Our home has a 50 gallon 4500w water heater. Since most of us in our household use the hot water generally around the same time of way, I would like the water heater to have a faster recovery rate. I would like to replace the 4500w elements with 5500w ones. The wire and breakers (30amp) are properly sized and the thermostats are rated up to 6000w. Based on napkin math, I think I'll achieve a 15-20% faster recovery rate. Has anyone ever done this? We plan on upgrading to an 80 gallon tank in the future but I'm looking for a simple improvement until this tank dies.
If the manual says it is an optional element replacement, it should still pass all certifications if you substituted a bigger set of elements.
If your house has enough vertical drop to accommodate one, a long-term savings may be to install a waste water heat recovery system. This will make the existing WH look bigger, as it preheats the incoming water from that going down the drain. It's discussed here often...just search on those terms. Depending on your utility rates, and the amount of hot water you use, would determine how quickly it might start saving money after the purchase and installation.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013