A hybrid car’s heating system has various different heat sources, eg. a heat pump or electrical heater as well as the good old fashioned internal combustion engine for hot air. The various options are all intended to add EV range and save you money.
Table of Contents
Why Do Hybrids Need Different Types of Heaters
Hybrid cars need different types of heaters because they operate differently from traditional gasoline-powered cars. Hybrid cars use both an electric motor and an internal combustion engine to power the vehicle, and the way that these two systems operate affects the type of heater that is needed.
When the car is in electric mode, the engine is not running, so an electric heater is needed to warm the cabin, this could be a heat pump or the less efficient electrical resistance coil.
It’s important to note that not all hybrids are so versatile. Some hybrids will require the engine to run to provide cabin heat. Unfortunately using an engine heater in this mode would defeat the purpose of driving in electric mode, which is to save fuel and reduce emissions.
When the engine is running, an engine heater can be used to warm the cabin. This is because the engine produces heat as it operates, and this heat can be used to warm the cabin. However, engine heaters are less energy-efficient than electric heaters, so hybrid cars may also use electric heaters to supplement the engine heater and reduce fuel consumption.
What is a Heat Pump
A heat pump is a device that can transfer heat from one location to another. It works by using a small amount of energy to move heat from the outside air, into the interior of your car. The key thing to note is that energy is not used to create heat, it is used to move heat.
In heating mode, a heat pump can extract heat from the outside air and transfer it inside, effectively warming the space. It’s like a sponge that can soak up water/heat in one place and then squeeze it out into another place.
Heat pumps can also operate in cooling mode. In cooling mode, they can extract heat from the inside air and transfer it outside, effectively cooling the space. This makes heat pumps a versatile and energy-efficient heating and cooling solution.
Believe it or not, Tesla were late to the ‘heat pump game’. They first launched a heat pump in the model Y. They are clearly proud of their complicated sounding simple design:
How Do Heat Pumps Work
Heat pumps work by transferring heat from one location to another. They do this by using a refrigerant, which is a substance that can absorb and release heat as it evaporates and condenses.
A heat pump has four main components: an evaporator, a compressor, a condenser, and an expansion valve.
- Evaporator: The heat pump in your car starts by absorbing heat from the outside air (the source), into the evaporator. The evaporator contains the refrigerant, which is in a low-pressure, low-temperature state. As the refrigerant absorbs heat from the source, it evaporates into a gas. In the sponge analogy, the evaporator is a dry sponge ready to accept water.
- Compressor: The compressor then compresses the refrigerant gas, which raises its temperature and pressure. This increases the energy of the refrigerant, making it ready for the next step. For our sponge analogy, the water is squeezed out of the sponge, heat will leave the fluid now in the condenser. The compressor is what uses all the power in this heating system, it’s actually considerably more efficient than simply creating heat through a resistive coil.
- Condenser: The refrigerant then enters the condenser, which is where the heat is transferred to the destination, such as inside a building or a car. The condenser contains coils that are cooled by air or water, and as the refrigerant releases its heat to the coils, it condenses back into a liquid.
- Expansion valve: Finally, the refrigerant enters the expansion valve, which reduces its pressure and temperature, preparing it to re-enter the evaporator and start the cycle over again.
In heating mode, the heat pump reverses the cycle so that the heat is transferred from the source to the destination. The process is essentially the same, but the direction of the heat transfer is reversed.
Heat pumps are energy-efficient because they use a small amount of electricity to move heat from one place to another, rather than generating heat from scratch. They can be used for heating and cooling your car.
Heater Efficiency
Another way of looking at this and understanding the justification for the various car heater options is to consider the efficiency.
| Type | Efficiency % | Power kW |
| Electrical Resistive Coil Element | 100% | 3 kW |
| Engine Coolant Heat | 0-100% | 100 kW |
| Heat Pump | 150-300% | 1.5kW |
The table above is more indicative. Designed to help you understand why the different heaters might be used in different situations. They all have their merits, here are some considerations for choosing the best heater for the situatoin. Some hybrids have all 3 systems onboard.
- When it’s cold outside, the heat pump is going to struggle, there is not much heat to grab from outside and bring into the car cabin.
- When the battery is flat the only option is to use the engine
- If the engine is warm, use that ‘free heat’ this avoids using up more battery than necessary
- If the driver is asking for a temperature that is far hotter than the cabin, the engine is very effective as a heater and may be switched on – my Mitsubishi Outlander does this
- Another option is to use the resistive heater to generate heat using 3kw of power and then once warm, switch across to the heat pump. This technique is used on the Nissan Leaf.
Is it Cheaper to Heat a Car with the Engine or Electricity?
Generally electricity is cheaper than fuel, in the UK fuel is heavily taxed. The ideal option would be to pre heat the car whilst plugged into the AC mains supply. That way, you pay to heat your car with electricity which is (presumably) cheaper than fuel. You also don’t lose significant range as the power is not all coming out of the battery.
The answer to this question depends on the specific make and model of the hybrid car, as well as the cost of electricity and fuel. In general, however, heating a hybrid car using electricity from the battery is typically more efficient and cost-effective than using the gasoline engine. Driver comfort may force automotive engineers to put the engine on in an effort to heat the cabin quickly.
When a hybrid car is driven in electric mode, the battery powers the electric heater, which is generally more efficient than the gasoline-powered heater. Additionally, the electric heater can be used without running the engine, which means that the car can be heated while idling or parked without burning any gasoline.
However, if the battery is low and the engine is required to charge it, the engine will need to run to provide the necessary power, which means that heating the car with the engine could be more expensive than using electricity alone.
Overall, the cost-effectiveness of heating a hybrid car depends on a variety of factors, including the specific make and model of the car, the cost of gasoline and electricity in your area, and how often you use the heater. It’s a good idea to consult your car’s manual or speak with a knowledgeable mechanic or dealer to determine the most cost-effective way to heat your specific hybrid car.
Before You Go
Why not check out these other articles I wrote – go on see what you think!
