Grid-tied but grid down

[JimLudden]

I have an Enphase grid-tied system, with manual disconnect switch for the fire department.
When the grid fails, how can I use power from my panels to run my refrigerator or gas furnace? I have installed a generator transfer switch, but have no generator (other than the PV panels). No batteries, other than in my car (which I cannot use for this).

[solardreamer]

The conventional solution is add a hybrid inverter/battery system that supports off-grid AC coupling and frequency-shift control for grid-tied inverters. Search for "AC coupling" on the forum for more info. A generator would be cheaper but cannot connect to the grid-tied system by itself.

[Mike 134]

You cannot use the panels for power unless the grid is up. When the grid goes down so do the panels. Unless you lose power often and for extended periods of time it's not worth the $$ to utilize the panels for power. I have a 6500-watt generator just in case in the next 10 years I lose power and need the frig running. So far 9 years into owning it and have not used it.

[Rade]

We have a 18kW battery backup attached to our system. During the summer, I've kept the system in "Self Supply" mode and used the battery power to keep the house alive overnight (when the nights are short). We would use about 80% of the battery power. For several weeks, we actually pulled nothing from the grid; the sun would fire up the panels at dawn and start generating power, recharging the batteries while also providing power to the house.

That said; in "Emergency Mode", we have fail-over that will provide battery power to 6 specific circuits in our home if the grid power goes out. Since installation, we have not had anything worse than a >Bink!< power blip that just managed to cause every digital clock in the house to reset. Nothing that failed over. I am of the impression that, much like the multi-day outage we experienced 8 or so years ago, that in emergency mode, the panels would recharge the batteries as much as they could while the sun would be up.

[ray188]

I have an Enphase grid-tied system, with manual disconnect switch for the fire department.
When the grid fails, how can I use power from my panels to run my refrigerator or gas furnace? I have installed a generator transfer switch, but have no generator (other than the PV panels). No batteries, other than in my car (which I cannot use for this).

You would need an Offgrid inverter. Your house circuit MUST be disconnected from the grid at the Main Breaker Panel before connecting the Offgrid inverter. If you have many inductive loads (i.e., appliances with motors, like fridge, aircon, well pumps) you need a LF (low frequency) inverter that has 3x surge power. HF (high freq) will die easily if your loads are mostly inductive. I am using 3KW LF offgrid from Solartorrents website, think they will have 6KW soon. You can also ask their support to determine what/how to setup offgrid. Electricity is not very forgiving to persons and eqpts, so must know what you are doing.

[Brightside]

As some have eluded to, your system is down when the grid is down. A very costly solar battery backup would be necessary for you to have power when the grid is down. You could swap out the inverter, which enphase isn’t an inverter because it’s AC coupled, you most likely have a combiner box. But all things considered you should just get a generator. That’d be the cheapest route. It’s all done through transfer switches and is plug and play. Grid goes down/solar goes down, transfer switch flips, and you probably wouldn’t even have ever noticed that the power ever went out

[Rade]

As some have eluded to, your system is down when the grid is down. A very costly solar battery backup would be necessary for you to have power when the grid is down. You could swap out the inverter, which enphase isn’t an inverter because it’s AC coupled, you most likely have a combiner box. But all things considered you should just get a generator. That’d be the cheapest route. It’s all done through transfer switches and is plug and play. Grid goes down/solar goes down, transfer switch flips, and you probably wouldn’t even have ever noticed that the power ever went out

On hindsight, a propane generator is probably the best option. We have three banks of panels (totally 32 panels). Two of the three banks are on a lower pitched garage roof, and when we get any accumulation of snow, they are essentially dead until the snow gradually melts off them or I get out the rubber snow rake and pull the snow down. The arrays on the higher, steeper pitched roof clears off sooner (that whole gravity thing). The batteries are going to be fine if we lose power, say, during a summer hurricane (that has happened) or some idiot takes out a power line on the block.

But I am not contemplating adding a generator for now.

[chrisski]

You would need an AC coupled inverter to take the AC back to DC, a battery pack to charge, and some type of load controller that chooses what will be powered for an outage.

I also recommend staying with the same brand Enphase, and staying with an installer familiar with the system. Sometimes both aren’t possible.

https://enphase.com/store/storage/gen2/iq-system-controller

the link I copied above shows all three products.

i think 95% of us with batteries use a hybrid DC coupled system and 5% of us on these forums have an AC coupled battery pack.

[solardreamer]

i think 95% of us with batteries use a hybrid DC coupled system and 5% of us on these forums have an AC coupled battery pack.

If true then the forum is not a good representation of the actual home solar market where AC coupled batteries dominate by far.

[chrisski]

If true then the forum is not a good representation of the actual home solar market where AC coupled batteries dominate by far.

You could very well be correct.

I am DIY for smaller stuff like the RV and small solar generator, and when I went with my house, I went DC coupled.

Do you have equipment recommendations for the OP? On top of Enphase, my installer likes Franklin Power.


If your familiar with AC coupling, can you comment?

for extended power outages is if the battery is depleted, then they may not start again until the power comes back up. I’m not sure if this has been fixed with the newer powerwall3. I also see that the newer IQ8 emphases will produce power in a grid outage, but the older ones need grid power sensed to products power

[solardreamer]

For Enphase microinverters, the best user experience is only possible with Enphase batteries in terms of fully integrated functionality and monitoring. The downside is the significantly higher cost. Tesla Powerwall (2) is the other leading AC coupled battery offering which is likely the cheapest if you can get it directly from Tesla. Many other choices are also available including Generac, Franklin, Canadian Solar, etc.

[azdave]

Our utility power very rarely goes out and the cost and maintenance to have back-up power for those few hours in total per decade is insane. I would buy a gas generator in your situation. In my case, I wouldn't even consider that due to the reliability of our grid but, if I did buy a generator, I could use the significant savings we've banked from our thankfully very simple and reliable grid-tie system.

[Mike 134]

Our utility power very rarely goes out and the cost and maintenance to have back-up power for those few hours in total per decade is insane. I would buy a gas generator in your situation. In my case, I wouldn't even consider that due to the reliability of our grid but, if I did buy a generator, I could use the significant savings we've banked from our thankfully very simple and reliable grid-tie system.

I'm in the same place as you a very reliable grid. Only long outage (more than 3 hours) I've experienced in 68 years was after a microburst and the power was out for 4 days 3 of which had clouds and rain. Small generator was enough to power the frig and sump pump.