CSI EPBB Calculator Question

[bando]

Like I said, I prefer larger system because I know I will NEED it. EV car will take about 4800kWh for 15k miles per year. In reality, my system is too small for my demand.

same here. we will need probably 4,000 more kwh for an EV, although this whole TOU thing is making me wonder if we will even need the extra production. for SDGE you can start TOU once you take delivery of an EV, and apparently the math on the combination of solar production during peak hours and TOU rates can be really powerful. i haven't delved into the details however if you get peak credits and then use mostly off peak kwh, that may be enough to offset the extra kwh the EV needs ... which essentially means that TOU customers with solar and EV are literally able to charge for nothing. i haven't studied it enough however, and will wait until after tax season to figure it all out.

[silversaver]

same here. we will need probably 4,000 more kwh for an EV, although this whole TOU thing is making me wonder if we will even need the extra production. for SDGE you can start TOU once you take delivery of an EV, and apparently the math on the combination of solar production during peak hours and TOU rates can be really powerful. i haven't delved into the details however if you get peak credits and then use mostly off peak kwh, that may be enough to offset the extra kwh the EV needs ... which essentially means that TOU customers with solar and EV are literally able to charge for nothing. i haven't studied it enough however, and will wait until after tax season to figure it all out.

I wont worry about it now, I'll figure it out before my EV arrives. ETA Summer of 2014.

http://www.mbusa.com/mercedes/future/model/model-B_Class_Electric_Drive

[Volusiano]

same here. we will need probably 4,000 more kwh for an EV, although this whole TOU thing is making me wonder if we will even need the extra production. for SDGE you can start TOU once you take delivery of an EV, and apparently the math on the combination of solar production during peak hours and TOU rates can be really powerful. i haven't delved into the details however if you get peak credits and then use mostly off peak kwh, that may be enough to offset the extra kwh the EV needs ... which essentially means that TOU customers with solar and EV are literally able to charge for nothing. i haven't studied it enough however, and will wait until after tax season to figure it all out.

I have an EREV (Chevy Volt) right now and it takes roughly about 13 kwh to charge up an empty battery (the battery allows about 11 kwh storage, but I throw in a couple kwh for charging inefficiency as well as keeping the battery cool in the summer while plugged in). I get an average of about 45 mile range per full charge. That gives me about 3457 kwh per year if I drive 12K miles per year.

It seems like you're under the impression that you will only have 1 combined bucket of credits for TOU since you're implying that the on-peak credits has higher "value", therefore allows you to draw more lower value off-peak credits from the same bucket. But usually the reality doesn't work that way. You may want to double check with SDGE to make sure that what you're thinking is correct. Usually the reality is that if you're on TOU, you'll have 2 credit buckets to manage, an on-peak bucket and an off-peak bucket (at least that's how it is here in AZ with SRP and APS). On-peak solar production goes into the on-peak credit bucket, and off-peak solar production goes into the off-peak credit bucket. During on-peak hours, you can only draw from the on-peak credit bucket. Same with off-peak hours -> draw from off-peak bucket only. Therefore the "value" of each bucket is irrelevant because you don't get to cross share them anyway. When you roll over from month to month, the 2 buckets still get maintained separately. The bottom line is that you don't get to "save" high-value on-peak credits to use during off-peak hours with more off-peak usage because the value of the on-peak credits is worth more.

[bando]

I have an EREV (Chevy Volt) right now and it takes roughly about 13 kwh to charge up an empty battery (the battery allows about 11 kwh storage, but I throw in a couple kwh for charging inefficiency as well as keeping the battery cool in the summer while plugged in). I get an average of about 45 mile range per full charge. That gives me about 3457 kwh per year if I drive 12K miles per year.

