Worth switching to net "time-of-use" metering for grid-tie solar system in NY (ConEd)

[MrBoylan]

Hey, folks,

Newbie here. Just went online in December with a grid-tie solar system (Sungevity Lease) in New York City. Building and fire safety codes limited me to a system size (STC-DC) of 1.47 kW so it's pretty small compared to the average PV system. So far I'm generating anywhere from 0.3 to about 5.5 kWh in a winter day, depending on the weather, but I'm expecting better performance in the spring and summer, which brings me to my question...

I'm wondering whether it makes sense to switch over from flat metering to voluntary time-of-use metering with ConEd. I work during the day, and the kids are in school. My wife is in and out of the house but doesn't use too much power during the day. In the summer, it's likely the house will be unoccupied for much of the peak generation hours, so most of our electricity usage will happen during the evenings and weekends (off-peak). With the flat rate, ConEd charges 8.89 cents per kWh for electricity delivery. For the time-of-use plan, ConEd currently has a *huge* discrepancy between peak usage and off-peak usage electricity delivery rates: 30.27 cents per kWh during peak (10 AM to 10 PM weekdays) vs. 1.16 cents/kWh off-peak. I believe our ESCO also offers time-of-use rates on electricity supply, but I have not verified that.

From my understanding, if we switch over to net time-of-use metering (from the current flat rate net metering), we'll be generating power at 30.27 cents/kWh during the day when our usage is low, and buying it back during the evenings and weekends at the lower rate. Of course we will have *some* usage at the peak rates but we will try to limit that by shifting dishwasher, washing machine, TV usage, etc. to the nights and weekends.

I'm wondering whether anyone in NY State (ConEd customers) with grid-tie solar systems have switched over to time of use metering and whether this has saved you additional money on electric bills? There really isn't any way for me to accurately test this in advance as I can only really track power usage once I have the new time-of-use meters installed. And once they're installed, I'll be on the new plan. ConEd says they will send me details on savings (or extra costs) in the TOU plan, plus I can also put together a savings spreadsheet for that once I start getting the usage numbers. I can cancel the time-of-use plan pretty quickly and go back to flat rate metering if it doesn't work out well, but then would not be able to switch back to time of use for 18 months.

So I know that those with larger solar arrays and low peak power usage generally save more by going with a time-of-use metering plan, but I'm wondering whether I'll see much benefit switching over in NY state with a smaller system, less usable sunlight (compared to SW US) and varying amounts of peak electricity usage.

Can anyone speak from experience or at least offer some suggestions or opinions?

Thanks,

-Chris

[Naptown]

Suggestion
If you have a smart meter and can get access to the use patterns of the house then certainly get them.
Now beware that if the TOU plan peaks during the summer in the afternoons then there may be peak times during the winter. Here in maryland the winter peak when they offered tou metering was peak was 6am-9AM mid was 9AM - 5 PM and peak was 5PM -9PM and low rate was 9PM-6AM
Think about what that scheme or a similar one if in effect would do to your costs.

[inetdog]

which brings me to my question...

I'm wondering whether it makes sense to switch over from flat metering to voluntary time-of-use metering with ConEd. ...
From my understanding, if we switch over to net time-of-use metering (from the current flat rate net metering), we'll be generating power at 30.27 cents/kWh during the day when our usage is low, and buying it back during the evenings and weekends at the lower rate. Of course we will have *some* usage at the peak rates but we will try to limit that by shifting dishwasher, washing machine, TV usage, etc. to the nights and weekends.
... I can cancel the time-of-use plan pretty quickly and go back to flat rate metering if it doesn't work out well, but then would not be able to switch back to time of use for 18 months.

So I know that those with larger solar arrays and low peak power usage generally save more by going with a time-of-use metering plan, but I'm wondering whether I'll see much benefit switching over in NY state with a smaller system, less usable sunlight (compared to SW US) and varying amounts of peak electricity usage.

Can anyone speak from experience or at least offer some suggestions or opinions?

Thanks,

-Chris

In California (PG&E land) there is no choice. All new grid-tie installations must use TOU metering, and in fact a TOU plan with partial peak times as well as peak and off-peak that seems to have been designed to reduce the advantages for solar PV (compared to the earlier optional plan with peak and off-peak only). Not as bad as the one that Naptown described though, since there is not as much early morning electric heat load to factor in here in Sunny CA. Summer AC is the name of the game out here. Fortunately I can get away with a swamp cooler where I am.

