Is selling from battery worth it?

I'm in California and expect to get PTO under NEM 2 soon (I'll celebrate it when I see it...). I have solar and battery, the TOU rates in the summer are $0.62 4-9pm, and $0.24 9-4pm. On an annual basis I expect to be buying a modest amount of energy, i.e., I don't expect a production surplus. Is it worth selling battery power during the peak time to get more credit?

Broadly speaking, I see four options:

1. never sell battery power: benefit from less battery cycling
2. use battery to maximize self-consumption, e.g. night-time use: benefit from avoiding NBC's (non-bypassable charges), i.e. $0.03/kWh ?
3. use battery to maximize sell-credits, e.g., sell battery power down to minimum reserve state of charge by the end of peak rate, thereby having capacity the next day to soak up solar and sell again during peak time

It seems that for someone who is a net importer on an annual basis option 3 may be the best, while for someone who is a next exporter option may be the best? Assuming some reasonable daily discharge depth, I guess, to reduce battery wear?

tve said:

Broadly speaking, I see four options:

1. never sell battery power: benefit from less battery cycling
2. use battery to maximize self-consumption, e.g. night-time use: benefit from avoiding NBC's (non-bypassable charges), i.e. $0.03/kWh ?
3. use battery to maximize sell-credits, e.g., sell battery power down to minimum reserve state of charge by the end of peak rate, thereby having capacity the next day to soak up solar and sell again during peak time

Click to expand...

I use option 2 primarily and due to an ideosycracy in my inverter I sell 500 Watts of battery power for an hour or two.
Avoiding paying peak rates and reducing NBCs has its benefits. In my case I ended my first TrueUp last September with a small dollar credit but a net kWh consumption of one megaWatthour. I only paid the minimums plus NBCs on what little power I consumed from the grid. I am even charging my EVs during the day from excess solar to avoid NBCs.
There is a concept called Virtual Power Plants which Tesla has done to aggregate Powerwalls into a VPP that sells into the grid at times that the grid is stresse and some people have reported being paid as much as $1.00 per kWh. Those events only occur in the summer.

Obviously if you can charge batteries from PV rather than exporting off-peak, then export from battery 4-9PM, you come out ahead $0.38/kWh on rates. Or, draw from PV to avoid exporting during peak.

Those are your #3 and #2, I think.

What chemistry battery? How much will its cost amortize out to, $/kWh, by end of cycle life?
Would doing so shorten its calendar life?

If the cycles claimed (4000ish) are correct, I believe my DIY LiFe PO4 batteries cost about 2-3 cents per kWh discharged.
So, not zero, but not very high cost either.
You may find one strategy works best during peak solar season (summer) and a different strategy will be best for the winter/poor solar season, especially if your home loads change (A/C use comes to mind) during the different of seasons.

tve said:

I'm in California and expect to get PTO under NEM 2 soon (I'll celebrate it when I see it...). I have solar and battery, the TOU rates in the summer are $0.62 4-9pm, and $0.24 9-4pm. On an annual basis I expect to be buying a modest amount of energy, i.e., I don't expect a production surplus. Is it worth selling battery power during the peak time to get more credit?

Broadly speaking, I see four options:

1. never sell battery power: benefit from less battery cycling
2. use battery to maximize self-consumption, e.g. night-time use: benefit from avoiding NBC's (non-bypassable charges), i.e. $0.03/kWh ?
3. use battery to maximize sell-credits, e.g., sell battery power down to minimum reserve state of charge by the end of peak rate, thereby having capacity the next day to soak up solar and sell again during peak time

It seems that for someone who is a net importer on an annual basis option 3 may be the best, while for someone who is a next exporter option may be the best? Assuming some reasonable daily discharge depth, I guess, to reduce battery wear?

Click to expand...

I would say a mix of 2 and 3; Primary focus is maximizing self-consumption (2), but if you have excess battery charge that might force you to export during the next day then you want to export extra during peak. It is tricky to optimize the second half, so I would try to have reserve battery that will always cover you from 4-9PM.

Thanks for all the suggestions! In the following scenario, what's the best thing to do:
- it's 8:45pm, i.e., shortly before the peak rate period ends
- the battery has 1kWh left that could be exported
Is it best to export that for a $0.58 ($0.62-NBC) credit or is it best to use that kWh to offset consumption later in the evening?

It seems that if I expect to be a net importer for the year then exporting at peak rate nets me $0.34 ($0.58 credit minus $0.24 I'll spend for that kWh in the evening) while offsetting consumption saves $0.24. If I expect to be a net exporter then at the point where I cross into surplus exports any export will result in a $0.07 net-surplus-credit (may 2023 rate) which is clearly worse than saving $0.24 later in the evening.

Do I have this right?

tve said:

...Do I have this right?

Click to expand...

That scenario will (currently) minimize your bill AFAIK.

I think the problem with it is that your utility can do a better job gaming the rates than you can with your patterns. They aren't going to sit around for long having to pay you more for fewer kWh, so the rules eventually change. Being a good citizen and maximizing self-consumption reduces your reliance on the utility.

Part of it likely depends on just how much net import you expect to do in the year. Oh, and do remember that you likely have an extra >15% losses on what you are using or exporting from battery.

If you are in the territory of one of the 3 investor owned utilities, I'd second Ampster's recommendation to look into a VPP.
I use Ohmconnect and made something around $700 in both 2021 and 2022.
We had 8 events in April and 2 so far in May, so not entirely just in the summer.

My system can push 6kw to the grid, in one (one hour) event I'll earn about $10

But, for those heat waves, they pay much better. There was an event in 2021 that I made $100 for 6kWh. The hot week in 2022, I made, umm "more" see this post:
Post in thread 'Is your payback too expensive?' https://diysolarforum.com/threads/is-your-payback-too-expensive.43462/post-594925

They are probably still running a referral bonus on both side, if you want some free money.