National security is not just arms and surveillance. It's also about economic strength and social stability. Power generation today is mostly handled by massive plants, which are inevitable targets, and electricity moves on vulnerable lines. A move toward micro-power plants, solar energy and other such systems would not only be smarter, but also safer.
Dan Gillmor, Technology Columnist, September 8th, 2002 San Jose Mercury News
Mar 24, 2006 PG&E has filed yet another rate case, this one lowers commercial users by up to a whopping 10% while raising residential users fees. Good if you need your company to stay in CA, bad if your're the resident who has to pick up the tab.
Dec 24, 2005 PG&E asks the CA Public Utilities Commission to increase electrical rates 8% for residential customers effective 2007. Additional rate increases for 2008 and 2009 are planned. But if you use less than 130% of basline allowance (described below) there is no rate increase. This is Application A.05-12-002 filed Dec 2nd, write PUC at 505 Van Ness Ave, Room 2103, SF CA 94102 or email public.advisor@cpuc.ca.gov
California Emergening Renewables program and the California Energy Commission
My wife and I completed a remodel of our 30 year old home in January of 2002. For five years prior to the remodel we had had a number of PG&E's power utility service outages. In August of 1996, we lost power for about a week. PG&E sent this letter from John. P. Duncan explaining that many western states were affected when the 'Pacific Intertie" has "significant voltage problems" and may have caused the largest transformer in San Jose to fail. The latest power laps was March 25, 2006 for 4 hours due to storms hitting Northern California. When they do supply power, it isn't often the full 120 Volts.
Our home is located in an urban district of the City of San Jose known as Almaden near: Latitude 37.24 degrees North Longitude: 121.58 degrees West.
These outages as well as the the power deregulation crisis that occurred during summer of 2001 convinced me it was time to consider reliable alternative energy sources to power my home. My goal was to lower my overall public power grid dependency and power consumption (total kwh/year) while increasing the absolute amount of power consumed at home. The data in the following chart demonstrates that this goal has so far been achieved. I have lowered my overall grid power usage per month an average of 36% over the monthly highs recorded for the past three years and the absolute cost in US dollars paid to the utility has dropped USD$30 per month.
Household Kilowatt Hours consumed per month
| KWH | Year | ||||||||||
| Month | 1996 | 1997 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 |
| Jan | n/a | 589 | 658 | 783 | 672 | 839 | 707 | 811 | 923 | 917 | 1070 |
| Feb | n/a | 541 | 571 | 727 | 623 | 815 | 662 | 796 | 712 | 760 | |
| Mar | 423 | 469 | 589 | 649 | 762 | 464 | 563 | 600 | 750 | ||
| Apr | 316 | 501 | 483 | 606 | 730 | 401 | 424 | 624 | 667 | ||
| May | 295 | 556 | 562 | 534 | 488 | 359 | 373 | 570 | 519 | ||
| Jun | 302 | 532 | 651 | 468 | 226 | 188 | 325 | 466 | 416 | ||
| July | 296 | 884 | 717 | 447 | 338 | 442 | 328 | 419 | 584 | ||
| Aug | 260 | 601 | 932 | 415 | 339 | 459 | 345 | 545 | 842 | ||
| Sep | 419 | 744 | 679 | 457 | 387 | 344 | 514 | 430 | 700 | ||
| Oct | 470 | 620 | 606 | 235 | 373 | 434 | 436 | 468 | 801 | ||
| Nov | 570 | 543 | 616 | 331 | 521 | 497 | 632 | 660 | 795 | ||
| Dec | 570 | 770 | 772 | 785 | 681 | 717 | 713 | 726 | 1126 | ||
| Total | 7449 | 8117 | 6222 | 6499 | 5674 | 6260 | 6220 | 8877 |
May 15 2002 - PV System Online, switch to
PG&E E7/ENET Rate Plan
I looked at Fuel Cell systems such as the HomeGen 7000. (www.plugpower.com) But they make noise, their life expectancy is less than solar, and require yearly maintenance. On the flip side, their power/price ratio is better than solar.
