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Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 11:20 am
by philip
sub3marathonman wrote:
OK, once again, I'm not from California, but I'd appreciate a bit further explanation about this. :oops:

I understand that ttweed ended up using 600kwh over the year, so he is a NET consumer of power. I understand what has been said that much more power could have been used without any financial impact to ttweed.

So the credit of ttweed's kwh (@ $0.04/kwh) sent to the grid went to offset the minimum $120/year charge. I think I'm understanding that.


In California, we have the choice of time of use or tiered billing (for the Investor owned utilities anyways). If you are on TOU, then the utility tracks both the retail dollar amount of NET generation plus the energy usage amount. The only time you will receive the ~.04/kWh generation credit is if you are a NET producer over the true up period. The retail amount that is tracked can only be used against energy purchases in the same true up period - if you have a credit at true up, you lose it.

sub3marathonman wrote:So why didn't ttweed get any further credit or payment for the other $550 of electricity (even @ $0.04/kwh) that was sent back? If the power company didn't get it from him, they would have had to purchase it somewhere else.


This is correct - he produced it and was not compensated for it in any way. So he could of had a smaller PV system and lowered his capital expense.

sub3marathonman wrote:And what would have happened if ttweed used 700kwh less, and was not a NET consumer of power?


He would get a generation credit for the 97 kWh he over produced - ~$4.00

sub3marathonman wrote:I will say, from my perspective, that the power company has a sweet deal there in this situation, as there was no usage at all during peak times, and the PV sent huge amounts, 2.5MW, of power back to the grid at the most critical times. Here in Florida, it is always being stated that PV customers are somehow taking advantage of the power company because the sun doesn't shine at night, but in my opinion it only matters if the sun is shining during peak periods, where by definition somebody with PV generation will use less, or even send back to the grid, as opposed to another customer who runs his dryer, A/C, and arc-welder during peak times because TOU rates are not the norm.


It is more complicated than that and depends on the time of the year.

In California, PV has pushed the peak into the afternoon/evenings. A lot of this has to do with utility-scale solar farms and lesser to residential rooftop PV. In fact, the grid-scale farms have to curtail production during the middle of the day at this time of the year due to over-production/low demand - yet at the same time residential NET metering customers are "selling" this power to the grid at peak rates. Residential installs do not have the capability to curtail production, so the utility "must take" the power generated from NET metering customers.

FWIW, the California IOUs have or are in the process of changing the peak times to the afternoon/evenings.

You can look at the current demand on the CA ISO page. If you scroll down to the NET demand chart, the green line shows what the traditional power plants are providing - look at the big dip in the chart in the middle of the day (for this time of year) - a lot of traditional plants have to go idle, which raises their net operating cost. Residential PV is "behind the meter" so it shows up as reduced demand on these charts. The solar shown is the utility scale plants.

http://www.caiso.com/Pages/TodaysOutlook.aspx

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 11:25 am
by davewill
sub3marathonman wrote:...
So the credit of ttweed's kwh (@ $0.04/kwh) sent to the grid went to offset the minimum $120/year charge. I think I'm understanding that.

So why didn't ttweed get any further credit or payment for the other $550 of electricity (even @ $0.04/kwh) that was sent back? If the power company didn't get it from him, they would have had to purchase it somewhere else.

...

The $0.04/kWh only comes into play if you are a net contributor of power. Under the net metering rules, that is the only way you ever get paid by the utility. It makes some sense. The TOU rates and net metering have more to do with incentivizing behavior than they do with economics. If it were economically based, a consumer would get credited (and reimbursed) at whatever wholesale rates were in effect at any given time. Instead net metering happens at retail rates, the trade-off being that you don't get reimbursed for overproduction at retail (or even really wholesale) rates.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 11:45 am
by ttweed
Thanks for the help in understanding my true-up bill, you guys! I suppose I should call SDG&E and ask them to explain it all, but I'm happy with the overall result, regardless. Sunrun did seem to make a good estimate of our generation vs. usage, which they revised at the last minute, BTW. Our original design showed 19 panels for a 5 Kw system, and when they arrived for the installation, they installed 21 panels for a 5.5 Kw total. I think they must have reconsidered our peculiar micro-climate and upped the capacity in order to meet their power guarantee. As it turned out, the system cost me $2.36/watt, and they have to monitor, insure, and maintain it for 20 years, and pay me if it doesn't produce what they promised.

At any rate, it looks like I can maybe be less concerned about charging the Leaf only at Super Off-peak times, a practice which I have always been very diligent in maintaining? I guess I can feel free to charge it in the middle of the day if need be from now on, if I am ending up with a total cumulative credit which I didn't use and isn't providing me any benefit?

I doubt we will increase our electric usage much unless we start using some electric space heating during the winter (the back bathroom does get a little too cold at times for my wife), or we buy one of the new 200-mile range EVs next year and start driving it more than the Leaf. I test drove one of the Bolts at the auto show this year and it was pretty tempting, but I'm waiting to see what Nissan, Tesla, and VW do in the next year or two.

Thx,
TT

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 12:00 pm
by philip
ttweed wrote:At any rate, it looks like I can maybe be less concerned about charging the Leaf only at Super Off-peak times, a practice which I have always been very diligent in maintaining? I guess I can feel free to charge it in the middle of the day if need be from now on, if I am ending up with a total cumulative credit which I didn't use and isn't providing me any benefit?


Yeah in your case, if your LEAF needs a charge, charge it. You have plenty of excess production for it. As you probably know, there is little difference from super off peak and off peak anyways. - If I need a charge during off-peak, then I do it. For you, you could even charge during peak during the summer - probably 100 times and not change your bill.

