Hooking a solar generator to a sub panel

[My Cool Spirit]

I have an 8,000 watt gas generator which I plug into a dedicated sub panel for my house when I have a power outage. I use a 30 amp power cord from the generator to the panel. I'm thinking of going solar to eliminate the cost of gas. Can I hook up a solar battery bank through an inverter to the sub panel via the power cord?

 

[WYtreasure]

Yep, ya can.

Welcome to the party Cool Spirit.

 

[MrM1]

All thinks being equal, properly designed and set up... Yes

 

[My Cool Spirit]

Awesome! I thought so. Thanks for the welcome WYtreasue. MrM1, I'll look at your links. I want mine to be portable. Looking for around 8-12K system. Don't want to be up on the roof or mounting them in the ground. I'm a newbie but did put in a sub panel before to hook up the generator.
Any thoughts?

 

[richard cabesa]

Awesome! I thought so. Thanks for the welcome WYtreasue. MrM1, I'll look at your links. I want mine to be portable. Looking for around 8-12K system. Don't want to be up on the roof or mounting them in the ground. I'm a newbie but did put in a sub panel before to hook up the generator.
Any thoughts?

Many thoughts,
An 8K array of panels would be in the neighborhood of 450 square feet or about the size of a two car garage. Hardly going to be made portable.
If this is just panels that you want to plug in to replace the gen, you will only have power when the sun is shining without battery backup. 8-12k worth of power from batteries is a lot of batteries.
If this is just to save the cost of fuel, the numbers will never pencil out in your favor

 

[MrM1]

MrM1, I'll look at your links. I want mine to be portable. Looking for around 8-12K system. Don't want to be up on the roof or mounting them in the ground.

If you mean array size, then What @richard cabesa said, that's a large number of panels .

If you mean 8-12k of output power this is also a large system.

Questions that need answering before you begin
- What is your goal? Education? Critical loads? Fully off grid?
- What is your budget?
- What are your power needs in daily watt hours?
- where do you live?
- How much average sun does your area receive daily? Here in N Fl we get on average 4.3 hrs per day
- how long do you need the system to operate with no or limited sun?

I would begin with a power audit to determine just how much power u need. Don't buy anything until you know the answer to these questions.

This spring I am building a 12kw watt off grid power set up with an 11840w array for an off grid farm. This system so far has cost about $15k and we have not yet bought /built the power shed, the array mounting system and only bought about half of the wires and cables (aka Balance of System)

So this is an idea. But it's difficult to help you without knowing your needs and goals.

 

[Supervstech]

Awesome! I thought so. Thanks for the welcome WYtreasue. MrM1, I'll look at your links. I want mine to be portable. Looking for around 8-12K system. Don't want to be up on the roof or mounting them in the ground. I'm a newbie but did put in a sub panel before to hook up the generator.
Any thoughts?

Do you mean watts or dollars?
Will has some videos where he lays out his panels on his driveway… so portable in a way.
But he isn’t attaching any output to a structure, he is only using it for charging things…
Attaching to a grid connected structure is more involved. Grounding regulations etc.

 

[Delmar]

I want mine to be portable.

Can't get more portable than a self-propelled system. $8-$12K can include a used 48V electric cart with good FLA batteries. Learn with lead before you upgrade to lithium. Equipment ruined = knowledge gained.

 

[MrM1]

Do you mean watts or dollars?

Good Point.

I have an 8,000 watt gas generator which I plug into a dedicated sub panel for my house when I have a power outage. I use a 30 amp power cord from the generator to the panel.

MrM1, I'll look at your links. I want mine to be portable. Looking for around 8-12K system.

From @My Cool Spirit 's 1st and subsequent follow up I assumed possibly output watts ??

 

[My Cool Spirit]

I was thinking of these all-in-one portable generator systems. I was hoping to get something that would at least match my gas generator output (7,000 watt running / 8,750 watt max). That worked all my critical appliances including my well pump and furnace. I have a sub panel (installed by the previous owners) and a 30 amp hookup box to the sub panel for the power cord from the generator. I would like to hook up the portable solar all-in-one battery generator to that sub panel via that 30 amp hookup. I am thinking of mounting the solar panels on towable trailer, hence the portability. Does this all make sense? I see a system which has the capability of 6,000 watts. For the record I meant 8-12k watts not $$.? Money wise, I'm looking at 6 to 10 thousand. The 30 amp Hookup looks like this:

 

[Delmar]

One extreme: running exclusively from the generator and paying for gas. Plus listening to the engine drone, even to power one light bulb.

