Skip to Content

Does Using the Car Heater Use Gasoline? (Explained By A Mechanic)

Does Using the Car Heater Use Gasoline? (Explained By A Mechanic)
Fact Checked and Reviewed by: Kris Jackson, ASE-Certified Mechanic
Kris Jackson has been a mechanic since 2010 after graduating from UTI. He’s worked with several master mechanics and holds several ASE Certifications. You can read more about Kris here.

One of the best ways to save on car costs is by optimizing how far you can get on a tank of gas. While fuel prices are almost always a source of stress, you can actually make stretching out every gallon into a game. I’m personally an absolute pro when it comes to coasting to the next light instead of hitting the gas pedal. But some tactics just aren’t worth it and running the heater comes to mind.

Does using the car heater use gasoline and is it worth it to stay chilly to save cash? 

Your car’s heater uses the heat from your engine’s coolant to warm you up which doesn’t really have an impact on the gasoline being used. The blower motor that pushes warm air runs on electricity and while that can tax the alternator a bit more, the impact is typically an extra 0.01 to 0.02 gallons of gasoline per hour or a savings of around $0.04 cents an hour. 

I don’t know about you, but I’d rather keep my eyes to the ground and try to find a nickel instead of going without heat for an hour! And compared to your fuel-hungry A/C, the heater’s gas demands are extremely small. 

That’s the quick answer and it’s enough to keep you warm and stay within your budget. However, there are some small exceptions and features like heated seats or defrosters, which are sometimes used at the same time and do burn a bit more gas. There are also some very specific situations where fuel will be used for your heater, like when you first turn on your car or are idling. 

But I’m going to dive deeper into everything you need to know about saving cash and staying warm!

Where Does Your Car’s Heat Come From? 

Let’s start by taking a closer look at exactly how your car’s heater works so we can understand when fuel would be used and when it isn’t. Here’s the step-by-step process: 

It All Starts With Your Engine

At the heart of your vehicle is the engine, where the combustion of gasoline produces power to drive the vehicle. This combustion also generates a significant amount of heat as a byproduct which is exactly what will be used to warm you up later. 

In Comes Your Cooling System

To prevent the engine from overheating, a cooling system circulates a mixture of water and antifreeze (commonly known as coolant) throughout the engine. This coolant absorbs the excess heat produced during combustion. However, this coolant is still hot. 

Heater Core and Blower Motor Moves The Heat

Positioned within the car’s dashboard is a component called the heater core, which is essentially a mini-radiator. Hot coolant flows through this heater core. Then, when you activate the car’s heater, a blower motor pushes air over the heater core. As the air travels across the heater core, it collects the heat from the hot coolant, resulting in warm air that’s then directed into the vehicle’s cabin.

If you want an even more detailed answer, this video does a great job explaining how your heater works: 

So, Does Your Vehicle’s Heater Use Any Gasoline? 

Because the heating system of a car is integrated into the existing engine cooling system, the majority of the heating process happens regardless of whether or not the heater is on or off. That’s why using the heater is so much less impactful on your mileage compared to using the air conditioner or defroster which require totally different processes. 

When the heat is on, the blower motor has to blow air and that leads to a very slight uptick in the work that alternator has to do. We’re talking very slight and somewhere in the ballpark of 200 to 400 watts on the absolute highest setting. If we convert this to horsepower (considering 746 watts equals 1 horsepower), we’re looking at about 0.27 to 0.54 horsepower.

In terms of fuel, burning 0.27 to 0.54 extra horsepower might result in a consumption of an extra 0.01 to 0.02 gallons of gasoline per hour for typical gasoline engines under typical conditions. That translates to a couple of pennies in terms of fuel cost. 

That’s a rough estimate, but even doubling some of those numbers still won’t lead to even 10 cents in fuel savings over an entire hour. 

What About When I’m Idling? 

When your car is idling, the engine is operating at lower RPMs which leads to less heat being produced. As a result, your heater can be a little less effective when your car is in idle but this won’t lead to any more fuel consumption than usual. 

If you’re idling at a stop light, you probably won’t even notice this. But if you’re starting your car cold, you’re going to notice that it takes a bit for your heater to warm up. However, even in those conditions, there’s no additional fuel being used by your heater just because your car is cold. 

But Using Heat And Defroster Is Different

Your car’s defrost system does use more fuel. It’s common to fire up both your heat and defrost at the same time so this is worth keeping in mind. 

Closing Thoughts

There are much better ways to save on gas when you’re driving. Simply going 55 mph instead of 75 mph on the highway can improve mpg by double digits in many cases.  Of course, you’re not going to make a lot of friends doing that but it could be worth it! 

Using the heater does, in the most technical sense, use a little fuel thanks to the alternator. So do plenty of other accessories in your car from the radio to your headlights but most of them don’t use much fuel. 

Just going easier on the gas pedal at the next green light or likely to save you just as much as not using the heater for an hour. So stay warm, and drive safe!

Have More Questions? Join Our Facebook Group!

Do you have any more questions that weren´t answered in this blog post? Join our free Facebook group and ask your question there. We promise you you´ll get an answer from one of our team members. Join the group here!