~8K Solar system advice request

[hardlymick]

Hello experts,

I'm looking for some advice.

First, some info I hope will help. I live in Los Angeles and our family used 13850 kWh over the last 12 months. It appears our monthly usage has increased about 7-8% over the last two months , since we leased an all electric car. Assuming this trend continues, we'd be well above 14600kWh by this time next year.

I've spoken with several different companies, and there is something of a fly-by-night nature to many of them. This does not fill me with confidence.

I am planning to use the PACE program to finance the purchase of a solar system. I'm looking at 2 options right now, but would welcome alternatives if someone thinks there's a better option:

Option 1: $31,625 ($3.70/watt before rebates)

8.5KW Solar photovoltaic grid-tied System whose system size is 8540watts (DC,STC) and whose system size is 6832 (AC) watts.
28 LG 305 Mono X Neon panels
28 Enphase M250 Micro-inverters

Option 2: $39,601 ($4.84/watt before rebates)

8.18 kW (DC), 7.20 kW (AC) SunPower System
25 x SunPower E20/327 Solar Panel
1 x SUNNY BOY 5000TL-US-22 - 240v (SPR-5002m) 1 x SUNNY BOY 3000TL-US-22 - 240v (SPR-3002m)


Both companies have provided a layout plan, with the LG option having 4 arrays, and the SP having 3:

Array 1 - 10 LG or 10 SP
Tilt: 20
Azimuth: 160 Deg

Array 2 - 7 LG or 7 SP
Tilt: 20
Azimuth: 250 Deg

Array 3 - 7 LG (SP said this is too oblique an angle, and would not install on this section)
Tilt: 20
Azimuth: 70 Deg

Array 4 - 4 LG or 8 SP
Tilt: 5
Azimuth: 160 Deg

Now, in reading this site it didn't take too long to discover two things: Micro-inverters, and particularly Enphase, are not widely endorsed and SunPower is considered not worth the price.

I am not a big fan of the micro-inverters, since the temp on a roof in the San Fernando Vally can get to over 110+ degrees during the hottest time of year. But, I do have some sizable trees around and micro-inverters have been advertised as a good hedge against shading. The SunPower rep claims that there technology, wherein each cell has its own diode, is all the hedge against shade needed for my roof.

The M250 inverter is also capped at 250 watts output. I spoke to an LG rep here in the United States and he suggested the 305 ACe panel. Essentially the same as the one in option 1, but with the LG micro-inverter built on, which can deliver up to 300 AC watts. This could be a third alternative, but I do not have pricing for this option.

In dealing with Sun Power Direct, I've been made more comfortable with the installation process and overall sense that I will have warranty service on parts and labor. I can't say the same about most of the other companies I've talked to. I get the same feeling from of them that I got from remodeling contractors during the housing boom in the early 2000's. Here today, gone tomorrow (when you need them). I'm not sure how to find any reassurance on this issue.

[J.P.M.]

1.) Either LG or S.P. equipped array will produce about the same annual output per installed nameplate (D.C.) kW.

2.) Run PVWatts for each orientation using the premium option and about an 8 -10% derate instead of the 14%.

3.) Stay w/the LG's for price and get more quotes. You ought to be able to get down somewhere close to $3.50/Watt. Look for reputable electrical contractors who have been around a long time and have sold solar for at last 5 years. Avoid Larry with a ladder types. The experienced pros were around before solar and will probably be around after tax credits expire. You might wind up paying a slight premium for quality work and professionalism, but it's worth it.

4.) Put as many panels as possible at the 160 deg. orientation, then the 250 deg. orien. Avoid the 70 deg. orientation as much as possible. I'd suggest not oversizing the system.

5.) Depending on your time of use pattern, going to T.O.U. tariff MAY enable a smaller array to offset an equal or greater $$ amount of your bill. Takes a bit of work to estimate - and it is still an estimate, but between that perhaps allowing LG to meet a smaller load, and thus getting rid of the 70 deg. orientation, you may save a few bucks. S.P. is good stuff, but overpriced and overhyped for what you get.

6.) FWIW, I haven't found my S.P. array to be very forgiving of shade in the late afternoon. ~~ 20% shade or so on a string pretty much kills the output by about 70-80% as a SWAG.

[hardlymick]

1.) Either LG or S.P. equipped array will produce about the same annual output per installed nameplate (D.C.) kW.

