New water heater seems to be using more electric?

50gal richmond heater started leaking decided to replace with rheem marathon 50 gal. both were 4500watt units and sense picked up the rheem first time i turned it on. i only had 3 weeks data on the richmond water heater. this last week if on the rheem. Could an older heater use less electric as it build up with mineral deposits? Screenshot_20211005-185215|225x500

What are the model numbers?

Some ideas:

Do they differ in insulation quality? If the new one is less well insulated, there will be more heat loss. Is the heater located inside or outside? (If outside, the air temperature will make a big difference in heat loss as it gets colder). How about the incoming water temperature? Can you compare to data from the same period from the previous year instead. Also check for leaks.

Your day-to-day variation in demand is significant. Although your Rheem has nearly double the usage on average, statistical variance could still account for what appears to be a trend. Data from next week will likely confirm or deny this theory.

Normally an old heater with a degraded anode rod will use more electricity because it has to work harder to heat the water.

Essentially the anode rod will flake off which is what they are supposed to do. This creates a blanket of “mush” at the bottom of the tank that acts as an insulator. The sensors for heat are normally at the top of the heater and in order for the heat to reach the top it “sometimes” has to travel through the blanket of mush. While this is ALWAYS the case with gas water heaters, electric water heaters normally have the elements above the bottom of the tank so the mush at the bottom doesn’t cause much of an impact. It will however reduce the amount of water that needs to be heated if it’s a significant amount.

It could also be that one of elements of the old heater wasn’t working correctly or was burnt out. This does happen and it’s not as easy as some may think to notice since there’s normally more than one element.

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so…my old water heater lower element was completely gone, open circuit. It was operating on only the top element. I would run out of hot water quickly. The new one has hot water for days, so I can only guess less power usage since only top half of the heater was getting warm? I’ve only had sense for few months so not much history on usage.

now almost 2 months after installing new water heater, est cost/year is $354 and ave% of monthly use is up to 14.8%

I can only speculate.

But obviously the top unit only, while working more to heat the water as the lower was out, still was not producing the same 100% output as the 2 elements properly working together. That’s why you quickly ran out if hot water with the ok’d setup.

The 2 operating together at 50% each for a total of 100% obviously use more energy than 1 operating at say 80%.

The simply inefficiencies of running 2 heating elements vs 1 heating element is the reason.

At least to me.