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:?: I have a question for you all. Did this ever happen to you? Today it was rainy and cold. I drove with my lights on during the day. I monitored my battery and noticed that the bars went down with the lights on.

I had noticed this earlier in May when I first bought the car. So during the day, I have rarely used the lights-- if ever.

Today I also used the heat. That seemed to affect the MPG. What do you all know about these 2 things? Have they happened to you? John? Daniel? Brian? Anyone? :?:
 

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Welcome to the world of cold weather and accessory impact on MPG!!!

Yea, the heat will have a pretty good impact on your mpg...indirectly you may see a lower SOC on the battery. I can't say I've ever noticed a significant change with just headlights, but in theory you're using more power and it could cause the battery SOC to drop a little more quickly. You'd probably notice it more at a stop or in stop and go traffic.
 

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Yes, I can very clearly say the headlights (I have HID) drain the battery-pack. During some of my 45 minute sunset photo sessions, I've intentionally left the lights on (for effect) without the Prius running. That causes the charge-level to just barely dip into the pink (2 bars).

So obviously, there is a minor MPG while you drive with the lights on.

Heat is a different story. You're screwed. Expect MPG to drop some. But you can also blame winter-formula fuel, worse traffic conditions, and the denser air.

The cold season is a pain. But then again, you can still be proud about Prius performance. It still shines in the winter. Everyone else's MPG takes a hit too.
 

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everyone is right in that everything that uses power in your car will create a "hit" on your mileage. headlights, heater, radio, everything.

but dont fret. you are still way ahead of the game. realize that in a regular car, headlights need the alternator to run to provide power to the headlights. when the headlights arent on, 90% of the power the alternator provides is wasted.

the heater in a regular car is run by taking excess heat (a very small portion i might add) from the engine compartment. When the heater isnt on, that extra energy in the form of heat is just vented to the world to share... well ok its really vented into space for the universe to share.

so yes, your heater and headlights do rob you of mpg's. but your car is still about 300% more efficient than the average car. so use your headlights if you feel the need. It can increase your visibility and safety so if you feel its a good idea, dont hesistate because you have plenty of cushion with your Prius.
 
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