I'm currently working on planning a roof-mounted solar system and need some help verifying my calculations. Based on some modeling I've done with OpenSolar, it looks like I could fit a 9kW system with 20 panels of 450W each. However, I'm concerned that my breaker panel might not handle that size.
I have a 200 amp GE PowerMark Gold load center, which is rated for a maximum bus bar of 200 amps, and there's a 200 amp breaker in my panel. From what I understand, this means I can only accommodate a maximum of 7.68 kW for solar input. Is that correct?
If that's the case, I see a few options moving forward:
1) Go with a smaller solar installation.
2) Replace the 200 amp breaker with a smaller one, although that would require a load calculation.
3) Upgrade the entire panel.
I'd really appreciate any feedback on whether my assessment and options are reasonable, as well as any advice on areas where I might be mistaken. Also, for clarity, I calculated the maximum I can tie into the panel as follows: 200A (bus bar rating) x 1.2 = 240A; 240A - 200A (main breaker) = 40A (solar breaker size); 40A x 0.8 (continuous load factor) = 32A continuous load; 32A x 240V = 7,680W.
2 Answers
It sounds like you're on the right track but don't forget to account for the additional components needed for a complete solar setup. You won't be able to determine the output amps without knowing your inverter's voltage specifications. Make sure you have a compatible charge controller and inverter for a grid-tied system, as they will really dictate the size of your solar array. You're definitely thinking straight, but those additional components can alter the equation quite a bit!
Your math might need some tweaking. I looked into the specs for that inverter you mentioned, and it seems like it can output up to 8kW on the AC side at 33.3A on a 240V split-phase. If you do the math, that checks out to around 7992W, which is close to your max. In theory, your main breaker allows up to 48kW (200A x 240V), so it seems like there's a discrepancy in your max load calculation—double-check your figures!
Thanks for pointing that out! I see where I might have messed up since I didn't factor in additional capacities properly.
Got it! I was just trying to focus on what the panel can handle right now. Thanks for clarifying that I need to consider the inverter and charge controller too.