We're going to time our recirc to get to the master bath in mornings and evenings since it's >100 feet away from the water heater. Our plumber was adamant about not keeping it running all the time for the very reason you state.

Hi @stephine2

I looked up the specs on that pump and it's showing 8.5 watts as the power draw. At that rate, it would have to run for about 118 hours to draw one kwh. I think something else is going on.

What I would believe is that your (standard electric?) water heater was turning on - possibly in response to the recirculating water.

My issue with recirculating systems is not typically the small amount of power used by the pump - it's the heat lost in the hot water loop - even the well insulated ones -- to keep them hot all of the time. Better to use timer / motion sensor / button than try to keep the pipes hot 24x7.

Just curious - if you don't have a hybrid electric heater, was hybrid electric heater an option? Hybrid electric plays very well with PV solar and is a lot less complicated and expensive than solar hot water.

Stratification is really only an issue with solar hot water.

You can start using your solar when there is a 20 degree difference between water and panel temp. So if you have 100 degree water in the bottom of the tank, the panels (actually the coolant in the panels) has to be 120 degree before it starts working. If you are not recircing, you have ground water temp (or at least colder than 100) in the bottom of the tank so it can start working earlier. Big difference in the winter.

You can add a button wirelessly. Whether that is something you want to deal with is another story. My father lives in a 1993 build north of the Bay area and he has a hard wired button under the kitchen sink. Way ahead of their time.

@opaone @Jake The Wonderdog
Yes, it is not the power the pump uses per se that is so wasteful and costly, it is the energy for heating and reheating the water that keeps cooling down in the pipes. I was told they were insulated, but haven’t gone under the house to check. The lines themselves are the standard blue and red plastic tube ones.
I will ask about a wireless button. Seems like an awful lot of trouble (install and all of pipes and pump) for saving a bit of water. We are on a septic tank, so using a bit extra doesn’t feel that wasteful since it goes right back into our soil...

@Jake The Wonderdog What is a hybrid electric tank?

@David Cary We have an indirect passive system as far as I can tell (sun bank style), that feeds into a regular electric water heater. I just hope they set it up correctly...?

A lot of bogus info in this thread.

opaone nailed it.

Now *I* am curious. We have no solar, but do have a recirculating pump on our paired 50 gallon tanks (basement). I hadn't thought the pump 'wasted electricity' and I love the 8 second wait for hot water at every faucet in the house (Chicago area, single story, 2900 sq ft tight construction). Should I be concerned about electical expense?

@chisue It is worth investigating if your usage seems oddly high. It depends on how long the pipes are and how many, if they are well insulated or not, where they are (conditioned basement or unconditioned crawlspace), etc. Our house is brandnew and our electricity usage strikingly high. The water heater is at one far end of the house (it is a cross shape and the heater is at one short tip, the kitchen at the end of the longest wing, the bathroom and shower at the opposite wing from the water heater). We are all electric. But we are also in California and the pipes are all insulated (claims the contractor) and in a conditioned crawl space... It is worth looking into.
Really the biggest issue is that you are keeping water hot in an incredibly unsuitable container - the water lines. Even insulated that can not possibly be as efficient as keeping it hot in an insulated tank. If we were doing this over I would insist on on-demand tankless heaters, one in the kitchen, one in the bathroom to supplement the solar. That was what we had signed off on before the set up was changed without informing us.

@stephine2

A hybrid electric heater pulls heat from the surrounding area (heat pump) and uses that to heat water. They are hybrid because they also have electric resistance heat.

They are generally the lowest cost way to heat water (other than solar) - lower than gas tankless.

The DOE guide for the linked heater shows an estimated cost of $104 a year based on a national average cost of 12 cents a kwh. Obviously that would vary if your electricity was more expensive.

It also outputs cool, dry air - so it can cool / dehumidify a garage or basement.

You REALLY don't want electric tankless - they will really spike your peak demand usage (not all locations charge for peak demand, but yours does).

Hybrid electric heaters use a small amount of electricity over a long period of time - so they work really well with solar PV.

As a bonus, many localities offer big rebates ( $500 or so) for installing a hybrid electric heater.

@Jake The Wonderdog
Aha, a heat pump one. I wonder why we did not seriously consider that one - we do have mini splits to heat and cool the house... I think we didn’t have a good spot for one - we have no garage, attic or cellar, and I guess you need a fair amount of space around the thing so that it can draw heat from the air...
Our electricity is about 40cents per kwh - we can only dream of 12 cents! Luckily we now have a ton of solar panels...
I think the solar water heater is actually serving us well... It was just cooling the hot water in the pipes all night long and reheating it with the resistance heater that was so wasteful.

Yes, they do require air around them from which to draw heat. Some of them have vent kits so they can be in a closet and still vent to the adjacent room.

