Panel and Inverter selection - Pricing - Socal

[fengshui]

I'm evaluating options for a Grid-Tie PV system in SoCal, and would appreciate any advice the group has:

Situation: I have a south-facing roof with excellent sunlight, about large enough to hold a 7-8kW system. There's a chimney in the middle of the roof, which creates some shade, but otherwise, it's an excellent location. I also have a secondary roof section that could hold another 2-3 kW with similar facing but an older roof and small shading concerns from a nearby tree, which could be regularly trimmed back.

My options are a 7.8kW Sunpower system squeezed onto the main roof at $40,500 Gross ($5.15/watt), or a 8.8kW Solarworld/REC (I have two similar bids) system on both roofs at $38,750 Gross ($4.27/watt).

Both systems project production between 13-14k kWh annually (depending on assumptions). I expect some increase in usage as my kids get older, and if I add more EV miles.

Questions:

1) How hard is expansion of a system? Given my unknown future usage, should I leave panels off of the older secondary section, and hold that space open for a future expansion when the roof is eventually replaced?
2) The vendors I have are quoting different sizes of inverters. The 7.8kW Sunpower is quoting an Inverter with a 7680 kW Output, while the 8.8kW Solarworld/REC quotes are split between the same 7680kW Output Inverter, and a 6.6 kW Output Inverter. Is there an advantage to having a larger inverter relative to the panel input? What about expansion? Were I to add a second bank of SunPower on the secondary roof in 5 years, am I going to want a new inverter for that bank anyways, or would I normally just use the available headroom on the existing inverter?
3) The general consensus seems to be that while Sunpower is a higher-quality and higher-performing product than the competition, that in most cases where space is not a constraint, it's not worth paying for sunpower compared to installing more panels of a lower-performing product. Based on my situation above, and the price difference of $0.90/watt, is Sunpower worth it?
4) The REC/Solarworld quote is using a single inverter. For an installation with limited shade, should I be asking about microinverters?
5) Despite the difference in size, all the bids project the same rough amount of solar generation. Is that accurate? Will I get the same solar production from a 7.8kW Sunpower system as a 8.8kW Solarworld/REC system, or are they just using projections with more or less conservative assumptions?

[Ian S]

Comments in bold:

I'm evaluating options for a Grid-Tie PV system in SoCal, and would appreciate any advice the group has:

Situation: I have a south-facing roof with excellent sunlight, about large enough to hold a 7-8kW system. There's a chimney in the middle of the roof, which creates some shade, but otherwise, it's an excellent location. I also have a secondary roof section that could hold another 2-3 kW with similar facing but an older roof and small shading concerns from a nearby tree, which could be regularly trimmed back.

My options are a 7.8kW Sunpower system squeezed onto the main roof at $40,500 Gross ($5.15/watt), or a 8.8kW Solarworld/REC (I have two similar bids) system on both roofs at $38,750 Gross ($4.27/watt).

Both systems project production between 13-14k kWh annually (depending on assumptions). I expect some increase in usage as my kids get older, and if I add more EV miles.

Questions:

