30 Oct

Expanding a Solar Panel System

Posted by Norman F

How to expand your Solar Panel system

We installed our original solar panels way back in 2004.  They have generated a ton of power for us, but after 14 years, it was time to think about adding on to our system.

Be sure to read our articles: Are Solar Panels for me?

Why Expand a Solar Electric System?

Our existing system had 16 panels generating 4.8kW of power. Back when we installed it, we were definitely an early adopter.

The main reasons why we needed to add capacity to our system:

  • Electric Car
  • More Consumption
  • Degradation of Panels

Our Tesla electric car gets charged every evening and single handedly increased our energy bill by a substantial amount.  The cost was way cheaper than gas, but we wanted to eventually cover this extra use.

Our home was using about 30% more power than the past.  Chalk it up to new wiz bang gadgets and family.

Solar panels degrade with time.  After 14 years, our panels output had declined, additionally 2 panels had failed and needed to be replaced.

  • Panels typically have guaranteed electrical production for 10 years at 90% of rated power output and 25 years at 80%.

Considerations on a Solar Panel Expansion

Here were the main criteria when we expanded our system:

  • Keep existing panels
  • Replace 1 of our 2 Sunny Boy inverters that had died
  • Add enough power in the small roof space allotted
  • Be reliable for many years on
  • Cost effective

We could have scrapped our existing system and replaced it, but decided not to because it was still generating power and we wanted to be eco and use our equipment longer.

An open spot on our flat roof could accommodate approximately 12 solar panels.  These needed to be very efficient and reliable.  We ruled out the Chinese panels due to reliability, and eventually selected LG.  Hyundai, Panasonic was also considered.

Power Inverter

We needed to replace one dead inverter. It was dead for over a year before we noticed.  A new one needs to be capable of alerting us!!

Instead of just replacing an inverter, we decided to buy a single big one capable of handling 3 different solar panel strings of varying power. New inverters support Rule 21 Interconnection.

Microinverters were ruled out because our existing system would have to be modified to accommodate it. We did not want to mess with a working existing wiring and fishing wires in conduits. Electrical wiring would be complicated. Occam’s razor – keep it simple. We wanted a permit that only dealt with the new string, messing with the existing stuff would complicate matters.

Our new more efficient inverter, the SMA Sunny Boy 7.7-US has 3 MPP trackers to handle 3 solar panel strings each with possibly different power output.  It has Wi-Fi and Ethernet for connectivity.  We would have to just run one more conduit from the new string to this Sunny Boy.  Every morning, this box emails us a daily power output report.  No problems detecting a problem.

This inverter allowed us to remove an unneeded array disconnect box and ac disconnect box.

Rapid shutdown support was added for fire safety.  This allows the panels to be de-energized through a switch near the inverter on the side of the house.

Solar Panel Pricing

Prices have fallen on panels, with our new 3.8kW string with 12 LG320N1CG4 panels costing around $9000 with installation cost, before 30% Federal tax credits.

Our existing solar electric system 4.8kW system (From 2004) had cost us $XXX with a 40% Federal Tax Credit and 10% California State Credit reducing the final cost.

Solar Panel Racking

Our flat roof allowed us to use a ballast mount with 10 degree of tilt.  We choose the Unirac system that was held down with heavy paver stones.

Finding a company to expand your System

Most solar panel companies want to install brand new system.  Few will help you expand an existing system unless you purchased it from them.  Even fewer want to maintain solar equipment.

We had to check on Yelp, Nextdoor, Google to find several vendors and get a decent quote.

Recycling Solar Panels

Recycling Solar Panels and Inverters will become more important in the coming years. This is HARD. There are only a few places to recycle solar equipment right now. Some can take them to e-waste recyclers or Household Hazardous Waste collection facility.

Solar Panel Expansion Results

Our daily reports show that we have effective doubled the output of our solar panels system!  Approximately 32-33kW a day is generated during the summer up from 16-18kW.

We will see how our energy bill comes out, it should definitely be lower.

Posted on October 30th, 2018
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