You will have to look at the exact times of the peak/off-peak switchover and compare them to your hourly production to be sure, but for almost everyone who is not home during the day the TOU plan will be a winner. If there is also a tiered rate plan based on the total amount of power you use, you stand to gain even more if your daytime production gets you into the high-rate tier (yes, they do apply it in reverse in CA!).
As long as you can save up your summer credits to apply them in winter, you should be in good shape.
Unfortunately it is hard to be sure without a year's experience and numbers to prove it.
Just because you have a small system is no reason that the TOU plan will not also work for you. As long as it is large enough to sell some power back above your peak period loads.

PS: A lot of heat-using appliances like dishwashers, washer/dryers, etc. now feature a delay timer feature that lets you set them to turn on during off-peak even when you are not home to do it manually.

PPS: How much do you want to be that the smart users in Maryland set their thermostats to heat the heck out of the house before 6am and then just coast until they leave for the day?

[Naptown]

PPS: How much do you want to be that the smart users in Maryland set their thermostats to heat the heck out of the house before 6am and then just coast until they leave for the day?

Guilty When we were on a tou basis.
We would also set the AC on refrigeration mode and coast through till the next low period.
Even considered putting the fridge and freezer on timers to prevent them from cycling during the generally 3-4 hours of peak time.

[Lomag]

From my understanding, if we switch over to net time-of-use metering (from the current flat rate net metering), we'll be generating power at 30.27 cents/kWh during the day when our usage is low, and buying it back during the evenings and weekends at the lower rate. Of course we will have *some* usage at the peak rates but we will try to limit that by shifting dishwasher, washing machine, TV usage, etc. to the nights and weekends.

I thought about this too but here in NJ you don't sell excess power back at the higher rate. Instead, you get a kwh for kwh credit for over production put into a "kwh bank". With the standard flat-rate plan you can draw from this bank at any time. Now, you can actually switch to a TOU plan but you would end up with 2 separate kwh banks, one bank for peak time and one bank for off-peak time. You can not draw from the peak bank during off-peak hours and visa-versa. So essentially, we'd always be buying power in the evenings costing real $$ because the off-peak bank would always be empty as solar doesn't produce in the evening and at night. You produce solar during peak time, but since most wouldn't be used, it'd go in the peak-bank. Unless we use the banked peak credits (during peak-hours), they would eventually get credited to us at the wholesale kwh rate and not the peak rate. I don't know what that is but probably something low like 5 cents per kwh. It makes no sense to switch to TOU given how it works here. I think NY might work this same way so be careful.

[MrBoylan]

Suggestion
If you have a smart meter and can get access to the use patterns of the house then certainly get them.
Now beware that if the TOU plan peaks during the summer in the afternoons then there may be peak times during the winter. Here in maryland the winter peak when they offered tou metering was peak was 6am-9AM mid was 9AM - 5 PM and peak was 5PM -9PM and low rate was 9PM-6AM
Think about what that scheme or a similar one if in effect would do to your costs.

NY (ConEd) seems to be 10 AM to 10 PM peak (weekdays), all year long (10 PM to 10 AM weekdays, and all times on weekends and holidays are off peak). The rates do change significantly during the fall/winter/spring months (September to May), when the peak delivery charge is only 10.98 cents/kWh (vs. 30.27 cents peak charge from June to September). And that's what I'm a little worried about - June and September. Even if we spend little time home during the day in July and August, those times when the wife and kids are home all day in the summer, they'll probably want to use the AC and maybe watch a little TV. And since we do not have time-of-use meters yet (and we don't have a smart meter), I really don't have a way to track usage by time of day, unless I install those power meter things on each outlet in the house.

I'm leaning toward switching over to TOU, will monitor the performance and see how it goes. We already blew in fresh insulation in the roof in the fall of 2011 and have been looking at other ways to conserve energy. I do have a Kill-o-watt which I plan to put on various outlets over the next few weeks to see where the real culprits are. I review and test electronic gear (Blu-ray players, TVs, DVRs, receivers, etc.) which can use a fair amount of power. I have two DVRs, two plasma TVs and a projector in the house now, along with a couple of receivers, etc. But we really use these more in the evenings and weekends, not so much during the day so I think switching to TOU will probably be a net benefit. Will definitely share my experiences here when I have some data.

Thanks for your reply.

-CB

[MrBoylan]

In California (PG&E land) there is no choice. All new grid-tie installations must use TOU metering, and in fact a TOU plan with partial peak times as well as peak and off-peak that seems to have been designed to reduce the advantages for solar PV (compared to the earlier optional plan with peak and off-peak only). Not as bad as the one that Naptown described though, since there is not as much early morning electric heat load to factor in here in Sunny CA. Summer AC is the name of the game out here. Fortunately I can get away with a swamp cooler where I am.