I'm glad you figured out what was causing your spike in usage - you really should be about net zero with your setup.

We added on a recirculating pump onto our gas water heater more than a year ago, and have not seen a spike in electric use. Our most used shower is the farthest water source from water heater. The pump has a timer, so it only runs during morning and night time bathing times. It has cut down winter time water waste, dramatically… it used to take over a minute to clear cold water from pipes, now we can hop into the shower in 14 seconds. Every day, I am happy we added this little device!

Ya think? Read the responses above! lol

BTW, I have a Hybrid Hot Water Heater, Probably saves us $25-$30 per month for two of us. Love it. The amount of dehumidification and cooling of the surrounding space is minimal. My unit is in a dank basement and maybe a pint of water per day is condensed - necessitating, however, a small condensate pump or a floor drain. Don't count on dehumidifying or cooling the surrounding space.. the effect is minimal.

The units are a little noisy and likely not suitable for an interior hall closet. Also, probably not suited for a garage in an arctic clime.

@Jj J @Stax Well, since you are on gas, Jj J, it wouldn’t raise your electricity use by more than what the pump uses, but your gas usage would have increased because the heater is working harder. That may not really register if the pump is not on most of the day, or gas prices very low. We are all electric and pay a lot per kwh, so the cost is significant.
It’s all coming back to me now about the heat pump hybrid heater... we didn’t have the appropriate space for it. Anyway, without that recirculation pump on 24/7 we are pretty good - we get a lot of sun all year round.

No gas available at my home.

"No gas available at my home." - I think many of us on here would beg to differ.

Stephine2, no gas bill changes until my partner had to start working from home (gas furnace, too)due to COVID mandate.

Simple test: turn off ( unplug) the recirc pump for a while to see if the spikes still occur. I have a pump that I control using X-10 technology on a gas water heater. I only turn on the pump only when hot water is need somewhere in the house. I have timed how long it takes to reach each outlet and turn it off at that time.

Ok, I looked at our usage again and found that we were actually using just over 15kwh per day extra with the pump always on, so roughly an extra $6 per day.... uff.
And I have an idea why they did that: the external sensor is not attached in the correct location. Which might explain why the pump isn’t functioning properly in the auto adapt mode right now. It seems like it is just off.

"Ok, I looked at our usage again and found that we were actually using just over 15kwh per day extra with the pump always on, so roughly an extra $6 per day.... uff."

$6/day? $180/month? Your electric rate is $0.40/kWh?

15kWh per day would be a BIG pump pumping a lot of water and doing a LOT of cooling of that water. IIRC our pump running continuously for a 9800 sq ft home is about $0.44 /day for pump + extra heating (DHW is from a gas fired boiler).

Your math doesn't seem plausible. It would seem to take a lot of big inefficiencies in your system to do that.

Yes, roughly $0.4 per kwh is what we pay here: California, tiered plan, always land in the top tier because we have 2 households but just one meter and so only get a base allowance for one meter; plus we are all electric and the increase in base allowance one gets for that is minuscule... Also, we are getting all renewable power from the geysers, so all in all yep, power costs a lot. Our total bill is around $700 and we almost never drive and we don’t use the heat or AC...
About the pump - what can I tell you, every time it comes on we get about a 5kwh spike.... I can post two pictures, one with the recirculation on 100% the other with it in auto adapt (which I think has essentially turned it off). And no, our big pump uses about 15kwh to come on and 5-7 to pump (3hp, variable speed).
Here’s the house power use (no car, no 2nd household, no big pump, no AC or heat, all new energy star appliances):

Sorry, before and after were turned around. Before is on the bottom, after on top.

3 HP pump! That's one big pump for a recirc system. Ours is about 1/25 HP and fits in the palm of my hand. Your pump must be doing something else other than just recir hot water. A Grundfos PM comfort auto adapt pump looks like this on Amazon: Grundfos 98420224 Comfort PM AutoAdapt Recirculation Pump NPSM, 1 1/4-Inch and is no where near 3 HP.

Were I you I'd grill the installer or whoever to find out what is going on.

15 kwh a day seems about right. When you are using cheap gas, it can be $15 a month. For much of the US, that 15 kwh is about $54 a month.

My builder quoted $15 a month with gas.

My usage was about yours but I was paying $.10 a kwh and my solar would keep up a lot better in July - I find it amazing that your spikes start so early - was it a really cloudy day?

For the most part, just by keeping my pump limited to 6am - 10 pm, I would be fine for much of the year. South facing, completely unobstructed panels - in NC.

No No, @pima74 not the recirculation pump, our main pump is a 3HP pump (on a well with a 5000gal holding tank. We have to have a powerful pump to supply the indoor fire sprinklers (mandated here).

