4.48kW system coming online in SF Bay Area (San Ramon)

[arvindag]

I am San Ramon area. Anyone got system installed recently. Please PM me installer.

[J.P.M.]

I'm a bit out on a limb here, but have enough string inverters been around long enough to accumulate an history of failures and thus probability of future failure even if mfg./tech. improves reliability ? While I appreciate the linkage of product robustness and warranty, a 10-12 year warranty period does not, in/of itself mean a guaranteed, unavoidable failure 1 day past the warranty period. Soon maybe, but not a 1.0 probability.

[kaisersoze]

I'm looking at installing about the same size system as yours, possibly a few more panels. Did you find that the string inverter bid was significantly less than the microinverter bid? Did you buy extended warranty for the inverter? My thought was that since most will die around the 10 year mark, purchasing the warranty now essentially covers the capital cost of the replacement inverter. Though I suppose one could argue the technology may be better and cheaper in 10 years when the original inverter needs to be replaced.

Forgot to add, would the cost of the extended warranty on the inverter negate the possibly higher bid cost for the microinverter system with its 25 year warranty?

[kaisersoze]

System Spec
16x SolarWorld SW280 Mono black panels
1x SMA SB5000TL-US-22 string inverter - 10 years warranty (including SWDM-US-10 Web Connect and SMA Secure Power Supply outlet)

I decided to go with SMA instead of the Enphsae micro-inverter primiarly based on the lack of real world history for the Enphase.
My system set up have 6 panels facing East and 10 panels facing West. Neither side have shade issues. The SMA has 2 trackers so each one can handle the panels on one orientation nicely.

SMA's web monitoring interface is sufficient for me. After a few days constantly checking the display on the unit as well as on the web page, i am already starting to get bored and checked less frequent.
The energy production is right around (or just a little bit higher than) the PVWatts estimation. So I am happy with the system design (which in hindsight isn't that tricky, especially for simple systems like mine).


Total (pre-tax credit) $14,784 --> That's about $3.3/Wdc

I'm looking at installing about the same size system as yours, possibly a few more panels. Did you find that the string inverter bid was significantly less than the microinverter bid? Did you buy extended warranty for the inverter? My thought was that since most will die around the 10 year mark, purchasing the warranty now essentially covers the capital cost of the replacement inverter. Though I suppose one could argue the technology may be better and cheaper in 10 years when the original inverter needs to be replaced.

[ltbighorn]

Would you mind PMing with your installer as well? Head spinning a bit taking in all the info, and it'd be helpful to have some points of reference. Do you know if they do installs in SF proper? Thanks!

[dshenmdyn]

can you PM me your installer? I am also looking for a 4.5kW system. Thx

PM sent

[almaden]

can you PM me your installer? I am also looking for a 4.5kW system. Thx

[solar_newbie]

Just found this thread... for a detailed explanation of how the E-6 tiering works, see this post:

http://www.solarpaneltalk.com/showth...ll=1#post73629

Thank you for sharing. It is good info and very clear how E-6 tiers are used... I assume if production > consumption, tier 1 is used.

[sensij]

Just found this thread... for a detailed explanation of how the E-6 tiering works, see this post:

http://www.solarpaneltalk.com/showth...ll=1#post73629

[ulrich]

Found this link on pg&e website and from what it looks like, TOU plan are still counted on monthly cycles

You're right - I was fooled by the rate sheet I linked which states Tier allowances in kWh per day (and doesn't mention the monthly period anywhere that I could find). The following page has a more explicit explanation of the TOU Tiers that agrees with your interpretation: http://www.pge.com/en/myhome/saveene...tou/index.page

Like the Tiered Rate Plan, as you use the electricity allotments in each tier, you move to the next tier and higher price.
This means pricing varies based on the time of the day and the usage tier you've reached. To save, avoid both higher price times and conserve total usage over your bill period.

Tier 1: Each monthly billing period begins at the lowest rate. While you want to stretch as far as possible, average customers use all of Tier 1 in about 15-20 days.
Tier 2: With about one third the allotment of Tier 1, Tier 2 costs slightly more (+3¢). If your Tier 1 lasts 15-20 days, Tier 2 could last another 5-6 days.
Tier 3: The rate increases dramatically (+5¢) in this tier. Customers who enter Tier 3 are consuming significant amounts of electricity.
Tier 4: Finally; if you enter tier 4, you are using more than twice your Tier 1 total, and the rate increases by an additional 7¢.

