Discussion: how large would you size this battery bank?

[areoseek]

Northern Pennsylvania, all gas appliances and heat, so winter usage will be a fraction of the summer usage, but so will the sun.

Summer usage is high because my A/C unit runs from sunup to sundown, and uses about 2kw if I count the furnace blower.

I have an 8kw array and 2x 6000xp's

The goal is to use the grid as little as possible, but I am still hooked in.

 

[DIYrich]

8kW array in Northern PA is about 40kWh per day. Something in that range will store one days production until you use it. You might produce a little more, and that offsets immediate use.

 

[42OhmsPA]

30KWh minimum...
I use coal for heat and kept the stove and dryer on the grid for the first winter.

Central PA
1st winter was ~23.5KWH bank and ~5.5KW panels at a crappy winter angle.
2nd winter ~49KWH bank and ~11KW panel (added a 3rd bank and angled ground mount array.
This winter I'll be ~67KWH and I'm building another ground mount, minum 3KW.

I added SA in Dec 22.

 

[Brucey]

30KWh minimum...
I use coal for heat and kept the stove and dryer on the grid for the first winter.

Central PA
1st winter was ~23.5KWH bank and ~5.5KW panels at a crappy winter angle.
2nd winter ~49KWH bank and ~11KW panel (added a 3rd bank and angled ground mount array.
This winter I'll be ~67KWH and I'm building another ground mount, minum 3KW.

I added SA in Dec 22.
View attachment 229967

So your stove and dryer have been on battery since the second winter?

 

[OffGridInTheCity]

I have 15kw PV and 121kwh of battery (Southern Oregon) with overall average of 2,477w/hour consumption. This is 59kwh/day of consumption that is hooked to the solar system. My overall, multi-year average is 35% DoD on the battery bank. This is a *larger* powerwall and provides...
- ~2days without sun of power
- Low DoD = longer life - hopefully an extra 5-10 yrs of cycles.
- Low Stress on the individual cells = lower chance of catastrophic cell failure?!? (don't know but hope)
- Longer ROI (I'm not going to live long enough to recover the $)

I would recommend at least enough battery to run 24/7 in spring/summer (during max PV) as a starting place but really, all this is up to you as there's no one right answer.

I have room for another 80kwh to approach a 200kwh powerwall but I must confess I'm not sure I need to go bigger as 35% DoD / 2 days / low-stress / long-life is probably good enough

 

[Offgrid Jungle]

We have an emporia vue as well. Our daily is 10kwh with peaks of 6 kw during the day on an all electric house. I bought 11 kw of battery and will use my generator for outages longer than a day.

 

[new off grid]

Northern Pennsylvania, all gas appliances and heat, so winter usage will be a fraction of the summer usage, but so will the sun.

Summer usage is high because my A/C unit runs from sunup to sundown, and uses about 2kw if I count the furnace blower.

I have an 8kw array and 2x 6000xp's

The goal is to use the grid as little as possible, but I am still hooked in.

View attachment 229945

add 2k more solar, make it 10k
30 - 35kwh batt bank is comfy

 

[42OhmsPA]

So your stove and dryer have been on battery since the second winter?

Correct, last fall I added them.

 

[areoseek]

add 2k more solar, make it 10k
30 - 35kwh batt bank is comfy

This is about what I was thinking as well.

I have 30kwh currently and I think I'll be able to make it through a night in the summer without falling back to grid

I'd love to do more than 8kw but I have no more room unfortunately. Small lot. Small house.

 

[new off grid]

This is about what I was thinking as well.

I have 30kwh currently and I think I'll be able to make it through a night in the summer without falling back to grid

I'd love to do more than 8kw but I have no more room unfortunately. Small lot. Small house.

we're in the same boat
I use around 1200 - 1300 kwh for summer ( ac ) and 1300 - 1500 kwh winter ( heater )
running on 8.2 kw solar + 25kwh batt bank + 8000w/48v inverter
summer almost 99% off grid, winter just wish for the best, maybe 50 - 60 % in average
the other 2 seasons is 100%, plus tons of unused due to no ac and no heater
this's the best balanced set up for me so far
more solar and batt are a big waste for 3 seasons, only winter help a bit, but not much, compare to the added cost
I'm in the Bay Area
after all, still need PG&E once in awhile
but they're only steal a few hundred bucks from me for a whole year
not too bad, compare to my brother's, use much less and pay 5 - 6k/ year

 

[DIYrich]

This is about what I was thinking as well.

I have 30kwh currently and I think I'll be able to make it through a night in the summer without falling back to grid

I'd love to do more than 8kw but I have no more room unfortunately. Small lot. Small house.

How much are you exporting or clipping? Any more than that, and you have no way to charge it (except from grid or generator).

 

[areoseek]

How much are you exporting or clipping? Any more than that, and you have no way to charge it (except from grid or generator).

I don't have net Metering. Inverter is Just a 6000xp. I never have excess. Either it's charging battery or I'm dumping it into A/C.

By the time battery hits 100% sun is going down and it starts draining. Usually dead before sun up.

 

[DIYrich]

I don't have net Metering. Inverter is Just a 6000xp. I never have excess. Either it's charging battery or I'm dumping it into A/C.

By the time battery hits 100% sun is going down and it starts draining. Usually dead before sun up.

Then more batteries won't help unless you want them for grid down, and charge from grid. You dont have enough pv to charge more batteries. If you have time of use rates, then you can charge from grid when price is low.

 

[areoseek]

Then more batteries won't help unless you want them for grid down, and charge from grid. You dont have enough pv to charge more batteries. If you have time of use rates, then you can charge from grid when price is low.

Flat rate 15 cents per kWh, I don't think I have enough battery to make it through winter without really leaning on the grid. But the post was just to see what other people would size it at.

 

[new off grid]

I have 15kw PV and 121kwh of battery (Southern Oregon) with overall average of 2,477w/hour consumption. This is 59kwh/day of consumption that is hooked to the solar system. My overall, multi-year average is 35% DoD on the battery bank. This is a *larger* powerwall and provides...
- ~2days without sun of power
- Low DoD = longer life - hopefully an extra 5-10 yrs of cycles.
- Low Stress on the individual cells = lower chance of catastrophic cell failure?!? (don't know but hope)
- Longer ROI (I'm not going to live long enough to recover the $)

I would recommend at least enough battery to run 24/7 in spring/summer (during max PV) as a starting place but really, all this is up to you as there's no one right answer.

I have room for another 80kwh to approach a 200kwh powerwall but I must confess I'm not sure I need to go bigger as 35% DoD / 2 days / low-stress / long-life is probably good enough

you got to be the solar addict friend, with all cost
that's an overkill system you have there
too much for what you need , especially the batt
solar/batt getting better and cheaper
looks like a wrong direction of future investment ?
( my lesson : wish I did not bought thousand of DVDs, $15-25 each, 25- 30 years ago, as a collections )