PV Solar sizing with and without EV
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dstjohn99
Well-known member
smkettner said:
I assume this is based on the bills I posted? I'm not sure where the 7kW on the bill comes from. My original system was 4.4 kW DC in 2001 (40 110 watt panels). Then I roughly doubled the size in 2009(?) with 40 120 watt panels. I installed both systems myself. In 2001 it was approx. $9 per watt commercially installed. Today's estimates are roughly $3.50 per watt commercially installed.
In 2001 My net cost after rebates and tax credits was about $4,000. I believe the 2009 system was about $12k without any rebates or credits with used panels and inverter. Both systems still producing very well. The EV was LONG overdue, but the right car/price did not exist until the Rav4 EV.
Spiffster
Active member
I created this app to do similar calculations:
http://www.empulserider.com/pvCalculator.php
Yeah, no RAV4 EV in the drop down menu yet, but you can manually specify range, battery size, and all kinds of other settings.
From experience, its pretty accurate.
http://www.empulserider.com/pvCalculator.php
Yeah, no RAV4 EV in the drop down menu yet, but you can manually specify range, battery size, and all kinds of other settings.
From experience, its pretty accurate.
Update.
According to this picture, it looks like SDGE is just adding up the actual production and usage and giving it a dollar value. Why? If they're going to use these three values, times their cost values, then it would be entirely different. If this is how they do it, then I've sized my system wrong.
Can someone please confirm that they do it by TOU cost?
According to this picture, it looks like SDGE is just adding up the actual production and usage and giving it a dollar value. Why? If they're going to use these three values, times their cost values, then it would be entirely different. If this is how they do it, then I've sized my system wrong.
Can someone please confirm that they do it by TOU cost?
miimura
Well-known member
It really bugs me that they don't show the kWh and $/kWh for the "Applied Generation Credit" the way they do the positive charges. By dividing the $82.45 by -367kWh you get a price of about $0.225/kWh for that peak generation. Of course, you have more detail than PG&E where they just show you the kWh for each period and the total net charge, with no $/kWh shown anywhere on the statement.
Fundamentally, they are calculating a dollar charge and generation credit for each billing period. The rates change so often, they have to convert the usage to dollars every month, just to stay on top of it. At the end of the year you will find that there will be some reconciliation of the usage charges and the generation credits. I assume they will completely wipe out your actual generation credits by offsetting your usage charges to no less than zero. If you have net generation, they will probably do a new calculation of net kWh fed into the grid times some small $/kWh for net generation. This is probably less than $0.05/kWh, but I've never seen a SDGE reconciliation statement.
Anyway, that's a long way to say that if you are a net user, but have a large surplus generation credit, it will just we wiped out because you're "In the Gap" between TOU charge calculation and true net generation.
Fundamentally, they are calculating a dollar charge and generation credit for each billing period. The rates change so often, they have to convert the usage to dollars every month, just to stay on top of it. At the end of the year you will find that there will be some reconciliation of the usage charges and the generation credits. I assume they will completely wipe out your actual generation credits by offsetting your usage charges to no less than zero. If you have net generation, they will probably do a new calculation of net kWh fed into the grid times some small $/kWh for net generation. This is probably less than $0.05/kWh, but I've never seen a SDGE reconciliation statement.
Anyway, that's a long way to say that if you are a net user, but have a large surplus generation credit, it will just we wiped out because you're "In the Gap" between TOU charge calculation and true net generation.
dstjohn99 said:
That's a cheap install. Paid retail for ours, but it was sign and go. Great savings you got!
After years in PGE land with solar; came down to SDGE last year and very different ways of crediting and a lot more information (but worse pricing) than PGE for solar.
Now dove into the EV world and compounding issues.
With Solar, looks like the deciding factor would be over three issues:
11am-12noon panel charge
evening super off peak: car charge
Weekend usage --- KEY issue: DR-SES is flat rate on weekends while EV-TOU2 gives you two additional days of pk time production. -- Am I reading this correctly?
Since SDGE only gives 0.24 credit and charges 0.19 (or 0.16 super off peak summer), the difference in charging throughout the day isn't significant as long as remain positive generators during the daytime.
