Thinking ahead to better time-of-use electricity rates

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DBoon

Minister of Fire
Jan 14, 2009
1,444
Central NY
I've been noodling around some ideas in my head and would be interested in getting some feedback.

I have a 15 kW grid-tied solar PV system with net metering (NY state is supposedly grandfathering net metering for me for the next 18 or so years, last I knew). It generates roughly 16-18 MWh/year, of which about 6-7 MWh/year is used for domestic household use (including hot water), 4-5 MWh/year for heating, and 4-5 MWh/year for my battery EV. I also give back 2-4 MWh/year (for now) and get paid a nominal amount for that. This offsets some of the non-electric energy I use and also offsets energy I use to charge my EV when I am traveling far from home (I personally feel that this is important to do).

Last I read, NY State offered the option to convert from net metering to time-of-use metering. I have no plans to do this in the near future because net metering is a pretty sweet deal, and the time-of-use metering plan isn't that good (for a lot of reasons) right now. But I could see the time-of-use metering getting more competitive to the point where I might be able to make money by shifting my demand to times of low-prices and low-demand. This is pretty easy to do with an EV and a newer charging system. I've also set up my geothermal heating system to permit this - I have a 180 gallong Stiebel Eltron tank and it can store 4-5 hours of hot water for my radiant floor heating system (which is pretty good at scavenging low-quality low-temperature BTUs from the water). Here in Central NY, power can sometimes get very cheap (<$10/MWh, not including distribution costs, or 1 cent/kWh, and sometimes it goes negative, e.g., when it is sunny and windy and not crazy cold). NYISO charts power prices real-time by region and shares the predictive power price a day in advance (which generators use to big generation into the system).

The geothermal radiant heat system is a single pump (Grundfos Alpha) with a single Tekmar 260 control with outdoor reset. The Tekmar control also has an Occupied/Unoccupied (OCC/UNOCC) settings, so if I want I can set up two different temperature settings and make the water warmer or cooler depending on the OCC/UNOCC status. OCC/UNOCC is just changed with a relay from a timer. The basic idea (which I've been playing around with some manual settings) is the following:
  1. When power is cheap and/or from 11pm to 5am and Noon to 3pm, I have the geothermal system make hotter water. This would require some sort of signal from NYISO or the utility, then the system would
  2. I turn all the thermostats up
  3. Grundfos pump goes to highest GPM setting
  4. Geothermal system runs continuously to charge the tank and dump heat into the floors
  5. Do the opposite at other times when power is expensive with some time duration before it would just revert to "normal" settings
  6. Run my woodstove when it is really cold out to augment geothermal.
I am wondering if there are off-the-shelf control systems for residential that can do all of the above (control thermostats, have a timer with relay switch output, control the pump speed (maybe newer pumps allow remote pump speed control?).

Yes everyone, I realize that this mostly makes no sense and won't be cost effective in the near term. I am mostly interested in understanding whether the technology exists today and not interested at all in a cost/benefit analysis (for now).
 
I've been noodling around some ideas in my head and would be interested in getting some feedback.

I have a 15 kW grid-tied solar PV system with net metering (NY state is supposedly grandfathering net metering for me for the next 18 or so years, last I knew). It generates roughly 16-18 MWh/year, of which about 6-7 MWh/year is used for domestic household use (including hot water), 4-5 MWh/year for heating, and 4-5 MWh/year for my battery EV. I also give back 2-4 MWh/year (for now) and get paid a nominal amount for that. This offsets some of the non-electric energy I use and also offsets energy I use to charge my EV when I am traveling far from home (I personally feel that this is important to do).

Last I read, NY State offered the option to convert from net metering to time-of-use metering. I have no plans to do this in the near future because net metering is a pretty sweet deal, and the time-of-use metering plan isn't that good (for a lot of reasons) right now. But I could see the time-of-use metering getting more competitive to the point where I might be able to make money by shifting my demand to times of low-prices and low-demand. This is pretty easy to do with an EV and a newer charging system. I've also set up my geothermal heating system to permit this - I have a 180 gallong Stiebel Eltron tank and it can store 4-5 hours of hot water for my radiant floor heating system (which is pretty good at scavenging low-quality low-temperature BTUs from the water). Here in Central NY, power can sometimes get very cheap (<$10/MWh, not including distribution costs, or 1 cent/kWh, and sometimes it goes negative, e.g., when it is sunny and windy and not crazy cold). NYISO charts power prices real-time by region and shares the predictive power price a day in advance (which generators use to big generation into the system).

