Water heater controller or system

A water heating system including a heated water storage tank and at least a first heater, the system including:

• two or more temperature sensors located at predetermined heights on or in the tank, the location of each sensor being adjacent to or within an associated volume of water in the tank, such that the sensor provides a practical measurement of the temperature of the water in the associated volume,
• a processor responsive to the readings from the sensors and their associated volumes to calculate an amount of energy resulting from changes in the sensor readings,
• wherein the calculation can be performed without the use of data derived from a flow meter, wherein the calculation of the amount of energy can be performed without the use of data from a flow meter.

A water heating system including a heated water storage tank and at least a first heater, the system including:

• two or more temperature sensors located a predetermined heights on or in the tank, the location of each sensor being adjacent to or within an associated volume of water in the tank, such that the sensor provides a practical measurement of the temperature of the water in the associated volume,
• a processor responsive to the readings from the sensors and their associated volumes to calculate an amount of energy resulting from changes in the sensor readings,
• wherein the calculation can be performed without the use of data from a flow meter.