Is there any benefit to running the Powerwall in self-powered mode if I have 1:1 net metering? I have no time of use rates.
Powerwall self power mode with net metering.
- Thread starter Rich121
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I don’t believe so, in fact, I think there is actually a disadvantage to it. The powerwalls are only 90% efficient, so for every 10kWh of power you put into the powerwall you only get 9kWh out. Whereas with 1:1 net metering for every 10kWh you put into the grid you can take out 10kWh later.
I have been running in backup only mode since I got PTO because I am in the same situation. (1:1 net metering, no TOU rates)
The only benefit would be to your "self powered" score - essentially, the benefit is an intangible one if your goal is to minimize grid interaction.
We are in the same situation, and run in backup-only because it is more efficient than losing energy by draining the PWs, and we know we have full PWs in the event of an outage.
We are in the same situation, and run in backup-only because it is more efficient than losing energy by draining the PWs, and we know we have full PWs in the event of an outage.
Thank you for your reply's I was not sure if I was missing something. I forgot about the efficiency loss from the power wall. Looks like it will be back up only for me. I guess it's nice to know you have a fully charged battery ready to go at all times.
Nope.
I stopped bothering with using and PW energy to lessen grid dependence.
Instead of using solar to charge them back up, it'll send all that power to the grid, and earn you dollars with the electric company.
I have 1:1 net metering here in Iowa. However, since this is my first year with one Powerwall and a tiny solar array, I want to know how I use energy and how the Tesla system works. Except for impending bad weather, I've stuck with self-powered mode. As a small example of the cost of doing this: From yesterday's energy usage, 12.2 kWh home, 9 kWh solar, 3.7 kWh from Powerwall, 4.4 kWh to Powerwall, 5.4 kWh from grid, 1.4 kWh to grid. Reserve set at 65%. (I've been moving the reserve around with the seasons.) The "to Powerwall" was all used up by 10:30 pm. If I lost 10% of my saved energy by diverting it from the grid, that's 0.44 kWh. At 9 cents per kWh, it cost 4 cents for the experience. So, maybe $9 for the year.
In a couple of months I'll switch to backup mode for all of the right reasons, including extending the battery life. For now, cheap and enlightening entertainment.
In a couple of months I'll switch to backup mode for all of the right reasons, including extending the battery life. For now, cheap and enlightening entertainment.
That is a good reason to use self-powered mode. We essentially did that between inspection and PTO (three months) except that we generally operated off-grid during the day and turned the grid on either for the evening or overnight since our system does not cover our use. It was good to get a feel for what our usage is like and what we would need to do in an outage. (This can also be done as a paper exercise, but it doesn't have the same impact, and it also won't catch any problems with the system as a real test will.) To me it is worth occasionally testing with the grid off (truly self-powered) to make sure everything is working for if and when it is needed.
All good comments here. I'm also in a 1:1 net-meter area, and I usually keep my two PW's in backup-only mode. One reason for using self-powered mode, ID'd above, is that's it's fun to play with for a while -- at least for the kind of person who spends time on an online solar energy forum. Playing with it really gives you a good idea of what you can run when you have an extended outage.
I'm actually in an outage right now in New Orleans after Hurricane Zeta whipped through yesterday. I'm at about 24 hours now, and it's all running fine. I'd learned enough from playing with self-powered to know how to manage two A/C units on two PW's yesterday and last night. Today it's much cooler, and sunny, so I turned off the A/C's and know I can pretty much do whatever I want without exhausting the batteries. The PW's are currently at 98%, and the system is shutting down panels to avoid overcharging -- I can't use all the power I'm generating with a 6.7kw system.
I have wondered whether using self-powered mode and setting reserves at 80 or 90% would be a good idea to save battery life -- lithium batteries have shorter lives when they're kept in a fully-charged state, especially in hot conditions. And my batteries are outdoors. But enough people here have said that the full-charge risk is not a big risk with Tesla, so I've decided it's not a big risk. PW's apparently have some excess unused capacity that keeps them from being "fully charged" in regular use even if they read 100% full. I figure Tesla knows a few things about battery management.
I'm actually in an outage right now in New Orleans after Hurricane Zeta whipped through yesterday. I'm at about 24 hours now, and it's all running fine. I'd learned enough from playing with self-powered to know how to manage two A/C units on two PW's yesterday and last night. Today it's much cooler, and sunny, so I turned off the A/C's and know I can pretty much do whatever I want without exhausting the batteries. The PW's are currently at 98%, and the system is shutting down panels to avoid overcharging -- I can't use all the power I'm generating with a 6.7kw system.
I have wondered whether using self-powered mode and setting reserves at 80 or 90% would be a good idea to save battery life -- lithium batteries have shorter lives when they're kept in a fully-charged state, especially in hot conditions. And my batteries are outdoors. But enough people here have said that the full-charge risk is not a big risk with Tesla, so I've decided it's not a big risk. PW's apparently have some excess unused capacity that keeps them from being "fully charged" in regular use even if they read 100% full. I figure Tesla knows a few things about battery management.
Yep big time!!! But, one cannot get this pricing now for a long time. We are forced to NEM2 and TOU.
djp
Model 3 Performance
In Ontario we have 1:1 net metering, but the feed-in and grid usage are treated as separate transactions with tax charged on grid use and no corresponding tax credit on feed-in. Pretty much equivalent to the round-trip losses in self-powered mode.
