Our solar production

[turbo2ltr]

1,105 kWh a/c production from my 7.59 kW d/c array for February 2013 :mrgreen:

Hmm, I only got 582 for Feb on my 5.5kW DC system

 

[SilverLeaf]

1,105 kWh a/c production from my 7.59 kW d/c array for February 2013 :mrgreen:

Hmm, I only got 582 for Feb on my 5.5kW DC system

My system is dead-on South at 180 degrees. It's also 7.59 kW dc.

 

[RegGuheert]

1,105 kWh a/c production from my 7.59 kW d/c array for February 2013 :mrgreen:

Hmm, I only got 582 for Feb on my 5.5kW DC system

My system is dead-on South at 180 degrees. It's also 7.59 kW dc.

Elevation is also important: A flatter array will tend to produce less in wintertime and more in summertime.

 

[smkettner]

How much solar would I need?

Annual usage 12,600 kWh, Southern California, roof with typical slope faces slightly west of fully south.

I don't want to zero out my bill but maybe cut in half.

Would 2 kW be enough? 3 kW?

 

[RegGuheert]

How much solar would I need?

Annual usage 12,600 kWh, Southern California, roof with typical slope faces slightly west of fully south.

I don't want to zero out my bill but maybe cut in half.

Would 2 kW be enough? 3 kW?

Our array is about 14 degrees west of south (solar noon for our array is about 1 PM) and this only reduces production by about 1.2%. Tony Williams' 8.3 kW array in San Diego produces about 14.5 MWh/year. So to produce 6.3 MWh/year I would estimate you need about a 3.6 kW array, assuming similar roof slopes.

 

[wsbca]

How much solar would I need?

Annual usage 12,600 kWh, Southern California, roof with typical slope faces slightly west of fully south.

I don't want to zero out my bill but maybe cut in half.

Would 2 kW be enough? 3 kW?

My 3.44kW DC/3 kW AC system also in SoCal with a similar orientation (maybe slightly more west) is making about 5800-5900 kWh per year so far (coming up on 3 years). It will drop slowly (few percent a year) but surely over the life of the system.

One thing to consider is that net cost per installed watt typically goes down as the size of the system goes up, because some of the costs are less variable with the # of panels - transportation (of the materials, and the labor force), labor time to prep the roof and install the racks, the conduit runs, even the inverter (a 4K inverter should not cost 4/3 as much as a 3K inverter.) And beyond all that, at least in theory vendors have more room to compete with each other as the gross margin goes up. A 2kW system can cost them about the same to install as a 5kW system except for the panels themselves (granted, those are a big chunk of the total, but by no means all of it).

Depending on how your rates are tiered, cutting your bill in half dollar wise may not be the same thing as cutting your usage in half, but the more you make and don't buy, the more fun it is.

My main advice is to go for more than you initially think you want. Rates aren't going to go down. You might get another EV or PHEV someday.

 

[TonyWilliams]

...Date......Monthly....Year to Date....Daily Peak

Jan 2012: 937 kWh..... 937 kWh..... 39.79 kWh
Feb 2012: 970 kWh....1910 kWh.... 43.57 kWh
Mar 2012: 1210 kWh.. 3120 kWh... 50.72 kWh
Apr 2012: 1267 kWh.. 4380 kWh... 54.18 kWh
May 2012: 1390 kWh.. 5770 kWh... 53.6 kWh
Jun 2012: 1455 kWh.. 7230 kWh... 55.1 kWh
July 2012: 1402 kWh.. 8632 kWh... 52.4 kWh
Aug 2012: 1318 kWh.. 9951 kWh... 50.0 kWh

http://enlighten.enphaseenergy.com/public/systems/Ukwf22392" onclick="window.open(this.href);return false;

September 2012 Total: 1.25 MWh
October 2012 Total: 1.12 MWh
November 2012 Total: 0.91 MWh
December 2012 Total: 0.716 MWh

2012 Year to Date: 13.9 MWh


January 2013 Total: 0.955 MWh
February 2013 Total: 0.999 MWh


Lifetime: 19.9 MWh



Estimated Production

Month Solar Radiation
(kWh/m²/day) AC Energy (kWh)
January 4.1 913.0
February 4.7 937.0
March 5.41 1191.0
April 6.08 1276.0
May 6.49 1400.0
June 6.67 1376.0
July 6.74 1403.0
August 6.57 1356.0
Sept 6.01 1213.0
October 4.99 1072.0
Nov 4.45 946.0
Dec 3.78 839.0

 

[Boomer23]

How much solar would I need?

