@Beachcomber, is your Sense usage more than 1% off from what your electric bill usage shows ? If you have a smart meter and you are seeing a greater the 1% difference for a monthly cycle, that would be far different than most experiences - I’ve been compiling cases where the numbers originally diverged, but users sorted out the discrepancies.
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Flume accuracy update… I just got my bi-monthly water bill…
It reports that I used 6.00CCF (the fact that they bill me in whole CCFs has me thinking that my accuracy is impacted by rounding errors)…
Six CCFs is equal to 4,490 gallons. My Flume reports that I used 4,926.76 during the billing period. That means that my Flume is over reporting by 9.7%. This seems high…but I don’t know how much rounding has impacted my numbers…
On a related topic, I am having some plumbing work done and was playing around with the idea of installing a “Flo By Moen” inline at my water main (for drip level accuracy)…
But there seems to be availability/supply-chain issues… Cuz they are difficult to find, and when you find them, they are way over MSRP…
I have a StreamLabs water monitor with is just one that straps on the side of the water pipe like the flume (ultrasonic transducers). I have been surprise how accurate it is when comparing it to my bill’s averages. Mainly because hard to figure out because I can only view today, this month (Jan 1 till current) or this year Then I have to compare it to where my meter readings are on random days of the month and WV American Water might have 38 days on my bill or 35 days and read it on the 16th this month then the 25 next month. However StreamLabs advertise they have an API which they do but you have to pay $6 a month to access it (which they don’t advertise) … Which I’m not willing to do.
The cost to access your API is the reason I would NOT recommend StreamLabs. The app will tell you when it detects a leak (push alert- which I get a lot of false alarms) and you can see how much you have used so far for just today, current calendar month or current calendar year. However everything you try to click on within the app lets you know they have all your usage records but to see them requires a subscription. It also has a away/home leak mode to help with the false alarms… However you have to open the app, and toggle to from home/ away.
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I would guess that it isn’t a case of rounding but the way their billing works. You didn’t use exactly 6ccf during the billing cycle, you used 6.59ccf (according to Flume). Since they only bill in whole ccf and not fractional, that 0.59 rolls to the next bill. Next month your Flume may under-report usage depending on when your meter “clicks over” to the next whole ccf. It is going to take some time to get a sense of how accurate the meter is. Check total usage across 6 months or a year and it should be much closer.
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Yup…100%…
That was what I meant by “rounding”… Not that they rounded my usage and was only billing me based on this rounding… But that their billing was somehow “rounding” (but in this case I guess it would be more accurate to say that they were “truncating” to the whole CCF and pushing the remaining fractional usage into my next billing cycle).
Ah, right. Sorry if my comment came across as insulting in any way. It will be interesting to hear what the accuracy is over time. I haven’t been able to justify a water meter just yet. Now if only I could find a natural gas flow meter at a reasonable price, that would be more interesting to me.
Thanks for the reply… And no, I did not take your comment in an insulting way… I have thicker skin than that… 
That said, I always appreciate people who keep themselves in “check” on stuff like that… Says a lot about your personality… I try to do the same…
The water meter would definitely be much more interesting to me if it could turn off the water remotely like “Flo by Moen”… The usage data is still interesting to me… It’s super interesting to me that my wife likes to take a 2.25GPM shower for 7-9 minutes, and I like to take a 1.25GPM shower for 12-18 minutes… I would have never known that without the meter… AND it was interesting to know that my toilet uses 2.5 gallons per flush…
All that data falls into the interesting but not actionable territory… The complete eye opener was how much water my outdoor irrigation use is, versus my interior household use… It’s clear that if I want to make an impact on my water usage, I really need to focus on the outside…
Natural gas metering would be great… According to PG&E, our natural gas prices have gone up 90% from last winter… I have been thinking about moving from my natural gas water heater to a hybrid heat-pump water heater, which supposedly is super energy efficient when in heat-pump mode… I have excess solar production, so the water heating would effectively be “free”… But how much free water heating to make up for the extra cost of the hybrid water heater, the electrician to run a 220v from my main panel to the garage, AND the plumber to hook up the new water heater?