[inetdog]

solar_newbie,
If you want text tables to show up in readable form you can either attach them as an image or pdf or you can place text inside CODE tags (the hash mark button in the format toolbar.)That forces a monospace font without automatic deletion of multiple spaces. Tabs are still iffy though.

[solar_newbie]

There are lots of discussions on whether to use EV-A or E-6 for homes with Solar AND EV
This is the thread I partially based my decision on. http://www.myrav4ev.com/forum/viewtopic.php?f=7&t=574

I came down to select EV-A because I found it easy to understand.
For EV-A, it's a simple Time of Use. So the solar generates at peak hour will earn me credit at the peak-rate. I will charge my EV at off-peak hour. In summer, the ratio between peak to off-peak rate is about 4:1. That means for each kWh solar generation at peak time, I earn credit enough for 4kWh EV charging.

I can't totally understand how the E-6 (Tiered TOU) plan work.
I can understand that if I use a lot more than my solar generates during each month, then I move up the tier and each unit of energy becomes more expensive (I need to pay or use my credit, all done during a ture-up year cycle)
What I don't understand if I over generates a lot during summer month (which will be very likely as every solar home rely on the over generation in summer to supplement the usage in winter), whether the rate for each over generation goes through tiered rate as well.
This gets complicated because it appears PGE calculate debit/credit for each month (even though you only ture-up once a 12 month period). So in summer, I could see a lot of energy that I generate but don't need.

To illustrate my question:

Tier 1 is 300kWh --> lowest rate for each TOU period
Tier 2 is 301kWh to 330kWh --> Middle rate for each TOU period
Tier 3 is 331kWh to 600kWh --> Most expensive rate for each TOU period


In winter months: because of the small amount of solar energy generated, I may not go up to higher tiers. But I will most likely use more than what I generate. In that case, I will be charged for the lowest rate for electricity used during each TOU period

In summer months, what if my system generates more than 330kWh AFTER covering what I use during the same month, will PGE give credit based on the tier 3 rate? (since I going beyond the tier on the opposite side).
To further complicate the matter, do PGE only give credit at high tier rate for the last a few days of each month during the summer after my over generation have pass the tier level?

I found my head spin thinking about all these. So I decided to try EV-A for a year. By then, PGE website will have historical data to simulate if switching to E-6 will be better.

For MEM, I would assume they do calculate at year end or month end. I just use the above spreadsheet in above link. Plug in current PG&E rate for E1, E6 and EV-A
Put in my PVWatts estimates (using default value, only change from south to west) for the 5.04 KW system of my home.
Assumption : peak is 80% in summer , off-peak is 20% in summer. For winter, peak/offpeak/other is 60%/20%/20%
EV car uses 4KW/miles and run 10K per year.
Here is the assumption number:
EV (yearly - off peak) 2500
Solar (summer - peak) -3647.2
Solar (summer - off peak) -911.8
Solar (winter - peak) -1423.8
Solar (winter - off peak) -474.6
Solar (winter - others) -474.6

Download my last year from Aug 14 to Aug 15 usage from PG&E.

Finally, I got the value with both solar and EV and current usage:

E1: Total : $192.27
Cost by Tiers ($)					
1 (to base) 	2 (101-130%)	3 (131-200%)	4 (201-300%)	5 (over 300%)	Total
$193.27            $0.00	        $0.00	        $0.00	        $0.00	        $193.27

E6: Total : -$430.67
				Cost by Tiers ($)					
				1 (to base)	2 (101-130%)	3 (131-200%)	4 (201-300%)	5 (over 300%)	Total
Winter	Peak		$0.00	    $0.00	        $0.00	        $0.00	         $0.00	        $0.00
Winter	PartPk	-$256.63	    $0.00	        $0.00	        $0.00	         $0.00	        -$256.63
Winter	Off Peak	 $387.89	    $0.00	        $0.00	        $0.00	         $0.00	         $387.89
Summer	Peak		-$934.84	    $0.00	        $0.00	        $0.00	         $0.00	        -$934.84
Summer	PartPk	-$46.88	    $0.00	        $0.00	        $0.00	         $0.00	         -$46.88
Summer	Off Peak	$419.79	    $0.00	        $0.00	        $0.00	          $0.00	         $419.79

