Small Home ongrid, get AC offgrid

[trad]

I use about 1000kwh per month, but the bulk of that is AC here in S Texas. The goal is to put the 3T 240v AC on solar while the sun is shining. When the sun goes down, the AC can switch to the grid.

I will make this investment looking for a quick payback, so large battery banks are out. I have room for 100 solar panels if necessary but I need to choose an All in One inverter, solar charge controller. What is the best 240v AIO that can use as little battery as necessary and seamlessly switch over to grid power when there isn't enough sun?

(the EG4 6500ex is awesome, but wouldn't that be overkill for this small load?)
(would this be a good use case for the much maligned Growatt 5000 ES ?)

 

[efficientPV]

Better invest in some soft starters for the AC too or the system will have to be way oversized.

 

[timselectric]

would this be a good use case for the much maligned Growatt 5000 ES ?

Absolutely
And no battery required.

 

[trad]

So you think I should upsize the inverter and go for more loads in the house. The 120v fridge would be next for priority to move offgrid. Then some computer and internet loads are also 24x7 and would be next.

Things like the microwave, toaster, kettle etc are all high power draw, but not used frequently. I don't mind paying for electricity for these type of loads.

Better invest in some soft starters for the AC too or the system will have to be way oversized.

 

[trad]

Absolutely
And no battery required.

This was what I was hoping.
But Sig Solar says this for SPF5000 ES "Please note: We recommend using this inverter with batteries."

 

[timselectric]

This was what I was hoping.
But Sig Solar says this for SPF5000 ES "Please note: We recommend using this inverter with batteries."

No batteries required for a single unit, in SUB mode.
Which would do what you described that you want.

 

[webbbn]

With no batteries, how do you deal with, say a cloud rolling by and dropping the solar output for some time period? Do you just overload on panels and not turn the AC on until there is plenty of power available? There must be a tradeoff calculation between the cost of extra panels and adding some battery.

 

[trad]

No batteries required for a single unit, in SUB mode.
Which would do what you described that you want.

So the only issue might be start up load to spin up the AC compressor. Thankfully the AC has an LG compressor installed last year. Maybe it will have lower inrush startup loads.

Either it will, or it won't

 

[trad]

With no batteries, how do you deal with, say a cloud rolling by and dropping the solar output for some time period? Do you just overload on panels and not turn the AC on until there is plenty of power available? There must be a tradeoff calculation between the cost of extra panels and adding some battery.

What would you recommend ? Small battery with large amp BMS to allow for this?

 

[timselectric]

With no batteries, how do you deal with, say a cloud rolling by and dropping the solar output for some time period? Do you just overload on panels and not turn the AC on until there is plenty of power available? There must be a tradeoff calculation between the cost of extra panels and adding some battery.

The grid handles anything that the solar doesn't.

 

[timselectric]

So the only issue might be start up load to spin up the AC compressor. Thankfully the AC has an LG compressor installed last year. Maybe it will have lower inrush startup loads.

Either it will, or it won't

The grid handles startup surge.

 

[webbbn]

The grid handles anything that the solar doesn't.

I didn't know the Growatt supported grid assist. That would work then.

 

[trad]

The grid handles startup surge.

I just looked at your signature, and see that you have heaps of 5000ES experience. I'm guessing you are using them with auto converters for split phase loads as well in spite of what Will recommends.

How well does the 5000 ES scale when daisy chained. Is this difficult to do?

 

[timselectric]

I just looked at your signature, and see that you have heaps of 5000ES experience. I'm guessing you are using them with auto converters for split phase loads as well in spite of what Will recommends.

For a split-phase output.
an Autotransformer is fine, for no grid connection.
If also connected to grid, an isolation transformer is the best option.

How well does the 5000 ES scale when daisy chained. Is this difficult to do?

You can stack up to six. It's very simple.

 

[trad]

For a split-phase output.
an Autotransformer is fine, for no grid connection.
If also connected to grid, an isolation transformer is the best option.

or a separate 120v solar AIO for the 120v loads?

 

[DIYrich]

I would install an EG4 18kPV or Solar-Ark 15k. Have it wired to the whole house. 1000 kWh/mo is about 33 kWh per day, which is typical for a mid-sized house. You can add solar as needed. Set for zero grid export, or export excess if net metering. Add batteries if you ever want it.

If you don't have net metering, some batteries can be beneficial to provide power into the evening (time shifting energy production).

 

[Vigo]

or a separate 120v solar AIO for the 120v loads?

Probably depends how much wattage you have in terms of 120v loads. 120v loads over 3kw generally require multiple inverters in parallel, at least if you're talking all-in-ones. There are some outliers but if you are trying to get going for the cheapest price then two separate AIO's for 2 separate voltages is probably not it.

 

[trad]

The refrigerator would be the obvious steady state load. The kitchen counter loads are bursty, and the grid is well suited for bursty loads.

 

[trad]

For a split-phase output.
an Autotransformer is fine, for no grid connection.
If also connected to grid, an isolation transformer is the best option.

The one Sig Solar lists alongside the 5000ES is the

ATS 5000T-ES​

They don't specify, but the forum is calling it an auto transformer. I don't see any isolation transformer on their site. What would I be looking for?

 

[timselectric]

The one Sig Solar lists alongside the 5000ES is the

ATS 5000T-ES​

They don't specify, but the forum is calling it an auto transformer. I don't see any isolation transformer on their site. What would I be looking for?

They don't offer an isolation transformer.
Used from places like Ebay is the cheapest option.
You're looking for a 240v input (most commonly 480v/240v) and a 240v/ 120v output single phase transformer.
Size should be 5kva per Growatt SPF-5000-ES.
So, 10kva for 2 stacked Growatt's.