@David Cary Yeah, PG&E has crazy prices and continues to burn down our homes or at least force us out of them for days at a time and live with apocalyptic smoke for weeks every single year. Now we get planned power outages on risky days, too. It’s worth it if that means they destroy fewer lives, but there definitely is another way.... Anyway....
Yes, I don’t know why our solar water heater isn’t doing more of the heavy lifting in the evening hours - these were relentlessly sunny, very warm days. I wonder if it is even connected?!?
Our solar panels worked just fine and we produced about 90 something kwh that day (we have a LOT of panels and battery back up. They have nor connected the well pumps, rental cottage and car charger to the system yet, which we will do asap - another miscommunication - that’s why the power generation is out of proportion for now).

Everyone else is doing things wrong, it seems.

@Stax hmmm. Not what I said and not the point. But sorry for griping. I do hold a grudge with PG&E for burning down our home and almost everything we had...

You can tell the spikes are gone during the day so the panels are clearly doing something. I know all about PG&E - but to be fair, energy is always risky and fires are gonna happen in dry areas. Most of the wildfires currently have nothing to do with PG&E. Doesn't absolve them of wrongdoing, just pointing out that they aren't responsible for everything and not most things.

We live in the Bay Area and have radiant heat, a gas hot water heater, and no A/C at our house. Given the many issues raised in this discussion thread we're considering installing a smart controller when we install an on demand recirculating pump in our upcoming remodel. Link for Smart Recirculation Controller

@stephine2

The original post was about a circulating pump.

As it turns out, you have a very complex system that includes a 3hp well pump, solar hot water, an ADU, car charger, solar PV, etc. The pertinent details are slowly emerging with each post. You didn't bring up the well pump until just a couple of posts ago. We also don't know roughly what size this home is.

Electricity is expensive where you are - but your electrical usage seems unusual, especially given the design of things. That said, it's too complex for us to analyze - particularly when you switch topics, leave out important information, etc.

Talk to someone who can look at all the data and see the entire system.

Thanks @Jake The Wonderdog. Yes, we have a little farm in the country, so there is a lot going on. That doesn’t change the original statement from my post at all. The graphs are showing electricity use for the main residence ONLY (because that’s how the solar power system was, erroneously, set up). Since it doesn’t show the well pumps, car, cottage or anything else, it is actually very helpful to help us see what using the recirculation pump does to our electricity bill. Since we are not using the heater or AC at all right now and fridge is pretty constant the only other appliances causing spikes are the induction stove and electric oven and the toaster. Dishwasher and washing machine barely register and we don’t use our dryer in the summer either. Anyway... Our contractor will come out to fix the sensor placement and double check everything, make sure the solar water heater (Sunbank) is online, too.
Thanks for everyone’s input.

Oh and I think the confusion started when I responded to @opaone when he said a 5kwh start up would have to be a BIG pump. I responded by saying no, our BIG pump uses way more at start up. By our BIG pump I meant our WELL pump and holding tank pump. The holding tank pump is a 3HP and starts with 15ish kwh... But that was beside the point for the issue, since those pumps don’t show up in our usage graphs....
Anyway, I assume the spikes are caused by the heater rather than the pump itself. Though we might have a bigger recirculation pump than most, since the water pipes are so long...
I will repost with any new information.

A pretty obvious statement - pretty long pipes equals large energy use.

Not that I ever favor a constantly running pump, but if somebody has a well insulated 50 foot loop, it certainly is better than someone with a 300 foot loop.

When I did the math on typical insulation, a tank loss was equivalent to about 20 feet of 3/4 inch pipe (by memory). So a 200 foot loop would have 10 times the losses and a typical tank might be 1 kwh per day. By my WAG, you have a 300 foot loop to get 15 kwh losses.

I stand by the statement that your solar is working just fine since the spikes disappear during daylight. Of course it could be working but not working well. Super easy to look on the control panel and see the panel temp, tank temp and whether the coolant pump is flowing. As long as those are working, you are probably fine. Panels get to 180 but only late in the day when there is no cold coolant to pump up there. You can turn up the allowed temp on your tank if you want but the contractors can be restricted by law on certain things. We had a thermostatic valve to limit the output temp - but the pump can challenge that too - topic for another day.

Thanks @David Cary. Yes, we have at least a 200f loop, and it might be close to 300’. It seems pretty crazy for our architect and contractor to decide that it’s fine to run 24/7... They must have thought about the pump energy use only, not the ongoing heat loss, especially during the night. I’ll go and try to find out where the control panel is for the sunbank - I have no idea. That would be good to see. Thanks again!

My recirc pump is loud and costs me about $50/month in electricity to run. I was advised to put it on a timer.

I have a question. I just got a new tankless water heater. My house is being remodeled so the plumbing is accessible. Our water heater uses gas (not electric). We bought a recirculating pump but have not yet installed it.

