PV Inventory

 Since I'm not able to make much progress on new PV installs, I'm going to address taking inventory of what I have that is producing.

My very first four panels were bought as a kit off of eBay.  The kit included the four ~250w panels, four Enphase microinverters, probably M250, mounting rails for roof top mounting, and an old electric meter.  As I recall the cost was about $1k.  I can place in time pretty well because Jean and I hauled the shipment home from the freight terminal in our new 2011 Leaf.  Sometime in 2011.  The kit sat around for a while, probably a few months.  Steve Clunn arrived here in Dale and stayed for a few weeks to work on my EV conversions, primarily my 2006 Hyundai.  One of the many services he provided was to install the four panels cantilevered off the south shed of the RV building.  The RV building had recently been built primarily to shelter a Sprinter RV conversion but was oriented with a roof facing due south.

Not long after the first four panels, Longhorn Solar, an advertiser in our electric coop magazine, did a "professional" install on that south facing roof in two stages which totaled 39 ~250w panels with Enphase microinverters.  So, total on that building was 43 panels totaling about 4.1kw.

Not long after, Longhorn did another install on a roofed over pair of shipping containers, the "PV Shed".  This gave me two meters that were inspected and blessed by Bluebonnet Electric Coop for PV production and sales to Bluebonnet.

A third meter, for my house, achieved Bluebonnet "blessed" status when a flybynight installer put 26 panels on my house roof.  300w panels, I believe.  The panels are served by a SolarEdge 5kw string inverter.

In 2020, I had Bluebonnet install a 4th meter, with 50kva transformer, to be used solely for PV energy sales.

• To get down to business: the first meter (known as "across the road") to get PV now has:

1) 43 panels on the RV building roof

2) Three two faced rails with 38 panels each, 19E plus 19W.  Total 114  panels

3) Seven two faced rails with 48 to 54 panels each, half E plus half W.  Total  364 panels.

4) Total for the meter: 521 panels.  This is currently my highest producing meter.  It was upgraded from a 15kva to a 50kva transformer.  Meaning that it's maximum production is 50kw.   Currently, peak production is around 35kw. At least one more rail of about 54 panels is planned.

• The house meter:

1) 26 panels on the roof

2) south facing rails: 27 + 6 + 15 + 9 + 24 = 81 panels

3) E/W facing rails: 64 + 52 + 54 = 170 panels

4) Total for the meter:  277 panels

The house meter transformer was upgraded from 15kva to 37.5kva and currently peaks out at around 30kw.

• For the "barn"/"pool"/"PV Shed" meter:

1) PV shed:  39 panels

2) Single rails: 17 x 3 = 51 + 6 = 57 panels

3) Two E/W rails: 20 + 44 = 64 panels

4) Total for meter:  160 panels

This meter peaks out at around 17kw, more than the 15kva rating for the transformer.

• For the new "hilltop" meter:

1) Seven E/W rails of  48 + 52  + 52 + 52 + 52 + 54 + 54 = 364 panels

2) Three more E/W rails of about 52 are planned.

3) Total for meter: 364 panels. 

Peak power currently about 25kw on a 50kva (50kw) transformer.

• Grand total for four meters: 521 + 277 + 160 + 364 = 1321 panels.  I currently have about 300 panels "in stock" unused on pallets.

Panels are all 60 cell rating mostly 250w, some down to 240, some up to 300.  Average about 250.  So, about 330kw of panel rating though panels never produce rated power.  Estimated peak power produced is about 110 kw.  There are planned expansions for all meters except for the "barn"/"pool" which has a 15kva transformer which peaks now around 17kw.

7/22/2021

I've decided to put all the above information into some estimates on payback periods.  The following should be considered:

1)  108 panels were "professionally" installed on roof tops.  Those panels cost in the range of $600-$800 per panel.  Payback period was expected to be around 15 years.   That payback period was inferred from offsetting retail rates of $.12-$.14/kwh.  I currently earn only $.06/kwh monthly cash.

2) My electric bill for the period 6/10/2021 through 7/12/2021 was a credit of $931.98.  That is above my use, which might be in the range $150-$200.  During that period, I had an estimated 75 panels not working for all or part of the billing period.  Not included in the credit amount are the 160 panels at the barn/pool; those are credited  only annually and only at $.03/kwh.  My pay rate is currently $.06.  It was $.0645 the prior year and changes annually.

3) I've had quite a bit of "educational" expense.  The above high priced roof top panels as well as tens of thousands for equipment, such as string inverters, which proved to be of no value to me.

4) I now think I can install panels and have them producing for about $75 per panel.  Real costs, including educational, have not been documented.  I consider the value of the panels that contribute to monthly credits to be about 1162 x $75 = $87k.

5) For a couple of years, I've been constantly been bringing additional panels into production so it has been difficult to know how many panels contribute to each billing period.  Recently, the number of panels has been mostly static.

For the recent billing period, my panels paid me $932 from the 1162 panels that are credited monthly.   So, those panels paid me about $.80 each for that billing period.  I could make the argument that only about 1100 panels were producing but I am uncertain.  It is difficult to extrapolate from one billing period to an average over an entire year.  That billing period should have been near peak production but wasn't due to rainy and cloudy weather.  An average month over the entire year might be expected to be about 75% of a peak (summer) month.  I make the conservative estimate that the billing period cited might represent a $8400 year.  That's about $7.20/panel/year.  A ten year payback.  That's not as good as I had expected.  I do not expect to be bringing more  panels into production for a month or longer and I believe I now have most of the panels producing.  So I will go through all this again at the end of the current billing period and maybe have more accurate numbers.  I probably should make the argument that the value of the panels should be increased by the $150-$200 per month that I am not paying for normal use.  That would increase the annual value to about $8.78  per panel.  More than a 8 year payback.

8/22/2021

My recent statement just became available.  A credit of $861.01 for 30 days ending Aug 12.  A real disappointment which does not shorten my payback period estimate.  The weather has been unusually cloudy and rainy.  Normal July/August weather should have produced a credit of $1k or more.  I can look forward to credits going down around $500 during the winter.

9/17/2021

New statement: credit of $932.48 for period ending 9/13/21; 32 days.  Check for $2411.74 (about three billing periods) is in the mail.  I seem to be stuck doing less than $900 every 30 days.

I figure I had 1162 panels in production for the 32 days.  $29/day.  $.025 per panel per day.

For installation cost of $75/panel, that would be a pay back period of 3000 days.  Over 8 years.  That's with a value of $.06/kwh.  For someone offsetting retail charges, the value would be about $.10/kwh or $.0427/panel or pay back of 1756 days.  Just below 5 years.

9/25/2021

Looking for low production meters.  Yesterday was a good sun day.  Production actually sold to Bluebonnet was:

1) ATR     290kwh 521 panels    .56 kwh/panel

2) House    174kwh 277 panels    .63 kwh/panel

3) Hilltop    146kwh 364 panels    .53 kwh/panel

Pretty much the same ball park.  ATR has some roof top with not shared inverter E/W panels.  House has some roof top and some south facing panels.  Hilltop is all E/W shared inverter panels.   WAG: E/W shared inverters costs me about 25%.  Maybe it is worse than that because the House production is reduced by house use of 30-40kwh.  So real House production per panel might be ~215/277 = .77 kwh/panel.