To oversize SolarEdge Inverter OR NOT?

[sensij]

5000W inverter is 30A breaker. 5000/240 *1.25 =26A
6000W inverter can be 35A breaker (probably a special order) 6000/240*1.25 = 31A

Fair enough, but the math around the service panel rating isn't really changed. If you go bigger than 3800A, a 100 A panel is too small. Since the OP already has 200 A, it is moot, but that hadn't been shared.

[sensij]

Some inverters have adjustable startup voltage.

Oops 20 Amp breaker that trips is what I should have typed. Also, I looked it up the 5000 can be set to limit power anyway, so if you didn't follow code you could limit power.

If you don't follow code, you'll have a hard time getting a permit approved. Without a permit, you won't have much luck convincing the power company to allow net metering. Without net metering, the whole thing is probably a waste of money.

[posol]

If you don't follow code, you'll have a hard time getting a permit approved. Without a permit, you won't have much luck convincing the power company to allow net metering. Without net metering, the whole thing is probably a waste of money.

Hi Sensij,
I see that you are also located in San Diego. Do you know whether we have to put the inverter inside or it can be also placed outside according to the county regulations?
Thanks,

[sensij]

Hi Sensij,
I see that you are also located in San Diego. Do you know whether we have to put the inverter inside or it can be also placed outside according to the county regulations?
Thanks,

It can go either inside or outside. If you run high DC voltage into the house, there are code requirements about how the conductors are protected and marked that are different from typical household 120/240 VAC.

I have mine outside, on a south facing wall. It has roof overhanging above it, which means it is fairly protected from the sun in the summer when the sun is high, but actually gets much warmer this time of year when the sun is lower and the eve won't shadow it.

[thejq]

However, I have heard that there is "startup voltage" for some of the inverters and if I go very oversize then the number of the panels may not be enough to reach the starting operation for a big inverter when the light is low (early morning or late afternoon).

Don't worry about it. If your installer follows the installation instructions correctly, the optimizers will automatically and collectively adjust the voltage so the inverter's input voltage is in the optimal range. There's a minimum of 8/string, so you're over that already.

[CoyoteVB]

I am curious if you have decided to oversize or not. I have been researching the same question. The SolarEdge design tool documentation and Technical notes encourages oversizing by 125% to 135% depending on the average high temperature. I was not actually able to use the tools since is for Windows. No MAC version. They state better performance in low light. They define oversizing when Pdc (STS) > Pac max. The calculation in the SolarEdge Technical note is Pdc(STC)/Pac max * 100%. I wonder if SolarEdge recommends oversizing since the optimizers/inverter system continuously adjust voltage based on light and shading. I am also wondering if I will clip on the peak summer days.

[sensij]

The oversizing they recommend is array size to inverter size... opposite of what the OP was suggesting. Any clipping is more likely to happen in the spring or fall, when temperatures are cooler, and less likely in the summer when it is hot and the array power drops. However, that is to some extent location and orientation specific.

You can use PVwatts to estimate clipping loss... in the Advanced parameters, use the DC:AC ratio. For example, a 4 kW array on a 3 kW inverter would be 4/3 = 1.3333.

[CoyoteVB]

Thanks sensji. Being new to solar I appreciate all the great advise on this forum

[TimeOrMoney]

As is typical for me over analyzing things, and probably going Solaredge, here are my thoughts:
1. We don't have efficiency curves for the inverters. They are probably not that different in the range you are looking at, however.
2. Depending upon your local jurisdiction, watt limits, permitting costs, add-on rules, etc., the whole idea of expansion may be not worth it ever. Probably best to figure what the maximum allowed that covers your power needs and do it all at once. Will you upgrade in the future? Odds are against it, but you may be the exception.

[cebury]

I agree, very few people will ever expand their existing array unless they significantly undersized for whatever reason (lack of funds, no space but now there is, inherited array, etc). If you still want to lower the elec bills further it'd probably be the energy efficiency route (insulation, envelope seal, Windows, appliances, etc).

[J.P.M.]

I agree, very few people will ever expand their existing array unless they significantly undersized for whatever reason (lack of funds, no space but now there is, inherited array, etc). If you still want to lower the elec bills further it'd probably be the energy efficiency route (insulation, envelope seal, Windows, appliances, etc).

Which, from a cost effectiveness standpoint, after simply turning stuff off, ought to be measures taken before solar, not after.