Hybrid water heater with adaptive temperature control

A method for controlling a hybrid water heater comprising a storage tank for holding water and a tankless heater fluidly coupled to the storage tank for producing heated water, the method comprising:

• determining a target output water temperature range for the tankless heater based on a temperature setpoint, the target output water temperature range comprising a lower threshold that is less than the temperature setpoint and an upper threshold that is greater than the temperature setpoint;
• measuring, by a first temperature sensor positioned in an upper portion of the storage tank, a temperature of water stored in the upper portion of the storage tank;
• determining whether the measured temperature of the water is less than a first minimum temperature;
• generating an adjusted water target output temperature range for the tankless heater based on a determination that the measured temperature is less than the first minimum temperature by increasing a value of both the lower threshold and the upper threshold;
• and
• operating the tankless heater to produce the heated water according to the adjusted target output water temperature range.

A water heater comprising:

• a storage tank for holding water, the storage tank having a lower portion and an upper portion;
• a tankless heater configured to produce heated water and to provide the heated water to the upper portion of the storage tank, the tankless heater positioned externally to the storage tank;
• a first temperature sensor configured to measure a temperature of the water in the upper portion of the storage tank;
• and
• a controller configured to:
• measure the temperature of the water stored in the upper portion of the storage tank using the first temperature sensor;
• determine a target output water temperature range for the tankless heater based on the measured temperature, the target water output temperature range comprising i) a first lower threshold and a first upper threshold if the measured temperature is above a first minimum temperature, or ii) a second lower threshold and a second upper threshold if the measured temperature is at or below the first minimum temperature, wherein a value of the second lower threshold is less than a value of first lower threshold and a value of the second upper threshold is greater than a value of the first upper threshold;
• and
• operate the tankless heater to produce the heated water according to the target output water temperature range.