Trying to decide if a new water heater would be beneficial. Looking to compare data

The water heater in our house is from 2003 and was there when we bought the house. I’m trying to decide if it would be cost effective to go ahead and replace it. It’s a standard 4500W electric tank heater. It’s in a small closet in the middle of the house, so as-is, I would not be able to go with a HPWH. Though, depending on how much it costs to move the water heater to my garage, this could potentially be an option. Though, a heat pump seems more complex and costly to repair, so I dunno…

I know newer electric tank heaters are “more efficient” only because they have better insulation. Here are a couple of pictures of my tank.

First, the model information:


Energy Guide sticker:

It estimates about 5kWh per year. I’m not sure how they come to those numbers, but we definitely don’t use hot water that much. Maybe it’s because we actively try to conserve power and water. We don’t use hot water when doing laundry for example.

I’ve had Sense since last August, and in November I had an incident where Sense merged my water heater with my stove and I had to delete it. So I have a full months data for Sep, Oct, Dec, and Jan. If I average those 4 months together, I get about 127kWh per month. Multiplied by 12, that’s about 1,518lWh for the year and about $210 worth of electricity. When I was researching solar, I put 2 years worth of usage from my bills into a spreadsheet; that amount of electricity is about 15% of our yearly usage.

Another data point: The Energy Guide sticker says estimated 4989 kWh. Looking at some newer Rheem models, the stickers say estimated use of about 3500 kWh. That’s about a 30% reduction in power used, presumably because better insulation means it turns on less often between uses. That would put us using about 1,067 kWh for the year and about $146. That’s a savings of only $65 per year. So it would pay for itself, but it would take 10 years to do so. But, I do have a toddler and a 5 month old, so I expect the amount of hot water I need to increase over the next 10 years, so we’ll just say payback period of 8 - 10 years, which coincidentally happens to be the same as my solar panels.

So how can you help me? I’m looking for info from people that have newer electric heaters, hybrid, or heat pump heaters. Post the info from your energy guide sticker, a general summary of your hot water usage, and if you have it, actual electric consumption usage from Sense.

Not looking to actually replace for probably a year or two. Just researching for now.

If you water heater is from 2003 it is at it’s end of life. I would ride it out till it kicks the bucket, then look at a more efficient model or maybe a tankless, that only uses energy at use (gas or electric). You definitely aren’t going to get another 10years out of your current unit, so I wouldn’t factor that into your return on investment.

1 Like

Agree with @billlokey here though I will add some thoughts:

  • Gone are the days when switching a tank was a straightforward decision … even if longevity vs cost; efficiency (direct resistive vs heat pump) and other factors seem, actually, like factors.

  • Annual kWhr will be significantly influenced by the local water conditions (water temp rise).

  • Hot water generation and STORAGE is a hugely important issue when you factor in the energy storage potential of a (large, well-insulated) tank in a solar scenario.

  • Do you have or intend to have solar?

  • Just like an EV battery or house battery charging is a great way to load shift usage to avoid sending watts to the grid, hot water storage is at least a partial consideration in the future of solar optimization. I harped on this here.

  • Instantaneous electric water heating is undoubtedly potentially more efficient than stored heat but the equation is less than trivial when considering embodied energy. Thought experiment: Everybody who is able decides that’s the way to go, instantaneous … the Utilities’ loads become untenable and force grid upgrades. Worst case, a mass consumer decision to convert their water heater results in the need for additional power stations due to synchronized morning ablutions! As a general rule these days, it seems if you can encourage end-user grid-demand CURRENT reduction you are on the right path. “Switch bulbs to LED!”. Same goes for a water tank: heat-pumps use less current (and energy). Caveat: In any given household there is distinct advantage in enabling HIGH current. e.g. quick EV charging. This, however, should be kept as local as possible and not increase grid demand. i.e. high current local solar charging is ideal.

As far as your actual question goes (!): I’m in a constant state of frustration regarding my own hot water supply: small apartment, no solar possible, low current max (100A), small space for water heater. I had to replace my EOL tank a few years ago (1,183 days ago to be precise) and couldn’t squeeze in a then-available HPWH so went with a Rheem Performance Platinum XE40M12EC55U1 with 4.13kW elements at the 208V supply. Energy label is 4,622kWh/yr and for the Sense period I have it monitored it’s clocking in at 2,728 kWhr/year. That’s based on the average of two native Sense detections over 290 days starting March 8th, 2019. This may be close to actual usage (2 people; NYC incoming water temps) but I’m not confident it is. I have data from actual monitoring of my tank that I will post after doing a comparison with the Sense native detection.


Here’s a chart for the same data period as above plotting both my Sense’s (#1 & #2) native detection variation from “actual”, which in this case is from Sense#2’s CTs, which were actually dedicated to my hot water tank alone.

Horizontal axis is actual DAILY kWh from Sense#2 Main CT (clamped to the hot water tank circuit).
Vertical axis is the % variation from that actual, where >0 means the native detection was over-reporting the wattage (rare) and <0 is under-reporting.