It seems like you're under the impression that you will only have 1 combined bucket of credits for TOU since you're implying that the on-peak credits has higher "value", therefore allows you to draw more lower value off-peak credits from the same bucket. But usually the reality doesn't work that way. You may want to double check with SDGE to make sure that what you're thinking is correct. Usually the reality is that if you're on TOU, you'll have 2 credit buckets to manage, an on-peak bucket and an off-peak bucket (at least that's how it is here in AZ with SRP and APS). On-peak solar production goes into the on-peak credit bucket, and off-peak solar production goes into the off-peak credit bucket. During on-peak hours, you can only draw from the on-peak credit bucket. Same with off-peak hours -> draw from off-peak bucket only. Therefore the "value" of each bucket is irrelevant because you don't get to cross share them anyway. When you roll over from month to month, the 2 buckets still get maintained separately. The bottom line is that you don't get to "save" high-value on-peak credits to use during off-peak hours with more off-peak usage because the value of the on-peak credits is worth more.

thanks Volusiano for the info on your experience with TOU. Yes, that is EXACTLY what i will be asking them about when we decide to get an EV. i have not yet looked into the use/production "buckets" for TOU customers in the SDGE territory and how it works. if it does works the same way as yours , then i don't see how it will benefit me if i am pretty much going to stay with Tier 1 and Tier 2 most of the year, which are 16c and 18c. it seems like with our potential overproduction we may not touch Tier 3 (even AFTER charging 350 kwh/mo) in the summer, so i'm not sure how TOU is supposed to benefit solar users that have full or near-full offset, when the TOU peak rate is ~ 26c. i guess it will depend how much energy we consume in the winter months too, and how far the EV charging pushes us into Tier 3 those times of the year.

this comes from SDGE's NEM page however i don't know how it would tie into TOU:

Weighing the Financial Benefits

The price of energy is much higher during on-peak hours, especially during the summer months, when your system typically produces maxiumum electricity. This means that every excess kilowatt-hour your system generates is credited to your account at the higher rate during the on-peak period.

If you reduce your energy usage during the on-peak period, your solar system sends the excess energy to the grid and you get credited for this. The higher credits you receive can offset the cost of electricity during times when you may need electricity from the grid.

If you use more on-peak electricity than your system produces, you’ll be charged the higher rate for the energy you use. It’s possible your bill could end up being higher than it would have been under the standard residential rate.

[silversaver]

thanks Volusiano for the info on your experience with TOU. Yes, that is EXACTLY what i will be asking them about when we decide to get an EV. i have not yet looked into the use/production "buckets" for TOU customers in the SDGE territory and how it works. if it does works the same way as yours , then i don't see how it will benefit me if i am pretty much going to stay with Tier 1 and Tier 2 most of the year, which are 16c and 18c. it seems like with our potential overproduction we may not touch Tier 3 (even AFTER charging 350 kwh/mo) in the summer, so i'm not sure how TOU is supposed to benefit solar users that have full or near-full offset, when the TOU peak rate is ~ 26c. i guess it will depend how much energy we consume in the winter months too, and how far the EV charging pushes us into Tier 3 those times of the year.

this comes from SDGE's NEM page however i don't know how it would tie into TOU:

Weighing the Financial Benefits

The price of energy is much higher during on-peak hours, especially during the summer months, when your system typically produces maxiumum electricity. This means that every excess kilowatt-hour your system generates is credited to your account at the higher rate during the on-peak period.

If you reduce your energy usage during the on-peak period, your solar system sends the excess energy to the grid and you get credited for this. The higher credits you receive can offset the cost of electricity during times when you may need electricity from the grid.

If you use more on-peak electricity than your system produces, you’ll be charged the higher rate for the energy you use. It’s possible your bill could end up being higher than it would have been under the standard residential rate.

My suggestion is check your electricity usage in next couple months and do the calculation later and see which is better for you.

[Volusiano]

this comes from SDGE's NEM page however i don't know how it would tie into TOU:

Weighing the Financial Benefits

The price of energy is much higher during on-peak hours, especially during the summer months, when your system typically produces maxiumum electricity. This means that every excess kilowatt-hour your system generates is credited to your account at the higher rate during the on-peak period.

If you reduce your energy usage during the on-peak period, your solar system sends the excess energy to the grid and you get credited for this. The higher credits you receive can offset the cost of electricity during times when you may need electricity from the grid.

If you use more on-peak electricity than your system produces, you’ll be charged the higher rate for the energy you use. It’s possible your bill could end up being higher than it would have been under the standard residential rate.