At the urging of an an associate that had installed a PV system before (Mike Thompson), I started looking at this technology. First off PV systems are not cheap. Surprisingly they are not complicated systems to own or operate either. The US Dept of Energy provides this useful information page: Photovoltaic (solar cell) systems for homeowners A residential PV system requires the same capital outlay as a new automobile. The California Energy Commission (CEC), an agency of our fair State, offers financial incentives for California residents installing PV solar systems. Unlike an automobile, these systems pay themselves off in time. They also have financial calculators on this site to help you determine if a system would be of benefit based on the information you input. Based on historical usage and current electrical rates, breakeven on my system is currently guestimated at eighty (80) years, see financial section for the calculations. The current E1 rate schedule most residential customers pay the utility Pacific Gas & Electric is as follows:
| Tier | Tier % of BaseLine | Cents /Kwh |
| Tier 1 | 0 - 100% | 12.6 |
| Tier 2 | 100% - 130% | 14.3 |
| Tier 3 | 130 - 200% | 19.3 |
| Tier 4 | 200 - 300% | 23.6 |
| Tier 5 | >300% | 25.8 |
My power utility defines baseline by territory here. It is supposed to cover 60% of a home's total yearly power consumption when on E-1 Standard Service Rate.. Baseline kilowatt hours for a home in Territory "X" is: 12.2 Kwh/day in summer and 13.0 Kwh/day in winter (November 1 to April 30). This provides for a total of 4264 Kwh usage regardless of the size of the home. This is an average of 383 (384 median) KwH per month with 341 minimum in February and 403 maximum in October. At baseline cost of $0.126 this is $580 year or $48 month.
If a home uses greater than 750 kilowatt hours a month and power use is minimal during the hours of 12-6pm Monday thru Friday, then E-7 Time-of-Use service may be the more appropriate billing plan described here.
I interviewed two local installers that have built many systems in the area. I also looked at the gov't web sites for expected power output in my area. Having someone that knows the local building and electrical codes very is helpful. There might even be specific city requirements to meet. My system passed city inspection the first time without problems on January 16, 2002 and I received PG&E utility signoff to operate in grid-tied mode on on May 14, 2002. The four month long delay was unusual and I suspect due to poor product management at Xantrex Corporation, one of the suppliers of equipment I used. The Details of that sorry event are described below in the section Product Safety Standard Issues.
Components as installed by Harmony Solar, Inc
Time to install: 7 days including electrician time to rerun some plugs for the fridge, etc.
Your first issue once you start is how much power you want to generate. Having lived in my home, I had PGE Utility power bills to provide daily averages from monthly readings. How much power a PV system can supply is constrained by space required for the panels, the ability to position the panels to follow the sun, general aesthetics, and money.
We did not want to see the panels from the street nor from the backyard. Since we were remodeling the house with a second story, there was roughly 320 square feet of usable due south facing roof. We decided to use two roofing materials. First we put on a regular asphalt shingle roof then installed the solar panels per the specs, then trim around with matching roof tile. My architect Keith Lee was concerned about weight of the panels while my general contractor Chong-su Chun, was concerned about how the panels bolt to the roof and any leaks he'd have to fix.
The last decision is whether to use poly or monochrystaline technology. The warranted lifetimes are the same, the performance for poly can be 1-3% less than mono type panels, but the key calculation is watts per square meter also called modular efficiency. BP Solarex provides a technical document on how to figure this in their support web page.
24 120 watt BP Solarex Polycrystalline Panels, South Facing Roof
The distance from the solar array to the inverter should be kept as short as possible, these are 48V DC lines. The twenty-four solar panels are 12VDC linked in series of four panels to produce 48 volt DC circuits. These circuits are tied into a combiner box that is then connected to the inverter, for a total distance of about 30 feet. My garage is on the other side of the property (~100 feet) so I built a special closet which vents outside much like a garage and wired the inverter to my computer rack in an adjoining closet and ran a long loop back to where the meter is per utility requirements.
