[RE-wrenches] PV watts question

[David Buckner]

We design around a 1.3 to 1.4 DC to AC ratio these days.  We do see others going higher but that's generally for multi-MW ground mount systems when utility interconnection upgrade costs can make big leaps as the AC capacity gets higher.  Back when an Astropower module was 4 bucks a watt, you'd never consider it, but at today's prices you can deal with a couple percent overall efficiency drop and still have better economics.
I also agree that the PV Watts run is actually KWH/KWp/YR.

David



David Buckner
President
Solar Energy Systems
917-848-0215
718-389-1545
dbuckner at solaresystems.com
www.solaresystems.com
41 Box Street 2nd Floor, Brooklyn, NY 11222
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From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> on behalf of Jerry Shafer via RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Monday, January 27, 2025 8:41 PM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Cc: Jerry Shafer <jerrysgarage01 at gmail.com>
Subject: Re: [RE-wrenches] PV watts question

CAUTION: External Email.
Interesting topic, what l am seeing is over throttling which will potentially contribute to mid day clipping. Many inverters now can be overdriven by as much as 200% but the inverter will only produce it's rated output and 150% well that's right in there.
But hey what do l know. Looking forward to other ideas
Fun times

On Mon, Jan 27, 2025, 11:56 AM jay via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
HI All

I’m working with a customer who’s pretty savvy and is using PV watts for his design.

What I can’t figure out is the kwh/year goes down if he uses dc/ac ration of 1.5 instead of 1.2 which is the default.

Hes in Santa Fe NM.

.8   ratio=  1663 kwh/yr
1.0 ratio = 1668 kwh/yr
1.2 ratio =  1671 kwh/yr
1.5 ratio = 1623 kwh/yr

I was expecting that more PV = more kWh/yr.

What am i missing?


standard module
fixed roof mount
14.08 loss’s
10 degree tilt
180 degrees



jay


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