Time of Use Bill Credits with SCE

[silversaver]

The #'s seem consistent, at least for 01/05 and 01/06.
Also, I'd suggest, without being too much of a rectum, that most every system in the northern hemisphere has its lowest production in winter.

Sorry, I meant to say East facing arrays tends to output little more than West facing arrays during Winter (My arrays were more close to the West. I do know the winter has lowest production of the year.)

[J.P.M.]

anyone care to show how his or her arrays looks like? and inverter placement?

My panels are on the roof, 4 X 4, landscape next to the solar water heater. Inverter is in the garage just about under the array. No A.M shading all year. Minor shade, say 50% of hourly output penalty after 3 P.M. solar time 12/21. No appreciable P.M. shade until about 11/15 to 01/25 or so. Estimate yearly shading penalty ~~1-1.5% or less using TMY3 data.

I'm sort of a Luddite, so I only have a brownie for pictures.

[silversaver]

My panels are on the roof, 4 X 4, landscape next to the solar water heater. Inverter is in the garage just about under the array. No A.M shading all year. Minor shade, say 50% of hourly output penalty after 3 P.M. solar time 12/21. No appreciable P.M. shade until about 11/15 to 01/25 or so. Estimate yearly shading penalty ~~1-1.5% or less using TMY3 data.

I'm sort of a Luddite, so I only have a brownie for pictures.

Got it. What do you think of my system. The arrays were facing SW 245, so I place the top panels to the right side to avoid chimney shadow.

[J.P.M.]

Sorry, I meant to say East facing arrays tends to output little more than West facing arrays during Winter (My arrays were more close to the West. I do know the winter has lowest production of the year.)

I'd suggest it depends more on where you are. A.M. coastal fog or just A.M clouds in general will penalize east facing, tend to give west facing greater production than east facing and make south facing more productive in the afternoon. Consistent or no temporal cloud pattern may tend to favor A.M. production slightly due to likely lower A.M. ambient temps. Maybe east facing would have a slight advantage there, but I wouldn't hang my hat on it. June gloom as is common in So. CA makes for low production A.M to mid afternoon - sometimes all day. A south facing array without a clear, consistent cloud regime, i.e., a random pattern, will likely see about the same hourly output for morning hours as afternoon hours with maybe some adjustment for temp./wind. I believe it's mostly the cloud patterns themselves, not the solar position or season. Plug your system into SAM and see the difference. Using TMY data, my ideal azimuth for the S.P.'s is about 186 deg. - a tad more south for panels w/ higher eff. penalties/deg. C., but I'm separating fly specks from pepper now. I think most of the off south optimum for me is mostly due to A.M. clouds being more common than P.M. clouds around here. Ideal azimuth for my stuff is also a weak function of elevation (tilt), but not easy to describe in a few words. Overall, getting as close to dead south as possible is probably still best.

[J.P.M.]

Got it. What do you think of my system. The arrays were facing SW 245, so I place the top panels to the right side to avoid chimney shadow.

Last picture's kind of sunny for 12:20 A.M.

[silversaver]

BSR,

I just switched to TOU-DT using SCE. My smart meter was installed about a month ago but my hourly usage tracking just went live a few days ago. As such what I'm stating here is what I understand it to be, but I have no real-world TOU billing experience so far.

Quick background - I had the system installed in March 2011 and it generated about 10,300 kWh for the year. This offset almost all of my usage for the year and I was at a surplus for most of spring/summer. I got a rude awakening when I realized that the credits I got on a monthly basis were the tier 1 rate (or something similarly miniscule) multiplied by my surplus for that specific month - usually something like $10.00. In the winter months when I didn't generate much I got into Tier 4 territory and paid that fare and had back to back bills in excess of $200 each (lower than my bills pre solar, but still more than I wanted to pay). I know life isn't fair, but it seemed like BS that I'm getting paid $0.05 when they really need my electricity in the height of summer and then charge me $.25 when I use it at night in the winter to heat and light up my house.

Because I couldn't roll my summer generation into credits for the winter I decided to explore TOU since I perceive that will effectively do that, and here is why. I believe that TOU Level 1 / Level 2 apply both for the generation and the usage. I don't recall what level 1 is, but I think it's something like 260kwh. Assuming that is right, if you generated under 260kwh during peak hours in the summer you would get paid $.1934 for each kwh. However if you generated anything above 260kwh you would get paid the $.5234. Because of this the credits can theoretically be larger in the summer, and those can be used to offset the higher winter bills.