Combiner access box in closet upstairs
During the remodel I built a special purpose 'power' room to house the inverter, charge controller and batteries. While most installs place the inverter in a garage, in this case the distance between the combiner box and inverter would be too far. I could have placed the batteries outside but did not want an unsightly box in the south garden. The city inspector only required that the door and walls match the same requirements as a garage. These requirements were a fire rated door and 3/4" plasterboard. I went one step further and mounted the plasterboard on 1/2 metal raisers and installed a smoke detector. Two large vents exist at the top and bottom of the room which are required for venting battery vapors, these are fitted with a fine metal bug screen. As can seen below, the sealed batteries are located on two shelves below the inverter. The shelves are finished with melamine and have a one inch lip to contain an acid spill from the batteries. The floor is finished with commercial grade (very thick) linoleum vinyl.
The Trace manual warns against placing the batteries under the inverter if using unsealed batteries as the corrosive fumes could damage the inverter.
Inverter, Charge Controller, and Batteries
Trace Engineering inverters appear frequently in home systems, all the bids I received used them. The CEC maintains a list of eligible inverters here. However if you are doing grid-tie without batteries, I would recommend using SMA inverters in home systems. From what I've seen in some other installations nearby, they are very reliable and efficient products.
One other bit I'd do differently had I read the inverter manual before I built the room was the air flow direction and specifications. I was able to create the proper offsets on the left side by notching the wall 7 inches deep. You can see in the second shot of the inverter above what it looked like before this was done. I also needed to attach the SWCA device to the left side as well and bore a hole to a communications rack in the adjacent closet. The serial DB9 connecter terminates on a serial port of an always on home PC computer running NetBSD operating system.
I recommend installing an inexpensive meter on the AC output line to track total power consumption. The SW Inverter does not track local consumption with a GTI installed. Nor does it keep any historical statistics. I've not measured how accurate the inverter reported measurements are either.
Completed System Inverter with GTI, Batteries covered
On page 83 of the Trace Owner's manual v4.01 which is available from their web site, this system can be configured to direct excess power generated back into the utility power grid. This setting is only allowed after the city permit is signed off and the utility (PG&E in my case) approves the paper work for E-NET metering service.
PG&E offers residential customers different
rate schedules. As of 11:30pm on May 14, 2002, I have changed
to E-7 time of use metering with this rate schedule.
| Season | Peak | Off-Peak |
| Winter Nov1 - Apr30 | 0.11636 | 0.08851 |
| Summer May 1 - Oct 31 | 0.31524 | 0.08515 |
This pricing works well with a PV system where the sun's output is strongest. Smaller PV systems will have to contend with the per day/month fixed costs involved including a meter charge, energy distribution and taxes. I don't have that breakeven number yet.
Here are my expenditures. These do not include cost building construction costs or other electrician costs which were included in the cost of the general home remodel.
| Item | Cost USD |
| BP Solarex 120 Panels | $16,600 |
| Inverter,Charger,Batteries | $6,262 |
| Other parts | $7,285 |
| Labor/Misc | $6,750 |
| San Jose City Permit | $300 |
| PG&E Utility Rate Change(E1->E7) | $277 |
| CA State Buydown | ($10,611) |
| Totals | $26,863 |
One other offset taken was this one time tax deduction.
The CA State Buydown is done through the California Energy Commission (guidebook)
and presently rebate is $4.00 per watt for systems less than 30 kW. It began
declining by 20 cents per watt every six months starting 7/1/2003.
PG&E bills me monthly a 'service charge' and a 'minimum charge' which ranges from five to seven dollars a month. This fee covers the E-7 dual meter monthly fee. If I go over the 'Tier 1' usage quantity, there exist additional energy surcharges.
Once a year, a settlement will be made for net energy consumed. My first year of production came to be a net usage of $388.22 or 50% of my grid usage for the past 3 years (99/00 to 01/02) for the same billing period (May->April). If I had a surplus, my utility would only credit my account against future consumption.
