There are many ways to heat up water in car. A radiator is not always required to heat the water in a car. Instead, you might need to use what is called an electric heater. This special device is heated with electricity and vents to move the warm air into the car. A thermostat regulates the temperature so that the water does not become too hot. The advantage of using one of these systems rather than a radiator is that you can start the car and leave it without a fuss, whereas a radiator has to be left running to ensure the correct temperature.
If you find that none of the above heaters are suitable for your car, then you may want to try an electric-heater. This is not as intrusive as the others and does not need a radiator unless you want to fill up the whole compartment with hot water. An electric-based heater also only requires one outlet and can be used on any car. However, if you cannot fit an heater under the hood, then you will probably have to install one in the trunk – an option that may not be too attractive for some people.