Does anyone know... does it affect MPG to run the radio or AC? I'd imagine the AC does for sure, but does running the radio also affect MPG a little?

And please - don't laugh if this is a really stupid question.

Not a stupid question. The radio draws from 0.3 to 0.7 amp at 12 V. Thats 3.6 to 8.4 watts. Consider 1 HP is about 750 W (too lazy to look up the exact number), and consider when "cruising" at 30 miles per hour you are using perhaps 5-10 HP, and you can see it's not going to be noticable.

The AC can use enough to show up. It's typically in the 1/4 to 1/2 HP (it's electric in the Altima Hybrid), so can lower your mileage about 10%.

Even the headlamps use power and lower mileage. They use up to 14 A for halogens at 12 V - so that's about 0.2 HP. You might be able to notice that if you average over a long enough time period (to take out the many other factors that cause mileage to vary).

Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)

great info... thank you

Actually, that's probably on the conservative side. With the other HSD models, it's between 13-17% of an MPG decrease by using the AC, the NAH isn't likely to suddenly be quite different, so I'd expect the MPG hit to be somewhere in that range, probably around 14-15%.

At the Ford Escape Hybrid Experience, where Ford invited owners out to their development facility to talk with the engineers and learn far more about their vehicles, one portion talked about just how much everything drains MPG, from windshield wipers to the fan on high. Everything that's electric will draw, but for the most part, it's very minimal, so don't worry about it. However, you're far better off avoiding AC as much as possible. As a rule of thumb, you're better off winding down the windows and keeping the fan on low up to about 72 miles per hour when it comes to fuel economy. AC with a high fan can cause as much as 23% hit on your fuel economy, which combined with speeding causes an easily noticed loss in your MPGs! For the FEH at least, running the windshield wipers, the headlights, the radio, the nav system, the fog lights didn't add up to half of what AC or the fan on high uses.

That said, don't worry about micromanaging your electronics. Use your headlights, your windshield wipers, listen to the radio, etc. Basically, just avoid high fan and AC use, and you'll continue to see good numbers.

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Pravus, great write up. Thank you.

Actually, my anti-Prius (see below) advises in the owners manual to roll the windows up and use the AC. The aero drag is worse than the AC drag. At highway speeds of course. That is, above about 80 km/hr - 50 miles per hour.

I tested it! On one road I frequent in summer there is a long mountain decent. The automatic will not hold the vehicle's speed to reasonable levels, in 3rd gear. 2nd gear is too slow. I tried turning on the AC. No difference, even when I lowered the climate control target temp. Opened the windows, and voila, it held the speed. Then I had to fiddle with the window open % to stop the "thumping" you get from air pressure resonance. It's a long decent, about 10 km, so I had lots of time to play.

Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)

It was 107 F here today I WILL be using the AC. !

Some thoughts on saving the KW's

I did add the King of Tints Hyber Optink all around for a claimed 95% heat rejection.
Park in the Shade (if possible) no matter how far I have to walk.
Turn off the AC about a mile befor I get to where I am going, still cool when I arrive.
Open all the windows when getting in to vent the hot air.
After initial cool down be sure the recirculate is on for the AC
Turn off the rear vents if not one back there.
I direct the AC vents toward me but not ON me and I remain cool with settings of 79F