Question: Inverter sizing

[pinamdar]

Hi,

Have a question about inverter sizing for a grid-tie residential system. Getting a system with 24 panel array (Sunpower SPR-240s) that is rated to produce 5014W PTC output. Should I be coupling that with 5kW (SPR-5000) inverter or a 6kW (SPR-6000) inverter. My guess is a 5014W array will generate peak output only for a very short time under optimal sunny conditions so a 5kW inverter should be sufficient. But the vendor is saying that he will throw in the SPR-6000 for the same price as the SPR-5000 (because he has them in stock), and it is better for me if I decide to add more panels in the future.

My question to the forum: what are the pros/cons of putting in a 6KW inverter on a panel that only generates 5KW? Should I go for that, or insist on the 5KW inverter?

-Prasanna

[Sunking]

No problem I am aware of using the 6 Kw

[vinniethePVtech]

SPR-5000 is what you will want. It will maximize efficiency of the total solar system. Its cost effective on initial install costs. Spending money on the 6000 is just losses in efficiency, and cost. (How ever I understand they are giving it to you at the same cost as the 5000).

Untill 5500 watts are installed then would you want to consider a 6000, its about maximizing MPPT tracking.
If you absolutely want the 6000 you can use it, how ever it my lose fractional margins on harvest efficiency. Inverters are most efficient when they are closer to there max limit.

[Mike90250]

One more consideration , is heat. The 6000w inverter will have a larger heat sink. Cooler parts last longer. If they have a fan, it will run less often. Depending on the mounting location, and summer heat, you may want the larger heatsink in the 6000, but it may fractionally hurt your overall efficiency.

[vinniethePVtech]

The 6000w inverter will have a larger heat sink. Cooler parts last longer. If they have a fan, it will run less often.

The SPR inverters are re-badged SMA inverters so yes they do come with fans. These inverters are 96.7% in harvest efficiency just so as long as the MPPT tracking is dead on and the temperature is cool enough. SMA claims that these inverters can maintain 96.7% up to and around 100degrees. How ever regardless if it is a 5000 or 6000, the inverter shuts down at 113*F that is basically the heating point on these inverters.