The Risks of Grid-Tie Solar

By Solari Staff

Originally published February 2022

Introduction

There has been a rush to put solar panels—aka photovoltaics or PVs—on homes across the world. In the U.S., a host of incentives, tax credits, and other government subsidies have helped grease the skids. Note: Code requirements vary by location.

There are two types of PV solar systems:

• Grid Tie: Where any excess power is sold back to your local utility across the grid.

• Off Grid: Not connected to the grid. (Note: This was the original solar PV system application, and it is now on the endangered species list.)

Grid-Tie Systems

What are the components of a grid-tie solar PV system?

• Photovoltaic panels/array (Direct Current [DC] source)

• DC wiring/fuses

• DC disconnect switch (for isolating the DC side)

• Inverter (the device that turns DC current into AC current)

• AC disconnect switch (for isolating the Alternating Current [AC] side)

• AC distribution panel (the device that routes AC power to your home and to the grid)

The incentives for solar PV vary greatly by state and the utility that will be purchasing your power. These incentives also can vary wildly over time. So, obtaining the most advantageous incentives package in your place will depend on the politics of your place.

I visited a friend’s home who had recently installed his own 7.3kW (7,300 Watt) solar PV system and was about to get it commissioned. Both of us had worked at the same large Southwest utility and have seen the evolution of solar PV applications over the years.

Some of the “features” I saw on this new system I found to be very interesting. The Euro-manufactured inverter he had purchased was renowned for being top of the line. However, it had a new feature I’d never seen previously—an internal web server. In days past, you could get an application for your computer that would pull data directly from your inverter or meter. And you could then share that data at your discretion. No more—this inverter was designed to be connected to my friend’s local area network (LAN). With onboard wired and wireless capabilities, it would then put your data on the web, and you could track other peoples’ solar PV production at the same time. The IoT (Internet of Things) approach. Oh joy!

What I found disturbing was the password for this onboard web server was assigned by the inverter manufacturer. Therefore, purchasers of this type of system have no way to fully password-protect their inverters, while any entity that has access to this password has access to the data and/or control of the unit.

Another interesting hardware/software addition was a code requiring a “Rapid Shutdown Switch” (RSS). Apparently, during the influx of cheap Chinese panels around 2005–2008, there had been an increase in roof fires in the L.A. area due to these substandard foreign-made panels. Therefore, a code change demanded the installation of “Rapid Shutdown Switches.” In other words, instead of requiring the Chinese to make safe panels, the burden fell to the consumer to take up the slack. These RSSs were installed on the back of each PV panel in the system, and the inverter would not allow the DC power to flow unless it could talk to each panel’s RSS. So, my question is, could these devices be used to selectively shut off individual panels remotely?

This also begs the question, why the need for total control of a simple residential system whose function is to simply supply any excess power to the local utility? Note, the AC meter keeps track of all power transactions and provides all the raw power usage for billing.

Also note that my friend jumped through several hoops attempting to get a backup battery bank to power his system in the event of a power outage. Oh, you didn’t know that with a grid-tie system, if the utility loses power, you lose power, too? Yes, that is the case, and this minor omission is sometimes not disclosed to the purchasers of grid-tie systems. (You have to ask.) Again, without battery backup, your solar PV system will not function during a blackout. Well, that’s a bit impractical, is it not? What my friend discovered was that the local Fire Department would not allow a battery bank unless it was manufactured by Tesla. Hmmmm? It appears some manufacturers are more equal than others.

So, let’s get to the meat in the coconut. Before, you can connect your solar PV system to the grid, you must sign an “Interconnect Agreement.” I have never read one that I would sign. Again, your Interconnect Agreement will be particular to your state and utility. The “Power Purchase Agreement” is what your utility will pay you for your power. Note that although some utilities will pay you the same rate they charge you for power, this is not the norm. Some utilities are very stingy on how large the PV array can be in kilowatts and will only pay you wholesale rates for grid-connected power.

Now let’s discuss the elephant in the room, namely, ownership of green/carbon credits (also known as green tags) in the above-mentioned Power Purchase Agreements. I have found the mention of green/carbon credits or tags to be nebulous in some agreements or, if they were mentioned, they belonged to the utility. If green/carbon credits or tags become the next big thing, whoever owns them will reap serious taxpayer-funded windfall profits. Could this be the real reason for the push to “green” America? (Please, if anyone has seen a case where a homeowner was awarded ownership of their green/carbon credits or tags in the U.S., let me know!)

Are there other risks of having a grid-tie system? There has been legislation floated that would tax homeowners on their power savings. This threat comes from being connected to the grid. Depending on your state’s whim, your solar PV system could be classified as a utility.

Summary

If you don’t mind the third parties monitoring your power usage, you can enjoy as much power savings as your electric utility allows. However, if you’ve accepted government subsidies and are connected to the grid, the hand that giveth might start to take it away.

Off-Grid Systems

Off-grid systems—systems consisting of a PV array, battery charge controller, battery bank, and DC and AC disconnects—have been under the gun of late. In California, people living the off-grid lifestyle were being told by the state of CA that they had to suffer the expense of running power lines to their systems and had to connect to the grid. Off-grid systems are frowned upon due to their dependence on batteries and the threat of fire. Note, that same concern doesn’t cover gasoline cans, propane tanks, or other fossil-fuel storage containers. Again, it’s location, location, location. But, the real reason for all this recent discrimination is that Mr. Global doesn’t like independent people living an independent lifestyle.

I’m a big fan of solar PV. I would choose to have a mobile unit that had a modicum of battery backup and a generator, so if I was ever forced to evacuate, I could take my alternative power with me.

Summary

In my opinion, off-grid PV systems are the only way to go. That power will be there if the grid goes down, and nobody needs to know when you are home via your electrical power usage. However, these systems aren’t for everyone. You need to understand AC and DC electricity and the associated safety procedures. Also, depending on your climate, your expenses and maintenance cycles will vary. However, besides having an alternate water supply, off-grid power is essential for anyone who wants to live an independent lifestyle.

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