This is my overview:
Installed in July 2021 so won’t take that month in the comparison:
Month: Flume Gal, 1 HCF=748 Gallons, billed by WaterDistrict in HCF
Aug: 1870 gallons ,2.5, 3
Sep: 1684 gallons ,2.25, 2
Oct: 1692 gallons ,2.26, 4 (<- fixed water leak this month)
Nov: 1132 gallons ,1.52, 1
Dec: 939 gallons ,1.26, 1
Jan: 1101 gallons ,1.47, 2
6months 8418 gal , 11.25 Flume vs 13 HCF water district
Still a 14% difference in measurements but our usage is on the low side.
Would be interesting to see after 12 months.
To quote your quote, “supposedly is super energy efficient”, is easily quantified by looking at the EF (Energy Factor). Standard resistive element water heaters are very efficient these days (around 97% or an EF of 0.97). Meaning: 97% of the electrical energy is effectively heating the water. Another factor in a water tank is the “efficiency over time” = how well the tank is insulated, but comparing standard and hybrid tanks you can rule that out because the insulation is basically the same.
A hybrid tank in heat-pump-only-mode will be somewhere between 200-400% (EF 2-4). How? Because it’s sucking heat from the air around the tank. So the caveat with a hybrid tank is that in winter, or when you are in heating mode in your house, if your tank is in a conditioned space and in heat pump mode it will be cooling the room. That said, in summer it will act as an air conditioner. The interaction between a heat pump tank and your house heating is somewhat complicated because there are so many variations on tank locations and heating systems. You can even selectively draw air from and vent air to the outside depending upon the seasonal temperature swings if you want to further increase the overall efficiency.
But back to the origin of this thread, it would certainly be useful to have a water meter on your hot water and then correlate that with the energy input to your tank gleaned from Sense. But wait, at a fixed EF you can easily calculate your hot water usage from Sense alone! Projecting out to a near (?) future when there is mass conversion from oil & gas-based house and water heating to electric-only, the data gleaned from hot water flow is going to be very useful. Start now!
And then of course there are high temperature boilers that can heat water and your house and are based around R744 (CO2) so much safer for the environment if the refrigerant starts leaking (that’s the real caveat of heat pumps).
And a final note: If you have solar and Sense you can do magical stuff and convert your water tank into a BATTERY. In the ideal world, for example, if you have a huge well insulated water tank and you dump excess solar into it then on cold days you can have lots of baths to stay warm. Joking aside, thermal storage in huge water tanks is crucial (IMHO) to a less lithium-dependent energy future. We should also be storing snow in straw-covered swimming pools but don’t get me started …
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I definitely agree with your thermal storage point. Water is a good medium since we use the hot water elsewhere, but there are much better options for thermal storage (although none yet that I know of are available in the US). Phase change material-based thermal storage is a superior option (in terms of energy storage potential) to water. SunAmp (https://sunamp.com/) comes up from time to time on Fully Charged. I’m sure there are others. The market in countries that use boilers in residential settings is higher than it would be in the US (where boilers aren’t nearly as common), so I guess it’s not surprising we haven’t seen something like that take hold here.
Yup… Thanks @ixu
In the spirit of being purposeful with my words, I know I used the word “efficient”…and I know that electric heating is very efficient… To your point, efficiency is in the high 90s when it comes to conversion of electricity to heat, as opposed to gas appliances that can’t match the efficiency of electricity since some of the energy will go up the flu with some waste… My gas furnace is (fortunately) 93% efficient, with only 7% waste…
I was using the word “efficient” very loosely and conversationally in my previous post… I guess the key driver for me is not efficiency, but cost… (surprise, surprise)… In the recent past, my natural gas water heater costs me about $10/mo to heat my water (so $120/mo)… According to my utility company (PG&E), natural gas has gone up 90% from last winter… So just so we are dealing in round numbers, let’s just make it simple and call it doubled… So $20/mo or $240/year…
Will a hybrid water heater cost me more than that in electricity if (and when) my net metering goes away? And while I have net metering, how much “free” electricity will it take to payback the cost of the higher cost of a hybrid water heater + the electric work to run a 220v line from my main panel to my garage + the added plumbing cost of installation? BTW, I am not asking you that question…it’s really a rhetorical question…
If you believe the energy guide for the Rheem Hybrid water heater, the annual cost of the water heater is $104 based on a 12¢/kWh. California pricing is about 3x that…so that would make the cost about $312/year and consume about 867kWh/year.