The following chart contains actual electrical costs paid including taxes. 1999 and 2000 represent normal usage patterns for two adults in a 1766 square foot home built in 1970. During March thru December of 2001, the house was remodeled and brought up to 2002 building standards for insulation of walls/doors/and windows, fire, and earthquake. The total square footage increased to 3100. During construction, my wife and I continued to live in one room with one bathroom but did not spend as much time at home than in past years.
| Cost | 1996 | 1997 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 |
| Jan | n/a | $72 | $73 | $88 | $81 | $130 | $70 | $85 | $99 | $107 | $181 |
| Feb | n/a | $65 | $63 | $81 | $69 | $119 | $59 | $80 | $70 | $87 | |
| Mar | $50 | $50 | $66 | $73 | $113 | $36 | $48 | $53 | $81 | ||
| Apr | $37 | $55 | $53 | $61 | $110 | $29 | $31 | $55 | $?? | ||
| May | $34 | $55 | $62 | $59 | $3 | $16 | $20 | $46 | $44 | ||
| Jun | $35 | $59 | $72 | $57 | -$2 | -$9 | $7 | $26 | $21 | ||
| July | $34 | $100 | $81 | $55 | $15 | $31 | $10 | $23 | $61 | ||
| Aug | $30 | $67 | $106 | $49 | $19 | $37 | $12 | $45 | $144 | ||
| Sep | $50 | $84 | $77 | $75 | $24 | $13 | $33 | $17 | $82 | ||
| Oct | $34 | $69 | $68 | $27 | $22 | $25 | $23 | $26 | $119 | ||
| Nov | $57 | $60 | $69 | $38 | $45 | $41 | $59 | $73 | $116 | ||
| Dec | $70 | $86 | $102 | $114 | $67 | $71 | $68 | $73 | $184 | ||
| Total | *$431 | n/a | $822 | $925 | $757 | $665 | $419 | $476 | $606 | $1046 |
My first 'fiscal' year (May 02->Apr 03) net energy consumption was $388.22 plus service charges (meter) of approximately $70. A total of 5,168Kwh were consumed from the grid in the first twelve months of operation in excess of what the system generated.
Take the average payout ($834) per year prior to installing the system then subtract what I'm saving per year (2002/3 comes to $416 + $84 in fees/taxes) so I save per year approximately $334 per year at current rates. Divide $334 into the system cost equals eighty years to break even. This estimate is on the conservative side. Some power generated is consumed locally and one also might figure a different cost for power produced when the utility is down. If the rate for power increases to 50 cents per kilowatt hour breakeven drops to to 25 years.
Current gross power production in kilowatt hours for the past twelve months till Nov 26 2003 is 1,404 or 4 kilowatt hours per day average. For the past twelve months total grid power consumption was 5,638 or 15.4 kwh/day average. PV Power production accounts for 28% of power consumed.
So I hired Almaden Window Cleaning to go up on the roof and wash down the PV panels for the first time on May 28, 2004. The grime was pretty thick due to 200+ new homes being constructed in the neighborhood.
You can't manage what you can't measure. -- Tom DeMarco, Author, "Structured Analysis and System Specification"
In order to estimate a more precise break even point, I need to track total kwh produced per day. I connected the SWCA serial connector to COM1 aka /dev/tty00 serial port on my home UNIX server: a Intel Pentium II/Celeron (Deschutes) 451Mhz with 128 Meg RAM running the NetBSD Operating System. The SWCA comes with a manual and an aging DOS software program which emulates the front display panel and a manual explaining the serial protocol. The manual was very helpful so that I could write a C program (available on request) to collect raw statistics directly from the inverter every fifteen minutes. The output from my program is an ASCII text file that looks like this:
1028680098,Inverter/charger amps AC, -06 -06 -06 -06 -06 -06 1028680098,Input amps AC, -06 -06 -06 -06 -06 -06 -06 1028680098,Load amps AC, 00 00 00 00 00 00 00 1028680098,Battery actual volts DC, 53.0 52.8 53.0 52.8 53.0 52.8 52.8 1028680098,Battery TempComp volts DC, 53.6 53.8 53.8 1028680098,Inverter volts AC, 123 122 123 123 123 123 123 1028680098,Grid (AC1) volts AC, 119 119 119 119 119 119 119 1028680098,Generator (AC2) volts AC, 00 00 00 00 00 00 00 1028680098,Read Frequency Hertz, 60 60The first field contains the unix timestamp: Aug 6, 5:28pm 2002, the second field is the field identifier as documented in the Inverter Manual, the next set of numbers represents the reading one would see on the LCD display. When viewing a given meter such as "Input amps AC" on the LCD, the reading may vary over a range. So for any given instant of time the measurement appears as a series of numbers.