In my case, I never charge on-peak in summer, since it is cheaper to drive on fossil fuels with the ridiculously high peak rate. When I leased my first LEAF I did not have solar as I didn't consider it cost effective - the summer on-peak back then was .27/kWh. When SDG&E raised the peak to .49/kWh - that changed the economics. I think I could run a diesel gen-set for less than that. :roll:

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 3:22 pm
by sub3marathonman
philip wrote:
sub3marathonman wrote:
OK, once again, I'm not from California, but I'd appreciate a bit further explanation about this.


In California, we have the choice of time of use or tiered billing (for the Investor owned utilities anyways). If you are on TOU, then the utility tracks both the retail dollar amount of NET generation plus the energy usage amount. The only time you will receive the ~.04/kWh generation credit is if you are a NET producer over the true up period. The retail amount that is tracked can only be used against energy purchases in the same true up period - if you have a credit at true up, you lose it.
...
When SDG&E raised the peak to .49/kWh - that changed the economics. I think I could run a diesel gen-set for less than that. :roll:


Thank you phillip, your entire explanation, as well as your other statements here, were a huge help in understanding it! It is not broken down by peak, off-peak, and super-off-peak.

Do all PV installations have to be on a certain rate (TOU2)? I wasn't sure if ttweed had a choice of the tiered billing, and if so I suppose it would have come out owing more money. Are there any residential demand rates? I didn't immediately see any when I looked.

I'm now wondering if you (phillip) have installed PV at your location, since the economics have shifted so.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 3:25 pm
by SageBrush
Phillip is right -- ttweed was a net consumer of electricity so there were no kWh credited at 4 cents per.
The credit accrued from kWh's sent back to the utility during peak and shoulder being worth more than a kWh consumed at night.

Look at this example (not the actual rates of ttweed):
peak: 20 cents per kWh
shoulder: 15 cents per kWh
night: 10 cents per kWh

Say
3 peak kWh generated, one used
1 shoulder kWh generated, 2 used
1 night used

Net zero use,
but generation worth 3*20 + 1*15 = 75 cents
Consumption cost 1*20 + 2*15 + 1*10 = 60 cents

That 15 cent credit could be used for
0.75 kWh extra peak consumption; or
1.0 kWh extra shoulder consumption; or
1.5 kWh extra night consumption

Addendum: Phillips says that the credits car only be used in the same peak/shoulder/night periods they accrued in.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 3:56 pm
by SageBrush
philip wrote:It is more complicated than that and depends on the time of the year.

In California, PV has pushed the peak into the afternoon/evenings. A lot of this has to do with utility-scale solar farms and lesser to residential rooftop PV. In fact, the grid-scale farms have to curtail production during the middle of the day at this time of the year due to over-production/low demand - yet at the same time residential NET metering customers are "selling" this power to the grid at peak rates. Residential installs do not have the capability to curtail production, so the utility "must take" the power generated from NET metering customers.

FWIW, the California IOUs have or are in the process of changing the peak times to the afternoon/evenings.

You can look at the current demand on the CA ISO page. If you scroll down to the NET demand chart, the green line shows what the traditional power plants are providing - look at the big dip in the chart in the middle of the day (for this time of year) - a lot of traditional plants have to go idle, which raises their net operating cost. Residential PV is "behind the meter" so it shows up as reduced demand on these charts. The solar shown is the utility scale plants.

http://www.caiso.com/Pages/TodaysOutlook.aspx

These utility scenarios of energy sources are in flux, and not just from renewables coming online. Currently hydro is running at about the same load throughout the day, and some 20% of CA energy is a mixture of nuclear and coal imports. My guess is that CA will not renew their contracts with the exporters as they expire, and in the near future hydro will be used for the early evening load not covered by PV.

I know that plans in my area of the SW United States are to close some coal plants in the next ~ 5 years and I'm reasonably sure the driver is anticipated drop in exports.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 9:16 pm
by philip
sub3marathonman wrote:Do all PV installations have to be on a certain rate (TOU2)? I wasn't sure if ttweed had a choice of the tiered billing, and if so I suppose it would have come out owing more money. Are there any residential demand rates? I didn't immediately see any when I looked.

I'm now wondering if you (phillip) have installed PV at your location, since the economics have shifted so.


No they do not have to be time of use. We have a choice of tiered, solar TOU and EV TOU. ttweed and I are both on EV-TOU2, which basically means that we have one meter for both our homes and EV charging and we get a "super" off-peak rate that is for EV charging between 12am and 5am.

I have a 5.7KW PV system - been running for almost two years. It generates about 70% of our energy use over the year, but our bill is near zero due to time of use.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 9:19 pm
by philip
SageBrush wrote:Addendum: Phillips says that the credits car only be used in the same peak/shoulder/night periods they accrued in.


Not sure where I said that - maybe I was unclear somewhere, but, in California, credits generated in one period can be used in another through-out the 1 year true up period.

Re: SDG&E, Solar, Net Metering, and Time of Use 2 (TOU2)

Posted: Mon Apr 10, 2017 9:23 pm
by philip
SageBrush wrote:These utility scenarios of energy sources are in flux, and not just from renewables coming online. Currently hydro is running at about the same load throughout the day, and some 20% of CA energy is a mixture of nuclear and coal imports. My guess is that CA will not renew their contracts with the exporters as they expire, and in the near future hydro will be used for the early evening load not covered by PV.

I know that plans in my area of the SW United States are to close some coal plants in the next ~ 5 years and I'm reasonably sure the driver is anticipated drop in exports.


I don't think we import coal power anymore, we do import quite a bit of hydro from the PNW - in fact there is a HVDC line that runs from Washington all the way to LA for this. Pretty interesting circuit if you have time to read up on it- it has the ability to use ocean/ground as a return path. Our in-state nuclear is down to about 2 GWs now, for better or worse...