2.) Run PVWatts for each orientation using the premium option and about an 8 -10% derate instead of the 14%.

Wow, you're right. I won't be putting any panels there for sure. That calculator is a great resource for projecting cost benefit, thanks for the referral.

3.) Stay w/the LG's for price and get more quotes. You ought to be able to get down somewhere close to $3.50/Watt. Look for reputable electrical contractors who have been around a long time and have sold solar for at last 5 years. Avoid Larry with a ladder types. The experienced pros were around before solar and will probably be around after tax credits expire. You might wind up paying a slight premium for quality work and professionalism, but it's worth it.

Solid advice. So would you recommend the LG with the built on micro-inverter, or a larger capacity panel with a string inverter? I noticed the SP option included two separate inverters, would this ideal for any string inverter setup?

5.) Depending on your time of use pattern, going to T.O.U. tariff MAY enable a smaller array to offset an equal or greater $$ amount of your bill. Takes a bit of work to estimate - and it is still an estimate, but between that perhaps allowing LG to meet a smaller load, and thus getting rid of the 70 deg. orientation, you may save a few bucks. S.P. is good stuff, but overpriced and overhyped for what you get.

Looked into TOU pricing, and it may be worthwhile, more study is needed. I also think we'll look to get a level 2 car charger with a separate meter as LADWP has incentives for equipment purchase, installation and utility pricing for electric car charging.

I am saddened to hear that about SP, they really do make a great impression.

6.) FWIW, I haven't found my S.P. array to be very forgiving of shade in the late afternoon. ~~ 20% shade or so on a string pretty much kills the output by about 70-80% as a SWAG.

So, would micro-inverters help this issue, or would any help they offer be countered by unreliability and overall system inefficiency?

Thank you very much for your reply

[J.P.M.]

Wow, you're right. I won't be putting any panels there for sure. That calculator is a great resource for projecting cost benefit, thanks for the referral.

Solid advice. So would you recommend the LG with the built on micro-inverter, or a larger capacity panel with a string inverter? I noticed the SP option included two separate inverters, would this ideal for any string inverter setup?

Looked into TOU pricing, and it may be worthwhile, more study is needed. I also think we'll look to get a level 2 car charger with a separate meter as LADWP has incentives for equipment purchase, installation and utility pricing for electric car charging.

I am saddened to hear that about SP, they really do make a great impression.

So, would micro-inverters help this issue, or would any help they offer be countered by unreliability and overall system inefficiency?

Thank you very much for your reply

For my part, you're welcome.

A word of caution: Question everything everyone says - even or particularly me. Reason: None of us is as smart as all of us.

As for micros: I'm not a big fan, but opinions vary. Also, without knowing your shading situation, if it's a great deal of shading, micros MAY make sense. A decent vendor can do a shading analysis. That may help in the decision making of micro vs. string. Depending on output, micros may clip a bit with the LG's and more so with S.P.'s which are a higher Wattage panel.

If you haven't done so already, check out the Solar for Dummies series. Older versions are on line for free download.

[solarddy]

String vs Micro inverter a few pros and cons

String inverter systems suffer from micro-fractures in a high-voltage solar panel array, this type of damage is common under mechanical loading of snow or high winds or flexing of the panels for any reason, and can short out a panel in the string and cause a panel fire. (500 degree C hotspots can form under loading) or a panel failure.

A string inverter failure means you are down, a single point of failure from either a large inverter quitting or a panel in the string electrically failing.

The electrically Isolated panels in M250 Micro-inverter arrays can effectively use micro-fractured panels without the same higher risk of fire due to the electrical isolation of the panels and the lesser load voltage of max 43VDC (in a 72cell panel) instead of 500-1000VDC when a micro-fracture failure occurs in a string array.

I like the implied safety of micro-inverters, I also do not mount my micro-inverters between the panel and the roof, as they get too hot IMO (greater than 130 F). P/N junctions break down Time-over-temperature and the cooler you keep the micro-inverters the longer they are going to last. I measured a less than .8VDC voltage drop on a 40' run to the ventilated cabinet I hung my M250's in, so I doubt there is any great loss there.

A micro-inverter array is many parallel inverters so one or two failing panels or inverters doesn't shut down your array production- normally.

