Options with no netmetering available

[svanand]

I have a grid tied system but my provider does not offer net metering. So on sunny days, when my solar system produces more than what I consume, the rest goes back to the grid for free. And then at night, when I use power, I get charged

My question is, what options do i have to 'store' the extra power I generate in a battery, and use it in the nights, and once the battery is low, continue pulling from the grid

I did read about ac coupling, but it sounds like it is a backup when the grid goes down, so it doesnt make economic sense (it does make strategic sense though)
I know the easiest option is to rip out my existing inverter (AP Systems microinverters) and replace it with a hybrid inverter, which could do everything, or get something like a sol-ark which is very expensive

Any other alternatives?

 

[dcg9381]

The only alternative I know of is what you have laid out. You store the excess and program the inverter(s) to discharge from the battery as a priority over a schedule (usually when the sun is not out). It's expensive.

I don't know that AC couple will be allowed everywhere with the inverter types that are doing it. It's essentially grid tie and lacks the protections of grid tie systems (perhaps).

I have a 6KW system at home - grid tied. I'd say that 80% of it is consumed. The other 20% is pissed away as our POC ended net metering also. I'm just not sure that it's worth another $10k in inverters and batteries to try to fix it. Payback, best case? Maybe 10 years. Isn't that about the life of batteries?

Where I would do it is if I could get something "else" out of it, like backup power. Then it makes a little more sense to me. Not economic sense, but functional sense.

 

[keymaster]

Mine bitcoin? not the best option but you can earn something back. Investment cost for used minors is pretty low right now. I used to have a moderately sized home setup that made money each month. Can't earn back with prices the way they are today so you have to buy the equipment used. You will also need to be a bit creative and set times for it to run using timers and limiting the watts consumed within the software to specific times of day as well.

 

[BentleyJ]

I did read about ac coupling, but it sounds like it is a backup when the grid goes down, so it doesnt make economic sense (it does make strategic sense though)

An AC coupled system with batteries can be configured for Self-Consumption. Any power not used immediately by your loads will go to charge batteries. Once the batteries reach full charge, excess production will still go out to the grid but will be a lot less than without batteries. At a designated time in the afternoon the new battery inverter can be programmed to enter Peak Load Shave mode which starts up the inverter to partially or fully power your household loads. This continues until the programmed PLS time ends or the batteries reach low voltage (or SoC) set point and the grid takes over. There are 2 ways this can be done.
1) Install a critical loads subpanel that is fed by the new AC coupled battery inverter to carry the smaller, important loads that you want to stay on in an outage. Requires a smaller, less expensive inverter but then there is the cost to install a subpanel.
2) Install a LARGE inverter that feeds the main panel and backs up the whole house. Sol-Ark 15K as you mentioned.
Either option will require a full featured, UL1741SA compliant battery inverter. Sol-Ark, Schneider, Outback, SMA.

I know the easiest option is to rip out my existing inverter (AP Systems microinverters) and replace it with a hybrid inverter, which could do everything, or get something like a sol-ark which is very expensive

Not at all. AC coupling eliminates the need to alter the existing grid-tie system with the possible exception that if a critical loads subpanel is installed the backfeed breaker for the AP microinverters would probably be moved into the subpanel.

Yes, inverters with all the necessary features and UL listings are more expensive but they tend to be more reliable.

 

[Texican]

how much power is going back to the grid for free ?
makes a big difference in what system makes sense
also how many months does this over supply exist ?

 

[svanand]

how much power is going back to the grid for free ?
makes a big difference in what system makes sense
also how many months does this over supply exist ?

In winter, i return about 30KW to the grid, summer, not much

 

[svanand]

An AC coupled system with batteries can be configured for Self-Consumption. Any power not used immediately by your loads will go to charge batteries. Once the batteries reach full charge, excess production will still go out to the grid but will be a lot less than without batteries. At a designated time in the afternoon the new battery inverter can be programmed to enter Peak Load Shave mode which starts up the inverter to partially or fully power your household loads. This continues until the programmed PLS time ends or the batteries reach low voltage (or SoC) set point and the grid takes over. There are 2 ways this can be done.
1) Install a critical loads subpanel that is fed by the new AC coupled battery inverter to carry the smaller, important loads that you want to stay on in an outage. Requires a smaller, less expensive inverter but then there is the cost to install a subpanel.
2) Install a LARGE inverter that feeds the main panel and backs up the whole house. Sol-Ark 15K as you mentioned.
Either option will require a full featured, UL1741SA compliant battery inverter. Sol-Ark, Schneider, Outback, SMA.

Not at all. AC coupling eliminates the need to alter the existing grid-tie system with the possible exception that if a critical loads subpanel is installed the backfeed breaker for the AP microinverters would probably be moved into the subpanel.

Yes, inverters with all the necessary features and UL listings are more expensive but they tend to be more reliable.

The problem (as I understand) is the current grid-tied if connected to the input side (along with the grid), the coupled inverter has no way to know if the power is coming from grid or my microinverters. If I connect the output of the microinverters to the output of this new inverter (like it says in sol-ark manual), it makes sense.
The sol-ark system seems to meet all the requirements, but like someone mentioned, the ROI on a 7K+battery investment just isnt there. I bought a sungoldpower IP6048 (clone of mppsolar lvx6048wp) but since it is limited to 6KW, it will 'smoke' when the microinverters produce more than 6KW excess, plus the manufacturer just refused to support ac coupling (even though they mention it as a key selling point on their website, sigh)
This IP6048 supports UL1741 (not sure of UL1741SA)

Any recommendations for an inverter (hopefully not too expensive so there is a viable ROI)

 

[BentleyJ]

Any recommendations for an inverter (hopefully not too expensive so there is a viable ROI)

With the limited info we have available lets take a run at an answer. This applies only when the grid is down.
Your grid-tie system is 10kW total so the AC coupled inverter and batteries have to be sized to handle 100% of the expected excess microinverter production when the house loads are at their minimum. For example lets say the minimum house power draw at noon, no one home, no appliances in use no heating or cooling is 1000W. The remaining 9,000W would be backfed through the inverter to charge batteries.
So the back up inverter has to be chosen based on its AC coupling capacity which points back to the Sol-Ark or 2 Schneider XW Pro's Etc.
Bottom line:
1) A smaller inverter will itself cost less but then you would have the expense of installing a critical loads subpanel AND removing some of microinverters and rewiring a few panels that would be DC coupled to a charge controller.
2) A Sol-Ark 15K may be large enough to back up the whole main panel and absorb all of the excess AC coupled production. No subpanel or rewiring need.

Unfortunately, both options are going to be expensive. Unless you can justify the cost simply because you want the convenience of back up power, economics alone probably will not give a resonable payback period. In CA its a different story. We are seeing rates of 49 cents per kWh between 4 to 9pm weekdays with ToU billing.