1) How hard is expansion of a system? Given my unknown future usage, should I leave panels off of the older secondary section, and hold that space open for a future expansion when the roof is eventually replaced? How well do you understand your current usage and potential for conservation apart from solar? Depending on the answer, you might be able to go with a smaller system. Generally speaking, you get the most bang for the buck by cutting higher tier usage and much less when replacing the lower tiers with solar. Expansion of the system to a second roof will incur new permitting and other fixed types of costs but that might be offset by the costs of removing and reinstalling of that portion if you install it now and redo the roof in a few years.
2) The vendors I have are quoting different sizes of inverters. The 7.8kW Sunpower is quoting an Inverter with a 7680 kW Output, while the 8.8kW Solarworld/REC quotes are split between the same 7680kW Output Inverter, and a 6.6 kW Output Inverter. Is there an advantage to having a larger inverter relative to the panel input? If you are saying that the 8.8 kW quotes utilize over 14 kW in inverter capacity, that's probably not the best setup. Panel nameplate wattage should be about the same as inverter capacity. What about expansion? Were I to add a second bank of SunPower on the secondary roof in 5 years, am I going to want a new inverter for that bank anyways, or would I normally just use the available headroom on the existing inverter? I don't think having that much headroom on an existing inverter is a good idea. Match the inverter with panel capacity now and just add another inverter later. Or look into microinverters.
3) The general consensus seems to be that while Sunpower is a higher-quality and higher-performing product than the competition, that in most cases where space is not a constraint, it's not worth paying for sunpower compared to installing more panels of a lower-performing product. Based on my situation above, and the price difference of $0.90/watt, is Sunpower worth it? You should look at the cost difference after all tax credits/incentives are figured in. You might also want to get additional quotes as your pricing sounds a bit on the high side - others more familiar with the SoCal area will chime in I'm sure.
4) The REC/Solarworld quote is using a single inverter. For an installation with limited shade, should I be asking about microinverters? Maybe, it depends on the nature and degree of shading. E.g., some early morning shading before 9 AM may not be worth worrying about.
5) Despite the difference in size, all the bids project the same rough amount of solar generation. Is that accurate? Will I get the same solar production from a 7.8kW Sunpower system as a 8.8kW Solarworld/REC system, or are they just using projections with more or less conservative assumptions? Projections can vary a bit but it may also be that the shading on the second roof is affecting the output of the those panels enough to significantly reduce the kWh output per nameplate wattage so you wind up with similar overall output to the SunPower system located entirely on the shade-free roof.

[fengshui]

How well do you understand your current usage and potential for conservation apart from solar? Depending on the answer, you might be able to go with a smaller system. Generally speaking, you get the most bang for the buck by cutting higher tier usage and much less when replacing the lower tiers with solar. Expansion of the system to a second roof will incur new permitting and other fixed types of costs but that might be offset by the costs of removing and reinstalling of that portion if you install it now and redo the roof in a few years.

I understand my current usage pretty well, with hourly data going back 18 months. Thanks for pointing out the balancing between the new permitting and the removal and re-installation of a system. There's going to be a few grand in costs their either way.

If you are saying that the 8.8 kW quotes utilize over 14 kW in inverter capacity, that's probably not the best setup. Panel nameplate wattage should be about the same as inverter capacity.

I wasn't clear. I have two bids for the 8.8kW system, one with a 7.6kW Inverter, and one with a 6.6kW Inverter. Sorry about the confusion. I certainly wouldn't want a 14.4kW Inverter. Is a 6.6kW Inverter too small for a 8.8kW system?

You should look at the cost difference after all tax credits/incentives are figured in. You might also want to get additional quotes as your pricing sounds a bit on the high side - others more familiar with the SoCal area will chime in I'm sure.

The pricing on the cheaper system is pretty good, based on the data in the CSI database. I saw few systems in my area installed for less than $5/watt. The net price delta after incentives is $0.60/Watt.

Projections can vary a bit but it may also be that the shading on the second roof is affecting the output of the those panels enough to significantly reduce the kWh output per nameplate wattage so you wind up with similar overall output to the SunPower system located entirely on the shade-free roof.

Interesting. I'm not sure that they're being that detail-oriented to incorporate the shading effect on the second roof, but maybe.

Thanks for your insights. I'll look for input from other people in SoCal, particularly people in SCE territory, like me.

[Ian S]

I wasn't clear. I have two bids for the 8.8kW system, one with a 7.6kW Inverter, and one with a 6.6kW Inverter. Sorry about the confusion. I certainly wouldn't want a 14.4kW Inverter. Is a 6.6kW Inverter too small for a 8.8kW system?


The pricing on the cheaper system is pretty good, based on the data in the CSI database. I saw few systems in my area installed for less than $5/watt. The net price delta after incentives is $0.60/Watt.

I'd say the 6.6 kW inverter is too small unless they're sizing it based on considerable shading on the secondary roof area. But in that case, the shading is really cutting into your overall output/kW making a system all on the shade-free roof more attractive. I think I'd avoid using the secondary roof since it has the shading issue and the costs of roof replacement in the not too distant future. YMMV. Maybe get a quote for Solarworld/Rec just on the shade-free portion of the roof.

