Rule and regulation for micro-inverters

[theoldwizard1]

Several years ago, I had a friend who added some solar power to his home in SE MI. His biggest issue was getting all of the permits and having the power company install a second meter. He also had to spend quite a bit of money for "safety equipment" (disconnects) to allow the PoCo to bypass his solar array from the grid.

Now a days, I read that with a micro-inverter, you just "plug it in" to an unused 120VAC outlet ! Clearly you won't be "selling" power back to the utility, but you will reduce your bill !

How do they away with no permits, inspections, meters, disconnects ?

 

[svetz]

What you need to pull a permit for varies with location. I've seen folks complain their counties don't do any inspections which is sad as there's no one keeping them safe, and no one ensuring the safety of future buyers.

It might be tough finding a UL listed 120V GT inverter, which might end up being a battle with the insurance company if anything burns down.

But, a UL listed microinverter that shuts off when the grid goes down (aka anti-islanding) should be safe. 240V versions are easy to find.

Usually, without a net-meter, any solar power they don't consume will be exported to the grid. But it won't run the meter backwards... it'll run forward (old meters just detect current flow, not direction). There are devices that can limit any exported power, so a net-metering agreement isn't needed (although, the net-metering agreement was the easiest part for me and provides credit so why not?).

 

[nosys70]

micro inverters are just another way to transport the energy from the solar panels.
instead linking them with thick expensive cable, you put a microinverter on each one.
so each solar panel become a small powerplant, and you can network all the inverter together.
the nice thing is you can add and remove panels by just plug/unplug it.
the bad thing is you get high voltage on the roof and a lot more electronics with potential failure.
if you inject the 120V directly in the cabling of your house, you still need the usual equipement to eventually isolate the panels from the main.
If you get an excess of power from panels they will go back to the main network.
if all microinverters are set to wait for the main to be present to start and synchronize, the drawback is despite you could have tons of power from the roof, it will be useless if the main goes down, because everything will be down (small problem for grid tie systems).
This also implies you will not use batttery.

 

[theoldwizard1]

So more info.

My local PoCo has gone to 100% electronic meters. No more spinning wheel ! The meter will detect "back flow" into the grid. It will not necessarily stop it, but it will NOT give you any credit for what you send upstream and it WILL report your meter to the company !

I don't think they will likely do anything to prevent this, but why give them your excess power. For a few, they will come out and "inspect" your system and agree to buy back at their wholesale rate (about 1/2 of retail).

 

[websolar]

Regulations and safety standards still apply, and selling excess power back to the utility may depend on the specific policies of the utility company. You still need follow to regulations like "NEC California Electrical Code 2019" and "California Fire Code 2019"

 

[Mike 134]

So more info.

My local PoCo has gone to 100% electronic meters. No more spinning wheel ! The meter will detect "back flow" into the grid. It will not necessarily stop it, but it will NOT give you any credit for what you send upstream and it WILL report your meter to the company !

I don't think they will likely do anything to prevent this, but why give them your excess power. For a few, they will come out and "inspect" your system and agree to buy back at their wholesale rate (about 1/2 of retail).

So your power company offers NOTHING if you send it back to the grid? I'm very lucky then getting a full one for one pricing plan.

 

[theoldwizard1]

So your power company offers NOTHING if you send it back to the grid? I'm very lucky then getting a full one for one pricing plan.

Yeah, sad isn't it ! This changed a couple of years ago. Makes you wonder who on the Public Service Commission got paid off !

 

[billvon]

micro inverters are just another way to transport the energy from the solar panels.
instead linking them with thick expensive cable, you put a microinverter on each one.
so each solar panel become a small powerplant, and you can network all the inverter together.
the nice thing is you can add and remove panels by just plug/unplug it.
the bad thing is you get high voltage on the roof and a lot more electronics with potential failure.
if you inject the 120V directly in the cabling of your house, you still need the usual equipement to eventually isolate the panels from the main.
If you get an excess of power from panels they will go back to the main network.
if all microinverters are set to wait for the main to be present to start and synchronize, the drawback is despite you could have tons of power from the roof, it will be useless if the main goes down, because everything will be down (small problem for grid tie systems).
This also implies you will not use batttery.

Two notes here.

1) Solar panels connect with their own cables if you are doing a series connection to a string inverter. So if you use string inverters, there is very little exta cost for wiring. However, microinverters have to use specific cables which can be expensive. The IQ6 inverters from Enphase (very common) used a truly absurd 5 conductor cable that was very pricey. IQ7/8 uses a 2 conductor cable that's less expensive - but still far more expensive than the wiring for a string inverter.

2) You get much lower voltage on the roof with microinverters. Microinverters run at 208 or 240 volts AC; string systems run at 300-500 volts DC.

 

[billvon]

So your power company offers NOTHING if you send it back to the grid? I'm very lucky then getting a full one for one pricing plan.

Depends on the plan. In California, under NEM 3.0, you get about 25% of the basic cost of electricity back for every kwhr you export. (In other words, if power costs you 20 cents per kwhr, you will get 5 cents back for exported power.)

 

[theoldwizard1]

Microinverters run at 208 or 240 volts AC

I am not an expert, but all the micro-inverters I have seen output 120VAC. You can run 2 if you plug them into opposite sides of the split phase.

 

[theoldwizard1]

so each solar panel become a small powerplant, and you can network all the inverter together.
the nice thing is you can add and remove panels by just plug/unplug it.
the bad thing is you get high voltage on the roof and a lot more electronics with potential failure.

Not a concern. Use good quality SJOOW cable with as few weather resistant connectors as possible.

if you inject the 120V directly in the cabling of your house, you still need the usual equipement to eventually isolate the panels from the main.
If you get an excess of power from panels they will go back to the main network.

If you use a standard NEMA 6-15P to connect to your home wiring, you have a disconnect. It can be mounted outside in a weatherproof box and labeled "solar disconnect".

 

[billvon]

I am not an expert, but all the micro-inverters I have seen output 120VAC. You can run 2 if you plug them into opposite sides of the split phase.

The only UL-rated inverter that I have ever seen that operated at 120V is the old Trace Microsine, an early microinverter that is no longer made.

You can get anything you like from overseas, of course, but in terms of devices you'd want in an installation, they are pretty much all 208/240V. The higher voltages reduce the need for copper.