Cabin Heating In The Tesla Model 3

This Model 3 has the Sunroof Insulation panels installed.

We can concede that traditional Internal Combustion Engine (ICE) vehicles do one thing well – they produce lots of heat. That’s useful when you need to heat the cabin but all that wasted energy going out the tailpipe isn’t anything to brag about.

Now that we are making the transition to EV’s we really need to start paying attention to efficiently heating our cars. The Model Y’s heat pump is a big step forward and will hopefully make it’s way into the Model 3 some day. There are a few ways to improve heating efficiency, they include using better technology such as a heat pump, smarter use of the heating system, use of the seat heaters, and of course interior insulation such as sunroof insulation.

How does the Model 3’s heating system work?

The Model 3 is designed to use “waste” heat from the infotainment unit, drive unit and battery to help heat the cabin, but during the winter there is no waste heat. Our cars struggle to even reach normal operating temperature let alone have any left over, so we rely instead on a very simple resistance heater which works the same as a baseboard or portable electric heater. These are very effective heaters and will warm your car quickly, but they are not at all efficient.

What’s the difference between Manual and Auto heat?

Manual heat will still automatically maintain the temperature you set but will not turn on the AC or manage the blower speed.

Auto mode is relatively sophisticated, it will:

• Maintain the desired temperature including turning on the AC as required.
• Increase the blower speed to change the temperature or defog quickly, then slow down again for better efficiency.
• Turn on the AC to help remove unwanted moisture and prevent fogging.
• Turn on recirculated air to reduce cabin air turnover which improves efficiency. This feature is cycled on and off to prevent fogging and keep the air fresh.

 

 
Which mode, Manual or Auto will consume the least amount of power?

The testing that I have done on my car indicates that I can use roughly half the energy in Manual mode vs Auto mode if I keep the blower speed on the lowest setting that will prevent window fogging. That’s usually a blower speed of 1 or 2 with occasional 3 if I see fog starting to form. By keeping the blower at such a low speed, you are reducing air turnover in the cabin – so you’re pumping less heated air back outside.

Using Manual mode takes more effort to ensure that you don’t fog your windows, but you do use up to half as much energy. If any of the windows do happen to fog up the windshield defogger works very quickly. Note: make sure that you push the defrost icon twice or you will only be getting cold air.

I usually use Auto mode for shorter trips and Manual for longer trips or if I’m trying to preserve my energy.

Use the seat heaters

Seat heaters can be individually selected and only heat the immediate area (your bottom!), they don’t attempt to heat the entire interior of the car. Most people find that they can select a lower cabin temperature and still be comfortable while using the seat heaters.

What makes the Sunroof Insulation so effective?

Using a lower blower speed in Manual or Auto’s cycling of recirculated air keeps the heated air in the car longer which increases efficiency, but our cars interior is 60% single pane glass.  Keeping a mostly glass interior warm takes a lot of energy. Cold air sinks which makes a cold soaked glass roof especially chilling. The Sunroof Insulation reduces the energy required to heat the cabin but also stops cold air from drifting down over the occupants.

We heat our homes very efficiently.

Efficient heating is the same whether you are in a house or a car, heat pump technology was first used in buildings as was insulation. We’ll have to wait for the heat pump but we can make the best use of what we have and add a little insulation as required.