Buying grid power to store in battery and sell back during peak with imbalanced loads sol ark

[byteharmony]

I was thinking about this today after I posted this article:

Off Grid and on Grid 120v vs 240v efficiency with Sol Ark without Net Meter

My sol ark is reporting about a 5x% efficiency and I wanted to share this information for educational purposes. Not because sol ark or anything is wrong with my system. There are a couple photos attached. You can see my panel is not balanced at all. I draw a lot more on one 120v leg than the...

diysolarforum.com

If I purchase power to charge my battery from the grid at night when there are off peak rates, my sol ark will use a balanced draw for the charger, this is ideal and efficient.

However if when I draw on that power I am imbalanced and I can not export power will the imbalance result in the difference in power being lost, aka wasted?

 

[ksmithaz1]

Depends on the delta between your peak and off-peak rates. Pushing power back into the grid from a battery charged from the grid is dumb because your return rate is likely lower than your off-peak purchase rate. You'll need a 20% or more delta for peak shaving to be useful, to cover the loss to and fro, not to mention wear and tear. Figure 10% loss each way to and from storage.

 

[Nobodybusiness]

I was thinking about this today after I posted this article:

Off Grid and on Grid 120v vs 240v efficiency with Sol Ark without Net Meter

My sol ark is reporting about a 5x% efficiency and I wanted to share this information for educational purposes. Not because sol ark or anything is wrong with my system. There are a couple photos attached. You can see my panel is not balanced at all. I draw a lot more on one 120v leg than the...

diysolarforum.com

If I purchase power to charge my battery from the grid at night when there are off peak rates, my sol ark will use a balanced draw for the charger, this is ideal and efficient.

However if when I draw on that power I am imbalanced and I can not export power will the imbalance result in the difference in power being lost, aka wasted?

What are your off peak rates to charge?

What are they paying you when you export?

You probably lose 10% in and 10% out so you should be able to figure out if a good idea or not based on those factors.

 

[glandpuck]

Here in San Diego, depending on the rate plan and summer charges, you could be paying $1 a kWh from 4-9 PM and only $0.15 from midnight to 6 AM. Makes economic sense to charge at night and sell during the day (NEM 1.0 and 2.0) and run batteries from 4-9 PM.

 

[zanydroid]

Here in San Diego, depending on the rate plan and summer charges, you could be paying $1 a kWh from 4-9 PM and only $0.15 from midnight to 6 AM. Makes economic sense to charge at night and sell during the day (NEM 1.0 and 2.0) and run batteries from 4-9 PM.

This (charge from grid / sell to grid) is prohibited though under PG&E (EDIT if a NEM customer) and presumably also SDGE.

EDIT: If the Power Control System function on the hybrid is smart enough then you would be allowed to charge from grid/solar and sell the solar portion only, however I'm not sure which hybrids are certified to do this.

Charge from solar / sell to grid at high price time is OK with PG&E.

 

[glandpuck]

Yes, sell only solar back to grid, charge from grid at night when cheap, disconnect from grid from 4-9PM when power is expensive and consume batteries power on premises. None sold back to grid.

 

[ksmithaz1]

This (charge from grid / sell to grid) is prohibited though under PG&E (EDIT if a NEM customer) and presumably also SDGE.

EDIT: If the Power Control System function on the hybrid is smart enough then you would be allowed to charge from grid/solar and sell the solar portion only, however I'm not sure which hybrids are certified to do this.

Charge from solar / sell to grid at high price time is OK with PG&E.

Do they buyback at a favorable rate or wholesale? Here you get like 0.02/kwh for the buyback, lowest rate is closer to 0.07, and current peak is like 0.10. Just doesn't compute. Now producing and storing for your own use is always gonna be a win.

 

[zanydroid]

Do they buyback at a favorable rate or wholesale? Here you get like 0.02/kwh for the buyback, lowest rate is closer to 0.07, and current peak is like 0.10. Just doesn't compute. Now producing and storing for your own use is always gonna be a win.

If you're on NEM1/NEM2 it's full retail rate at the time of export. Which is why they don't let you do it :laugh:

On NEM3/Solar Billing Plan it's currently something like 20% of retail, and it will go down to pennies within a few years. So I imagine they don't give a F.

 

[zanydroid]

Yes, sell only solar back to grid, charge from grid at night when cheap, disconnect from grid from 4-9PM when power is expensive and consume batteries power on premises. None sold back to grid.

I think the best way is to hoard the solar during the day (zero export), then when it ticks over to 3PM or 4PM (peak/superpeak start) full send the saved solar into the grid. Alternatively, locally consume until the end of superpeak and then dump the whole battery into the grid.

This is the Way if you don't generate enough in winter since it lets you export at the highest possible prices of the year, then consume it back for heating during the winter

The feature is called "Forced Export" on 18kpv and probably other hybrids

 

[byteharmony]

What are your off peak rates to charge?

What are they paying you when you export?

You probably lose 10% in and 10% out so you should be able to figure out if a good idea or not based on those factors.

Off peak - $0.09

Peak $0.24

I haven't finished my system yet so no inspection or net meter yet.

Is it the norm that the power company will pay you the rate during the time you export? I couldn't get good answers from my utility yet nor do I have a bill yet to address with them.

 

[byteharmony]

Depends on the delta between your peak and off-peak rates. Pushing power back into the grid from a battery charged from the grid is dumb because your return rate is likely lower than your off-peak purchase rate. You'll need a 20% or more delta for peak shaving to be useful, to cover the loss to and fro, not to mention wear and tear. Figure 10% loss each way to and from storage.

Agreed, I see the loss on my charge and discharge efficiency. Given that the rates more than double it makes sense even with degradation of the battery cells.

 

[Nobodybusiness]

D

 

[Nobodybusiness]

Off peak - $0.09

Peak $0.24

I haven't finished my system yet so no inspection or net meter yet.

Is it the norm that the power company will pay you the rate during the time you export? I couldn't get good answers from my utility yet nor do I have a bill yet to address with them.

Honestly if you just charged off peak and used that power while on peak you would save a lot.

Wouldn’t even need panels.

No they won’t pay you what they charge peak rate.

You need to look at your net metering agreement when you get one to see what they will pay you for export.

It’s usually pretty dismal like $.02 kWh

 

[Solarcabin Channel]

When you calculate the cost of the system and increased cycle rate you are probably not going to make money doing that without solar included in the mix.

That does work for an emergency backup system in a power outage if you only use the power system infrequently and could save you money and your families lives when used that way.

JMO

 

[byteharmony]

Honestly if you just charged off peak and used that power while on peak you would save a lot.

Wouldn’t even need panels.

No they won’t pay you what they charge peak rate.

You need to look at your net metering agreement when you get one to see what they will pay you for export.

It’s usually pretty dismal like $.02 kWh

That is exactly what I do!

 

[glandpuck]

NEM 3.0 in California is based on several factors, all of which pay homage to special interest groups:

Poor people cannot afford solar so they should get supplements to reduce their electric bills.
Native Americans on reservations cannot afford solar so they should get supplements to reduce their electric bill.
Renters cannot install solar so they should get supplements to reduce their electric bills.
Homeowners with solar are wealthy so they should not be able to sell energy to the utility company except at a loss.
Utilities have to provide electricity to everybody so they should receive tax dollars for connecting the poor.
Utilities have to provide electricity using more and more clean energy and requiring ginormous battery storage banks to utilize clean energy at night. Utilities do not want to pay any money to build, manage and operate the grid. Only the rate payers should be paying and bearing all costs of the grid which they do not own but use.