Putting it all together, the entry above says that at 5:28pm my PV system was producing 738 watts of apparent power (VA) as measured by multiplying 6 amps AC times 123 'Inverter' volts AC. The minus sign represents power being supplied by the sun or by the discharging of the batteries. A positive values would indicate net power consumption from protected household loads or the charging of batteries.
Next I wrote a perl script that is started once a day to generate a report from the raw data. In this case, the number series above must be reduced to one value. The perl script computes a set of modes and from the modes it then computes a median value to use in further calculations culminating in a daily production report.
This report is prepared each night from from data collected from the SW 4048 Inverter via SWCA. Here is the previous days PV power production report.
The following section describes household electric loads as measured with a Brand Electronics Model 4-1850 Watt Meter.
One 60 amp AC protected circuit located in the sub panel near the power room is broken down into various 20 amp AC circuits. A main panel powers all the unprotected loads.
Here is an interesting US Department of Energy report on typical appliances found in urban homes and their power consumption.
Unprotected loads include the original home main electrical panel and parts of the new sub panel. Unprotected circuits supply power to the garage (door, plugs, lighting), exterior house lighting, all AC power plugs, oven, kitchen appliances, automatic landscape watering system, entertainment electronics (tv, vcr, stereo), wireless phones, gas furnace/air conditioning system. Also, office appliances: computer/fax/data network comprised of both wired and IEEE 802.11b wireless access point, a 150Kb DSL modem for internet access via SBC formerly Pacific Bell, formerly ATT.
Protected loads including lighting in all bedrooms, halls, and smoke detectors. All fixed interior lighting consists of recessed low voltage halogen 50W bulbs.
Separate circuits exist for powering a refrigerator and a hot water recalculation pump that runs for a few hours twice a day. The rest of the house electrical remain on existing unprotected circuits in the main panel.
The Warren-Alquist Act provides information on California Energy Commission
During my installation, Underwriters Laboratories changed its "UL" standard by which systems that connect to utility grid are measured. Here is my story as to why getting my rebate check and getting the system authorized to sell to the grid was delayed by four months.
Dec 13, 2001 I got a letter from California Energy Commission de-listing my particular inverter due to a UL safety advisory found when testing out older gear with newer UL standards: Islanding and Harmonic Distortion .This will only occur when a system is running in a mode that supplies power back to the utility grid.
Jan 24, 2002 Trace/Xantrex states that systems will be upgraded to support new ul listing for SWII systems with GTI accessory. So am now waiting for when the replacement parts will arrive.
Apr 16, 2002 Trace/Xantrex finally ships a new SW4048 and GTI a month later than they said it would, the reason given was poor behavior (I heard something like lights would flicker) with the GTI device. Called PG&E last week and left a message with David Ore, assistant Pat, as well as emailed gen@pge.com. I am still waiting to hear back from him on getting a final inspection for E-NET metering done.
May 6, 2002 Harmony Solar finishes replacing SW4048 inverter and added the GTI device. The GTI makes a large amount of noise when the grid AC disconnects then reconnects. It settles down to a nominal high pitched hum which is slightly worse than the inverter itself. My bigger issue is that the SW4048 Meters(4) Load display no longer reports any valid data.