EV-A: Total -$652.51
Cost by Tiers ($)					
 1 (to base)	2 (101-130%)	3 (131-200%)	4 (201-300%)	5 (over 300%)	Total
 $201.41	        $0.00	        $0.00	        $0.00	        $0.00	         $201.41
 -$222.69	        $0.00	        $0.00	        $0.00	        $0.00	         -$222.69
 $176.10	        $0.00	        $0.00	        $0.00	        $0.00	         $176.10
 -$1,041.65	$0.00	        $0.00	        $0.00	         $0.00	         -$1,041.65
 -$14.79	        $0.00	        $0.00	        $0.00	         $0.00	          -$14.79
 $249.11	        $0.00	        $0.00	        $0.00	        $0.00	          $249.11

It looks like EV-A wins ... However, there will be zero rebate from PG&E since the true up production vs consumption is negative (The delta is 1,181KWh. That is shown on E1)

I guess I will use E-6 for 1 year to get the true production of the solar power and EV car consumption to revisit with this spreadsheet before changing to EV-A as there is no turn back for E-6. I can lock for 5 years only.

[justthinking]

Are you saying the "tiering" (for lack of a better term) is on a daily basis? I would think that is incredible unfavorable to the customer.
At least for E-1 (NOT E-6), I think the tiering is based on monthly basis even though the allocation of the baseline amount is per day.

Put it another way: each day per account get a baseline amount (say 10kWh), then you get to use 300kWh (10kWh x 30 days) over the entire month. PGE does not determine if you are over the baseline on a daily basis. In stead, it make the decision over a billing cycle (typically 30 days). Over this 30 day period, you get the benefit of averaging the usage over the period. You get to use all the baseline amount for the entire 30 days period first. So if there are several super hot days in the beginning of the month, but the rest of the month is cool, then you still have a chance to stay in the lower tire for the month.

On the other hand, if the "tiering" is on daily basis, then you will immediately be penalized for the AC use on any single hot day.

Found this link on pg&e website and from what it looks like, TOU plan are still counted on monthly cycles

http://www.pge.com/en/myhome/myaccount/explanationofbill/etoub/3/index.page?

another page with info related NEM

http://www.pge.com/en/myhome/myaccount/explanationofbill/nem/index.page?

[dshenmdyn]

E-6 is gone, but will be replaced with another tiered TOU plan, so the problem will still exist.

The answer to your (and dshenmdyn's) question is in this document: http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_NEM.pdf

It still requires interpretation, and I'm not sure I completely understand the nuances, but the content starting on Sheet 8 of the document describes your case.

Section 2.b covers TOU rates and says:


(OAS stands for "Originally Applicable rate Schedule" - i.e., the rate that would apply independent of net metering)

Basically the way that I read this text is that each TOU period (peak/part-peak/off-peak) is totalled up independently. So a typical day might look like:
Peak: Net generator 12 kWh
Part Peak: Net consumer 9 kWh
Off-Peak: Net consumer 5 kWh

Each period will be billed (or credited) according to the appropriate rates for the period.

Section 2(b) is not specific on how Tiers get calculated, so we have to look to section 2(a) for information on that (2(a) is titled (For an OAS with baseline rates) and says:

Basically what this is saying, by my interpretation, is that tiers apply both to net generators and net consumers.

Unfortunately, this still leaves some ambiguity.

The baseline rates for E-6 are determined on a daily basis - so it's total consumption for the day, independent of the time the consumption happened that would normally determine which tiers apply. The percentage of usage that comes from each tier would then be applied back to each period - so if 20% of total usage for the day was in Tier 2, 20% of your peak usage would be billed at Tier 2 rates, as would 20% of your part- and off-peak usages.

The question would be, if you're a net generator in some TOU periods, and a net consumer in others, how the Tiering is determined - is it determined by the magnitude of usage/generation in the individual period or over the whole day?

I would say the most consistent way of interpreting this (and thus the way I believe it will work), is that the Tier is determined by total net usage during the day. So in my example, total net usage was 3 kWh, which is Tier 1 for all geographies (The baseline numbers also vary by region, so geography is important for calculating rates under E-6).

If net usage had been high enough to put 20% of the usage in Tier 2, then the same rules as base E-6 would apply, except that it would apply to both net generation and net usage during the individual periods. So in my example, 20% of the net generation during peak hours would be credited at Tier 2 with the remaining 80% credited at Tier 1, etc.

