Tesla Model Y’s Secret: Heat Pump

Tesla Model Y’s Secret: Heat Pump

One of the biggest problems with Tesla vehicles up to this point may have just been fixed with this new feature on the Model Y that Tesla decided to hide from us until now. Driving a Tesla can be somewhat scary because of “range anxiety” which means you’re worried about running out of battery before reaching your destination.

In cold winter conditions an electric vehicle can lose up to 40% or more of its estimated range. In February I was on a road trip in my Model 3 and lost a lot of my estimated range while driving highway speeds when it was around 30 degrees F.

Electric vehicles lose range in cold temperatures because: colder air which means more drag, energy loss from heating the battery, and the energy used to warm up the vehicle’s cabin. All Tesla vehicles (prior to Model Y) warm the cabin through a resistive heating system where electricity is sent through a resistive heating element, which creates heat that’s blown out of the air vents. .

This means for an EV  to warm up the cabin, energy from the battery must be used which of course decreases the estimated range. Electric resistance heating is considered 100% energy efficient in the sense that all the incoming electric energy is converted to heat.

Well it doesn’t get any better than 100% efficiency, right? Actually there is something better. It’s called a heat pump, and the Model Y is the first Tesla to have one. In the manual it says “Model Y uses a heat pump to maximize efficiency; therefore, your air conditioning compressor and external fan may run and make noise even when the outside temperature is cold and your vehicle is heating or Supercharging"

A heat pump can be thought of as an air conditioner that has the ability to work in reverse. An air conditioner works by using refrigerant to trap the heat inside of an area, then move it outside. A heat pump works in exactly the same way, only it has a reversing valve which allows it to reverse the flow of the refrigerant and heat an area when it's cold out.

Heat pumps help efficiency because they move heat rather than generate it. The electricity is used by the compressor to send refrigerant around the system and capture the heat from outside, then bring it inside. It can do this because the refrigerant has an extremely low boiling point. And the best part is a heat pump can typically produce around 3kW of thermal energy for every 1kW of electrical energy resulting in an “efficiency” of 300%.

So this “300% efficiency” sounds awesome, right? Well, heat pumps are usually not effective below a certain temperature range and typically don't work well in extremely cold temperatures. However, heat pump technology has recently improved, and in some cases can be rated for outdoor temperatures as low as -4°F.

Why is the Model Y’s heat pump so important? A heat pump should be able to heat the cabin while using less energy which should lead to longer battery range when driving in cold temperatures compared to all the other Tesla models. This is a huge advantage!

Why didn't Tesla implement this before the Model Y? Most likely it was because a heat pump adds cost, complexity, and weight. But for a Tesla, which already has an air conditioner, a heat pump seems like a no-brainer because the added complexity would be pretty minimal.

The biggest questions now are: where does the heat come from in the Model Y heat pump and does the Model Y always use a heat pump or does it alternate between heat pump and resistance heating? From the Model Y manual it looks like it could be taking excess heat from the motor and battery, which would probably make it efficient even in extremely cold temperatures which would be nice. Teslas already have the ability to use the motors to heat the battery, and if the heat pump is powerful enough it can potentially heat both the battery and the cabin.

Either way, we can’t wait to see how the Model Y handles driving in the winter. It sounds like it will be the best Tesla for that task.