What is your current annual kWh usage? I would not be inclined to have a system that fully offsets that usage. IMHO, the utilities are going to squeeze solar customers as much as they can in the future. There is going to be pressure to cut reimbursements at the margins if not deeper. Anyone who thinks they will be allowed to have a zero electric bill indefinitely may be in for a rude awakening. Many places in the US are tacking on fees and limiting net metering to the extent that those with the biggest systems will be hardest hit. Something to think about. If you've studied the CSI database, then you've a good idea of pricing in your area.

You may also want to try to get an estimate of production using PVwatts and see how it correlates. Just use a derate of about .85 instead of .77.

[Naptown]

The rules have changed with the new dual mppt inverters. If all facing in one direction yes keep it sized about the panel wattage. If arrays are oriented in different directions use the manufacturers design tool to size accordingly. You can potentially go much larger on the array than you would think.

[Ian S]

The rules have changed with the new dual mppt inverters. If all facing in one direction yes keep it sized about the panel wattage. If arrays are oriented in different directions use the manufacturers design tool to size accordingly. You can potentially go much larger on the array than you would think.

Rich, I interpreted the O.P.'s describing "a secondary roof section that could hold another 2-3 kW with similar facing but an older roof" as meaning it was exactly the same orientation but maybe he can clarify for sure. They quoted both 7.6 kW and 6.6 kW inverters for the same 8.8 kW system but maybe the 6.6 was one of the more flexible newer models and the 7.6 wasn't.

[fengshui]

I'd say the 6.6 kW inverter is too small unless they're sizing it based on considerable shading on the secondary roof area. But in that case, the shading is really cutting into your overall output/kW making a system all on the shade-free roof more attractive. I think I'd avoid using the secondary roof since it has the shading issue and the costs of roof replacement in the not too distant future. YMMV. Maybe get a quote for Solarworld/Rec just on the shade-free portion of the roof.

What is your current annual kWh usage? I would not be inclined to have a system that fully offsets that usage. IMHO, the utilities are going to squeeze solar customers as much as they can in the future. There is going to be pressure to cut reimbursements at the margins if not deeper. Anyone who thinks they will be allowed to have a zero electric bill indefinitely may be in for a rude awakening. Many places in the US are tacking on fees and limiting net metering to the extent that those with the biggest systems will be hardest hit. Something to think about. If you've studied the CSI database, then you've a good idea of pricing in your area.

You may also want to try to get an estimate of production using PVwatts and see how it correlates. Just use a derate of about .85 instead of .77.

Annual usage is about 14,500 kWh. Does that fit with a 8.1 kW system?

I don't intend to fully eliminate my usage, but I do want a system that gets closer to it than I might normally as I'm expecting to increase usage in the coming years (a second EV (+200 kWh monthly) plus natural usage increases of kids).

Rich, I interpreted the O.P.'s describing "a secondary roof section that could hold another 2-3 kW with similar facing but an older roof" as meaning it was exactly the same orientation but maybe he can clarify for sure. They quoted both 7.6 kW and 6.6 kW inverters for the same 8.8 kW system but maybe the 6.6 was one of the more flexible newer models and the 7.6 wasn't.

This is correct. Both roof sections are identically facing. The two inverters were both newer models. (One SMA, and the other Power-One)

[J.P.M.]

I understand my current usage pretty well, with hourly data going back 18 months. Thanks for pointing out the balancing between the new permitting and the removal and re-installation of a system. There's going to be a few grand in costs their either way.


I wasn't clear. I have two bids for the 8.8kW system, one with a 7.6kW Inverter, and one with a 6.6kW Inverter. Sorry about the confusion. I certainly wouldn't want a 14.4kW Inverter. Is a 6.6kW Inverter too small for a 8.8kW system?


The pricing on the cheaper system is pretty good, based on the data in the CSI database. I saw few systems in my area installed for less than $5/watt. The net price delta after incentives is $0.60/Watt.


Interesting. I'm not sure that they're being that detail-oriented to incorporate the shading effect on the second roof, but maybe.

