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Community and Q&A

Water Heater Morass

MPEB | Posted in Mechanicals on

Hi all. I’m in the midst of a seemingly one-step forward one-step back basement renovation. On the “step-back” side, our water heater is nearing the end of it’s life. From what a can glean from the label/internet, It’s a ~10 year old AO Smith, .54, 60,000BTU, 48 gallon tank, with a stated 90-gallon 1st hour rating and 61 gallon recovery rate. We’re a family of four (with a 4 and 2 year old) in a 2 bath (probably soon to be 3) house in mid-Ohio with a detached garage.

I’ve read a lot on the site and following Martin’s decision tree (, our target should be a sealed combustion or direct (or power) vent gas model, probably 75 gallon with an eye towards our kids getting bigger and based on the performance of the existing model.

I’m leaning towards a direct vent model, but had a few questions:

-We have an $800 incentive ($500 rebate and $300 tax credit) for the purchase of a hybrid water heater. We have a 300-400 sf storage/utility room in our basement where we could locate the unit. It’s a low ceiling (6’10”), so it might be tight to fit an 80-gallon unit, but we could probably make it work. With the incentives, the cost of the HPWH will be less than the equivalently sized direct vent gas model. Does the pricing start shifting the analysis between gas/electric? Taken with a large grain of salt, the annual “cost to operate” estimates from the manufacturers look pretty equivalent.

-Does anyone have an opinion on the Rinnai RH180 ( It’s a 40-gallon tank/tankless combo. I’m trying to get a handle on whether it’s the best/worst of both worlds. I’m not seeing much in the way of reviews, so thought I’d see if anyone has experience with it.

If anyone has thoughts/comments/product recommendations, I’d love to hear them. Thanks.

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  1. charlie_sullivan | | #1

    What climate are you in? Do you have any hope to eventually add solar panels and go net-zero? In a humid climate, the summer dehumidification benefit of the heat pump would sway me in that direction.

    I'm not particularly impressed by the Rinnai hybrid. The concept seems reasonable, but the results are not as good as you might hope. An energy factor of 0.8 is better than an ordinary gas fired water heater, but there are both tank and tankless units with higher scores. But that's my opinion just based on that one number, not based on experience with it or anything.

  2. user-2890856 | | #2

    Matt ,

    I would not put much stock into those annual cost to operate numbers . The manufacturers all use the same lab parameters and all the numbers always look the same . The real world is far from a lab setting . Look at the HTP Phoenix Light Duty water heater . Similar numbers in the lab but in the real world there is not a heater out there that performs like this one . PERIOD !

    Don't fall into the tankless trap either , it takes an immense amount of energy to heat water an average of 70* almost instantly , much more energy than a tank unit uses when it heats up 7* after losing 1/2" per hour .

  3. MPEB | | #3

    Thanks for the quick responses. To answer your question, we're in Zone 5/dfa-humid continental, so generally humid summers with colder winters. We periodically run a dehumidifier in the basement, so that aspect is appealing. My biggest question marks on the hybrid are (i) costs to operate vs gas and (ii) noise. I'm having trouble coming up with an apples to apples cost comparison for my region on gas vs electric. On noise, I've read anything from "refrigerator running" to "window hvac".

    Richard, I've looked at the Westinghouse flavor of the Phoenix unit ( It looks great, but the cost is an issue. Factoring in rebates, the Westinghouse would run about $2,100 and, to take as an example, the Geospring 80g would run about $800. Not sure if the ROI justifies the price.

  4. ruffryder | | #4

    To the op, if you are still monitoring this site, it would be great to know what your final decision was and not it is working out for you.


  5. MPEB | | #5

    I was on here posting for a different project and saw that I had never responded to this. Sorry, poor etiquette on my part. So, for a tremendously tardy reply, we ended up going with the GeoSpring 80g HPWH. Generally, we're happy with it. We've typically run it in hybrid mode. When our 7 year old discovered that warm showers in winter are amazing (and would run them for 15 minutes), we flipped it to the boost mode, as even in hybrid mode, whoever was shower number 4 in our house would start to get cold water. Switching to the boost mode helped. I haven't tracked the energy usage in detail, but at least anecdotally we haven't seen a significant jump in our electric bill and didn't see much differentiation between the hybrid and boost modes. In all, we'd make the same choice again. There were some other factors - namely venting would have been painful for gas and I had/have a bias toward electric because of the prospect of solar (we're currently pricing an installation for a garage). Hope that helps.

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