Off-Grid Home -- Best connection for a portable emergency generator

[S610]

I am in the initial planning phase for a 1000 sq ft offgrid home (using a general contractor, no DIY stuff). Will have a 5-8KW solar system with battery backup however I think a portable propane generator may be wise (I don't want to lose a freezer full of food if the solar goes out, plus will need water from the well pump).

What is the easiest way to connect that? I would like to just have an exterior plug-in that could power the whole house instead of a transfer switch if the building code allows (Georgia). Not that I would try to power everything off a portable generator but would rather have it available to more than just the freezer.

Any suggestions? An electrician will perform the work, I just want to keep it simple. If I buy a well pump suitable for a solar system I am hoping it won't require a huge generator OR maybe I could use the generator to top off the batteries enough to start the pump? I am a clueless newbie in case that isn't obvious.

 

[BentleyJ]

Most inverters will have at least 1 AC Input so your generator could be connected directly to an All in One inverter such that gen power will pass through the inverter to your loads and depending on the menu settings will also charge batteries. Some inverters are a sensitive to AC quality so it would make sense to get a good, inverter type generator.
Since you are off-grid I would recommend installing a Generator Receiver plug that feeds directly to a breaker in the main panel. This gives you an alternative gen connection if the inverter fails and needs repairs, your house still has electricity.

https://www.amazon.com/WELLUCK-Generator-SS2-50P-Receptacle-Weatherproof/dp/B08GLK5HJJ/ref=asc_df_B08GLK5HJJ/?tag=hyprod-20&linkCode=df0&hvadid=475746627269&hvpos=&hvnetw=g&hvrand=13566587582012289133&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1014327&hvtargid=pla-1057601925006&th=1

 

[S610]

Most inverters will have at least 1 AC Input so your generator could be connected directly to an All in One inverter such that gen power will pass through the inverter to your loads and depending on the menu settings will also charge batteries. Some inverters are a sensitive to AC quality so it would make sense to get a good, inverter type generator.
Since you are off-grid I would recommend installing a Generator Receiver plug that feeds directly to a breaker in the main panel. This gives you an alternative gen connection if the inverter fails and needs repairs, your house still has electricity.

https://www.amazon.com/WELLUCK-Generator-SS2-50P-Receptacle-Weatherproof/dp/B08GLK5HJJ/ref=asc_df_B08GLK5HJJ/?tag=hyprod-20&linkCode=df0&hvadid=475746627269&hvpos=&hvnetw=g&hvrand=13566587582012289133&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1014327&hvtargid=pla-1057601925006&th=1

Thank you! I didn't realize the inverter usually had a plug. Will definitely have the electrician install a backup plug too.

 

[BentleyJ]

Thank you! I didn't realize the inverter usually had a plug. Will definitely have the electrician install a backup plug too.

The inverter AC input would most likely be some kind of lug to be hardwired rather than a preinstalled plug, your electrician will know what to do.

 

[S610]

The inverter AC input would most likely be some kind of lug to be hardwired rather than a preinstalled plug, your electrician will know what to do.

Thank you. I am writing all of this down.

 

[SoVT]

Most inverters will have at least 1 AC Input so your generator could be connected directly to an All in One inverter such that gen power will pass through the inverter to your loads and depending on the menu settings will also charge batteries. Some inverters are a sensitive to AC quality so it would make sense to get a good, inverter type generator.
Since you are off-grid I would recommend installing a Generator Receiver plug that feeds directly to a breaker in the main panel. This gives you an alternative gen connection if the inverter fails and needs repairs, your house still has electricity.

https://www.amazon.com/WELLUCK-Generator-SS2-50P-Receptacle-Weatherproof/dp/B08GLK5HJJ/ref=asc_df_B08GLK5HJJ/?tag=hyprod-20&linkCode=df0&hvadid=475746627269&hvpos=&hvnetw=g&hvrand=13566587582012289133&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1014327&hvtargid=pla-1057601925006&th=1

This true that most inverters do have a generator charging option. However you will need a very large generator that can handle the charging as well as operate the house at the same time. For most small homes that requires a very large generator 14-20kW. Most inverter companies won’t warranty an inverter that is damaged by an under powered portable generator. EG4 had so many warranty claims they came out with a dedicated charge for use with smaller portable generators.

