Heat Pumps and Electric Heating - Electric Thermal Storage (ETS)?

A search on these forums appears to produce only one <A HREF="http://forum.doityourself.com/heat-pumps-electric-heating/201021-electric-thermal-storage.html">thread</A> which mentions electric thermal storage (from '05) and at that time, it seems that the OP was the only person who had heard of it.

I've got to quickly turn around this fixer-upper that I've been working on for years (with the help of these forums) and I had been planning on installing a heat pump, but the back-of-the-envelope price I was quoted for installing (attic) ductwork was prohibitively expensive. Not only because it was something I had been planning to eventually do myself, but you could buy a decent new car for the same price.

This means that unless the next estimate comes in at around half the price, I'm either going to need to replace these antique gas wall furnaces with newer models or I'm going to install several ETSs. (Please note, both furnaces and ETSs were plural and either option would require three or four units)

I still haven't found anyone around town who has an ETS and though nobody has pointed toward any experienced person in particular, I've been getting mostly negative opinions from the laypeople I've asked. Though, they could also be colored by recent controversies concerning our co-op.

Tuesday, the guy from the power company is supposed to come by to try and sell me a few and I'll be talking to the electricians who have bid on my upgrade over the next couple of days, but presumably all of these folks might be biased and I can't help but notice that even the product <A HREF="http://www.steffes.com/offpeak/">literature</A> mentions the idea of "supplemental" in between positive claims.

So, by chance does anyone here have any experience, knowledge or opinions about ETS?

Thanks in Advance

Sounds like they aren't any more efficiently than normal resistive heat, but can make sense if your off-peak rates are significantly different. How much is your difference?

Have you considered putting in multiple PTAC units? If you know how to do 220V wiring for something like an ETS, a PTAC should be just as doable.

The point of an ETS is to store heat during off peak hours when it is cheaper. The only time you would want to use and ETS is if your electricity rates are monitored and charged different rates for peak and off-peak usage. You would then use the ETS to store heat created during the off-peak hours and then provide heat during the peak hours to save $$$ and reduce grid traffic.

Sounds like they aren't any more efficiently than normal resistive heat, but can make sense if your off-peak rates are significantly different. How much is your difference?

After reading what I can on the subject, I have to say that's my impression also. I generally see stuff about how they're more efficient for the utility, but nothing which implies they're more energy efficient for the consumer and I've even seen something that says a heat pump is more efficient. (Somewhere in the product literature, it talks about using an ETS like a heat pump's "emergency back-up". Though one that would have to recharge every night, I have to assume)

The per/kW saving would be about 49% for off-peak, 9pm to 6am, off of their regular rate. Though, I guess like other utilities, they charge their time-of-use customers a higher rate for on-peak, about 19%, which would bring the off-peak to getting a 57% discount from this higher rate.

But, it's about a 49% discount off of the regular rate, or .049 vs .0925.


As for the PTAC - The wife and I have been calling the ETS units, motel heaters because they look the part. My impression of the actual motel-like things are that they're wider (or thicker) and they'd need to be put through the wall. My exterior walls are vermiculite-filled cement block, so I can't really put a lot of holes in it, especially since we're moving and because I wouldn't want to marry the house to that solution.


The heating and air guy mentioned the possibility of the "<A HREF="http://us.lge.com/products/category/list/home%20appliances_air%20conditioners_art%20cool.jhtml">Art Cool</A>" line from LG because they don't need outside access, but he didn't know how much they cost and his brother who has the heating and air franchise in the next town didn't have time to do any calcs, when my local guy called.

A quick Google says they might range from $1300 to $1900, which is higher than the power-company subsidized cost for the ETSs ($900-$1300) and though the cooling part would be a desired bonus, if I had to put one in every room, it'd quickly add up.


Basically, though I call my house the museum of antique heaters, all I've been using are big, fan-forced wall furnaces and swamp coolers (evaporatives) and each unit is responsible for multiple rooms.

It was suggested that the ETSs could do the same.

The ETS you linked are straight electrical resistance heat from what I could tell. Unless your rates increase by 3x during peak hours, a heat pump will be much more economical.

What you might want to do, though, is set your setback times to coincide with your peak demand hours to reduce the call for heat during the peak hours.

As a side, I have a really hard time believing they haven't combined an ETS with a heat pump. Those ceramic blocks would work the same with a heat pump and be much cheaper to run.

The ETS you linked are straight electrical resistance heat from what I could tell. Unless your rates increase by 3x during peak hours, a heat pump will be much more economical.

I see your point and didn't realize there's quite so much difference, but the "problem" is that I've got to quickly turn this place around, finish what I've started and haven't completed over the past six years, do some other things that need to be done, then move to another part of the country and sell this house.

If I thought that the ETSs would be a strike against resale or if it'd affect my appraised value, I might be able to justifiably turn against it, that's why I'm fishing for opinions around town and with this post.

Unfortunately, the only authorized dealer that I have found who'll serve this town said he'd want at least $10k to run just the ductwork (pretty much a straight shot through my attic) and the only other suggestions that I've gotten from laypeople and a couple of contractors is a company that everyone thinks would be cheaper on the ducts, but they're not an "authorized dealer".

I'm still waiting to hear from the less expensive company and as you might imagine, they're kind of backed-up. Perhaps one of the biggest differences is that I don't expect their bid to be "this is what I charge for new construction, so a retro would be x", but they also know their competition, so I wouldn't be surprised.

What you might want to do, though, is set your setback times to coincide with your peak demand hours to reduce the call for heat during the peak hours.

My understanding is that the ETS would be set to primarily charge during off-peak, so the on-peak heating would be pulled from the store and unless it's under-sized, it'd probably never charge during peak.

Of course the power company guy says that he'd rather sell me too big of boxes, so that I'd never run out of heat, but logic tells me that a too big would probably cost more to recharge and because we'd need to keep the units out of the way, I couldn't really go for the largest units, anyway. (The choice can't be a couch or a 5', 600 lb heater)


Otherwise, thanks and I appreciate this, plus any other thoughts.

My understanding is that the ETS would be set to primarily charge during off-peak, so the on-peak heating would be pulled from the store and unless it's under-sized, it'd probably never charge during peak.


Yes, that is the principle and it works. But, like I said earlier, I don't think the savings from storing heat during off peak hours with electric strips would be better than the 250% to 300% increase in efficiency that a heat pump would provide.

IMO, from purely an operating standpoint, the ETS probably isn't the best choice unless your peak rates are more than 2.5x higher than the off peak rates. I can't speak for your duct work concerns.

Good luck.

IMO, from purely an operating standpoint, the ETS probably isn't the best choice unless your peak rates are more than 2.5x higher than the off peak rates. I can't speak for your duct work concerns.


Curiosity question: My understanding is that a heat pump removes moisture from the air during the cooling season, though I don't know what it does with heat; But, I live in a place with a winter monthly humidity average between 25 and 40% depending on the month, so would that dramatically effect the overall efficiency of a heat pump and how would that compare to the dry heat of an ETS?


Thanks, again for all the help.

The heat pumps works like a typical A/C during cooling months. It will reduce the humidity just like an A/C would.

During heating seasons, the heat pump doesn't care about humidity. Humidity only effects the ability to cool.