is mimicking what a normal car does but it comes into its own in summer.

I do tend to waffle but hope this helps.

[timberwolf]

<snip>

When the car is warming up in a morning and when stationary at the traffic lights try turning the heater on and off and you will find that the engine will cut out when you turn the heating off and then fire up again when you turn the heater on again. The Prius isn't worse than a normal car in winter, all it is doing is mimicking what a normal car does but it comes into its own in summer.

I do tend to waffle but hope this helps.

The petrol engine also has to run more often to keep itself warm. The Prius gains some of its fuel advantage by being able to switch the engine off, in cold weather when the engine is off, the engine block is radiating the heat away - with a scangauge2 (or similar device) you can see how the engine coolant level can struggle to reach the normal operating temperature in winter. There are a number of other reason for poorer MPG in winter including the HV Battery and the catalytic converters.

[Aeneas]

I've read here and on other posts that MPG on the Prius is reduced greatly in winter, and in fact this is what I am finding in the current cold spell. Could someone explain the elements that go into the reduced MPG and why; eg why does the heater reduce MPG but not the air conditioning?

The a/c runs off the HV Battery and under normal load it hardly uses much juice. As such the petrol engine doesn't have to run much to put that charge back into the HV Battery and when the engine isn't running fuel isn't used and the mpg's remain high. In a normal car the a/c runs off a belt connected to the engine and the drag it causes means the engine has to work harder to power the a/c (esp in start stop town traffic) and hence uses more fuel.

However, to get heat the petrol engine must run to warm up the coolant (the water in the radiator) which is then pumped around the engine but also into the heater inside the cabin which then has a fan to blow it onto you keeping you warm. This system is the same in the Prius as well as normal cars and all that happens is that the Prius has to run its engine more often than it would normally do to heat this water (whereas a normal car will have the engine running all the time) and running the engine uses fuel.

When the car is warming up in a morning and when stationary at the traffic lights try turning the heater on and off and you will find that the engine will cut out when you turn the heating off and then fire up again when you turn the heater on again. The Prius isn't worse than a normal car in winter, all it is doing is mimicking what a normal car does but it comes into its own in summer.

I do tend to waffle but hope this helps.

Not waffle at all. Very helpful. For the first time I understand how these things work.

[Aeneas]

I've read here and on other posts that MPG on the Prius is reduced greatly in winter, and in fact this is what I am finding in the current cold spell. Could someone explain the elements that go into the reduced MPG and why; eg why does the heater reduce MPG but not the air conditioning?

The a/c runs off the HV Battery and under normal load it hardly uses much juice. As such the petrol engine doesn't have to run much to put that charge back into the HV Battery and when the engine isn't running fuel isn't used and the mpg's remain high. In a normal car the a/c runs off a belt connected to the engine and the drag it causes means the engine has to work harder to power the a/c (esp in start stop town traffic) and hence uses more fuel.

However, to get heat the petrol engine must run to warm up the coolant (the water in the radiator) which is then pumped around the engine but also into the heater inside the cabin which then has a fan to blow it onto you keeping you warm. This system is the same in the Prius as well as normal cars and all that happens is that the Prius has to run its engine more often than it would normally do to heat this water (whereas a normal car will have the engine running all the time) and running the engine uses fuel.

When the car is warming up in a morning and when stationary at the traffic lights try turning the heater on and off and you will find that the engine will cut out when you turn the heating off and then fire up again when you turn the heater on again. The Prius isn't worse than a normal car in winter, all it is doing is mimicking what a normal car does but it comes into its own in summer.

I do tend to waffle but hope this helps.

Not waffle at all. Very helpful. For the first time I understand how these things work.

[capnbirdseye]

reading all this stuff before my car arrives in a couple of weeks is invaluable, saying that I've just perused this forum from way back to 2004 and some of the advice is way off the mark,

Some bloke asking advice as to the transmission is told that its like on a Daff, i.e. belt driven CTV plus loads of stuff about turning the aircon on can cause a slight surge as the ICE raises revs to allow for the extra engine load.

Have any of you guys blocked off the back of the upper grill to speed engine warming up?I used to do this for years with a bit of old carpet and it definitely worked. I've just been reading about doing it on a Prius and if your in a really cold area then partially block off the lower grill as well

[Ancient Nerd]

Some bloke asking advice as to the transmission is told that its like on a Daff, i.e. belt driven CTV plus loads of stuff about turning the aircon on can cause a slight surge as the ICE raises revs to allow for the extra engine load.

You do get the occasional non-Priushybrid owner who is trying to help. Unfortunately...

Have any of you guys blocked off the back of the upper grill to speed engine warming up?I used to do this for years with a bit of old carpet and it definitely worked. I've just been reading about doing it on a Prius and if your in a really cold area then partially block off the lower grill as well

Yes, I've done this a couple of times. Once with a Gen II, and for part of last winter with the Gen III, I blocked most of both upper and lower grills with tubes of 15mm foam pipe wrap. It worked very well.