Will Prowse did a great video on the EG4 Chargeverter. I highly recommend checking it out before connecting your generator to your inverter. It changed my mind. Signature Solar also has a good video explaining this issue.

Here is my setup operating on a 7kW Harbour Freight Special that is only connected to that yellow charger on the side of my battery cabinet. You can tune the charger to your generators sweet spot. Mine is set up at 75amps to the batteries. Puts about 7kwH of energy into the batteries every hour of operation.

 

[S610]

I don't use much power now (about 5-6Kw a day) and the new house will use even less with a propane stove etc... I was hoping I could get a small portable generator (about 1800 running watts) and use that to charge the battieres so the well pump and freezer can be run for an hour or so. I am female and a small portable 40lb propane generator would be much easier to handle. I hate the big heavy gas ones for a lot of reasons (noise, weight, fuel storage/rotation etc...). The house will have a large propane tank anyway.

If the batteries had some charge on them could they start the well pump? It will be a solar compatible pump. I do realize the pump likely couldn't be started directly from a generator that small.

 

[SoVT]

So I’m no expert but I did just complete this exact task so it’s fresh in my mind. Take my advice with a grain of salt.

I would definitely go with the biggest open frame generator you can move by yourself on wheels. Propane is fine but know that drops the power output by ~20% so you will need an even a larger generator. Highly recommend 240V generator over 120V and that pushes you to a larger generator.

My current generator is just what I used during construction. It’s a cheap one from Harbor Freight that is rate for continuous operation of 7,000 watts at 240V. Currently that’s my only means of charging my batteries because I don’t have PV yet. Takes me about 1 1/2 hours each day to charge my batteries which are 10kWh.

In my opinion a small <2kW 120V generator would have to run several hours a day to provide your estimated 7kW of daily energy needs. If you charge via the inverter directly the amperage to the batteries is going to be pretty low <20amps. Takes doing to take 4-6 hours I would guess as I’m throwing 75amps to mine and it takes 1.5 hours to go from 25% to full.

 

[S610]

So I’m no expert but I did just complete this exact task so it’s fresh in my mind. Take my advice with a grain of salt.

I would definitely go with the biggest open frame generator you can move by yourself on wheels. Propane is fine but know that drops the power output by ~20% so you will need an even a larger generator. Highly recommend 240V generator over 120V and that pushes you to a larger generator.

My current generator is just what I used during construction. It’s a cheap one from Harbor Freight that is rate for continuous operation of 7,000 watts at 240V. Currently that’s my only means of charging my batteries because I don’t have PV yet. Takes me about 1 1/2 hours each day to charge my batteries which are 10kWh.

In my opinion a small <2kW 120V generator would have to run several hours a day to provide your estimated 7kW of daily energy needs. If you charge via the inverter directly the amperage to the batteries is going to be pretty low <20amps. Takes doing to take 4-6 hours I would guess as I’m throwing 75amps to mine and it takes 1.5 hours to go from 25% to full.

Yeah I knew the type of generator would be a headache. If I had to use one I would really only want it to keep the freezer cold (run it for an hour or so every day or two) though of course the well pump is another issue. Will probably also go with rain water storage or maybe a second shallow well.

I bought a 7Kw gas generator a few years ago and it has been used once because I would rather go without (it is still sitting in the shed). Having said that I do plan to have a chest freezer so don't want to risk losing hundreds in groceries.

I am taking notes on all of this especially the part about a small portable generator voiding the inverter warranty. I will end up getting a solar installer and ask these questions but honestly I do NOT want to depend on the installer or worse, a salesperson, when it comes to these details.