You will have to look at the exact times of the peak/off-peak switchover and compare them to your hourly production to be sure, but for almost everyone who is not home during the day the TOU plan will be a winner. If there is also a tiered rate plan based on the total amount of power you use, you stand to gain even more if your daytime production gets you into the high-rate tier (yes, they do apply it in reverse in CA!).
As long as you can save up your summer credits to apply them in winter, you should be in good shape.
Unfortunately it is hard to be sure without a year's experience and numbers to prove it.
Just because you have a small system is no reason that the TOU plan will not also work for you. As long as it is large enough to sell some power back above your peak period loads.

PS: A lot of heat-using appliances like dishwashers, washer/dryers, etc. now feature a delay timer feature that lets you set them to turn on during off-peak even when you are not home to do it manually.

PPS: How much do you want to be that the smart users in Maryland set their thermostats to heat the heck out of the house before 6am and then just coast until they leave for the day?

Yeah, we already use the timer on the dishwasher to run that at night. And being able to run the AC and clothes washer up until 10:00 AM should allow us to get creative in how we schedule tasks. (our dryer and heat are both on natural gas so not as applicable here).

I've also put in a bunch of CCFL lights where I can, but they don't work well with dimmers so I still have a *LOT* of incandescent bulbs, particularly for the open fixtures that are more decorative. If LED lights were cheaper, I'd say, "looks be damned" and buy a ton of those, but at $20-$25 a bulb, replacing all the incandescent bulbs in the house with LEDs would cost a fortune. If anyone knows of a good source for quality LED lights in bulk, please let me know. Meanwhile, anyone with hand-on experience in NY, please feel free to chime in!

Thanks,

-CB

[MrBoylan]

Guilty When we were on a tou basis.
We would also set the AC on refrigeration mode and coast through till the next low period.
Even considered putting the fridge and freezer on timers to prevent them from cycling during the generally 3-4 hours of peak time.

Interesting about the fridge idea. We could do that for our little fridge in the basement (rarely used) but if we do that on the main fridge, wouldn't the temperature vary too much, with all the opening and closing of the door?

-CB

[Naptown]

Interesting about the fridge idea. We could do that for our little fridge in the basement (rarely used) but if we do that on the main fridge, wouldn't the temperature vary too much, with all the opening and closing of the door?

-CB

If no one is there who will be opening the door?

[bonaire]

Your array is too small to make TOU work for the house (even if it is a small one). The TOU range of 10am to 10pm has 4-5 hours of peak time while you are home after work and school hours.

If you are net-metering at 8.89c / kWh, you will be fine. Spring/Fall, you may generate 4-5kWh day max on some good days.

Are you really paying 8.89c now or is that before delivery charge? How does your whole bill look in terms of all the per-kWh prices today? Factor in generation and delivery plus ancillary prices per kWh. 8.89/kWh delivered would be fantastic electric rates. In my area of SE PA, we are at about .17/kWh delivered.

Consider doing 2013 at your current rate, 2014 with TOU rate, compared, keep what's best.

[MrBoylan]

I thought about this too but here in NJ you don't sell excess power back at the higher rate. Instead, you get a kwh for kwh credit for over production put into a "kwh bank". With the standard flat-rate plan you can draw from this bank at any time. Now, you can actually switch to a TOU plan but you would end up with 2 separate kwh banks, one bank for peak time and one bank for off-peak time. You can not draw from the peak bank during off-peak hours and visa-versa. So essentially, we'd always be buying power in the evenings costing real $$ because the off-peak bank would always be empty as solar doesn't produce in the evening and at night. You produce solar during peak time, but since most wouldn't be used, it'd go in the peak-bank. Unless we use the banked peak credits (during peak-hours), they would eventually get credited to us at the wholesale kwh rate and not the peak rate. I don't know what that is but probably something low like 5 cents per kwh. It makes no sense to switch to TOU given how it works here. I think NY might work this same way so be careful.

I've had a couple of e-mails back and forth with the ConEd folks about it, but I think this is fairly new ground for them too. The rep said he *believes* it works the way I described it (selling back at peak rates for power generated at peak times), and referred me to a couple of massive documents which explain in more detail,. This was his most recent reply:

"Although I am not involved with the billing and crediting of net metering accounts, what you are saying is my understanding. Since there are some variations on how the service is set up, I would refer you to the Rider that pertains to net metering:

http://www.coned.com/documents/elecPSC10/GR24.pdf#nameddest=riderr

The time-of-use (TOD) rate as it pertains to net metering is referenced on leaf pages 250 and 251."

When I read those sections, it seems as if I will be credited at the TOU rate. Specifically this line leads me to believe that is the case:

"Any kWhr of net energy provided to the Company will be converted to the equivalent monetary value at the per-kWhr rate applicable to the Customer’s Service Classification"

Since my "service classification" should be TOU, I'm pretty sure I'll get credit at the TOU rate.