The bold part above seems to imply something, but exactly what is very ambiguous at best. By saying "higher credits", they imply a value associated with the credit. But how that value translates exactly, they didn't say. It seems like they almost word it to intentionally lead you on to assume something that can be misleading.

[albert436]

Sounds more complicated than I can understand at first look.

That does not usually bode well.

[J.P.M.]

Like I said, I prefer larger system because I know I will NEED it. EV car will take about 4800kWh for 15k miles per year. In reality, my system is too small for my demand.

FWIW, I absolutely support your right, or mine or anyone else's right to do what they want, including having any type or size solar generator they want - Period.

Perhaps the key is to understand that the CSI calculator is NOT a sizing tool and understanding why.

What I'm saying is that using the CSI incentive calculator for system sizing is a poor use of that tool, and when used as a sizing tool, often leads to unknown (by the customer) and unintended (if done by the customer) oversizing, and perhaps intended oversizing if done by an unscrupulous vendor to less than savvy and overtrusting customers for the purpose of selling more product and thus, winding up with a system that may be less cost effective.

The CSI calculator does not allow changing the PV Watts derate factor from its very conservative .77 to what may likely be a more realistic number (numerically higher).

I'd suggest a better estimate of performance can be had using PV Watts 2 by itself - NOT the CSI calculator which is for calculating the CSI incentive, not system sizing per se.

If, after understanding how PV Watts 2 works, including understanding of how derating per PV Watts 2 influences system performance, I choose to go with a different system size than PV Watts 2, or other reliable sizing/performance tools come up with, I'm free to do what I please, oversize, undersize, anything in between, or nothing. The big advantage in doing it that way, as I see it, is I'll have more accurate information on which to make my decision. If I choose to oversize, as is my right and choice - so be it - I'll glory in the freedom and live with the results. Whatever the outcome, I'll be doing it with probably better information and a better understanding of what's involved.

All I'm suggesting is : Do what you want - Just make sure you have good information that you understand.

Caveat Emptor.

[silversaver]

FWIW, I absolutely support your right, or mine or anyone else's right to do what they want, including having any type or size solar generator they want - Period.

Perhaps the key is to understand that the CSI calculator is NOT a sizing tool and understanding why.

What I'm saying is that using the CSI incentive calculator for system sizing is a poor use of that tool, and when used as a sizing tool, often leads to unknown (by the customer) and unintended (if done by the customer) oversizing, and perhaps intended oversizing if done by an unscrupulous vendor to less than savvy and overtrusting customers for the purpose of selling more product and thus, winding up with a system that may be less cost effective.

The CSI calculator does not allow changing the PV Watts derate factor from its very conservative .77 to what may likely be a more realistic number (numerically higher).

I'd suggest a better estimate of performance can be had using PV Watts 2 by itself - NOT the CSI calculator which is for calculating the CSI incentive, not system sizing per se.

If, after understanding how PV Watts 2 works, including understanding of how derating per PV Watts 2 influences system performance, I choose to go with a different system size than PV Watts 2, or other reliable sizing/performance tools come up with, I'm free to do what I please, oversize, undersize, anything in between, or nothing. The big advantage in doing it that way, as I see it, is I'll have more accurate information on which to make my decision. If I choose to oversize, as is my right and choice - so be it - I'll glory in the freedom and live with the results. Whatever the outcome, I'll be doing it with probably better information and a better understanding of what's involved.

All I'm suggesting is : Do what you want - Just make sure you have good information that you understand.

Caveat Emptor.

Like I said, doesn't matter V1, V2 or CSI calculator, they came pretty close in CA 92887. If you base on your zip code, you probably getting 600 to 700 more with PVWatt. I have never said vendor or I using CSI calculator as sizing tool, it just happen those datas were used as expected generation in Locus monitoring.

[albert436]

About over sizing -- it occurs to me that likely the cost of a system could broken down in many ways, here is one hypothetical.

