[RE-wrenches] 1.56 Rule

[Mark Downing]

Back in the day, the old used Carrizo "Super Gold" 105W modules would do about 6 amps normally, but 10A plus on a cold Indiana day.
I had 12V customers with 4 of these blowing 40A fuses.
But that was years ago, in a different world.
________________________________
From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> on behalf of Drake Chamberlin via RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Monday, May 18, 2026 9:09 AM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Cc: drake.chamberlin at redwoodalliance.org <drake.chamberlin at redwoodalliance.org>
Subject: [RE-wrenches] 1.56 Rule


The logic of this rule for calculating PV amperage seems a little off to me. - It is a calculation that is set in stone as a bedrock truth of the solar industry. (1.25 X 1.25 = 1.56).

The multiplier of 1.25 for a continuous load is relevant for sure. To multiply again by another 1.25 seems excessive.

Although it is certainly true that modules put out considerably more power when it is cold out, in my experience that is almost all due to the increase in voltage. The amperage goes up a little, but no where near 25%.

Just because I haven't seen it doesn't mean it can't happen. Are there circumstances where the amperage of a PV module can go up by 25%?

Thanks,

Drake


Drake Chamberlin

Athens Electric LLC

Ohio Electrical Contractor’s License 44810

NABCEP Certified PV Installation Professional

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