I looked through the multiple posts relating to water heaters, but did not find any describing my problem. I have a 1958 ranch home on Long Island with 1.5 baths, one kitchen, and hot water baseboard heat which is supplied by a gas furnace. I have a separate 40-gallon gas water heater which appears to be less than 5 years old. During warm months, we (just my wife & I) have no problem with the amount of hot water. We take what I believe to be average length showers in the morning and the 2nd person has all the hot water they need. However, in the winter months, this is not the case. Often times, the hot water runs out prior to the completion of the first shower, and the second person ends up with a cool shower. I can hear the heater turn on while the first shower is being taken, and it remains on during the second shower. What could be causing this? The water heater is a standalone unit with no additional tanks. Do I need some sort of reserve tank? I don't think that our showers are significantly longer in the winter, and since the home's heat is supplied by a separate furnace, I do not see that as the problem. I don't mind accepting the possibility that I may need a larger heater, but we have only the two of us in the house, and think that the 40-gallon size should be sufficient. Any thoughts?