A method of using a thermal energy store capable of accepting, storing and releasing thermal energy at a range of more than one temperature to/from at least one thermal energy source and/or sink, said thermal energy store comprising: a configuration of three or more thermal energy storage banks, (102a - 102h) each of said thermal energy storage banks having an operating temperature range; at least one or more of the thermal energy storage banks contains thermal energy storage material comprising a single material or a mixture of materials; wherein said thermal energy storage material in at least one bank contains at least some of one or more types of thermal energy storage material that undergoes at least one energy absorbing and/or releasing phase transition at one or more temperatures or one or more sub-ranges of temperatures within the operating temperature ranges of each bank; wherein each phase transition is associated with a change in physical and/or chemical properties of said thermal energy storage material; and two or more independently controlled thermal energy transfer connections, wherein each connection comprises one or more devices for transferring heat from a lower temperature body to a higher temperature body, each connection linking two or more banks; wherein one or more multi-bank phase change material thermal stores includes a control system that regulates the amount of and source of electricity drawn by the system or thermal energy store electrical elements of the system due to a pump and/or a heat pump and/or a thermoelectric device which draws and use electricity based on one or more of the following criteria: • Stability of the electricity grid; • Availability of electricity; • Cost of electricity; • Carbon intensity of electricity; • Signals from an electricity grid operator; • The criticality of the operation of elements of the system. wherein the source of electricity is a local energy source that co-generates combined heat and electrical power, also known as a local CHP Generator; and wherein there is controlling electronics and power electronics required for the chosen local electrical generation source, which regulates the amount of and source of electricity drawn. a configuration of three or more thermal energy storage banks, (102a - 102h) each of said thermal energy storage banks having an operating temperature range; at least one or more of the thermal energy storage banks contains thermal energy storage material comprising a single material or a mixture of materials; wherein said thermal energy storage material in at least one bank contains at least some of one or more types of thermal energy storage material that undergoes at least one energy absorbing and/or releasing phase transition at one or more temperatures or one or more sub-ranges of temperatures within the operating temperature ranges of each bank; wherein each phase transition is associated with a change in physical and/or chemical properties of said thermal energy storage material; and two or more independently controlled thermal energy transfer connections, wherein each connection comprises one or more devices for transferring heat from a lower temperature body to a higher temperature body, each connection linking two or more banks; wherein one or more multi-bank phase change material thermal stores includes a control system that regulates the amount of and source of electricity drawn by the system or thermal energy store electrical elements of the system due to a pump and/or a heat pump and/or a thermoelectric device which draws and use electricity based on one or more of the following criteria: • Stability of the electricity grid; • Availability of electricity; • Cost of electricity; • Carbon intensity of electricity; • Signals from an electricity grid operator; • The criticality of the operation of elements of the system. • Stability of the electricity grid; • Availability of electricity; • Cost of electricity; • Carbon intensity of electricity; • Signals from an electricity grid operator; • The criticality of the operation of elements of the system. wherein the source of electricity is a local energy source that co-generates combined heat and electrical power, also known as a local CHP Generator; and wherein there is controlling electronics and power electronics required for the chosen local electrical generation source, which regulates the amount of and source of electricity drawn.