[RE-wrenches] Adding on to existing PV installation

[Jason Szumlanski]

One of the benefits touted by microinverter and AC module manufacturers
is the ability to add on to a system at a later time. There are a few
problems with this concept as I see it.

 

First, there is a cost associated with design and engineering. Surely
you could design the system, and even produce engineering (permit
packages) that take into account future expansion, but there will always
be some cost associated with preparing a new permit package. And
designing the system from the start for expansion could increase the
initial cost. Oversizing subpanels and wiring may be required. System
expansion may require different overcurrent protection as the system
expands. System labeling would need to change.

 

Second is the cost of the permit itself. I've heard of installers who
told customer that they could add one or two modules at any time. With
permit and inspection costs in some local jurisdictions running over
$300, that could add over $1/w to a single panel add-on.

 

Finally, product obsolescence may make this strategy difficult or
impossible. Engineering documentation would become obsolete if product
specifications change. We have already seen the Enphase D380 go
obsolete. The M190 is probably not far behind. Most would want to expand
an M190 system with M215's anyway to get the extended warranty. I
realize that you could add additional branch circuits, but that's akin
to a new system, not an add-on.

 

This came to mind after listening to the Sunpower AC Module technical
overview webinar yesterday. Easy system expansion just doesn't seem like
a real benefit to me. It may be a nice selling point, but is it really
practical? Adding 5kW to an existing 5kW system would not be a problem.
Adding one or two modules at a time does not seem realistic.

 

Jason Szumlanski

Fafco Solar

 

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