Annual usage 12,600 kWh, Southern California, roof with typical slope faces slightly west of fully south.

I don't want to zero out my bill but maybe cut in half.

Would 2 kW be enough? 3 kW?

I'm also in OC, similar roof orientation. I'm expecting to exactly zero out my bill with my 5.16 kW DC system for my net metering year ending now with SCE on rate schedule TOU-D-TEV:

Total year power usage 11,134 kWh
Total EV charging 3,100 kWh
Total solar power generation 8,448 kWh
Net power usage from SCE 2,686 kWh
Net bill at NM year end: ZERO

Notice that I didn't cover all of my usage with solar, but since I'm on a TOU EV charging plan, with charging over night, I'm still going to zero out my bill.

All EV charging was done between midnight and 6 am. No home air conditioning, so minimal power usage during Peak solar hours.

This rate plan works fantastic with solar, not quite as well if you use a lot of power during Peak weekday hours, and works terrible if you don't have solar and you do use a lot of Peak power (Summer Peak rates are very high, currently about 70 cents/kWh in Tier 2. This is wonderful if you have solar because you get the full retail credit for net generation during those hours.)

If you are currently on the standard Domestic Tiered plan, you could probably cut your bill just by going on TOU-D-TEV without going solar as long as you don't use a lot of Peak weekday power and you charge your LEAF late at night. If you do use a lot of Peak power (air conditioning, usually) I agree that a solar system of about 3 kW DC would go a long way toward cutting your bill in half. But zero is more fun than half, so I recommend going the extra 2 kW.

 

[smkettner]

I am already on TOU-DTEV-SDP according to my bill.
I was TOU-D-TEV or the whole house EV rate plan until it was updated.
Not sure that it is any different.... the rates just keep going up

Thanks for the comments. I don't want to get over sold by the solar people and become a net producer.
I just want to cut most of the top tier off.

 

[RegGuheert]

I am already on TOU-DTEV-SDP according to my bill.
I was TOU-D-TEV or the whole house EV rate plan until it was updated.

Sorry, my numbers are just for energy production without any consideration for TOU. And it looks like my estimate for Tony's production was a tad high.

Not sure that it is any different.... the rates just keep going up

To me that is the beauty of solar: you purchase it once and basically lock in your electricity rate IF your system is reliable.

At this point I will make a plug for microinverters instead of a central inverter. While they may be slightly more costly up front, they should provide higher reliability and a lower TCO than central inverters. Microinverters carry the same 25-year warranty that the PV panels carry and their real-life MTBF has proven to be up there with PV panels. My own calculations of Enphase microinverters in the field indicates just 3 failures after over 1000 unit-years of operation for a demonstrated MTBF of over 350 years. One of those three failures was at installations and arguably should be excluded from the calculation as an infantile failure. That would yield an MTBF over 500 years!

By contrast, you can expect to replace your central inverter after about 10 years.

 

[thankyouOB]

3kw system south facing in LA yields 6000 kWh each year for five years.
with TOU, i get a bonus in terms of how much cost I can offset.

that originally was going to do all my power and zero it out, but when DWP added TOU, I got enough bonus to zero out my LEAF use as well. Of course, the LEAF was added in 2011.

Most solar companies, at least three years ago, will give you a true read.
be a savvy consumer, ask 2 or 3 to your home to propose a system, and ask each to cut your bill 50% 75% and 100%, or whatever choices you prefer.

 

[RegGuheert]

3kw system south facing in LA yields 6000 kWh each year for five years.

Very nice! What is the elevation angle of your array (alternatively, roof pitch)? TIA!

 

[HighDesertDriver]

Smkettner,

We are located near you, but do not experience the coastal effects you may. Our 5/12 rooftop pitch array is oriented at 180 degrees and consistently delivers 12,000 kWh/year. Interestingly, the total annual production has remained remarkably level over 7 years with none of the expected aging drop-off. (Monthly production varies year-to-year, but the annual total has been only +/- 100 kWh.) The single SMA 6000 inverter just hums along in the garage and consumes 4W in standby at night.