I have about one mWh of excess production today…so the water heater would pretty much clean most of my excess production out…
LOL… Yes, I am over thinking things… That is what I do…
@qrnef, I was wondering if somebody would mention PCMs as storage. As a storage medium, PCMs are great but the big advantage of water is the easy retrofit to a heat pump where the hot refrigerant pipes are cooled by the water. You get the 2 or 4 EF because you are using outdoor heat to heat your water. Typical PCM applications (SunAmp) use direct grid or solar resistive elements so there is no energy gain as such. That’s not to say you can’t use PCMs as the “water” substitute in certain heat-pump configurations. I think that’s evolving technology.
My main issue with PCMs is the practicality at scales that really matter. I’ve done calculations for my house and oil-fired boiler and determined I would need about 1,000 gallons (!) of H2O stored at regular heat-pump-capable temps of 50C. That volume goes down a bit for 80C (high temp heat pump). Meaning: perhaps a 200-250 gallon tank of PCM. That certainly seems more manageable volume-wise but there are reasons why BIG tanks favor H2O. The tank and materials are easier/cheaper to make I believe and if you get an inevitable tank failure you don’t have such a cleanup nightmare.
Almost seven years and counting … I’ve posted this before. It doesn’t mention heat pumping but it’s more about the philosophy of integrating large water volumes as storage:
@MikeekiM Something you can consider is that HPHW (Heat Pump Hot Water) tanks can be run on 120V only if you don’t have resistive elements so you could perhaps save on the electric install.
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I installed a 40 gallon Rheem hybrid unit in July 2021.
It is at the side of the house in a dedicated area where the gas unit used to be.
Relative out in the open. Good for the summer, not so good in the winter:
Aug: 58 kWh
Sep: 58 kWh
Oct: 64 kWh
Nov: 64 kWh
Dec: 94 kWh
Jan: 114 kWh (coldest month of the year, and it seems to have switched to the conventional heating elements during the night when it was freezing)
Feb: 54 kWh till the 16th
I have NEM2.0 and pay about $0.022/kWh for getting overproduced electricity back from the grid at night. I am pretty sure it is cheaper than the old gas unit.
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I love the data @dannyterhaar!
@ixu - I didn’t realize there was a heat-pump only water heater option available… I’ll have to do some research…
Honestly, at this point, part of me is thinking that a gas heater ain’t that bad an option to stick with… Fast recovery, reasonable cost (even if natural gas prices are on the rise)… And it’s a problem that can be solved with natural gas… Maybe I should save my excess solar production to power stuff that doesn’t have a natural gas option…
That’s my current thinking…but as always, I reserve the right to change my mind!!! LOL
Nice… I just got an email from Flume informing legacy customers that we are now grandfathered into their “Flume Insights” premium subscription service at no additional cost…for life (yes, they actually used those words…).
Prior to today’s announcement, Flume had indicated that they were moving some of the detailed metrics from their standard offering to this new premium service… But that existing customers would keep these services… All additional services offered in the future would be part of the “Flume Insight” service and not available to legacy customers without a subscription…
Here’s the email I just received (you might need to use the zoom on your browser to see the smaller font):
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On closer scrutiny of their website and email links…they aren’t doing us early adopters any special favors at all… I guess they’ve discovered that no one wants to subscribe to their service… So they are eliminating the subscription model and going back to the model of selling the hardware for the higher price and including all features to everyone for the hardware price… Apparently anyone who bought the lower priced hardware and never subscribed will need to pay another $50.00 to “level up” to everyone else now…
Interesting…
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