Will have to try it and see how it goes. I'm sure if it's too favorable, ConEd will change it.

-CB

[MrBoylan]

If no one is there who will be opening the door?

I meant year-round, but it makes more sense to do it just during the summer.

-CB

[MrBoylan]

Your array is too small to make TOU work for the house (even if it is a small one). The TOU range of 10am to 10pm has 4-5 hours of peak time while you are home after work and school hours.

Except when the family is away during parts of the the summer and I get home late from work. In those weeks, I could cut our peak electric usage down to almost nil.

If you are net-metering at 8.89c / kWh, you will be fine. Spring/Fall, you may generate 4-5kWh day max on some good days.

Should do a bit better than that. Yesterday the array generated 5.4 kWH. Good sun but not many hours of daylight. But cloudy/rainy days suck. I've had January days well under 1 kWh. The generation meter is network-connected (Sungevity) so I can see the generation in near real time. The current net meter is not, so I can only see that by physically looking at it or waiting for the bill.

Are you really paying 8.89c now or is that before delivery charge? How does your whole bill look in terms of all the per-kWh prices today? Factor in generation and delivery plus ancillary prices per kWh. 8.89/kWh delivered would be fantastic electric rates. In my area of SE PA, we are at about .17/kWh delivered.

No, that's the delivery charge only, not the supply charge. The delivery charge is all that ConEd will quote me since I have a different ESCO. I haven't gotten the supply rates yet from the ESCO but I'm assuming they will also vary once I switch over to TOU with ConEd (but have not confirmed that yet).

Consider doing 2013 at your current rate, 2014 with TOU rate, compared, keep what's best.

Thanks. That's a good suggestion. And I may go that route. But I could also switch over now and monitor TOU myself vs. what the flat rate would have been. Once I have the net TOU meters, I'll be able to compare the two plans and see which is better each month. ConEd also said they would do that on our bill. We can switch back just about immediately but then cannot switch to TOU again for 18 months. I guess they don't want people switching back and forth between TOU and fixed rate depending on when they go on vacation (which is exactly what I would do, given the chance!).

Thanks for the reply,

-Chris

[inetdog]

I've also put in a bunch of CCFL lights where I can, but they don't work well with dimmers so I still have a *LOT* of incandescent bulbs, particularly for the open fixtures that are more decorative. If LED lights were cheaper, I'd say, "looks be damned" and buy a ton of those, but at $20-$25 a bulb, replacing all the incandescent bulbs in the house with LEDs would cost a fortune. If anyone knows of a good source for quality LED lights in bulk, please let me know.
Thanks,
-CB

I am currently enthusiastic about the EcoSmart 864 680 which is currently for sale at Home Depot for $9.99. It is an A type bulb but with only a little over a half-sphere of light output. Somewhat directional even within that. But no glare, dims very well with a standard dimmer (but not a balanced dimming when on the same circuit as an incandescent or CFL), works in the cold, 3000K color temperature, tolerable CFI based on observation.
8 watts for 430 lumens, 40 watt incandescent replacement. Claims 46 year life at 3 hours per day, but only has a five year warranty.

They would look "different" in an open fixture, especially the aggressive heat sink portion, but not unattractive.
I also find that IKEA has a good selection of small sizes, etc. useful for fixtures that cannot take a full size A bulb. Both Medium base and Candelabra and Intermediate base. I hear that IKEA is discontinuing their CFL line in favor of LED units. Both are still available AFAIK.

[MrBoylan]

I am currently enthusiastic about the EcoSmart 864 680 which is currently for sale at Home Depot for $9.99. It is an A type bulb but with only a little over a half-sphere of light output. Somewhat directional even within that. But no glare, dims very well with a standard dimmer (but not a balanced dimming when on the same circuit as an incandescent or CFL), works in the cold, 3000K color temperature, tolerable CFI based on observation.
8 watts for 430 lumens, 40 watt incandescent replacement. Claims 46 year life at 3 hours per day, but only has a five year warranty.

They would look "different" in an open fixture, especially the aggressive heat sink portion, but not unattractive.
I also find that IKEA has a good selection of small sizes, etc. useful for fixtures that cannot take a full size A bulb. Both Medium base and Candelabra and Intermediate base. I hear that IKEA is discontinuing their CFL line in favor of LED units. Both are still available AFAIK.

Thanks for the tip. Not a bad price. In the kitchen, we currently have about 8 40-watt (or maybe 65-watt?) Incandescent spots in the high hats. These aren't on often, but when they are, they do suck up the power. Wondering how these LEDs would look in the hi-hats.

Gotta see if I can rustle up some PR contacts at Philips to maybe send me some "review samples" of their LED lights.