Yesterday (the 14th) I generated 25.6kwh during the peak hours and used 19 off peak. I created a quick spreadsheet that shows how I think it could play out if each and every day were the same. Recognizing I don't think "Summer" has started yet, I used the summer pricing. You need to remember that Sat/Sun are off peak, so that daytime generation that is usually during peak hours is actually off peak. My 4.33 multiplier was trying to take the weekly and convert to monthly. I also took a quick guess at Winter usage with those rates rounded to the nearest cent (I only jotted them down once). Clearly in the height of summer we'll probably use the AC more, and in the dead of winter perhaps more heat, but here is my guess at how the bill could work. It's late now and I need to get to bed, so it's possible this version has a major error I didn't see yet. If anything jumps out at you (or anybody else viewing it) let me know.

https://docs.google.com/spreadsheet/ccc?key=0As5_Lei9YFCCdGIwNGVIRXNmT2w1R09mWWNBWlZDRmc

Derek

hmm I need to look into this....

[inetdog]

In Northern CA, (PG&E land) the usage credit is zeroed out once per year, but the date at which that happens can be selected by the customer.
The effect is that you can choose between banking usage during the winter and offsetting it the following summer or banking production during the summer and using it to offset the following winter's usage.
Even though the rate structure may change during the year, the balancing happens on a dollar basis rather than a kWh basis.

If SCE is doing it differently, they may not be complying with California's Net Metering laws.

If you first put you installation into operation in the winter and the account balancing date is less than a year out for some reason, then you could have a problem the first year only.

[Bubbletips]

What system size for TOU with sce?

My main question is what is most cost effective - to buy enough solar panels to zero my bill or just to cover my non super off peak hours.

I have an electric vehicle on the TOU plan with SCE.

My rate plan and kWh usage is as follows:
Winter Peak (12p-6p): Lvl 1 $0.16 x 30 kWh, lvl 2 $0.36 x. 50 kWh
Winter off peak (6a-12p, 6p-12a) Lvl 1 $0.11 x 110kWh, lvl 2 $0.30 x 220kWh
Winter super off peak (12am-6am). $0.10 x 700kWh

Summer peak : Lvl 1 $0.28 x 30 kWh, lvl 2 $0.47 x 55 kWh
Summer off peak: Lvl 1 $0.12 x 110 kWh, lvl 2 $0.32 x 215kWh
Summer super off peak: $0.10 x 700 kWh


My electricity usage doesn't vary much between summer and winter.
My average electric bill is almost $200. About 60% of my kWh usage is for the electric car. The remaining
$80 electric bill comes from the electric tiers listed above.


Finally, because my electric bill is so low for my non-super off peak usage, would this be equivalent to a home owner with an electric bill of $80 who asks about buying solar panels? Does it still make sense for me to look into solar?

I understand that with TOU net metering, there is a bigger payback if you buy a larger system because SCE credits you with tier 1 credits (130% off baseline) before paying you the more expensive tier 2 credits.

Much thanks.


-Tom

[silversaver]

My main question is what is most cost effective - to buy enough solar panels to zero my bill or just to cover my non super off peak hours.

I have an electric vehicle on the TOU plan with SCE.

My rate plan and kWh usage is as follows:
Winter Peak (12p-6p): Lvl 1 $0.16 x 30 kWh, lvl 2 $0.36 x. 50 kWh
Winter off peak (6a-12p, 6p-12a) Lvl 1 $0.11 x 110kWh, lvl 2 $0.30 x 220kWh
Winter super off peak (12am-6am). $0.10 x 700kWh

Summer peak : Lvl 1 $0.28 x 30 kWh, lvl 2 $0.47 x 55 kWh
Summer off peak: Lvl 1 $0.12 x 110 kWh, lvl 2 $0.32 x 215kWh
Summer super off peak: $0.10 x 700 kWh


My electricity usage doesn't vary much between summer and winter.
My average electric bill is almost $200. About 60% of my kWh usage is for the electric car. The remaining
$80 electric bill comes from the electric tiers listed above.


Finally, because my electric bill is so low for my non-super off peak usage, would this be equivalent to a home owner with an electric bill of $80 who asks about buying solar panels? Does it still make sense for me to look into solar?

I understand that with TOU net metering, there is a bigger payback if you buy a larger system because SCE credits you with tier 1 credits (130% off baseline) before paying you the more expensive tier 2 credits.

Much thanks.


-Tom

Hi Tom,

I'm in Orange County as well. We are in baseline region 8 which Summer 10.1kwh per day and Winter 9.2 kWh per day. I have the same concern as you, "which plan is better for me and how big should I get". I know I will be getting an EV before the year ends and I need 15k miles per year which is about 4800kWh per year. Before you even think about the TOU-EV plan, you have to know how big of system your roof can handle + where do your roofs facing? We know the peak hours are 10 to 6pm. Lets say if you have your solar panels facing Northeast and Southeast like my neighbor, The TOU will not work for you because majority of solar production will be before 1pm and TOU will not work for you. It will be best to say in regular tier net metering. Take a look at your TOU-EV plan, once you go over 130% of baseline, the rate are much higher even at off peak rate (I find that is hard to believe and that is how the SCE gets you).