Thanks for your insights. I'll look for input from other people in SoCal, particularly people in SCE territory, like me.

Not being in SCE terr., but SDG & E, & FWIW:

1.) Make sure you will have an EV and remember it can probably be charged w/ EV rate electricity at close to tier one.

2.) Replace all but the tier 1 & tier 2 electricity if not positive of EV. If you're sure of an EV, add 4000 kWhr./yr to current annual load for the EV and 1st guess solar array size to replace 80% of that total load, +/- some for a SWAG.

3.) Equal kW sized arrays of different panel manufacture in same orientation, location and shading conditions will initially produce about equal annual output. Sunpower may produce a bit more in the future, yet to be proven, as are advantages of what is arguably a better warranty. At $.60/Watt extra after incentives that may be a tough sell to some for initially equal output and what is likely low warranty claims by most/all reputable manufacturers. Pay your money, take your choice.

4.) Be careful on shading. It can take a bigger toll than just the size of the shadow.

5.) Eyeball and crystal ball alert: As unlikely as this may sound, AB 327 may well accomplish one of it's stated, intended effects of lowering the upper tier rates and raising the lower tier rates. Depending on usage I'd study your rate structure and how it's changing with an eye how it may influence your decision. I don't know about SCE, but SDG & E rates have changed in those directions 2 months running, about 1% per month and although 2 months is far from a trend, given the legislative mandate, it may worth an eyeball look once in a while.

6.) I'd be w/ Ian on the pricing. Seems a bit high. $4.50/Watt for 16, S.P. 327's w/a 5kW string inverter is a fact (SD-CSI-17646). If memory serves, one poster here claims $4.43/ watt for Sunpower. I don't remember if that was for 327's, 335's or 345's. Solarworld around here seems about $3.80/Watt or so. LG & Kyocera maybe a bit less. Check the CSI database.

7.) If you are south facing w/little or no shade, tilted about 20-30 deg., expect 1500-1700 kWhrs./yr. initial system output per kW of system size, +/- 20% or so in SO.CA. unless you're close to the beach. Check a website called PVoutput .org. If you get lucky, you may find a system close to you. Just be mindful of the orientation and size.

8.) Don't be rushed. A good deal today will still be good tomorrow.

[Severum88]

SoCal

Fengshui. Sent you a pm on pricing.

Severum

[fengshui]

Not being in SCE terr., but SDG & E, & FWIW:

1.) Make sure you will have an EV and remember it can probably be charged w/ EV rate electricity at close to tier one.

2.) Replace all but the tier 1 & tier 2 electricity if not positive of EV. If you're sure of an EV, add 4000 kWhr./yr to current annual load for the EV and 1st guess solar array size to replace 80% of that total load, +/- some for a SWAG.

3.) Equal kW sized arrays of different panel manufacture in same orientation, location and shading conditions will initially produce about equal annual output. Sunpower may produce a bit more in the future, yet to be proven, as are advantages of what is arguably a better warranty. At $.60/Watt extra after incentives that may be a tough sell to some for initially equal output and what is likely low warranty claims by most/all reputable manufacturers. Pay your money, take your choice.

4.) Be careful on shading. It can take a bigger toll than just the size of the shadow.

5.) Eyeball and crystal ball alert: As unlikely as this may sound, AB 327 may well accomplish one of it's stated, intended effects of lowering the upper tier rates and raising the lower tier rates. Depending on usage I'd study your rate structure and how it's changing with an eye how it may influence your decision. I don't know about SCE, but SDG & E rates have changed in those directions 2 months running, about 1% per month and although 2 months is far from a trend, given the legislative mandate, it may worth an eyeball look once in a while.

6.) I'd be w/ Ian on the pricing. Seems a bit high. $4.50/Watt for 16, S.P. 327's w/a 5kW string inverter is a fact (SD-CSI-17646). If memory serves, one poster here claims $4.43/ watt for Sunpower. I don't remember if that was for 327's, 335's or 345's. Solarworld around here seems about $3.80/Watt or so. LG & Kyocera maybe a bit less. Check the CSI database.

