Even if plain heaters are 100% efficient, which they basically are, heat pumps can deliver many times more energy than they use (pay for). Entropy increases as the high grade electrical energy is used to concentrate the much lower grade heat energy outdoors to not much higher grade room temperature. It is much more efficient (and less heating required anyway) the warmer the outside (or geothermal, lake water etc.) temperature.
Note that heat pumps can claim to be 300% and greater efficient, which is true, but that is not thermodynamic efficciency, just that it delivers more heat than the energy that it uses directly.