I was looking even closer and got to thinking about all this generation credit.
Since SDGE only gives generation credit without distribution; it would actually be worthwhile to CHARGE my EV during all times generation is made except On-Peak Summer where SDGE pays 0.35/kwH
All other times the credit for over generation is <0.10/kwH so any overproduction should be balanced as much as possible by charging my EV in the semi-peak and DURING DAYTIME during the winter months. (costing only 0.08 kwH of our own generation vs charge 0.19 kwH for charging overnight)---this is with the assumption of overgeneration.
Since SDGE only gives generation credit without distribution; it would actually be worthwhile to CHARGE my EV during all times generation is made except On-Peak Summer where SDGE pays 0.35/kwH
All other times the credit for over generation is <0.10/kwH so any overproduction should be balanced as much as possible by charging my EV in the semi-peak and DURING DAYTIME during the winter months. (costing only 0.08 kwH of our own generation vs charge 0.19 kwH for charging overnight)---this is with the assumption of overgeneration.
Not to make money, no. We just built larger knowing that we'd have future expansion needs - like the new EV, and future spa coming next few months.
The question now with the EV is WHEN to plug in and make the most of current overproduction. The way I'm reading this pay amount that SDGE gives, for anyone with access generation, it's worthwhile to use to Charge during that time period instead of super-off peak/non-peak times--except summer On-Peak times.
The question now with the EV is WHEN to plug in and make the most of current overproduction. The way I'm reading this pay amount that SDGE gives, for anyone with access generation, it's worthwhile to use to Charge during that time period instead of super-off peak/non-peak times--except summer On-Peak times.
I don't understand what you're saying.montreid said:
If you understand the concept of buy low and sell high, then you would produce at peak ( no choice), and consume at super off peak. During summer, it's a 3:1 ratio.
Yes, concept is sound IF SDGE plays along with logical reimbursement/charges, which it doesn't for off-peak. The problem is it's NOT a 3:1 ratio cause SDGE buys generation rate only. Sells Generation + distribution. 0.19 for off-peak is ridiculously high. Other states is 0.04-0.06/kwHFerdball said:
Take a closer look at your Buy Low, Sell High concept:
Summer: Peak Sell: 0.35/kwH Buy: Off peak: 0.19 ---makes sense = don't charge.
SemiPeak Sell: 0.10/kwH Buy Off peak 0.19 --- doesn't make sense. = Charge during this time IF one is overproducing
OffPeak Doesn't matter since usually no sun. = Charge as usualy
Winter: Semi-Peak: Sell: 0.08 Buy: off peak 0.19 = Charge during the day if overproduction
--The point is IF one has overproduction either in the Semi-Peak Summer of Semi-Peak in the winter == Charge during that time instead of charging at night.
You'll save even more than the 'buy low' since SDGE 'buys even lower'
I don't know where you're getting your numbers from. Are you on TOU2 and NEM? Do you have a bill from your 12th month? If so, let's see it.montreid said:
Otherwise, everyone on this thread is under this assumption:
smkettner said:
This is verified from an SDGE employee:
http://www.teslamotorsclub.com/showthread.php/9088-Understanding-SDG-E-rates/page4?p=349829&viewfull=1#post349829
I'm on NEM and DR-SES.
The problem with SDGE bills is that the bill grid is setup for simple Net Metering and doesn't break down the true delivery/generation #s that arrives at the Applied Credit column--one can't simply take the applied credit and divide the negative # unfortunately because there is production in off-peak times too that's factored into the applied credits but not reflected on the left side of the bill grid.
These are the current rates.
http://www.sdge.com/regulatory-filing/2227/time-use-tou
https://www.sdge.com/sites/default/files/regulatory/2-1-15%20Schedule%20DR-SES%20Total%20Rates%20Table.pdf
My understanding on OVER generation credit on TOU is based on the second to last column which reflects retail generation costs (not the distribution costs--UDC). If this is true, then the credit of OVER Generation on semi-pk times appears LESS than the actual costs to charge during off-peaks.