14,500 kWh/year would be required to cover all our electricity needs, including the Leaf's 16,000 annual miles. We just finished our first full NEM year with the Leaf, sending SCE $364 in the true-up. For your production goal, 3-4kW would be reasonable. Orientation, shading, and local weather variations will determine the actual size.

 

[thankyouOB]

3kw system south facing in LA yields 6000 kWh each year for five years.

Very nice! What is the elevation angle of your array (alternatively, roof pitch)? TIA!

roof is flat, the pitch is whatever is the optimum. i believe it was ~30 degrees.

 

[smkettner]

2.94kW DC guaranteed production 5,011 kWh, $17,155 or net $12,008 after fed tax credit. ( usage ~12,600 )
I am a little befuddled by the purchase vs lease. They sure push the lease... makes me think more value to me in the purchase.

Not really a lease but a "SolarPPA Prepay Plan" where I am buying power at 8.1 cents for 20 years.
Lots of graphs showing higher return due to low up front cost.

Purchase shows break even at 7 years and we will be around for at least 10.
I think production could be higher where they get the credit in leasing and I would get the bene if purchased.

I would really like to see how SCE TOU-EV net metering looks on a bill. If someone could send me a PDF with just the tier graph showing cost summary

Have the option to go a bit smaller.

Any aditional thoughts? What would you do? I am inclined to buy because I think I understand it better and potential upside.

 

[HighDesertDriver]

The consensus from various forum topics and solar publications is that owning gives you all the benefits in exchange for all of the risks. That said, the "risks" are pretty low. I have yet to hear of the inverter that wore out in ten years. The panels have a manufacturing defects warranty, but that is effectively superseded by the 25-year performance warranty in California. If one fails, it is not producing and will be replaced.

Second choice is getting your own loan, and third is leasing with an option to buy after an agreed time. Solarcity, Verango, or the various large leasing installers may be best for households that generally prefer to be concerned with just paying the monthly bill for a straight-forward design. How large to build is more a matter of preferences and goals than ROIs which can be reasonably accurate (for the given assumptions) but may not be equally representative of actual operation.

 

[Phoenix]

..... I have yet to hear of the inverter that wore out in ten years........

The fan in my 3500W Sharp SunVista Inverter failed right before the 5-year anniversary. I'm anticipating that the replaced fan will fail again within the next five years or sooner.

 

[RegGuheert]

I have yet to hear of the inverter that wore out in ten years.

I have yet to see an inverter that lasted 10 years.

For reference, here is a thread in which we discussed this topic: Grid tied PV system with battery backup. Note that about eight years ago many heads of central inverter companies did not think it is possible or reasonable to make long-lasting inverters:

In case you do not believe my MTBF estimates, here are some quotes from executives at the major makers of large inverters:

A Government study by America interviewing all major Solar inverter manufacturers. Interesting most expect 15 year lifespan is considered good/great. Capacitors seem to be the weakness. Something to factor in when buying your system,,,,

•Xantrex, Managing Director: “Why make inverters with a longer life when the customer is better off replacing the inverter every 10 years or so anyway? The inverters available in 10 years will be better products with higher efficiency.”•SMA America, President: “Why focus on higher reliability? Our customers worry only about first-cost. In any case, it’s more cost-effective to just replace the inverter in 10 years.”•Sustainable Energy Technologies, Director of Operations: “A 20-year lifetime for PV inverters is at least 10 years away.”•Mitsubishi: “A 20-plus-year life for inverters is impossible. Some parts of the inverters would need to be replaced over such an extended period.”•SMA, Head of Solar:“A 20-year lifetime is not possible.”•Fronius, Head of Sales (Germany):“Inverter MTBF may reach 12 years by 2015. A 20-year lifetime can’t be achieved.”•GE Energyindicated that 20-year life would not be practical without a significant impact oncost. A 15-year life is more reasonable, and that should be reviewed based on life-cycle costs impact.•Contrary to statements made in a recent Photon International article (April 2005), manufacturers and other industry experts we spoke to do not believe that capacitor improvements alone will result in inverters that can “keep going for more than 20 years.”

