A self-contained portable heating system to heat a stored liquid in a storage tank to a desired temperature is provided. The system can comprise operatively connected components such as a generator to power a burner that can transfer energy from a combustion product, from for example, a fuel supplied by an attached fuel tank, to a heat transfer fluid through the use of a boiler. The heat transfer fluid can transfer heat from the boiler to a heat exchanger which can then transfer heat to the stored liquid in the tank. The tank can also comprise a circulating pump that can circulate the heat transfer fluid and an expansion tank that can receive the heat transfer fluid when it expands as a result of being heated. In some embodiments, the heating components can be supplied separately from storage tank so that they can be retrofit onto an existing tank.