7.) If you are south facing w/little or no shade, tilted about 20-30 deg., expect 1500-1700 kWhrs./yr. initial system output per kW of system size, +/- 20% or so in SO.CA. unless you're close to the beach. Check a website called PVoutput .org. If you get lucky, you may find a system close to you. Just be mindful of the orientation and size.

8.) Don't be rushed. A good deal today will still be good tomorrow.

I have one EV already, so I'm pretty confident about the second.

As you note, it's right on the edge as to whether $0.60/watt is worth paying to keep the system physically smaller. The CSI database provides phenomenal data for the educated consumer. I think I can use that data to push down the local vendors based on other installs they've done in my area, but I don't know if I'll get below $5/Watt for S.P. 327s here. I'd love to get better pricing, but my area has high costs, and is isolated from the larger markets in LA proper.

It's really hard to project how rates will change up here, especially with the EV-TOU plan in the mix. Tier 1 EV-TOU rates are 28/12/9 cents per kWh, and Tier 2 rates are 47/31/9 with Peak running from 10am to 6pm. Even if I end up pushing my peak solar down to Tier 1, I can still get a decent credit at $0.28/kWh to offset my overnight EV charging. Of course, things can change at any time. Trying to predict anything is probably a SWAG, and I think your recommendation of producing to 80% of known existing use may be the best one.

As for rushing, I definitely am trying not to feel rushed, but I would like to have the system up and running by mid-May so that I can offset the $0.47/kWh Peak charges for pumping the water up to the solar pool heating system. When would you think the latest I could order to make that happen would be?

[silversaver]

My suggestion is plan your solar to cover 100% of your usage and use the base tier rate to cover your EV (work with TOU-EV) if you have South, Southwest or West facing roof. (East facing roof is no good for any TOU.)

Your ROI will be lot shorter with an EV. Going this route, you don't care how utilities company play with pricing with different tiers or TOU. you can just staying in standard net metering plan 1 for 1.

If you are just plan your solar to keep you away from high tier now, that's an bad idea. in other word...short vision. I'm trying to go larger after my solar installation, but everything is $$$$$ now.... too late.....

Unless you really think your electricity demand will stay the same in next 20 years,,,lol

[J.P.M.]

I have one EV already, so I'm pretty confident about the second.

As you note, it's right on the edge as to whether $0.60/watt is worth paying to keep the system physically smaller. The CSI database provides phenomenal data for the educated consumer. I think I can use that data to push down the local vendors based on other installs they've done in my area, but I don't know if I'll get below $5/Watt for S.P. 327s here. I'd love to get better pricing, but my area has high costs, and is isolated from the larger markets in LA proper.

It's really hard to project how rates will change up here, especially with the EV-TOU plan in the mix. Tier 1 EV-TOU rates are 28/12/9 cents per kWh, and Tier 2 rates are 47/31/9 with Peak running from 10am to 6pm. Even if I end up pushing my peak solar down to Tier 1, I can still get a decent credit at $0.28/kWh to offset my overnight EV charging. Of course, things can change at any time. Trying to predict anything is probably a SWAG, and I think your recommendation of producing to 80% of known existing use may be the best one.

As for rushing, I definitely am trying not to feel rushed, but I would like to have the system up and running by mid-May so that I can offset the $0.47/kWh Peak charges for pumping the water up to the solar pool heating system. When would you think the latest I could order to make that happen would be?

I'd optimistically SWAG 8 weeks contract sign to completion, but I'm ignorant of vendor workload in your area. I'd also keep in mind POCO signoff can take additional time after vendor completion as other SCE customers have written on this forum. FWIW, I had a clause written into my contract that the vendor would pickup the difference in bills, solar vs. non solar, if they missed the contract completion date - that was 8 weeks after signing, until actual completion. Seemed fair and they bought off on the idea. They made the 8 weeks BTW. SDG & E took 10 days to inspect which seems about ave. for SDG & E, but that's not SCE.

That CSI database is sumpthin', ain't it ? Vendors don't seem to talk about it much. I wonder why (?!)