DIY Solar Design: Understanding the DC to AC Derating Factor Posted on 15 Aug 11:32

DIY Solar Design

At Solar GOODs, the DIY solar design process begins with a few questions about your home and your system preferences. But what if some of the terminology is unfamiliar to you?

The DC to AC derating factor is one industry term that can confuse solar do-it-yourselfers. What does this mean? And how does it affect the design of your photovoltaic system? 

What Is the DC to AC Derating Factor?

Every photovoltaic panel has a nameplate with a DC power rating. Expressed in watts, this figure tells you how much energy the PV module can produce. The power rating is based on how the panel performs under standard test conditions at 77 degrees Fahrenheit and with 1,000 watts per square meter of solar light.

But real life is not like these test conditions, and several factors  called derate factors  can affect how many watts of power a solar panel actually will produce. Some derate factors, such as shading, are environmental. Others, including wiring, connections and inverter losses, have to do with your DIY solar energy system components.

The DC to AC derating factor takes all of the potential environmental and system losses and adds them up into one percentage factor. This percentage indicates the overall efficiency of the PV module.

How Derate Factors Affect DIY Solar Design

The National Renewable Energy Laboratory breaks down how each derate factor affects the energy output of a photovoltaic system.

Inverter and transformer losses can range from 0.88 to 0.98, for example, while DC wiring issues can cause losses between 0.97 and 0.99. To determine the total derating factor for a system, the losses are multiplied.

The default derating factor on the Solar GOODs DIY solar calculator is 83 percent. For most photovoltaic systems, this figure provides a reasonable estimate for determining energy production.

DIY Solar Design Tips to Improve DC to AC Derating

While many of the derate factors may be unavoidable, you can take steps to reduce your system losses.

For instance, if you get rid of shading, you’ll increase your solar efficiency. And if you opt for micro-inverters instead of a string inverter, you’ll eliminate losses caused by a mismatch between modules.

You can tweak the derating factor on the Solar GOODs calculator to reflect any improvements you have made, but be careful. If you underestimate your potential system losses, you could end up with a photovoltaic system that doesn’t produce enough energy for your needs.

Solar GOODs is your go-to source for all of the components you need to design the perfect do-it-yourself solar kit or custom PV panel system. Visit us online today to learn more about how you can benefit from our DIY solar kits and systems.