Other extreme: running exclusively from solar and battery. Will require lots of expensive panels and batteries.

What is your location? The further north, the less sun and more panels required. Also the further north the steeper the panel angle where they will act as a sail. Can easily overturn a portable trailer unless you have a method to securely anchor to the ground. Mount the generator on the trailer as ballast, and lead batteries make dandy ballast too.

I recommend a hybrid system that can operate 8-10 hours from battery, then the generator kicks in and runs the house plus recharges the batteries. My power outages are typically 8-10 hour rolling blackouts where my golf cart easily handles the load. Then again I am in south Texas with good sun and minimal furnace required.

Look into inverters that have a generator start provision with transfer switch for battery power. Start your search here.

 

[My Cool Spirit]

Hi Delmar. I live in Virginia. My house is on a small plateau, if you like, facing WSW. I had 2 solar companies come out and both said I am in a perfect position for solar. I know they want to make a sale ($100K), but my sun exposure is awesome so the angle I assume needs to be 30 degrees. The trailer will be on level ground. This one system I had been eying generates 6,000 watts with 4-200 watt panels. I don't get many blackouts or power outages. And if I do there short in duration except this past storm earlier this month. I was without power for 3.5 days. I here what your saying about a Hybrid situation so all options are on the table. I'll check out your link. Much obliged.

 

[MrM1]

I do not think a portable solar generator will have a large enough battery to run a large load very long

 

[vejeriego]

Hi Delmar. I live in Virginia. My house is on a small plateau, if you like, facing WSW. I had 2 solar companies come out and both said I am in a perfect position for solar. I know they want to make a sale ($100K), but my sun exposure is awesome so the angle I assume needs to be 30 degrees. The trailer will be on level ground. This one system I had been eying generates 6,000 watts with 4-200 watt panels. I don't get many blackouts or power outages. And if I do there short in duration except this past storm earlier this month. I was without power for 3.5 days. I here what your saying about a Hybrid situation so all options are on the table. I'll check out your link. Much obliged.

I'm a bit lost with the Watts...

Okay, I understand an 8kW generator, which will push out 8kW of electrical energy all the time, even if it's only running a 100W light bulb. But then there's a 30A cable and panel. So, if this is a US system, that's 30x120= 3.6kW (running all the time)

However the trailer system quoted at 6kW with 4x200W panels just doesn't make sense. The solar panels will generate a maximum of 800W (more like 600W on average, if you're lucky), not 6kW.

Is this a 6kWh battery bank? Which would make more sense. 10 hours of sunshine would fill a 6kWh battery, assuming you are taking nothing out of it. But, then, from what you have above, you are currently "supplying" 3.6kW for consumption from your generator. That's less than 2 hours of what's stored in your battery, and around 6 times the production of your cells.

Put another way: how much power are you actually consuming (rather than currently supplying)? From there, you can decide whether 4 panels are enough. Given that the sun doesn't shine 24 hours a day, you probably need 18 times the number of panels to equal you gas generator consumption and with a battery many times the size.

 

[My Cool Spirit]

Yes, a 6k battery bank. I'm totally ignorant of this all. I don't know how much power I consumed with my generator, but at the 7, 000W running and 8,750W max output, it handled a lot of appliances: Well Pump, Lights, Plug outlets running coffee pot, water Kettle, Dish Satellite, TV, 2 Fish Tanks, Refrigerator, Whole House Water Filtration system, etc. So I assumed (my bad?) that I could use a portable solar system with a battery bank with at least 6k watts.

 

[MrM1]

I'm no rocket scientist and hardly understand anything, But

I'm a bit lost with the Watts...

Okay, I understand an 8kW generator, which will push out 8kW of electrical energy all the time, even if it's only running a 100W light bulb.

