Water heater with reserve capacity, and method of operating the same

A method of operating a water heater, comprising:

• determining a predicted variation of a first variable over a future time period, the first variable relating to hot water consumption rate;
• calculating a total required operating time of the water heater over the future time period using the predicted variation of the first variable;
• determining a plurality of possible operating profiles over the future time period, each one of the possible operating profiles providing a total operating time that is equal to the total required operating time;
• calculating a minimum hot water reserve over the future time period for each one of the plurality of possible operating profiles, using the predicted variation of the first variable;
• selecting one of the plurality of possible operating profiles based at least partially on the calculated minimum hot water reserve of said one of the plurality of possible operating profiles not being less than a predetermined desired reserve capacity;
• and
• operating the water heater over the future time period according to the selected one of the plurality of possible operating profiles.