Our new Solar Panel Installation

[mwalsh]

I've got a great new picture of a grounding rod! LOL! Gonna give the guys a chance to get something done. Right now they're concertinaing on getting the inverter and the conduit in.

 

[DaveEV]

You might want to rethink that. The area under the curve truncated by the "flat top" more than makes up for the slight inverter inefficiencies at low light. Inverters quickly get to peak efficiency (96%?), and the low-light range where you see inefficiency is just producing a trickle anyway.

The Enphase inverters are ~95% efficient from 10%-100% rating - the 190W inverters actually will push out up to 199W of power.

If your inverters are underrated, and regularly saturating, I don't see how that translates to Win.

It depends on what your criteria is. While clipping output will reduce your overall output some, the overall reduction in power over the lifetime of the array won't be significant.

I would guess that ERG4ALL is perhaps losing a max of 200W for 2 hours (when his array is clipping - looking at the past 7 days it doesn't really clip all that much). So he's "lost" .4 kWh out of 50 kWh or so or less than 1%. The rest of the time the bigger panels will be pumping out more power - especially in the hot Arizona summer when temperatures really depress power output.

Man - I wish I could generate 50 kWh this time of year - I'm lucky to get 12 kWh with the low sun and lack of southern tilt in my panels this time of year. But even with "ideal" tilt year-round power output would only increase by ~10% or so.

 

[ERG4ALL]

Drees, thanks for the input. It looks as though you've taken a look at our system. I edited my previous reply to "groundloop" to perhaps better explain how you get a more optimum power generation with 235W panels and 190W inverters. I hope he takes a few minutes to play around with the graph paper. It is immediately obvious how you get that extra power. You must also have Enphase inverters because you are spot on with their "under promise" and "over deliver" with the rated output. My inverters up here consistently put out 198-199 watts.

I also included the link to get to the Enphase position paper on how they came up with the 235W/190W combination.

 

[Coffee_Slurry]

I re-read your post, and think I understand better. You're comparing oversized (high output) panels on the microinverter vs "rightsized" panels that match the inverter exactly. In this sense, you're right -- the bigger the panel, the more power you will get out of them throughout the day, especially when hot.

I'm looking at a comparison between the beefy panels you got and the 190w inverters, vs a system that has more inverter capacity (exceeding the peak of the fine panels).

I suppose it comes down to the incremental cost in inverters. (For the same reason I undersized mine.) I wouldn't benefit from spending $800 more on inverters just to absorb the five or six days where peak power exceeds inverter capacity.

I'll read the whitepaper as well, later on.

Cheers.

 

[Heynow999]

HI

New here, I love the Leaf and look forward to buying a used one a few years down the road.

Sorry to continue to hijack this thread. I have installed a few Enphase systems( I'm an installer) and I am putting an Enphase system on my house. About oversizing panels, I just don't see the point of it. I would imagine a system would output more power if there was no clipping. Why would you not use a 230 watt panel and not get clipping? I know it is really splitting hairs, but isn't the whole point to design a system that can capture as many watts as possible? I guess you save a bit on inverters, but they are only $200 each.

For my house I didn't want any clipping. I am near Toronto so we get some cold days here so I am going with 185 watt panels and 190 watt inverters. I may have gone as high as a 210 watt panel but the 185's fit well in the available space I have on my roof.

I am not trying to come off as an expert, I am only trying to get a better understanding of how Enhase works. I appreciate everyones input and experiences

 

[DaveEV]

Let's use my house as an example:

I have 180W STC rated panels - I have only seen them push out their STC rated power level once for 5 minutes. That was in between clouds on a cool day in May. If I had ~230W STC rated panels I might have lost 10-15% power for 5 minutes - that's enough even going to be enough to be measurable.

The rest of the time the panels rarely push out more than 80-85% of their STC rating or ~150W - and then when they do it has to be the right time of the year and cool out - and then they only do that for an hour or so.

So why did I use 180W panels instead of larger ones? Cost - I got a great deal on these panels that more than made up for the increase in number of inverters I had to buy to make up the difference - about $0.50/watt cheaper than the larger panels.

If I were to do it all over again today? I would very likely try harder to get ~220-230W STC panels at a better price - and possibly paid the premium. I could have 4 fewer panels/inverters with the same total power output which would make panels that cost ~$0.25/watt more cost the same overall - plus any time you reduce the number of parts you reduce the complexity which will increase reliability.

It also gives me more room for easy expansion in the future with the ability to double the array size with the same wiring - as it is now I'm a bit limited and longer strings reduce efficiency slightly as well because of the additional wiring. Or I could have used one string instead of 2 which would have reduced costs further. Enough to offset the cost of the bigger panels? Very possibly...

As the price difference between panels/inverters continues to narrow - any possible benefits of "undersizing" your panels to avoid possible clipping is reduced.

