The heat pump.
A form of efficient energy heat supplier is the heat pump. Extensive details concerning the working of this can be found at Dimplex technology.
Below the Dimplex schematic representation of the heat pump:
Making such a pump optimally efficient on Mars one needs to drill a hole in its soil till +2 degrees Celsius has been reached. Mars has volcanic activity like Earth. It is known Mars has magma. I hope a mere 100 to 300 meters drilling is sufficient.
Instead of drilling one may find a relatively warm spot near the base camp. Think of the sewage or a pressurized tank outside. Let us not worry about where to find the brine source and concentrate on the working of the heat pump itself.
In the brine cycle the gas R407C eventually heats up the heating cycle where oil or water fluid transfers the obtained heat of the heating cycle.
R407C gas can obtain energy from a source (brine) far below freezing temperature but preferably higher than -
The ratio between the useful energy generated and the electrical energy consumed for this process is about 3.5. (Or in other words: The heat supplied divided by the electrical energy required) So for every unit of electricity used by the heat pump 3.5 units of energy to usable heat are created. In other words the heat pump has an efficiency of 350 percent. In technical terms: a Coefficient Of Performance (COP) of 3.5 (about 30%).
Parabolic heat technology
See how a parabolic 70" (1.78 meter) solar satellite dish collects sunlight to transform it into heat on the youtube explanation of greenpowerscience.
Every time a capsule descent to Mars it throws away its heat shield once the capsule has entered the atmosphere. A total waist knowing that this shield is parabolic and theoretically can be constructed as such that its inside is made of reflecting (chrome) material. Its diameter is not a 'mere' 70" but even 200" or 5 meter. Likely able to produce sufficient heat to warm up Mars one base. In spite of that the Sun on Mars has 41% the strengths of that on Earth and the outside temperatures are well below zero degrees. See my schematic representation here below:
I don't know how much heat the dish can produce on Mars but it is certainly worth testing it. It may save a lot of electrical energy you now don't need for heating and maybe several dishes (they have plenty) may produce enough heat keeping the cycle inside the base warm enough during the night. NASA just needs to reconstruct their heat shields and drop them by parachute.
In the households on Earth, certainly possible on Mars, the heating cycle warms up a water boiler for heating the house or on Mars the base.
On the left a photo of a heat pump for households.