I plan my solar that cover 100% of my current usage (that is as large as you can get anyway....) My electricity demand go up every year from last 3 years. I'm not going into detail how you calculate ROI....etc, but one simple idea -- use the baseline to cover EV. If your solar is big enough, you don't really have to worry about how SCE change the rate plan since you are only usng their tier 1 rate.

Yes, you can alway add more panels to your solar system, but you don't really want to go that route. You can only add 10% or <1Kw without getting permit again and contact utilities. Price? SUPER HIGH!!!

PS. The only good thing that SEC change the peak hours from 12 to 6 to 10 to 6pm actually benefits some East facing solar systems.

[inetdog]

You can only add 10% or <1Kw without getting permit again and contact utilities. Price? SUPER HIGH!!!

I think that this is a local decision. According to most building codes any change to the system other than maintenance, even if it only adds less than 10% capacity would still require a permit.
And if the POCO knew about it, many would want a new inspection and interconnect agreement even for a small percent change too.

[J.P.M.]

I think that this is a local decision. According to most building codes any change to the system other than maintenance, even if it only adds less than 10% capacity would still require a permit.
And if the POCO knew about it, many would want a new inspection and interconnect agreement even for a small percent change too.

Also, maybe not worth considering just yet, but with an eye to possible future expansion (perhaps way down the road and still a long way from any firm direction), AB 327 will probably have something to say about how much expansion can be grandparented into the net metering qualification for an existing system. A 10% additional limit is being bandied about just now, for systems installed prior to 2017, but who knows ?

[fengshui]

My main question is what is most cost effective - to buy enough solar panels to zero my bill or just to cover my non super off peak hours.

I have an electric vehicle on the TOU plan with SCE.

My rate plan and kWh usage is as follows:
Winter Peak (12p-6p): Lvl 1 $0.16 x 30 kWh, lvl 2 $0.36 x. 50 kWh
Winter off peak (6a-12p, 6p-12a) Lvl 1 $0.11 x 110kWh, lvl 2 $0.30 x 220kWh
Winter super off peak (12am-6am). $0.10 x 700kWh

Summer peak : Lvl 1 $0.28 x 30 kWh, lvl 2 $0.47 x 55 kWh
Summer off peak: Lvl 1 $0.12 x 110 kWh, lvl 2 $0.32 x 215kWh
Summer super off peak: $0.10 x 700 kWh


My electricity usage doesn't vary much between summer and winter.
My average electric bill is almost $200. About 60% of my kWh usage is for the electric car. The remaining
$80 electric bill comes from the electric tiers listed above.

Finally, because my electric bill is so low for my non-super off peak usage, would this be equivalent to a home owner with an electric bill of $80 who asks about buying solar panels? Does it still make sense for me to look into solar?

I understand that with TOU net metering, there is a bigger payback if you buy a larger system because SCE credits you with tier 1 credits (130% off baseline) before paying you the more expensive tier 2 credits.

You can calculate this with an excel spreadsheet (I just finished mine), but the long and short of it is that the payback for the incremental cost of solar power generation capacity used to charge an EV is really long due to the low cost of that power, and the high value you get for mid-day power on the EV-TOU plan. However, that doesn't apply if SCE eliminated EV-TOU.

Personally, I'm sizing my system to cover about 10% more than my usage excluding the Super-Off-Peak hours. If SCE drops the EV-TOU rate, I'll probably have to expand my system, but I'm willing to take that risk, because the alternate for me is to jump to Sunpower or install onto an older roof that may need replacing during the lifetime of the panels. I'll evaluate what the environment is for expanding my system when it's time to redo the roof.

For you, I'd probably scope a system to cover 100% of your peak and off-peak, and 33% of your Super-Off-Peak usage, plus a 10% cushion for degredation. That would hopefully mean you'd generate enough credits during the day at $0.30+/kWh to offset all of your Super-Off-Peak power.

One data point you may find useful is that Tier 1 kWh are split based on usage amongst Peak, Off-Peak and Super-Off-Peak, so when you generate during Peak, you'll have to push through about half of your low-paying Tier 1 kWh before you're in the high-paying Tier 2. Not too bad, and the rough reason I used a blend on Tier 1 and 2 rates when calculating the correction factor for sizing the array for EV use.

Does that all make sense?