The geothermal radiant heat system is a single pump (Grundfos Alpha) with a single Tekmar 260 control with outdoor reset. The Tekmar control also has an Occupied/Unoccupied (OCC/UNOCC) settings, so if I want I can set up two different temperature settings and make the water warmer or cooler depending on the OCC/UNOCC status. OCC/UNOCC is just changed with a relay from a timer. The basic idea (which I've been playing around with some manual settings) is the following:
  1. When power is cheap and/or from 11pm to 5am and Noon to 3pm, I have the geothermal system make hotter water. This would require some sort of signal from NYISO or the utility, then the system would
  2. I turn all the thermostats up
  3. Grundfos pump goes to highest GPM setting
  4. Geothermal system runs continuously to charge the tank and dump heat into the floors
  5. Do the opposite at other times when power is expensive with some time duration before it would just revert to "normal" settings
  6. Run my woodstove when it is really cold out to augment geothermal.
I am wondering if there are off-the-shelf control systems for residential that can do all of the above (control thermostats, have a timer with relay switch output, control the pump speed (maybe newer pumps allow remote pump speed control?).

Yes everyone, I realize that this mostly makes no sense and won't be cost effective in the near term. I am mostly interested in understanding whether the technology exists today and not interested at all in a cost/benefit analysis (for now).
The sacrifices needed to make time of use “scrounging” payoff just won’t be worth it to most people.

I think a lot could be done with smart thermostats and home integration. Honestly just putting timers on your storage tanks would do a lot. After 9 pm tank tank temp is test to xxx. At 6 am is goes back.

To me the biggest advantage / complication is for people with air source heatpumps. You need to know the wether forecast and how much heat your house can hold and what swings the occupants are willing to endure. But my calculations just on waiting untill 10-11 and letting it warm up above 45 outside i can save 10%


To answer your question not that I’m aware of. There are some smart load centers coming to the market and they could have something really allowing more extreme load shifting. But your use case is so unique no one could make money on something like that. That said. It’s fairly simple to program these routines in to a raspberry pi or arduino.

You could read the current price from a website.

But before I’d do anything use calculate the possible savings. Are we taking 500$ a year or $5000

Emporia i think is the closest and have long term ideas like that. But really what you are after needs to interface with the utility company. And do they really want to promote extreme load shifting. They definitely do when demand soaked and they run short on generating capacity. But for the everyday normal they’d make more money if everyone just had a dumb thermostat under a locked box.

Auber makes some pretty neat PID controllers that aren’t to expensive.

What I don’t like so that we get charged a surcharge for the highest hourly peak usage age for the cycle. One slip up or a steam shower on peak times would cost me more than I could save switching to time of use. Sooo…. I burn wood below 45 degrees, hang out 90% of the laundry year round and have a big heatpump water heater. My electric bill averages 1100 kWh a month and we’re charging th EV 2-400 of those. I could add some insulation and quit growing vegetables under grownlights. That’s about it to reduce my cost.
 
I have no answer. But I wonder why you are thinking about those - evidently not for the money.
Then the environment? I'm not sure you switching in this way would put significant weight in the environment scale...

Finally, d*mn 1100 kWh per month? Mine is 350-400 a month. Less.AC but more heat pump heating.
No EV, but then still half ebs-p...(1100-400 EV=700)
(Only thing not electric is hot water here.)

But I won't derail this and go back to the "why" as I do think that factors in what solutions might be appropriate?
 
My guess is you would need a PLC to do what you want to do. There may be a fancy front end on it but ultimately its a PLC hidden underneath. Alternatively someone good with Arduino could rig something up. I have always avoided PLCs as they need software to program them and unless you go with the big industrial stuff, at some point in the future the software is out of date and no longer supported on the current operating systems.
 
I have no answer. But I wonder why you are thinking about those - evidently not for the money.
Then the environment? I'm not sure you switching in this way would put significant weight in the environment scale...

Finally, d*mn 1100 kWh per month? Mine is 350-400 a month. Less.AC but more heat pump heating.
No EV, but then still half ebs-p...(1100-400 EV=700)
(Only thing not electric is hot water here.)

But I won't derail this and go back to the "why" as I do think that factors in what solutions might be appropriate?
I like to think I do quite well for not trying too hard. We are a family of 7 (constantly doing laundry) living in 3000 sq (which includes a 17’ wide glass garage door). Someone is always home working or parenting.

I figure 300 kWh for the EV and 200 for hot water (we use a lot!) and 50 for grow lights.

I really think once batter prices drop and they are widely deployed it will have effects of narrowing the peak/off peak price difference.