Debora at PG&E replied to my repeated calls to PG&E and quickly setup an inspection date so my system can be placed into SELL mode/enable E-NET service with PGE.
May 7, 2002 Shellie Bogart at Xantrex responded quickly to my GTI issues. The Load display under Meters(4) is broken now, they acknowledge it and say it will never be fixed. The unit makes a high pitched noise. With my hand on the GTI, one can feel a very strong vibration too. Xantrex agreed this is a defect and say they will fix as soon as possible. What bothers me is that I specifically asked for release notes that would document any known defects prior to install and was told by Xantrex support didn't have any. New gear has been in operation since Friday, I'm seeing up around 17-20 amps AC being created at 12pm.
May 12, 2002 Today I sent Shellie Bogart at Xantrex a note that one can still notice lights dim/flicker, so the problem Xantrex reported that delayed the initial shipment has not been entirely fixed.
May 14, 2002 Tom Wilson from PG&E reviewed my PV system by shutting off all loads on PV system and measuring the system's current peak generation. He then installed a GE bi-directional meter (cost me $277 to switch to E7 service, details below) and explained how to read the meter. This meter has a digital display and cycles through date/time, initial setting of 5000 kwh, current usage, and all diagnostic (LEDs lit) display. At 0940 on December 3, 2002, system is producing .61 kwH.
PGE Time of Day KiloWatt Hour Meter
Spoke with Xantrex Tech support. They confirmed the flickering may still occur. I asked to be on some list to get any fixes/updates to the system now that official Xantrex message board has been shut down due to 'technical difficulties.'
May 20, 2002 I've seen flickering some more and the noise from the GTI is bad. I can't recommend the SW+GTI to combination for a home grid-tie system. If you are building a Grid-Tied system, I'd presently avoid Xantrex products till they get their act together.
June 10, 2002 I've received a letter from PG&E giving me written permission for running in E-NET (sell) subject to Rule 21 agreement, but it took more than 10 days (as is specified in the contract) after the PG&E inspection and install of the new E7 bi-directional meter. The letter did come promptly after a call to David Ore. Now I am working with the CEC to obtain my buydown claim check. I spoke with Ida Hasni at CEC who stated I needed the following additional paperwork.
June 20, 2002 I got a call from Payam Norvath that my paperwork is now in order and I should receive my claim check in 2-3 weeks. I also worked with my tax advisor, Eric Martin, EA to get California State Tax form 3508 completed, which provided a 15% deduction on the net cost of the system in the year th system was installed. If my system were commercial, a Federal Tax form 8835 "Renewable Electricity Production Credit" would apply next year but only to commercial entities.
July 11, 2002 Today I finally received my CEC rebate. It was slightly less than what my installer said it would be...
March 11, 2003. Xantrex and PG&E send a letter giving stating that a SW Series Firmware Upgrade also known as a bug fix for anti-islanding is available and I must respond within 30 days
The return address on the envelope is for PG&E which reads:
Mail Code B8M PO BOX 770000 SF CA 945177And the Xantrex Corporation letter is from
Harold Hirsh Tim Attridge, VP Marketing Xantrex 8999 Nelson Way Burnaby, BC Canada V5A 45B
So I call them up at 800-446-6180 and provide this information which they already have since Xantrex had to upgrade my inverter at their cost previously and I could not get my CEC rebate without.
The Xantrex (Trace) manual and user interface on this device were very well done not to mention you can drive it remotely via terminal emulation from your computer systems. Manuals in Adobe PDF format are online on in their document depot. The manual for the inverter is a must read, Xantrex appears though to be moving away from this product, the manual is now in their archive section: SW II Inverter .
If you build a PV system, review your product's manuals and specs early, they provide key information on space, noise, and other such requirements.
Here is a list of other useful residental PV home installs.
All images and text copyright 2001-2007 by Michael MacFaden mrm@macfaden.com,
no republication without express permission.
