Hacker News Reader

Comment by bigyikes | Hacker News Reader

I live in Texas and got a “smart” thermostat recently. I was delighted to find that my energy company is offering a $25/year credit for having one. It’s not much, but it’s nice to have.

…or so I thought. It turns out that accepting this $25/yr alllows the grid to remotely control my thermostat.

I was sweating in my living room, wondering why it felt so hot. Apparently the grid was facing peak load, so they raised my thermostat temperature by 2 degrees!

Thankfully there is a manual override when this happens, but I have to call my energy company to disable this “feature” completely.

I’m sorry, you cannot pay me $25/yr to sweat on my sofa.

View on HN

$25?

I live in a northern, Midwestern state and our coop (part of MISO) offered a one time $1500 and continued discounts (11%) per month on electricity for the capability to control utility curtailment (power control to the unit, no ability to adjust set-point or collect any other data). For winter it can only be in buildings that are non-primary living and can only shut off power to an electrical heating appliance (heat pump, boiler, etc). In the summer they can curtail your heat pump / AC for up to 15 minutes at a time.

I see the curtailment notification on my thermostat on hot days. But the house never gets warm. I have a newer heat pump that is rated up to 22 SEER2 and compared to my old on/off AC unit the variable speed unit makes a huge difference in performance, cost and noise levels. I never hear it running when it is and so during curtailment I don't notice it unless I see the notification.

Is it really only 15 minutes at a time, or is it 15 minute units with possibly multiple in a row? Heat pump efficiency requires long cycles, so turning it off, on, off, on within the course of an hour to make some "never off more than 15 minutes" guarantee would be counterproductive.

The unit basically runs all day during the day on hot days. The difference is, as you state, it runs long cycles. The 15 minutes it's off is the break in the cycle itself. The unit I have is a communicating unit that "learns" the house in terms of all the internal and external changes. So it knows what fan speed and compressor rate to run to get to the setpoint - it doesn't just ramp up to the highest rate after a curtailment event. So it's basically running at a very low rate all day long, curtailment happens, and it ramps slightly if there's a need to bring any zones back to setpoint - but the thermostat is aware of the curtailment event and, as I was told, responds different after the curtailment is lifted. I talked to both the installer and the manufacturer regarding whether or not curtailment would negatively impact the system (performance, cost, longevity) and the consensus was that unless the curtailment events happened every hour there wasn't any downside to cooling. Heating would be another story, but I don't have any curtailment contract for heating in my home.

And I believe the contract states curtailment events can only happen up to 4 times in a given day and cannot happen more than once an hour.

Ah, so basically the variable speed and feed-forward PID make it so the unit is running all the time, so it's not like the 15 minute curtailment will come right after it kicked on to satisfy cooling demand. Rather your house is continually cooling, stops for 15 minutes, then goes back to it. That makes a lot of sense!

I do find it interesting that these terms are still valuable to a power company. Obviously being able to shed the load for 15 minutes is fantastic, but I would think the system would then just use more energy (say for the next 45 minutes) to make up for it. But perhaps staggering the curtailment times, and paying the debt of more draw from the units that were curtailed by doing even more curtailments, can kick the can down the road enough for the few hours they need to smooth peak load?

Also just a guess: is the story with heating that your heat pump is sized based on your max heating load, and so losing up to 25% of its capacity on the coldest days means it would never be able to catch up?

> Also just a guess: is the story with heating that your heat pump is sized based on your max heating load, and so losing up to 25% of its capacity on the coldest days means it would never be able to catch up?

The unit I have has a HSPF2 rating of 10.5. It's very efficient at the transfer of the heat available. Heat pumps can extract more energy than the consume. New heat pumps can operate over 300% efficiency. The best furnaces are generally in the mid-90 percentages.

I have a dual-fuel system and can set where the heat pump locks out. The system is rated to a COP of 1.75 at 5F. Meaning it's still over 100% efficient at that temperature. The unit will operate down to -22F but would be at, likely, less than 50% capacity of output. To save on wear and tear of the unit, however I have my setpoint lockout at 15.

It would have to be significantly below 0 for days on end to have a problem. But even then the furnace would be providing primary heat. There are people in my area that heat their entire home with ductless heat pumps [0]. My unit is rated at 48k BTU. The furnace at 100k BTU. I only really "need" the furnace for emergency. But we do have sub-zero highs rather often and during those days the heat pump would be running continuously.

I also have an 80 gallon hybrid heat pump water heater which has saved us thousands over the last few years. 98% of the year it only uses the heat pump.

[0] https://www.energyvanguard.com/blog/can-a-heat-pump-work-in-...

It seems you took my comment as an attack on heat pumps, which I certainly didn't intend! Such is life in our needlessly polarized information environment. Thank you for the description of your system though! I've got thoughts of a heat pump in my future, and I will be well involved in the design if I don't outright DIY, so it's nice to hear about other people's setups.

By "lose 25% of its capacity", I mean because with curtailment it could be off up to 25% of the time (assuming the same curtailment schedule as summer). The focus on "coldest days" is because that is when your house needs the most heat (regardless of source type). Based on the climate, I assume your heat pump was sized based on the minimum it needs to supply for heating loads on the "design day" (coldest day generally expected for your climate), meaning on the coldest days it requires most of its capacity to keep the house temperature steady. Whereas it's oversized for summer so it can still keep up even if it loses a bunch of capacity due to curtailment.

I'm a bit surprised with a solid backup heat source that winter curtailment isn't more attractive to you (it would also help exercise your backup heat). Does it really not make financial sense? Or is it more of an idealistic thing of not wanting to burn oil/gas as much as possible?

>I have a newer heat pump that is rated up to 22 SEER2

Can I ask why you got a heat pump with such a high SEER rating? I look at flyers advertising heat pumps near me and the price differential between 16 SEER and 18/20 SEER units just doesn't seem worth it at all even accounting energy savings.

