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stevehull · 06-07-16, 08:51 AM

Jeff and Memphis,

Note that a 250 watt panel is rated at very narrow lab conditions. This is the STC value. In the field, we use PTC - which is about 90% of the STC. So, a 250 watt panel will only put out maximum about 225 watts.

Then the microinverter converts the DC into 240 V, 60 Hz AC with about a 90-97% efficiency. Lets assume it is an Enphase and it is 97%.

The net you get out is now 97% of the PTC 225 watts or now about 218 watts.

The vast majority of solar installers will quote STC (lab) ratings and will not tell customers that their net is some 85-88% of that.

The nice thing with an Enphase system is that you can monitor each microinverter and also your total system (DC amps and voltage in, AC voltage, current and power out, microinverter temperature, etc.) with a computer of cell phone app. Makes trouble shooting a snap.

Steve

06-07-16, 08:51 AM	#26
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Jeff and Memphis, Note that a 250 watt panel is rated at very narrow lab conditions. This is the STC value. In the field, we use PTC - which is about 90% of the STC. So, a 250 watt panel will only put out maximum about 225 watts. Then the microinverter converts the DC into 240 V, 60 Hz AC with about a 90-97% efficiency. Lets assume it is an Enphase and it is 97%. The net you get out is now 97% of the PTC 225 watts or now about 218 watts. The vast majority of solar installers will quote STC (lab) ratings and will not tell customers that their net is some 85-88% of that. The nice thing with an Enphase system is that you can monitor each microinverter and also your total system (DC amps and voltage in, AC voltage, current and power out, microinverter temperature, etc.) with a computer of cell phone app. Makes trouble shooting a snap. Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990