I wonder how much business these companies have lost to Enphase by not understanding the critical importance of reliability in terms of how it affects life-cycle costs?

 

[AndyH]

I have yet to hear of the inverter that wore out in ten years.

I have yet to see an inverter that lasted 10 years.

I've got an old 150W 12VDC square wave inverter in regular use that's 12 years old. I know, that's not what you're talking about though.

For reference, here is a thread in which we discussed this topic: Grid tied PV system with battery backup. Note that about eight years ago many heads of central inverter companies did not think it is possible or reasonable to make long-lasting inverters:

In case you do not believe my MTBF estimates, here are some quotes from executives at the major makers of large inverters:

A Government study by America interviewing all major Solar inverter manufacturers. Interesting most expect 15 year lifespan is considered good/great. Capacitors seem to be the weakness. Something to factor in when buying your system,,,,

•Xantrex, Managing Director: “Why make inverters with a longer life when the customer is better off replacing the inverter every 10 years or so anyway? The inverters available in 10 years will be better products with higher efficiency.”•SMA America, President: “Why focus on higher reliability? Our customers worry only about first-cost. In any case, it’s more cost-effective to just replace the inverter in 10 years.”•Sustainable Energy Technologies, Director of Operations: “A 20-year lifetime for PV inverters is at least 10 years away.”•Mitsubishi: “A 20-plus-year life for inverters is impossible. Some parts of the inverters would need to be replaced over such an extended period.”•SMA, Head of Solar:“A 20-year lifetime is not possible.”•Fronius, Head of Sales (Germany):“Inverter MTBF may reach 12 years by 2015. A 20-year lifetime can’t be achieved.”•GE Energyindicated that 20-year life would not be practical without a significant impact oncost. A 15-year life is more reasonable, and that should be reviewed based on life-cycle costs impact.•Contrary to statements made in a recent Photon International article (April 2005), manufacturers and other industry experts we spoke to do not believe that capacitor improvements alone will result in inverters that can “keep going for more than 20 years.”

I wonder how much business these companies have lost to Enphase by not understanding the critical importance of reliability in terms of how it affects life-cycle costs?

A couple of points. First, things have changed since those often-requoted comments were passed around in 2009 (hmmm...apparently they're from NLT 2006). Since then, the root cause for a world-wide bad capacitor problem has been identified and fixed. That means that ALL of the capacitor-centric issues have to be reworked. Second, SMA has central inverters today with a 20 year warranty. That in itself negates many of the quotes. Lastly, as I've reported in other threads, older-tech inverters (prior to the quoted comments) have lasted beyond 15 years and have been known to last more than 20. Central inverters manufactured since the 1990s are expected to routinely operate 20 years and many are expected to last for 30.

Lastly, on the subject of capacitors and other components many think are the common failure points, I offer this:
http://engineering.case.edu/centers/sdle/sites/engineering.case.edu.centers.sdle/files/peshek.pdf

Note that this presentation suggests that the above quotes predate 2006, and note that once the counterfeit electrolytic problem was solved, the rest of the reliability challenge was fixed by making different engineering choices. This progress - exactly the type of developments that allowed Enphase to increase their warranty from 15 to 25 years - also applies to current-tech central inverters.

One additional factor in inverter life is the expansion of highly accelerated life testing (HALT). This process has given manufacturers much better failure data - and has also resulted in inverter lifespan improvement.

Cheers.

edit...fixed quote tags

 

[devprius]

I'll play:

4.94 kW DC / 4.31 kW AC leased system from Sungevity. 26 Suntech 190W panels hooked up to a PowerOne PVI-5000 central inverter. Array is pointed at 116 degrees azimuth, with a 15-degree pitch. Installed in June 2012, and went live towards the end of July. Estimated annual production of 6178 kWh for the first year (5869 kWh guaranteed).

Full month production numbers.

• August 2012: 699 kWh
  September 2012: 643 kWh
  October 2012: 502 kWh
  November 2012: 358 kWh
  December 2012: 256 kWh
  January 2013: 408 kWh
  February 2013: 456 kWh