I studied the usefulness of solar for the average homeowner and found some glaringly obvious conclusions, the installation industry would like everyone to remain mystified and confused about solar, so they can continue to make money on excessive installation fees (average $5-6K per 10KW of power). They know how easy the plug and play, click-together micro-inverters are. Honestly, anyone who can hook up 4 wires in the breaker box can electrically install a micro-inverter array.

They want you to use 500-1000vdc systems so you must hire one of their servicemen to repair or work on said systems. Keep the voltages up and the average homeowner will not even think about touching a high voltage array, and they would be wise not to. Not to mention the cost when a $2500 inverter fails vs a $150 micro-inverter, it's a no brainer for me after considering the options.

[SunEagle]

String inverter systems suffer from micro-fractures in a high-voltage solar panel array, this type of damage is common under mechanical loading of snow or high winds or flexing of the panels for any reason, and can short out a panel in the string and cause a panel fire. (500 degree C hotspots can form under loading) or a panel failure.

A string inverter failure means you are down, a single point of failure from either a large inverter quitting or a panel in the string electrically failing.

The electrically Isolated panels in M250 Micro-inverter arrays can effectively use micro-fractured panels without the same higher risk of fire due to the electrical isolation of the panels and the lesser load voltage of max 43VDC (in a 72cell panel) instead of 500-1000VDC when a micro-fracture failure occurs in a string array.

I like the implied safety of micro-inverters, I also do not mount my micro-inverters between the panel and the roof, as they get too hot IMO (greater than 130 F). P/N junctions break down Time-over-temperature and the cooler you keep the micro-inverters the longer they are going to last. I measured a less than .8VDC voltage drop on a 40' run to the ventilated cabinet I hung my M250's in, so I doubt there is any great loss there.

A micro-inverter array is many parallel inverters so one or two failing panels or inverters doesn't shut down your array production- normally.

I studied the usefulness of solar for the average homeowner and found some glaringly obvious conclusions, the installation industry would like everyone to remain mystified and confused about solar, so they can continue to make money on excessive installation fees (average $5-6K per 10KW of power). They know how easy the plug and play, click-together micro-inverters are. Honestly, anyone who can hook up 4 wires in the breaker box can electrically install a micro-inverter array.

They want you to use 500-1000vdc systems so you must hire one of their servicemen to repair or work on said systems. Keep the voltages up and the average homeowner will not even think about touching a high voltage array, and they would be wise not to. Not to mention the cost when a $2500 inverter fails vs a $150 micro-inverter, it's a no brainer for me after considering the options.

My only pushback to your reasoning would be, what is the over all cost of a micro inverter system compared to a string?

I am not worried about the loss of a string inverter especially if the cost of one is over a $1000 less then the total cost of all the micros. While there is always the potential of an early failure for an inverter they will more than likely last as long as the manufacture has claimed.

Now if the labor cost is lower to install a micro system compared to a string inverter then it could be less costly but it still comes down to the installed $/watt cost.

[solar_newbie]

String inverter systems suffer from micro-fractures in a high-voltage solar panel array, this type of damage is common under mechanical loading of snow or high winds or flexing of the panels for any reason, and can short out a panel in the string and cause a panel fire. (500 degree C hotspots can form under loading) or a panel failure.

A string inverter failure means you are down, a single point of failure from either a large inverter quitting or a panel in the string electrically failing.

The electrically Isolated panels in M250 Micro-inverter arrays can effectively use micro-fractured panels without the same higher risk of fire due to the electrical isolation of the panels and the lesser load voltage of max 43VDC (in a 72cell panel) instead of 500-1000VDC when a micro-fracture failure occurs in a string array.

I like the implied safety of micro-inverters, I also do not mount my micro-inverters between the panel and the roof, as they get too hot IMO (greater than 130 F). P/N junctions break down Time-over-temperature and the cooler you keep the micro-inverters the longer they are going to last. I measured a less than .8VDC voltage drop on a 40' run to the ventilated cabinet I hung my M250's in, so I doubt there is any great loss there.

A micro-inverter array is many parallel inverters so one or two failing panels or inverters doesn't shut down your array production- normally.

I studied the usefulness of solar for the average homeowner and found some glaringly obvious conclusions, the installation industry would like everyone to remain mystified and confused about solar, so they can continue to make money on excessive installation fees (average $5-6K per 10KW of power). They know how easy the plug and play, click-together micro-inverters are. Honestly, anyone who can hook up 4 wires in the breaker box can electrically install a micro-inverter array.

