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I have an Apollo brand 12 Volt Cooler/Warmer, designed to plug in to my car's 12 V cigarette lighter.

I am wondering if the power this device uses will significantly affect my car's performance or gas mileage. I have a 2010 VW Jetta 2.5 liter gasoline car.

The transformer for the 100-240 V AC connection (another option for running the device) says it is designed to output 4 A at 12 V DC. Since power = current x voltage, the transformer will output 48 W of power.

The transformer also says that it takes 60 W of power for the input.

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up vote 6 down vote accepted

You should not notice any difference. Here's why:

1 hp = 746 W. This means that 60 W is 0.08 hp.

The worst possible scenario from a load perspective is at idle. Assuming the engine is outputting a measly 5 hp at idle, the extra load would work out to 1.6 % of this value. The change in fuel consumption is barely sensible.

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Is it so even though the energy is getting drawn indirectly from the engine through the alternator and the battery rather than straight from the engine? – Joshua May 23 '14 at 5:09
Joshua, it doesn't matter - 0.08hp is so low it has negligible effect. – Rory Alsop May 23 '14 at 8:29
@Joshua : the alternator gets power from the engine, so yes. – Zaid May 23 '14 at 10:30
Obviously, this assumes that you're only running the cooler when you're driving around. If you fire up the car just to make things cold, you're going to be wasting a lot of fuel. – Bob Cross May 23 '14 at 13:18

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