Even a 20 kWh battery (no solar) charged off peak and drained peak could pay for itself if the rate structure is favorable. California had a pilot program where the residential batteries were used for peak power days. Made decent money for the owners but I don’t think the utilities are liking it.

I think this whole idea depends a lot on how comfortable you are with 5-8 degree temps swings of your house.
 
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The sacrifices needed to make time of use “scrounging” payoff just won’t be worth it to most people.
Agreed that they aren't worth it now, and I am also not "most people". I'm just curious, thinking ahead to a time when I don't have net metering for my solar and what I might do to prepare for that, and maybe even be able to (optimistically) come out ahead (queue all the replies from those who will chime in that the utilities will find a way to screw me/us out of that - let's just keep this thread on theoreticals and possibilities).
After 9 pm tank tank temp is test to xxx. At 6 am is goes back.
Yeah,I can do this today with a (max) $250 timer. That's the simple, least cost, most benefit thing to do.
But before I’d do anything use calculate the possible savings. Are we taking 500$ a year or $5000
Just to be clear, I'm not going to do anything in the near future. I'm just trying to understand the commercial, off-the-shelf possibilities.
 
My guess is you would need a PLC to do what you want to do. There may be a fancy front end on it but ultimately its a PLC hidden underneath. Alternatively someone good with Arduino could rig something up.
I appreciate the ideas. Certainly, something could be custom designed, but I am specifically thinking about commercial off-the-shelf systems. It sounds like suppliers haven't really addressed this need yet, probably because primarily they haven't been asked to (i.e., there is no demand driven from the consumer side). I thought maybe what is happening in California with power prices and the duck curve would be creating some innovation in this area.
 
But I wonder why you are thinking about those - evidently not for the money.
There is no money in this yet. In fact, I would be giving away money if I gave up net metering and went with time-of-use rates now. I'm thinking ahead to what 10-15 years might like look.

Bluntly, I have a belief that the archaic way we price utility power has to change to solve the problems of the future (more variable supply). One of the methods that will be employed are time-of-use rates, and if we employ those types of rates, consumers who can monitor and take advantage of those rates would benefit most, and (if the rates are structured fairly) come out ahead for their investment and trouble.
 
My guess is the solution will be web based. Look at Nest technology that Amazon bought so they could get an inside look at home heating use. Amazon could very easily tweak the Nest settings to line up with TOU billing. A very large amount of home appliances come with connectivity even if its not used very well but if the link is there someone on the web could access it and control it. The Internet of Things is going to even further reach into homes. Arc Fault breakers contain microprocessors to do their thing and no doubt someone could figure out a way of making those breakers communicate with the internet so they could be remotely switched on and off. Several firms have figured out how to look at the raw energy demand of a house and make an educated guess at what loads correspond to specific equipment.

A firm like Amazon could offer cheap power in return for access and control of home usage data which they could monetize by selling to other firms. They also could do things like delay a refrigerator or a heat pump from cycling for a few minutes when there is sudden demand for grid power where power is very expensive until reserves kick in and the power demand drops. One of the many profitable wholesale power markets is selling 5 minute reserve power, when an event like a power plant goes down or transmission line trips out, generation based plants can only ramp up or down at a certain rate, a nuclear power plant takes days while a gas turbine combined cycle plant can take minutes if they can get the gas, during these periods anyone who has power available right now can sell it for a bundle to fill in the gaps, that is where big commercial battery plants makes some of their money, they get paid just in case they are needed whether they are actually needed or not doesnt make a difference they still get paid. (except in Texas that does not have capacity payments) So an Amazon could sell into the 5 minute capacity market and when there is sudden power demand they would send out signals to all their enrolled homes to reduce power usage by delaying equipment from running. They are not generating power, they are just guarantying a reduction in demand. To a typical homeowner they would not even notice.
 
I thought Google bought Nest...
 
Okay, wrong major conglomerate out to rule the world ;)
 
My guess is the solution will be web based.
I would agree, and that would be fine by me. I could imagine that a larger provider could aggregate the demand reduction and shop it in bulk as a virtual power plant (VPP) (firms do this today). Likely, that firm would also be a retail electricity provider in those markets that offer that choice.

Utilities have shown little interest in offering good time of use (TOU) rates for low-volume on-off consumers (and I can't say I blame them), so having an aggregator offering retail electricity, TOU discounted rates to consumers, and then provide to the utility a VPP service would be pretty smart. If that aggregator was also smart enough to figure out how to monetize all of the demand and usage info, so much the better (for them).

I think New York State is going to go retail TOU rates when net metering sunsets. I haven't checked what the dates/deadlinesare, but it is more than 15 years out but less than 20 years out, last I knew.