Should I upgrade our water heater

I am regularly looking at all our appliances and stuff and wondering whether or not I should upgrade them, i do not want to spend our money all kinds of extra currency because our a/c or our water heating system or our dishwasher are using all this extra energy because they are seasoned and inefficient… Recently, I have begun to consider replacing our water heating system and asking myself should I honestly upgrade our water heater? I assume I have had our water heating system for at least 10 or 15 years, then how long is a water heating system supposed to last? Plus, I assume that they have these on demand water gas furnaces now, then are those more energy efficient? are they worth the cost of the item itself plus the replacement fees? Are they reliable or do they need a lot of service? These are all things that I am wondering right now about our water heater. One thing I do assume for sure is that I want our water heating system to be as efficient as possible and I do not want to be without boiling water. I assume that one of the things Mother Teresa did when she started her important Ministry that she had was that she detachd all the a/cs and all the water gas furnaces from her building, then she said that the poor could not afford costly air conditioning and they also could not afford water heaters, so if it was superb enough for them, it was superb enough for her. however let me tell you I am no mother teresa.I need boiling water and I need air conditioned comfort.

a/c installation