Three quotes. Three solutions?

I have 3 quotes in hand. Because I am in a new (to me) house I am estimating my usage to be 1,000 kWh per month. My roof faces 160 degrees and there is no shade.

Everything Solar has quoted 22 325w Q Cell panels with a SolarEdge inverter. Predicted production is 10,446 kWh for the 7.15 kW system. Efficiency of 71%

SolarRay proposes 28 300w SunSpark panels with an SMA inverter. PP is 13,277 from the 8.4 kW system. Efficiency of 76%

SEM proposes 27 320w REC panels with Enphase Micro Inverters. PP is 13,961 from the 8.64 kW system. Efficiency of 78%

I have calculate the system efficiencies by dividing the Predicted Production by the Rated Production (system kW x 365 x 5.67 average hours per day).

Comments are welcome. Why are the efficiencies so different? More downtime for the Q Cell/SolarEdge system?

Hi interesting method to determine efficiency. The issue with the predicted production (provided in quote) is that various companies might use different methods and calculations, so could be inaccurate.

What you should be asking is what size system do I actually need to cover my consumption - Do you know your ‘load profile’ which is when you use energy? Do you have a smart meter which logs your energy use?

Also what is the quality of the panels being offered and is the installation company reliable?

There are guidelines to estimate output, but as Jason says everyone will use different figures. It’s nothing to do with more down time, more to do with different assumptions. There are so many figures to calculate output, starting with solar irradiance, and assumed derating, the actual panel and inverter derating are a very small part of that equation. I would say Everything Solar are probably just being more conservative.

Is this the Melbourne based Everything Solar? I thought they were wholesalers, and their retail arm was called Solar Sunworx. Has that changed? They’re a pretty good mob if it is them.


Thanks for your input. I spoke with Everything Solar and they assume 4 hours per day average even though our average is 5.67 (according to PVWatts). They say this takes into account various weather paterns the afternoon thunderstorms we get here in Central Florida during the summer.

I do not have a Smartmeter (yet), so I cannot construct a Load Profile which is too bad because…

The gris power comes from SECO, which is a cooperative and is allowed to credit my excess solar production at thier wholesale purchase cost. This means that I buy power from the grid at 10.0 cents per kWh and I sell power to the grid at 8.3 cents per kWh.

Hi Dale

Ah, I assumed you were in Australia, which might have been confusing, because I understand there is a Melbourne in Florida also.

Wow, SECO sounds like a winner. Great deal.

I like that Everything Solar is conservative in their estimation. Not overselling. That’s a good sign.