An electrical water heater adapted for energy management and a method of controlling the consumption of electrical power from the power supply grid of a utility is described. The bottom resistive heating element of the water heater is a dual element resistive heating element which has a high power rated resistive heating element to heat water and a further low power rated resistive heating element. The power rating of the low power resistive heating element is calculated to be lower than the supply grid diversified mean load. A controller has a communication link with a utility which manages the power supply grid. The utility can control the resistive heating elements of the dual element in such a way, and depending on conditions of the grid, to conserve energy and regulate its frequency thereby resulting in a cost saving to the consumer and the utility. The low power rated resistive heating element is also connectable to an alternative power source.

A solar photovoltaic (PV) water heating system includes a tank (1.020) including at least a first heating unit (1.016) having at least first and second heating elements (1.016.1 . . . 1.016.x), at least one of which is switchable (1.014.1A . . . 1.014.1m); a PV solar collector (1.002); an inverter (1.004) adapted to convert the output from the PV collector to an alternating power supply; a modulator (1.060) to modulate the alternating power supply from the inverter; a controller (1.040) adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PC collector.

A solar photovoltaic (PV) water heating system includes a tank (1.020) including at least a first heating unit (1.016) having at least first and second heating elements (1.016.1 . . . 1.016.x), at least one of which is switchable (1.014.1A . . . 1.014.1m); a PV solar collector (1.002); an inverter (1.004) adapted to convert the output from the PV collector to an alternating power supply; a modulator (1.060) to modulate the alternating power supply from the inverter; a controller (1.040) adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PC collector.

An electrical water heater adapted for energy management and a method of controlling the consumption of electrical power from the power supply grid of a utility is described. The bottom resistive heating element of the water heater is a dual element resistive heating element which has a high power rated resistive heating element to heat water and a further low power rated resistive heating element. The power rating of the low power resistive heating element is calculated to be lower than the supply grid diversified mean load. A controller has a communication link with a utility which manages the power supply grid. The utility can control the resistive heating elements of the dual element in such a way, and depending on conditions of the grid, to conserve energy and regulate its frequency thereby resulting in a cost saving to the consumer and the utility. The low power rated resistive heating element is also connectable to an alternative power source.

Provided herein are systems and methods directed to using renewable energy sources with hot water heating systems. The system and method provide for interconnecting a single electrical heating element of a hot water heater to first and second electrical power sources. Typically, these first and second electrical power sources include a utility provided electrical power source (e.g., a fossil fuel AC power source) and a renewable energy power source. A controller selectively connects the first or second power sources.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A water heater control system includes: a photovoltaic power generator interconnected with a commercial power supply, an electrical load circuit including a storage-type electric water heater using power from the commercial power supply and generated power of the photovoltaic power generator to perform a water heating operation of heating low temperature water to high temperature water and storing the high temperature water, and a HEMS controller limiting a water heating operation of the storage-type electric water heater by stopping or suppressing the water heating operation of the storage-type electric water heater when a power fee data for purchased power supplied to the electrical load circuit from the commercial power supply exceeds a standard monetary amount.