Good evening fellow auto enthusiast!

Does anyone else notice a slight reduction in power (HP) when the A/C is on? It is my understanding that the A/C compressor is powered by an electric drive motor due to its ability to operate even when the vehicle temporarily enters the AUTO STOP state, and does not rely on the traditional belt/pulley systems employed by most non-hybrid vehicles. If my understanding is correct then we can assume that running the A/C compressor must place an additional demand on the electrical system particularly the motor assist (IMA), and that is what is causing the car to feel like it is working slightly harder to maintain highway speeds with the A/C on. I can also observer/confirm this via my average MPGs on my routine work commutes. I recently bought a ScanGuage II so I hope to utilize it to help me make a better educated guess as to the average MPG differences when the A/C is off and on.

 

Your understanding is incorrect.

The A/C compressor is a "hybrid" belt and electric drive, so in most cases, it is no different than a non-hybrid auto A/C compressor with a noticeable power loss.

The electric component of the compressor is only used when maximum compressor power is required and when the climate control is already at the set temp or near it, and the car is in auto-stop.

It is not at all like the all-electric compressor of the Toyota systems.

In any case, it takes about 3-6hp to run a compressor, and it doesn't matter whether that power comes from gas or electric, it's ultimately coming from gas, so you should expect a 10-15% mpg drop with typical A/C use even with the Toyotas. There is no free energy.

 

Thank you for taking a moment out of your day to clarify and educate us Keith! Much appreciated!

 

YW.

It actually operates in 3 modes in forward and reverse order as follows:

1) Pulley + electric when there is maximum demand.
2) Pulley only
3) Electric only.

It will never go from 1 to 3 or 3 to 1 without passing through 2 first.

Both 2 and 3 represent optimizations over a "standard" system. Pulley-only pulls less mechanical power than a traditional compressor due to its sizing. Electric only pulls even less power.

Efficiency gains can be had by providing a steady power to the compressor that is sufficient to maintain the set temperature rather than like a "Standard" system that just cycles the compressor on and off or mixes the cold air with warm.