Inverter over-sizing?

[sigfreund]

I plan to have a system installed soon and I want to over-size the SolarEdge inverter for future expansion. I want to start with 5 - 6 kw and double or triple that amount in the next few years. My installer is fighting me on my desire to initially install a SolarEdge 14.4KW inverter saying that I would lose a significant amount of power generation because a properly sized inverter will start producing much earlier. I would think the lose would be minimal and as long as I meet the min string length, any opinions?

[sensij]

There will definitely be an efficiency hit. The bigger problem might be that the 14.4kW is a three phase inverter. What is your electrical service?

[ButchDeal]

The SE14.4KUS is a 208V 3 phase system. Do you have 3 phase power?
With it you will have to use the double optimizers (P600, P700, P730, P800) as well.
As for your plan to install the system now and grow it over time. This is generally a poor idea. It is like getting a 2 door car, then expanding it to a 4 door, then a minivan, then a bus.
It will cost considerably more than just installing what is needed from the start and will void any interconnect grandfathering as well.

Also design string length on the 208V systems is very limited with the allowed optimizers, voltage limits etc. It would be quite difficult to design a system that could be grown using this inverter.

[Wy_White_Wolf]

IMHO - You'd be better off to go with a properly sized inverter and add another when you add more solar.

WWW

[J.P.M.]

IMHO - You'd be better off to go with a properly sized inverter and add another when you add more solar.

WWW

+1. Plans and situations can change. More flexibility adding on later, as well as probably more practical.

[sigfreund]

Definitely have eliminated the 14.4kw inverter because it is 3-phase but what is the downside of installing a 10kw inverter with an initial 6kw of panels? Are you saying going with a Solaredge 5kw would produce noticeably more power than a 10kw inverter which would give me room to add more panels down the road?

[ButchDeal]

Definitely have eliminated the 14.4kw inverter because it is 3-phase but what is the downside of installing a 10kw inverter with an initial 6kw of panels? Are you saying going with a Solaredge 5kw would produce noticeably more power than a 10kw inverter which would give me room to add more panels down the road?

There are several down sides.
One you are spending money on a larger inverter than you can use for potential future expansion.
You are paying for older technology for future use.
In Solaredge this is blatently apparent as they are replacing their systems starting with the smaller ones and working up.
The 5kw is the new HDWave and the 10kw is not going to be upgraded for a year or so.
The HDWave is more efficient.

Then you have the added cost of interconnecting a 10kw system, which would require a line side tap or MSP upgrade, or derate, all are costly, but installing the SE5000H would usually not require that.

You may change your mind on future expansion or sell the home before doing it.
regulations could change making the expansion less tenable (usually you lose grandfathering in the old interconnect when you expand )

Think of it like buying a big dump truck with a little 4 cylinder engine. You are only going to haul around a little with it now but you might expand it latter....

There are two things I would recommend doing instead of getting the large inverter for expansion.
One is get a loan and dull the full install now
the other is install with the SE5000H now and in years to come if you still want to expand it, you can add another SE5000H (or whatever is the current model) at that time.

[sigfreund]

I am being charged $3/watt for the install. With the price of panels currently, I can easily add another 6kw myself and save $9,000. I can handle adding panels myself, but adding an inverter is beyond me.

[NEOH]

Definitely have eliminated the 14.4kw inverter because it is 3-phase but what is the downside of installing a 10kw inverter with an initial 6kw of panels? Are you saying going with a Solaredge 5kw would produce noticeably more power than a 10kw inverter which would give me room to add more panels down the road?

I am being charged $3/watt for the install. With the price of panels currently, I can easily add another 6kw myself and save $9,000. I can handle adding panels myself, but adding an inverter is beyond me

The efficiency of an SE10K Solar Edge Inverter is nearly the same at 5KW input vs 10KW input.
One 10K Inverter is cheaper than 2 @ 5K inverters.
If you install a 10 KW Inverter, are you sure you want to install two strings at 6 KW each?
If you have the skills then install the 2nd string yourself.