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(970) 403-5004

We will be glad to provide a free, no obligation consultation and custom design to meet your solar power goals in the Durango area.

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Durango, CO 81301


Based in Durango, Colorado, Flatrock Solar is a locally owned and operated solar panel contractor and installer serving the Durango area from Cortez to Pagosa Springs and Silverton to Ignacio.  Flatrock Solar has been helping businesses, homeowners and non-profits convert Colorado sunshine into clean, renewable energy since 2010.  

Durango Solar - FAQs

Frequently asked questions about solar photovoltaic systems in Durango and their answers.  

Why does my 5.2 kW system not produce 5.2 kW?

Matt Helms

So a lot of people ask why their 5.2 kW in solar panels doesn't produce 5.2 kW at the inverter.  Its a good question and one that isn't super easy to explain.

This is a chart of the peak power of a 5.2 kW system:

Output of a 5.2 kW solar electric system in the Durango area.

Here is a chart of another system that I installed in the same area that is 8.5 kW with little or no shading:

Output of a Durango solar system with 8.5 kW of solar panels.

Neither system has reached its theoretical maximum of the installed size of the system and never will.  The inverter on the 5.2 kW system has a maximum output is 5 kW AC and the 8.5 kW system has a 7.6 kW inverter.

There are a couple of reasons why the installed capacity (5.25 kW) doesn’t equal the output of the inverter (charts above).  One is inefficiencies of the system (wiring losses, inverter not being 100% efficient, etc.) and the other is that solar panels are rated at what is called Standard Test Conditions (STC).  This is a laboratory test that uses artificial lighting to produce 1,000 watts per square meter, at a solar cell temperature (not ambient air temperature) of 25 degrees celsius, and an air mass of 1.5.  So for a 250W solar panel to produce 250W of power these three conditions would have to occur in the ‘wild’.  This is theoretically possible, but not likely.  You have to also remember that this 250 watts of power will equal something less than 250 watts of AC power (output of the inverter) because of inefficiencies.  

The chart above does highlight the potential spike in the fall and spring that you might see (in this case in November).  The fall and spring are when you’ll see conditions most like STC; low temps with high irradiance (sunlight).

The important number to look at with a solar system is how many kWh it produces in a month or year.  System designers look at all the environmental factors (location on Earth, weather patterns, azimuth and tilt of panels, etc.) to model the estimated output in kWh of the system.

I welcome comments or questions so I can improve on the explaination.