Which electric heater will cost more to run?

The option that indicates a 4 kW electric heater will cost more to run is accurate because the cost of running an electric heater largely depends on its power rating, measured in kilowatts (kW). Higher power ratings indicate that the heater draws more electricity while operating.

In practice, this means that a 4 kW heater uses more energy compared to a lower-rated heater, such as a 1.5 kW or a 2 kW heater. The greater the power consumption, the higher the electricity bill will be, as energy is billed based on the amount consumed over time.

For instance, if all heaters are run for the same duration, the 4 kW heater will consume significantly more kilowatt-hours (kWh) than a 1.5 kW or a 2 kW heater, leading to higher running costs. Thus, it is clear that the 4 kW electric heater is the most expensive to operate among the choices given.