The problem with SDGE bills is that the bill grid is setup for simple Net Metering and doesn't break down the true delivery/generation #s that arrives at the Applied Credit column--one can't simply take the applied credit and divide the negative # unfortunately because there is production in off-peak times too that's factored into the applied credits but not reflected on the left side of the bill grid.
These are the current rates.
http://www.sdge.com/regulatory-filing/2227/time-use-tou
https://www.sdge.com/sites/default/files/regulatory/2-1-15%20Schedule%20DR-SES%20Total%20Rates%20Table.pdf
My understanding on OVER generation credit on TOU is based on the second to last column which reflects retail generation costs (not the distribution costs--UDC). If this is true, then the credit of OVER Generation on semi-pk times appears LESS than the actual costs to charge during off-peaks.
The other question I have for PV+EV users on TOU; what schedule is more advantageous:
https://www.sdge.com/sites/default/files/documents/86469412/2014-dst_dr-ses.pdf
https://www.sdge.com/sites/default/files/documents/1269645843/2014-dst_ev-tou2.pdf
EV gets pk times all year long, including weekends. I'm thinking this is even better for PV since even in Dec, between 12n-6p we're still net generators.
https://www.sdge.com/sites/default/files/documents/86469412/2014-dst_dr-ses.pdf
https://www.sdge.com/sites/default/files/documents/1269645843/2014-dst_ev-tou2.pdf
EV gets pk times all year long, including weekends. I'm thinking this is even better for PV since even in Dec, between 12n-6p we're still net generators.
So took a closer look at the SDGE bills and dove into the numbers and readings.
I was incorrect about the credit for generation. They actually give full retail and distribution credit until trueup--I wasn't carrying over the balance correctly. So still best option is to charge super-off peak.
Also been debating the whole EV-TOU2 v DR-SES situation. Since our panels are on the west side; generation matches nicely to both schedules.
EV-TOU2 might be shorter 1 hour, but includes weekends so over the 5 summer months; that equals to 200 hours additional solar generation time for the summer.
Tie that in with the super off peak discount differential; thinking of moving over to EV-TOU2.
Trouble is that SDGE has been moving the rates of EV all over the place and the prospect of them lowering the pk rates and closing off DR-SES with new legislation to remove the fallback situation makes me think twice about moving over
I was incorrect about the credit for generation. They actually give full retail and distribution credit until trueup--I wasn't carrying over the balance correctly. So still best option is to charge super-off peak.
Also been debating the whole EV-TOU2 v DR-SES situation. Since our panels are on the west side; generation matches nicely to both schedules.
EV-TOU2 might be shorter 1 hour, but includes weekends so over the 5 summer months; that equals to 200 hours additional solar generation time for the summer.
Tie that in with the super off peak discount differential; thinking of moving over to EV-TOU2.
Trouble is that SDGE has been moving the rates of EV all over the place and the prospect of them lowering the pk rates and closing off DR-SES with new legislation to remove the fallback situation makes me think twice about moving over
miimura
Well-known member
If you can save money now, take it. You never know what the future will bring. I had a similar situation with PG&E. They have been saying that they would be kicking people out of E-9 and I could have saved money over the winter on EV if I had voluntarily changed. However, it's now May and they haven't kicked me off, so now my energy charges are lower on E-9 again. I'm just going to wait it out and see what happens.montreid said:
ravisekhar
Active member
- Joined
- Mar 13, 2013
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With The Release of Tesla Power Wall for Just $3500 for 10 KW. Has any one calculated what will be the Total cost with Inverter and installation.
Based on the webpage http://www.pge.com/en/mybusiness/save/solar/sgip.page PG&E has a rebate of $1.46 per W. So for 10 KW installation are we going to get back a rebate of 14,600 from PG&E. Too good to be true or my calculations are wrong.
Based on the webpage http://www.pge.com/en/mybusiness/save/solar/sgip.page PG&E has a rebate of $1.46 per W. So for 10 KW installation are we going to get back a rebate of 14,600 from PG&E. Too good to be true or my calculations are wrong.
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