They want you to use 500-1000vdc systems so you must hire one of their servicemen to repair or work on said systems. Keep the voltages up and the average homeowner will not even think about touching a high voltage array, and they would be wise not to. Not to mention the cost when a $2500 inverter fails vs a $150 micro-inverter, it's a no brainer for me after considering the options.

One more note: if you ever wash panels with string inverter (possible happen every few months), wash it at midnight or risk to cook yourself (dream about 600-1000 DC V run through your body ...)

[solar_newbie]

Enphase starts release enphase S280 and envoy-S and will shipped by November to get ready for smart grid. This will be a great option for you, but might result a bit higher price.

[SunEagle]

One more note: if you ever wash panels with string inverter (possible happen every few months), wash it at midnight or risk to cook yourself (dream about 600-1000 DC V run through your body ...)

If water on the panel will always cause someone to get electrocuted then every time it rains (we sometimes get rain even though the sun is shining) you have a potential problem.

All pv panel wiring connections should be "sealed" against water intrusion. So putting water on the panel face to wash it has a very very low chance of the panel frame being electrified and shocking the "washer".

The main reason not to wash your panels during the sunny period is; 1; you reduce the production output by causing shade, and 2; better chance of water spots or uneven drying when the sun is out. It is just better to wash in the early morning before the panels get hot.

[J.P.M.]

If water on the panel will always cause someone to get electrocuted then every time it rains (we sometimes get rain even though the sun is shining) you have a potential problem.

All pv panel wiring connections should be "sealed" against water intrusion. So putting water on the panel face to wash it has a very very low chance of the panel frame being electrified and shocking the "washer".

The main reason not to wash your panels during the sunny period is; 1; you reduce the production output by causing shade, and 2; better chance of water spots or uneven drying when the sun is out. It is just better to wash in the early morning before the panels get hot.

Also, some daylight helps visibility. Being able to see what you're doing can come in handy sometimes. Daylight is usually in short supply at midnight.

[solar_newbie]

In general for string inverter, you can wash when daylight. There is no issue at all in most of the time.
Let say for some reasons, one of the wire insulation is cracked. When you wash the panel and decide to wipe them out, somehow you touch the water that is running through that wire.... You will get electric shock by the whole string (which is around 300-1000V range -- Depending on how many panels in that string)

For Enphase or Solaredge, you shutdown the breaker. The whole string shutdown. If the wire insulation crack, you can get electric shock by 1 panel (which is around 30-40V).

How about during raining, you never go next to the panel during raining You will hide inside the house. So there is no issue.
Plus during raining, I would hope no sun will be hanging around.

[J.P.M.]

In general for string inverter, you can wash when daylight. There is no issue at all in most of the time.
Let say for some reasons, one of the wire insulation is cracked. When you wash the panel and decide to wipe them out, somehow you touch the water that is running through that wire.... You will get electric shock by the whole string (which is around 300-1000V range -- Depending on how many panels in that string)

For Enphase or Solaredge, you shutdown the breaker. The whole string shutdown. If the wire insulation crack, you can get electric shock by 1 panel (which is around 30-40V).

How about during raining, you never go next to the panel during raining You will hide inside the house. So there is no issue.
Plus during raining, I would hope no sun will be hanging around.

Do you currently have an array ? If so, have you washed it ?

[SunEagle]

Also, some daylight helps visibility. Being able to see what you're doing can come in handy sometimes. Daylight is usually in short supply at midnight.

Good point.

Maybe that is why they now sell those really bright lights that attach to a hat.

[J.P.M.]

Good point.

Maybe that is why they now sell those really bright lights that attach to a hat.

I thought only gynecologists use those.

[solar_newbie]

Do you currently have an array ? If so, have you washed it ?

We just wash our panels for the first time after 2 weeks... Sequence:
- Shutdown the grid breakers --> All inverters are shutdown, so the string is safe.
- One person goes to the top of the roof. Water them down. Stay from the top to clean the top panel row using microfiber cloth with extension pole.
- One person stays on the ladder at the bottom and do the same for the bottom row.
The person at the bottom will be wet ... Around 1/3 of the panels (close by), we just clean using the cloth directly (like to dry a car).

The time is around early morning (7AM or so) when the sun just start moving up ...

Since I am not good at height ... I found a person in my house (wife) that can do the top part hahahaha.