What increases the fuel consumption of your vehicle considerably?

Heated seats and air-conditioning both increase your vehicle's fuel consumption significantly because they require additional energy to operate. Heated seats use electrical power, which comes from the engine and leads to more fuel being burned. Similarly, running the air-conditioning system puts extra load on the engine as it powers the compressor, which also increases fuel usage. In contrast, devices like a navigation system use relatively little power and have a negligible effect on fuel consumption. Understanding this helps you manage your energy use in the vehicle and save fuel where possible.