What is the labor cost to install a 40 gallon hot water heater?
Close to what a 50 gallon install takes. The work is the same whichever size goes in, so the hours come from the location and the connections. Ten gallons either way barely changes them.
The labor covers draining and disconnecting the old tank, carrying it out, setting the new one in place, making new water connections, fitting a new relief valve and discharge line, and adding any code items it needs.
What makes the labor bigger is location and change. Tight utility closets, attics and crawl spaces slow the job compared with an open basement, and so does a steep stair. Changing fuel or rerouting a vent adds real work.
You will not get the labor as a separate bill. It is part of one written price for the whole replacement, given before anything starts.
If you are weighing a 40 against a 50, the labor question drops out of the decision entirely. Pick the size the household needs, and the only difference you will see on the written price is the tank itself.
Want it looked at?
Tell us where the 40 gallon heater sits and whether it is gas or electric, and we will quote the full job.