1. Fixed "set up" or "start up" -- design, shipping, transportation of materials, minimum cot to get job going, etc
2. Materials, mostly panels
3. Labor

What I'm getting at is that incremental increase in kW of system will be incrementally lower cost than that kW proportion of system itself. Hypothetically anyway (disclaimer).

This might lead to "do it all now" thinking in scenarios with greater future uncertainty. Eg. Changing rates, changing electricity use (family size, lifestyle, electric vehicles, etc.)

On the other side of the unknown is advances in technology. Look at the differences in phones from just ten years ago.

While I'm on the subject is there a rule of thumb for improvement in solar cell improvements analogous to Moore's Law, which has been accurate since 1970 in stating that processing power will double approximately every two years?

One smart guy here has back calculated the increase in power rates for San Diego over the last ten p,us tears, has anyone computed that for solar panel electricity production?

[russ]

On the other side of the unknown is advances in technology. Look at the differences in phones from just ten years ago. A totally different thing - the only item with anything in common would be the inverters - one big part of PC and cell phone prices is mass production which you do not have in solar electronics. Solar cells have really dropped over the past few years until most suppliers are history.

While I'm on the subject is there a rule of thumb for improvement in solar cell improvements analogous to Moore's Law, which has been accurate since 1970 in stating that processing power will double approximately every two years? Zero in common - look at the market for PV (very small) and the PC market - immense.

One smart guy here has back calculated the increase in power rates for San Diego over the last ten p,us tears, has anyone computed that for solar panel electricity production?

Depends on what metrics do you want to use and how you want to look it. Form a green prospective rates have been astronomical while from a more balanced point of view the base rate hasn't increased that much most places.

[albert436]

Ok well extend the analogy to prices then, same general principle in a broader view -- leaving aside the question of whether or not tech has improved over the years to have more W per panel. (hasn't it?)

And sure looking at the CSI graph of price per watt of installed systems shows a definite trend.

From here it looks like you are hearing something defined in a very narrow sense rather than the general sense in which it was intended.

And remember, there are two types of people in the world, those who think there are two types of people in the world, and those who don't.

[Volusiano]

What I'm getting at is that incremental increase in kW of system will be incrementally lower cost than that kW proportion of system itself. Hypothetically anyway (disclaimer).

I was asking my installer about expanding my system from 11 KW (44 250W panels) to 14 KW (12 more 250W panels on top of the original 44) because I'm considering buying another EV so I may need to expand for a new EV. And they should be able to just connect the new panels to the existing 2 inverters I already have and still be able to get 99.9% energy usability factor (I worked it out on the Sunny Design web page and showed them that a new inverter is not needed and they agreed).

They quoted me a price per watt for the new panels which is only 8% lower than the original price per watt for the whole system which included the inverters and all hardwares. I was hoping it'd be a little more than 8%, considering that they'd only have to add more panels, but no new inverter, no other new hardware except some more wiring and racking, of course. And they'll probably have to redo the permits all over again. What this is saying is that the inverter and labor to install it only accounts for about 8% of the cost of the system, maybe, which I don't know whether it's true or not. Seems a little low to me.

[albert436]

Thanks Vol, that's really interesting and surprising. Especially since as you said new inverters aren't needed. Did they explain their rationale? Do you have a pretty high level of trust and confidence in them?

I don't remember which panels you have but many have prices online.

[russ]

Ok well extend the analogy to prices then, same general principle in a broader view -- leaving aside the question of whether or not tech has improved over the years to have more W per panel. (hasn't it? Watts per panel improved? Physically larger panels and all the way up to 21.5% efficiency from 15% - not a big deal. 43% efficient panels are available but unless your name is Gates or Ellison they are probably out of reach.

And sure looking at the CSI graph of price per watt of installed systems shows a definite trend. Sure - the manufacturers are eating it - many no longer are in business

From here it looks like you are hearing something defined in a very narrow sense rather than the general sense in which it was intended.A statement was made about Moore's Law which was totally wrong in the case of solar. Matter of fact it is a common misapplication of Moore's Law.

And remember, there are two types of people in the world, those who think there are two types of people in the world, and those who don't. People that believe in facts and figures plus BS artists and what else

Comments in bold within the text