No. an 8000w generator connected to a 100w light bulb will push out 100 watts. (plus or minus losses)

But then there's a 30A cable and panel. So, if this is a US system, that's 30x120= 3.6kW (running all the time)

There is not really such a thing as a 30 amp cable, there would be a cable rated for 30 amps. Cables are messured in AWG size or mm sizes.. 30 amps at 24vdc requires a different size cable than 30 amps at 48vdc or 30 amps at 120vac. And then distance comes into play too. chart here

DC wire size calculator

But it would be true to say, 30a x 120v = 3600w.

10 hours of sunshine would fill a 6kWh battery, assuming you are taking nothing out of it.

There is no place in north america where the suns peak solar performance is 10 hours a day. NA Solar Chart

Yes, a 6k battery bank. I'm totally ignorant of this all. I don't know how much power I consumed

Let's assume, connected to the grid your monthly power bill is 990kWh per month or 33kWh per day. That mean you use 33,000 watts of power per day.
- a 6000 watt battery would provide 18% of your daily load or would be good for about 4.5 hours of power. So this 6k battery would not last all night on an average family household load.

And none of that takes into consideration, the design of a small solar and battery based generator.

To run the loads you are taking about will take a large to very large solar system.

General rule of thumb
1. Grid if available is always cheapest
2. A fuel based generator is cheaper than solar
3. Solar + Battery storage is always more expensive than all the above.

I do not believe you are going to run a whole house very long off a portable solar battery based generator.

 

[Delmar]

Yes, a 6k battery bank. I'm totally ignorant of this all. I don't know how much power I consumed with my generator, but at the 7, 000W running and 8,750W max output, it handled a lot of appliances: Well Pump, Lights, Plug outlets running coffee pot, water Kettle, Dish Satellite, TV, 2 Fish Tanks, Refrigerator, Whole House Water Filtration system, etc. So I assumed (my bad?) that I could use a portable solar system with a battery bank with at least 6k watts.

Generators, inverters and solar panels are rated in watts, or the amount of power they can produce at any time.

Batteries are rated in watt hours, normally KW hours, or the amount of power they can store.

A 6 KWh battery bank will run a 6000 W inverter load for one hour (actually much less with losses and battery type).

An easy way to estimate your normal daily usage, look at your monthly electric bill KWh and divide the billable days. However during an outage you are in survival mode and need to decide (in advance) what watt items to sacrifice. The water filtration and water kettle would be a big & easy savings. In cold weather turn off the fridge and move your food to the garage for cold storage (been there, done that). The fish have to survive, and you won’t survive the family if you turn off the TV’s and go without coffee.

 

[chrisski]

For the record I meant 8-12k watts not $$.? Money wise, I'm looking at 6 to 10 thousand. The 30 amp Hookup looks like this:

Is this a 120 volt system If so, a 30 amp jack will supply 3600 watts of power, and a 240 volt system 7200 watts of power? If it is a 120 volt system, the rest of that 8k generator gets used for Surges, and may bring down the requirements of the system,

Based off my RV build, if you built a battery pack the size of a Tesla Powerwall, I would expect this to cost $15k with DIY, probably more. That would never be permitted though. 200 LBS of lithium batteries would probably not get a permit or pass inspection on a house.

I see no way to build a 30 amp solar generator you’re asking without this being fixed.

There are the solar trailers for sale left over from a defunct company that have a 50 amp RV jack, but that won’t really supply the power you’re asking for without the generator coming on.

 

[740GLE]

If he wired up his sub panel for a 8k portable unit it should be going to a 240v 30amp breaker.

BTW that bankrupt company was DC solar, tons of units around to be had on the cheapish.

Well pumps and other large induction loads are tough to source via cheap inverters. IMO if he’d need a low frequency inverter capable of 8kw with at least +20kw of battery storage to be worth lasting any sort out “outage” and handle the surge loading, that alone will almost double his cost he’s looking to spend. The standby losses of those large inverters eat up battery storage just like a generator eats up fuel.

Some times has generator that gets used 5-10hr a year is damn cheap and the right option. In the 9 years we’ve lived at our house we’ve averaged about 1hr/yr on our standby generator, knock on wood!

 

[chrisski]

Now that I look at the 30 amp jack, looks like split phase. I did not expect that since I deal with RVs and the single phase 30 amp jack.