Because it was a wash. I was paid a higher rebate from the state, the coop we have for power and the manufacturer. It didn't make financial sense to buy anything less.

Your manufacturer gave you a rebate on top of the state and coop rebate? So you have $1500 from the coop, what kind of rebates did you get from the state and manufacturer?

Yes. The manufacturer (Carrier) has a program called "Cool Cash" - the linked PDF is an example. The "Cool Cash" program I had was different [0]. The state also had passed a new energy law that provided rebates [1]. It's been so popular that they're expanding that even further in 2023 for air source heat pumps with, potentially, more money. [2]

[0] https://yourallweatherhvac.com/media/2022-Carrier-Cool-Cash-... (PDF) [1] https://techxplore.com/news/2021-07-minnesota-energy-law.htm... [2] https://www.minnpost.com/greater-minnesota/2023/03/dfl-energ...

I got a $1400 rebate from the manufacturer at the time $2000 tax credit from the fed and another $1200 from the state.

> I’m sorry, you cannot pay me $25/yr to sweat on my sofa.

I mean, if the grid goes down because everyone refuses to sweat a tiny bit during a massive heat wave's peak load, you might be sweating anyways... for longer and $25 poorer.

The ability of the grid companies to rely on the fact that they can lower people’s electric usage centrally might prevent them from appropriately scaling up the system.

If they can smooth out peaks - if, say, a bunch of people set their thermostats to cool at 2pm so they spread that out over a 10-15 minute period, or they have some folks run AC at 2-3 and others 3-4 - they might need to also run a lot less wasteful energy production.

As with most things, there are good and bad ways to use this ability.

I would prefer if the two entities are separated though. The thermostat should come from a private company that optimizes for the weather locally and possibly takes in data from the electric company through an API so the end user has more control and the motivations for both entities stay intact.

I’d argue the cost of scaling up the grid, both economic and environmental, are too great when the problem can be resolved by raising everyone’s thermostat to 76 for a couple hours a year. Peaker plants are wildly expensive to keep in service, and usually run off of coal or oil.

And not just whether it goes down but it can save money. During summer peaks the cost of electricity to the utility on the open market can spike 10x or more. Almost all utilities have regulated profit which allows them to recover (most) costs, so shaving those peaks ultimately saves ratepayers.

I have ecobee thermostats that I’m generally happy with - HomeKit integration, seemingly comprehensive privacy controls, overall well designed and functional - but they have all kinds of dark patterns designed to force you into these programs. And you really have to go in to a bunch of different settings to excise the utility’s ability to take over your thermostat if you’ve happened to opt in.

I think demand reduction is generally a great idea, but considering what that two degree increase is saving your utility, there really ought to be a 50/50 split of savings than kicking back a pittance of $25 a year.

It would be interesting (better?) if it was a market in which homes with these thermostats could set prices at which they are willing to reduce energy use.

100% agree.

Actually, 99% agree. In Texas, up until one of our recent power debacles, there was a retail energy provider whose schtick was passing through spot rates to retail customers. Normally this was a small fraction (30%) of typical retail pricing. Until the grid went under stress, spot prices skyrocketed, and retail customers who opted into that limited-upside potentially-unlimited-downside plan were paying something like 10,000% of typical pricing. To quote a former Texas governor who forgot which cabinet agencies he wanted to eliminate, “Oops.”

I’m not sure how something like that could happen with what you suggest, but I’m a little wary of unanticipated consequences so as to degrade my degree of confidence slightly given recent events.

I believe you’re enrolled in Smart Savers in addition to having the thermostat. They might’ve rushed you by the agreement. It’s not supposed to be an opt-out program.

In Illinois, Exelon has a similar program. In exchange for $40/year, they install a control on your AC that lets them cycle it off during summer months for a period of time each day. Connecting the program to a smart meter would let them make finer adjustments, and probably more frequently.

We stay enrolled in the $40/year program because if they’re cycling us, it’s unnoticeable. I’m not sure how much discomfort we’d tolerate.

Also, I am fairly sure, they got the right to collect a ton of usage and personal data for those 25 bucks.

> so they raised my thermostat temperature by 2 degrees!

I’m sorry, but you get much less sympathy from me for this generic comment. Raising your temp from 68 to 70 means nothing. Changing your temp from 78 to 80 is totally different. I’m also supposed to feel sorry for you because you didn’t read the fine print? Sure, maybe I’m victim blaming, but come on

I'm genuinely curious, what did you think the $25/year they were paying you for if not to do this?

Smart thermostats can do things like turn off A/C when you leave the house.

Things I like about my ecobee:

1. That (but never really set it up due to the number of people going in and out, but nice to turn things back when we’re all away for an extended period and turn it back on before we return)

2. Run the fans for a little bit every hour (i wish it could be smarter within which part of the hour it could run tho)

3. Disable the AC entirely when it’s cool outside (but had to use some unintended setting designed to prevent « heat pump » stress). Though lead to some head banging by family members asking why the ac isn’t running (answer: open some windows).

4. Tried and failed to get it set up to properly account for humidity when it comes to AC (25C and dry is nice, 25C and humid can feel too hot)

5. Set up too much programming to properly pre charge for in anticipation of time of day price increases and step back when it’s going to go down soon. IMO, this should have been out-of-the-box functionality, not require the complex scheduling i had to do. Even though we have gas heat, I still have some programming for this because its electric load is still like 1kw.

I did immediately turn off the « community electricity savings » thing. You gotta pay me for that!

I didn't install the smart thermostat my power company sent me. I don't run the AC lower than 80° and the heater higher than 65°. I'm already doing my part.

Reply on news.ycombinator.com