Temperatures on a typical Las Vegas afternoon can reach 115°F, which is already near the operating limit for a lot of home solar inverters. An unventilated attic, or a west-facing stucco wall in full sun, exceeds that temperature range. When an inverter “folds back,” it is protecting itself by making less power, and the part that usually fails first in the field is not the power electronics. It’s the little box that talks to your phone.

While 115°F is the temperature reported on the news, it’s not necessarily the temperature at the inverter. Three ordinary conditions make it worse: full sun on a west wall, or still air in a garage or an attic runs 40 to 60° hotter than the air outside. On a 115°F day, an unventilated attic can hit 150°F or more. A sunbaked wall runs hotter than the official reported temperature. The inverter does not care about the forecast — it cares about the air it can pull across its metal fins.

To deal with this, inverters use a feature called foldback, which is a planned slowdown. Inside, when the inverter gets too hot, it cuts the power it’s sending out, which cuts the heat it is making, and it ramps back up when it cools.

Many home inverters hold full power into the mid-40s in Celsius (the mid-110s in Fahrenheit) and then taper when that temperature is exceeded. They’ll operate at reduced power up to about 140°F.

For example, in a note from SolarEdge published January 2025, several of its single-phase inverter models hold full power to 120°F.

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