 

[LEAFfan]

Ours is to be installed Dec. 6-8. We bought the new (Can you say, "Experimental"?) Honeywell A/C panels (240W) with built in micro-inverters (on the back) of each panel. The panels come with the rack included, but for some reason, my installer added racks as a separate item. When I asked him about it, he told me that he separated the two plus he lowered the labor because these are much easier to install, and it's easy to add more later. Also, our EU's rebates (we made it by about 3 weeks) have run out ($2.15/W up to 5 KW max.) and won't be available again until March or April at a lower rate...maybe $1.75/W or lower.

 

[ERG4ALL]

LeafFan you bring up a good point, the utility subsidy. We were lucky in that even though the major utilities in AZ (APS and SRP) had cut back their subsidy and now have stopped it altogether until sometime next year when they have more money, we live in the mountains and our utility (NEC) is still paying $3.00 per watt of collector output. We went ahead and maximized our rebate (limit $25,000 per installation) and thought the clipping and higher panel output was the best deal. Interestingly, NEC initially was paying $3.00/watt based on inverter capacity. What happened was that people were buying single inverters with a much larger capacity than the panel output. This would allow them to add panels later as they could afford it. The utility soon realized that they were paying more subsidy than they were getting in generation capacity on their grid. They then changed to panel output irrespective of inverter capacity. In our case this was a benefit because our panel capacity was greater than the inverter capacity. This isn't such a bad thing for the utility because as my graph exercise submitted earlier shows that the utility is getting more generation than 190W inverters coupled with 190W panels. With other modifications to our home we are generating more electricity than we are using and hope that it holds true during the winter months when we will be charging our LEAF as well.

Regarding the amount of time our panels are clipped, they are clipped nearly every day in our climate which means more energy is generated than if we had the smaller panels. Another advantage is that the generation capacity has some buffer in it for when the panels degrade over time (although they are guaranteed for 80% of rating at 25 years), or accumulate some dust on them. I believe that the best way to work with the solar companies is to get them to commit to a cost per installed watt of output (ours was $6.00/watt) and to guarantee the annual kWh generated for your particular local. The company I used indicated a maximum output of 6,460 watts with an annual output of 14,686 kWh. So far we have seen maximum output of 6,760 watts so I am hoping that they will exceed their 14,686 kWh for the year. I must admit that we have one other advantage here. The temperatures are much cooler here than in Phoenix so our output is a little higher.

As funds/subsidies become available I encourage all to "go green".

 

[garygid]

In CA the rebate is based on estimated average annual production of AC energy (kWh) over 10 or 20 years, considering specific (tested) panels, the inverter make and model, sun angle and direction, local weather and expected clouds and fog, any local shading effects, and some factors for aging.

The whole calculation is available on-line, so one can "play" with the proposed system's parameters.

 

[Azrich]

Just wanted to report that we have averaged a production of 30.5 kW a day for the first 24 days our system has been working. We have only had clouds about 4 days in the last few weeks so production has been very good -- about 800 kWh since November 2.

 

[ERG4ALL]

AZRich - What is your system set up? What panels did you use? What inverter/inverters? How many panels? This field changes so rapidly I'd be interested in what you had installled.

 

[Azrich]

Some of you asked for photos of our new solar panels. Here is a link to a blogspot I did about the installation.

http://randdsrayhome.blogspot.com/

The county inspector has signed off his approval. We are waiting for the electric company to install the meter that will record our production, then we will be able to flip the switch. Hopefully, that will happen in the next few days.

We are so excited!

ERG4ALL, go to the link above. It has all the info and a few photos too. Where are you located? We had a company called Technicians for Sustainability install ours - see the link to their website in my blog. They are sending someone to take photos of our system and will include it in there "residential" section along with a link to our data monitoring system. I'll let you know when you go see it.

 

[ERG4ALL]

That really looks like a nice clean installation. We're happy for you and have really gotten into encouraging our friends to "go green" as well. Our system is located outside of Show Low (near Vernon). You can look up our output on a real-time basis at: https://enlighten.enphaseenergy.com/public/systems/xpWw4801 It will be so great when we can tell everyone that we are "driving on sunshine". We have a Mini Cooper that gets over 30 mpg. We got a guy in Phoenix that does custom graphics for cars make a racing stripe that has imbedded in it: "Super Duper Cooper". So we have enlisted a few of our friends to come up with names for our LEAF. What do you think you will name yours?

 

[planet4ever]

Just wanted to report that we have averaged a production of 30.5 kW a day for the first 24 days our system has been working. We have only had clouds about 4 days in the last few weeks so production has been very good -- about 800 kWh since November 2.

Wow, that's pretty impressive this time of the year for a 5.8 kW system. I'm sure you realize that Dec 20 or 21 is the shortest day of the year and thus the low point in solar production. My 7 kW system is only averaging about 15 kW/day right now, but we've had a bunch of days when we never saw the sun, and we've had some rain.

 

[Boomer23]

Super, Rich. You should be able to drive lots of clean miles on that kind of production in November!

We've had a pretty good November here in SoCal, too, but I'm projecting only about 550 kWh for the month, about 18.5 per day, which is average for November for me from my 5.16 kW system