Heat system for an electric or hybrid vehicle, having an overall cooling circuit, having a refrigeration circuit, and having multiple switching states, - wherein the overall cooling circuit has a cooling circuit to which a heat source of the electric or hybrid vehicle is connected, - wherein the overall cooling circuit has an HVA circuit to which a high-voltage accumulator, for providing a supply to an electrical drive train of the electric or hybrid vehicle, is connected, - wherein a first surroundings cooler, for exchange of heat with the surroundings, is connected to the cooling circuit downstream of the heat source, - wherein a chiller, for transfer of heat from the HVA circuit into the refrigerant circuit, is connected to the HVA circuit, said chiller also being connected to the refrigerant circuit, - wherein it is possible for there to be set a first switching state, in which the HVA circuit is connected to the cooling circuit downstream and upstream of the heat source, so that there is formed an extended HVA circuit in which the high-voltage accumulator and the heat source are connected in series, for heating of the high-voltage accumulator by means of the heat source, characterized - in that it is possible for there to be set, as a further switching state, a second switching state, in which the HVA circuit is connected to the cooling circuit upstream and downstream of the chiller such that the heat source, the chiller and the first surroundings cooler are connected in series in such a way that the heat source is arranged upstream of the chiller and the first surroundings cooler is arranged downstream of the chiller, for cooling of the heat source via the chiller or via the first surroundings cooler or both. - wherein the overall cooling circuit has a cooling circuit to which a heat source of the electric or hybrid vehicle is connected, - wherein the overall cooling circuit has an HVA circuit to which a high-voltage accumulator, for providing a supply to an electrical drive train of the electric or hybrid vehicle, is connected, - wherein a first surroundings cooler, for exchange of heat with the surroundings, is connected to the cooling circuit downstream of the heat source, - wherein a chiller, for transfer of heat from the HVA circuit into the refrigerant circuit, is connected to the HVA circuit, said chiller also being connected to the refrigerant circuit, - wherein it is possible for there to be set a first switching state, in which the HVA circuit is connected to the cooling circuit downstream and upstream of the heat source, so that there is formed an extended HVA circuit in which the high-voltage accumulator and the heat source are connected in series, for heating of the high-voltage accumulator by means of the heat source, characterized - in that it is possible for there to be set, as a further switching state, a second switching state, in which the HVA circuit is connected to the cooling circuit upstream and downstream of the chiller such that the heat source, the chiller and the first surroundings cooler are connected in series in such a way that the heat source is arranged upstream of the chiller and the first surroundings cooler is arranged downstream of the chiller, for cooling of the heat source via the chiller or via the first surroundings cooler or both.