Currently my water heater is centrally located and has 3 seperate lines that go out to different parts of the house. The slowest area takes about 2 minutes for the water to get hot. I’m order to use the recirc pump, I need to combine all of these onto one long stretch of pipe. And since my water heater is tankless, I would only have the recirc pump running at certain times of the day.

The problem I’m worried about is this…. For the times that the recirc pump is NOT on. If I use the hot water faucet that is furthest down the line, won’t it now take several minutes to heat up? It already takes 2 minutes. It will take much longer if I add 2 more areas of the house in front of it and the pump is off, correct?

If you build a loop and don't run a pump, it does usually take longer for the water to get hot. Much of that is because the loop is larger diameter - but that certainly depends on your setup now. It is fairly common to use a 3/4 pipe for a distance and then branch 1/2 off to fixtures. When you design a loop, it is always done this way. So it depends a lot on what you have now.

You can homerun a 1/2 in pipe to speed things up without a pump. A 3/4 inch pipe carries just about double the water 1/2 does - which means double the time. Your 2 minutes could become 1 minute if it is currently off a 3/4 main and you homerun it with 1/2 inch. Can be even better if you remove elbows/tees. And even better if the route is less direct because it comes off a main.

And then copper does not equal Pex. Copper steals a bit of the heat and doesn't flow the same.

Does your tankless say it is ok to use with a pump? In the past, it was not recommended to run a pump with tankless but that has changed. The overly frequent cycles is not something the tankless were designed or warranted for. I know that there certainly are ones that are designed for a pump nowadays but not sure all of them are. Could mean a warranty denial if it says to not use with a pump. I have to think extra wear and perhaps more maintenance is a consequence of having a pump. The tankless will fire say every 15-20 minutes when the pump is running. I had a monitor on a pump and the pump ran 7 minutes in every 20 to keep the loop warm. Then the heater would run once every 20 minutes to reheat the tank for about 5 minutes. Length and insulation characteristics would change this of course.

"My recirc pump is loud and costs me about $50/month in electricity to run. I was advised to put it on a timer."

Kind of old but for others reading this. It should be less (and often much less) than $50/YEAR, not anywhere near $50/month.

And FWIW, good advice above from @David Cary.

How would the cost factors change if instead of a return pump for each homerun, or putting the homeruns in series, a secondary set of small electrical tankless heaters were put at the distal ends of the homeruns? These would provide immediate heat on demand and then shut off when the primary tankless heated water made it to them after 2 minutes.

@opaone It’s not the pump using the electricity, it’s the water heater reheating all that water that cooled down in the pipes all day.

@opaone It’s not the pump using the electricity, it’s the water heater reheating all that water that cooled down in the pipes all day.

Not even close. I've a 9700 sq ft house with a 24hr recirc and an average of 5 people living here at any one time (and a good bit of entertaining) and our entire cost for gas for DHW is $64/mo.

@kaseki, I think for that it'd make more sense to just have multiple THW's? When we looked at it the cost diff between a small and large THW wasn't that great, install cost is identical. Operating cost would likely be less to have multiple primary as the amount of energy lost in transport from THW to user would be less.

FWIW, we looked at multiple THW's for our house vs a tank+recirc and the numbers didn't work. I do have a THW in my studio.

We just discovered how much extra gas we were buying each month to heat the water in the pipes.

I looked at our online web portal for the gas company and it pointed out that we used a large amount more gas than any of our neighbors. This is odd as we are empty nesters and our air conditioning is electricity (so minimal gas usage at that time). We turned off the recirculating pump. Our next bill dropped from $60 to $40. Who would have thought it was costing that much $$.

I think that is pretty typical - $20 a month in gas for a recirc system. To some that seems like very little, to others it is very wasteful. I remember getting quoted about $15 a decade ago.

For those that haven't noticed yet, NG is way up - close to doubling. Not always reflected on bills depending on the utility. But it will be eventually.

Opaone - I don't think you meant to disagree with Steph. In your case, the electricity is probably $5 a month and the gas is probably close to $20 - but surely more than $5.

For our family of 3, we had a $10 a month gas bill for DHW in a rental using tankless gas. Taking baths or having teens can really change that number. Just looking at occupant count doesn't come close to telling a full story. And climate matters a bit also - colder ground water makes a difference and the shower temp goes down in the summer. HE washers and/or using cold water and then modern dishwashers make a sign difference.

I have a recirculating pump that I put on a smart plug like WeMo  or Kasa.  Then just install the app on your phone and program to run when you're likely to be home or just turn it off and on through the app on your phone.  Easy peasy.

Opaone, how much the water cools down on the pipes depends on the layout of the house and the resultant length of your pipes. The cost for reheating all that water over and over depends on the temperature of the environment and the cost of your fuel. We have an electric water heater. Power costs a lot here… so $60 is entirely possible.