How did my local solar company do?

[foggysail]

THANK YOU-------- I will devote more time to this!!!

 

[SunPWR]

OK, I guess I'll just go with what they recommended and hope they know what they're doing!

 

[OPTIMALSOLAR]

I recently had a 10 kW grid-tied solar system bid by a local electrical company that also specializes in solar. I live at:
48.5126° N, 122.6127° W and they specified the following system:

25 400W panels with micro-inverters:
Silfab 400HC+
Enphase IQ7+

I'm far from being a solar expert but I asked about the potential for clipping with micro-inverters rated at 295W with 400W panels. The person who specified the system said if I wanted less clipping and didn't mind spending more, I could go with Enphase IQ8H for about $100 more per micro-inverter. When I looked at the specs I noticed the latter had a higher minimum voltage. I don't know if that will limit my production under heavy cloud cover or not. How do I weigh the clipping potential during optimum conditions against the minimum voltage (which I assume might limit my production at the low-light threshold? I'm simply not confident enough that the person spec'ing the system knows the details well enough to get a solid answer.

I'm not really doing this to save money (although it will in the long run). I am more interested in helping the grid use less energy from traditional sources so low-light production early and late in the day and in the winter is a bit more important to me than peak generation or total annual production. I'm a firm believer that the current rules around net metering (at least in Washington State) are not necessarily incentivizing solar panel installs tailored to the most beneficial production. I'm glad solar is being incentivized, but I think it's important to incentivize morning, evening and winter production so we don't end up with such a huge surplus of mid-day energy while neglecting first light, late afternoon and winter production.

The town I live in is in the rain shadow of the Olympic Mountains so it's actually considerably sunnier here than even 15-20 miles away and it has a strong influence from the marine breezes that will help peak production during warm weather. I doubt this is taken into account in the models used to specify solar systems because it's a very local effect. In short, it's brighter and cooler here.

I realize no one can design an ideal system without more information than what I have provided, but I'm looking for feedback on how these particular panels mated to the two micro-inverters listed (or any other Enphase options that might improve the system). The panels themselves are manufactured locally but they are a new model, so we only have the brand name and the specs to go on.

TIA for any informed feedback about any of the mentioned aspects.

The unsubsidized system price is just under $1200/panel. The more powerful inverters will increase system cost by 8% and I'm pretty sure I won't get 8% more total generation. I would fork out the extra money if I knew it wouldn't impact the generation during marginal solar production hours, but I think the specs of the higher output inverter with a higher minimum voltage indicates it would "clip" on the low end (but I still haven't received a clear answer to that). That's mostly what I'm looking for.

Most of the panels will be due E and W facing at a relatively shallow angle (about 25 degrees) which is one reason I want to maximize production during marginal hours when other panels in the region are not contributing. It's not all about money savings, I will be happy if I break even but since I have full net metering with an annual reset I will do better than that. I don't have room for more panels so I will only be able to offset about 75% of my annual consumption and I'm not interested in generating during outages.

How does the minimum voltage spec of the inverter affect generation during marginal hours of generation? I can't seem to find graphs specific to these panels that will answer that question for me. I think I would like the Enphase inverter that will perform the best under low light levels (assuming the clipping on the high end is not too excessive).

Maybe too late, but the iq7a(366) should help the clipping issue about the same and for far less than the I8.

 

[HarryN]

At least in this area ( San Jose CA area) the power rates are moving toward being much higher during peak hours (roughly 3 - 9pm) so anything that you can do to arrange your panels to generate power during this time of day can be very helpful.

I have a small shop that is off grid and a solar test stand that allows pointing panels sort of morning / late afternoon and mid day.

Very approximately it looks like one of the better arrangements (for my use) is to have the panels facing:
~ 25% facing early morning sun - essentially vertical wall type mount
~ 25% facing ~ 12 - 2 pm
~ 50% facing late afternoon sun - essentially vertical wall type mounting.

 

[Hedges]

But avoid "vertical" which would ensure half the swept angle is shaded by the Earth.
Maybe something like 30 or 45 degrees off vertical.
(long path through atmosphere also makes early sun less productive.)
Besides, at a slight angle, the area presented to sunrise is hardly reduced at all. The later time before it drops rapidly is what you get in return.