Fuel Economy diagram with and without Air Condition

Interesting information. This does not differ much from my own anecdotal observations while on the street.

 

thank you rainer, that looks like a lot of work! well done, you must be bob wilson's german cousin.

 

Am I read that correctly, that essentially keep the AC off until you reach steady highway speeds, then its really no loss to turn it on?

 

Not only that ... the biggest lesson is that A/C (cooling) is a lot less an affect then heating (especially when you are not going full power highway speed!!! Although, I do not know about you, I would not consider setting 75.2 F the heater during winter time !!!

This is why grill blocking is a BIG help in the winter under especially low load/speed.

 

No, just drive with them down until the cabin cools off some then turn it on. If the cabin is hot then you are going to suffer a big mpg hit regardless of how fast you go. The important take home message is keep the cabin cool, use the A/C sparingly (temp 78F or higher), and pre-cool the car by driving with the windows down for a few mintutes before turning on the A/C. How to Reduce MPG loss Because of A/C Use | PriusChat

 

Older cars would run the A/C full blast, then add heat from the engine to adjust the temperature coming out the vents. I used to have to rev the engine in my old Integra to get a decent amount of cooling, since the A/C compressor speed was tied to the engine speed. It had minimal cooling at idle.

The electric A/C in the Prius doesn't depend on engine speed. It works just as well when the engine is shut off.

The Prius will reduce the power used by the A/C when the temperature setting is raised. Even a high temperature, maybe 78+, will still reduce the humidity, which helps a lot.

 

Note that it's easier to see the effect in the German link because they show it in l/100km. For showing difference in consumption we'd be better of with gal/100mi instead of mpg since the difference in mpg depends on the starting mpg value so you can't really see how much each number is really worth in terms of consumption.

Anyway, remember that A/C use depends on time. So, it's only "better" to wait if your fuel cost is higher per minute. From the l/100km graphs it seems it could be slightly better, but having only 1dp in the l/100km it's not clear how much.

For example, at 20C, 30km/h it's 0.3l/100km more but at 60km/h it's 0.1l/100km more. Of course, if the numbers are rounded it's possible there's actually no difference in consumption/minute.

 

LOL! I hope he sees this thread.

 

Great work, it's good to see somebody putting in the time to chart things. While the numbers look good for the parameters you have posted, the parameters themselves are "ideal" and not likely. Smooth roads, 0 wind? lol Not here.