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. <EOS>