Provided is a heat pump system (10, 10A) for a conditioned space comprising a first thermal fluid circuit adapted to selectably operate to circulate a thermal fluid therein, and a second thermal fluid circuit adapted to selectably operate to circulate the thermal fluid therein. The first thermal fluid circuit may comprise a compressor (15), a first heat exchanger (11), and a passage (55) of a heat accumulator (50). The second thermal fluid circuit may bypass the first heat exchanger (11), or the passage (55) of the heat accumulator (50), or both. The second thermal fluid circuit may comprise the compressor (15), and a second heat exchanger (12).