[Bubbletips]

You can calculate this with an excel spreadsheet (I just finished mine), but the long and short of it is that the payback for the incremental cost of solar power generation capacity used to charge an EV is really long due to the low cost of that power, and the high value you get for mid-day power on the EV-TOU plan. However, that doesn't apply if SCE eliminated EV-TOU.

Personally, I'm sizing my system to cover about 10% more than my usage excluding the Super-Off-Peak hours. If SCE drops the EV-TOU rate, I'll probably have to expand my system, but I'm willing to take that risk, because the alternate for me is to jump to Sunpower or install onto an older roof that may need replacing during the lifetime of the panels. I'll evaluate what the environment is for expanding my system when it's time to redo the roof.

For you, I'd probably scope a system to cover 100% of your peak and off-peak, and 33% of your Super-Off-Peak usage, plus a 10% cushion for degredation. That would hopefully mean you'd generate enough credits during the day at $0.30+/kWh to offset all of your Super-Off-Peak power.

One data point you may find useful is that Tier 1 kWh are split based on usage amongst Peak, Off-Peak and Super-Off-Peak, so when you generate during Peak, you'll have to push through about half of your low-paying Tier 1 kWh before you're in the high-paying Tier 2. Not too bad, and the rough reason I used a blend on Tier 1 and 2 rates when calculating the correction factor for sizing the array for EV use.

Does that all make sense?

Fengsui, everything you said makes sense.
I had believed that the payback replacing my super off peak electricity with solar panels would be slow because the cost difference of between super off peak electricity vs. solar is small. So by using this premise, I agree that I should only replace only my peak and nonpeak electricity with solar. I have been quoted a system with a break even point after 8 years.

However, another way to look at the problem is if I size my system to cover about 75% of my electric bill ($200). Then even though my superoff peak rate is so low, I still spend about $80 for the super off peak electricity. If I increase my system size to try to also cover the super off peak time also, I can STILL BREAK EVEN in about 8 years. The main differences between going with small vs. larger system is that after the 8 years, I will have a bill much closer to zero from SCE but had to payout more for a larger system. Also, with a larger system, the TOU plan is less important as you produce a 1:1 kWh for the electricity that you use vs. the electricity that you make. Please correct me if any of my statements do not seem sound.

Thank you fengshui for your conclusions from your spreadsheet, as I'm not as mathematically inclined for precise calculations.

I am leaning towards Sun power panels for aesthetics as my roof is very visible to the neighbors, and I am near 40 and don't want to have to repurchase solar again.

[J.P.M.]

You can calculate this with an excel spreadsheet (I just finished mine), but the long and short of it is that the payback for the incremental cost of solar power generation capacity used to charge an EV is really long due to the low cost of that power, and the high value you get for mid-day power on the EV-TOU plan. However, that doesn't apply if SCE eliminated EV-TOU.

Personally, I'm sizing my system to cover about 10% more than my usage excluding the Super-Off-Peak hours. If SCE drops the EV-TOU rate, I'll probably have to expand my system, but I'm willing to take that risk, because the alternate for me is to jump to Sunpower or install onto an older roof that may need replacing during the lifetime of the panels. I'll evaluate what the environment is for expanding my system when it's time to redo the roof.

For you, I'd probably scope a system to cover 100% of your peak and off-peak, and 33% of your Super-Off-Peak usage, plus a 10% cushion for degredation. That would hopefully mean you'd generate enough credits during the day at $0.30+/kWh to offset all of your Super-Off-Peak power.

One data point you may find useful is that Tier 1 kWh are split based on usage amongst Peak, Off-Peak and Super-Off-Peak, so when you generate during Peak, you'll have to push through about half of your low-paying Tier 1 kWh before you're in the high-paying Tier 2. Not too bad, and the rough reason I used a blend on Tier 1 and 2 rates when calculating the correction factor for sizing the array for EV use.

Does that all make sense?

FWIW, makes a lot of sense to me. How do you figure your electric load as a function of time, if at all ? How does SCE break down ? Do you have your usage history as f(time) ?

[fengshui]

FWIW, makes a lot of sense to me. How do you figure your electric load as a function of time, if at all ? How does SCE break down ? Do you have your usage history as f(time) ?

If you have a Smart Meter, you can download hourly data for the past 13 months from SCE.com. Login and hit the Green Button download on the left side of the screen. You'll get a CSV file you can import into Excel. The date fields in that file will need to be transformed using DATEVALUE into fields that Excel understands as dates, but once that's done you can create a pivot table that aggregates all the data together by month and hour.

From there, you have lots of options. PVWatts will also give you projected production of a solar system on an hourly basis for your location, which is great for combining with your historical usage data to create projected net usage.