Energy sources The use of an Akvaterm accumulator tank is independent of the heating system or energy source. Besides the sun, wood, chips, wind or geothermal heat, the heating source can be traditional electricity, oil or gas heating, or their combinations. If required, energy sources can be modified or the heating system can be supplemented. Akvaterm is part of an entity that facilitates the production of pleasant and balanced heating for living, as well as domestic hot water, with the same system.