The E-6 rate is described in this document, btw: http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_E-6.pdf

Are you saying the "tiering" (for lack of a better term) is on a daily basis? I would think that is incredible unfavorable to the customer.
At least for E-1 (NOT E-6), I think the tiering is based on monthly basis even though the allocation of the baseline amount is per day.

Put it another way: each day per account get a baseline amount (say 10kWh), then you get to use 300kWh (10kWh x 30 days) over the entire month. PGE does not determine if you are over the baseline on a daily basis. In stead, it make the decision over a billing cycle (typically 30 days). Over this 30 day period, you get the benefit of averaging the usage over the period. You get to use all the baseline amount for the entire 30 days period first. So if there are several super hot days in the beginning of the month, but the rest of the month is cool, then you still have a chance to stay in the lower tire for the month.

On the other hand, if the "tiering" is on daily basis, then you will immediately be penalized for the AC use on any single hot day.

[ulrich]

I have the same head ache, BUT E-6 is gone by this Dec So I am thinking to try E-6 first ... as you do not have chance to do the change later.

E-6 is gone, but will be replaced with another tiered TOU plan, so the problem will still exist.

The answer to your (and dshenmdyn's) question is in this document: http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_NEM.pdf

It still requires interpretation, and I'm not sure I completely understand the nuances, but the content starting on Sheet 8 of the document describes your case.

Section 2.b covers TOU rates and says:

If the eligible customer-generator is a net consumer during any discrete TOU period, the net kWh consumed shall be billed in accordance with that same TOU period in the eligible customer-generator’s OAS.
If the eligible customer-generator is a net generator during any discrete TOU period, the net kWh produced shall be valued at the same price per kWh at the same TOU period in the eligible customer generator’s OAS.
In the event that at the end of the monthly billing cycle, an eligible customer generator’s
net usage for all TOU periods totals zero (i.e. net generation in one or more periods exactly offsets the net usage in all other periods), then
the value of usage and/or generation will be calculated using Tier 1 rates (as set forth in the OAS).

(OAS stands for "Originally Applicable rate Schedule" - i.e., the rate that would apply independent of net metering)

Basically the way that I read this text is that each TOU period (peak/part-peak/off-peak) is totalled up independently. So a typical day might look like:
Peak: Net generator 12 kWh
Part Peak: Net consumer 9 kWh
Off-Peak: Net consumer 5 kWh

Each period will be billed (or credited) according to the appropriate rates for the period.

Section 2(b) is not specific on how Tiers get calculated, so we have to look to section 2(a) for information on that (2(a) is titled (For an OAS with baseline rates) and says:

If the eligible customer-generator is a net consumer, the eligible customer generator will be billed in accordance with the eligible customer-generator’s OAS.

If the eligible customer-generator is a net generator, the net kWh generated shall be valued at the rate for the kWh up to the baseline quantity, with any excess kWh generated, valued at the rate for the appropriate tier level in which the equivalent kWh of usage would fall.

Basically what this is saying, by my interpretation, is that tiers apply both to net generators and net consumers.

Unfortunately, this still leaves some ambiguity.

The baseline rates for E-6 are determined on a daily basis - so it's total consumption for the day, independent of the time the consumption happened that would normally determine which tiers apply. The percentage of usage that comes from each tier would then be applied back to each period - so if 20% of total usage for the day was in Tier 2, 20% of your peak usage would be billed at Tier 2 rates, as would 20% of your part- and off-peak usages.

The question would be, if you're a net generator in some TOU periods, and a net consumer in others, how the Tiering is determined - is it determined by the magnitude of usage/generation in the individual period or over the whole day?

I would say the most consistent way of interpreting this (and thus the way I believe it will work), is that the Tier is determined by total net usage during the day. So in my example, total net usage was 3 kWh, which is Tier 1 for all geographies (The baseline numbers also vary by region, so geography is important for calculating rates under E-6).

If net usage had been high enough to put 20% of the usage in Tier 2, then the same rules as base E-6 would apply, except that it would apply to both net generation and net usage during the individual periods. So in my example, 20% of the net generation during peak hours would be credited at Tier 2 with the remaining 80% credited at Tier 1, etc.

The E-6 rate is described in this document, btw: http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_E-6.pdf