Some numbers for the 290 days measurement:

Sense#1-native, daily average: 7.53 kWh ==> 2,750 kWh/year
Sense#2-native, daily average: 7.42 kWh ==> 2,705 kWh/year
ACTUAL (using Sense#2 CT) : 7.94 kWh ==> 2,899 kWh/year

Conclusion: Average under-reporting was 94% of actual. Not bad!

i.e. Add about 6% to Sense-native reporting. Your mileage may vary of course.

Oh, and I’m at about 63% of the Energy Star Label. That’s gotta be the 1.9 kids we don’t have. Actually, NO, bad stat to quote … average household is 2.6 so were at 2/2.6 of that ==> about 82% of label.

Phew, I need a shower!

1 Like

Great analysis… You’re going to convince me to get that second Sense and 4 CTs for looking at my biggest 240V users.

I’d replace it before it dies. If feasible I’d start the work to install a HPWH . The savings would be worth it, also the old water heater could fail with a flood. It’d be more complex but a hybrid, like my Rheem, has resistive mode so I figure if/when the heat pump breaks I’ll put it in resistive mode until repaired
My personal experience is sense underreports my HPWH by a large amount but that’s my experience with all major devices. The EcoNet app shows about 8 times as much electrical consumption as Sense.

1 Like

One thing that has me hesitant about a HPWH is the long term cost. With them being more complex than a traditional WH if I run into an issue, I doubt I’d be able to fix it myself. I don’t know anything about how to diagnose AC units or repair them. A traditional WH basically works by sending a large amount of electricity through a resistive element. That’s super simple to troubleshoot.

I guess the main thing to look at first would be the feasibility of moving the tank to the garage and re-doing the plumbing, because there’s no way to put a HPWH unit in the small closest the tank is currently in. If that ends up costing thousands, then I might as well just get a newer traditional WH and keep it in the closet.

EDIT: Oh… moving the tank to the garage would also require running a new 240v line to it as well. I forgot about that…

HPWHs still have regular resistive elements and can run in non-HP mode if the AC unit fails.

If you do end up relocating the tank to a larger space I would carefully consider the tank size with a look toward scaling up to an even bigger tank. As detailed here, upsizing can really work to the grid’s advantage (and especially if you have solar). Load shifting smarts love such things.

1 Like

Definitely need to replace your “6 Year” water heater ASAP.
After working in construction and restoration work for years, water heaters are the number one cause of catastrophic flood damage in a home.
I’m not a fan of instant water heat but do think going with high efficiency heat pump is the way to go.
I replaced my water heater last year and moved it from the utility room to the crawl space so if it does leak, it won’t damage the home.

I have a HPWH that I installed this past April in my storage room but just this past weekend I helped the buddy replace his standard electric water heater with a Stiebel eltron on demand electric. I tried to steer him towards the heat pump but he was really looking towards the space savings. I was quite surprised to find out that the water heater I helped him replace was installed in the year 2000…

I’m not super handy myself. My father-in-law helps me with a ton of stuff. He’s been very dismissive about replacing the water heater though. He says the water heater in their house is about 30 years old, so we “should have plenty of life left”. He hasn’t come out and said it, but I get the feeling he does not want to help me replace something when he deems it unnecessary.

My parents had theirs fails last year. A very small leak developed, and of course it was in the back where you couldn’t see it, and water seeped under the floors for months. Did a ton of damage. Has made me very nervous about ours.

I was planning on replacing ours within the next few months but then a few days ago we had termites coming out of our wall and swarming around, so finances dictate pushing it back to the end of the year.

A new tank should ideally go on a pan, into which you can put a water leak detection rope (my Rheem tank has the EcoNet attachment for that).
You could potentially try and implement that with an existing tank with the knowledge you should have it for the new one anyway. It really depends where the tank is. On a second floor over a library you really need one. In a garage with drainage it’s probably not going to do any damage.
Use common sense.
The pans and basic leak sensors are cheap and readily available.
A sneakier solution (again, not always possible due to plumbing, and certainly not industrial strength) would be placing a small sump pump into the drain pan … or even using a gravity-based drain hose to somewhere with safe drainage.
It may seem daunting with a full tank but if you drain the tank you may see it differently … depends on your plumbing and “the room”.
That said, an old tank is possibly best left alone.


Well from what I know most leaks do start small. Longevity depends on a lot of things, is it flushed out regularly, what is the quality of the local water supply, and ideally has anyone ever changed the cathodic rod. Like the other poster my Rheem Econet has a built-in leak detector, I put it on a pan and plum the pan outside using PVC. I also plumbed out the emergency blow off and the condensation drain in the same area. For additional protection I have a smart things hub so I put a leak detector on the floor by the water heater which also serves to monitor the temperature.

1 Like

It’s code these days to have a pan

1 Like