Is my Powerwall an energy vampire?

[power.saver]

Your numbers for 4 PW are close to twice mine, so probably correct. This is just the PW recharging the batteries after they self-discharge (internally) and any use by the PW itself. The charging seems to occur when they drop below 99% charge, and they don't really need much to get back up there. This is normal. The randomness is due to when and how much they have discharged. May be once a day or once every other day.

 

[JayClark]

Sorry to mislead you. My electric use last month was 1700 kWhs. The 4 Powerwalls are for Peak Energy in the unlikely event evert thing starts simultaneously.

I worked pretty hard to get my use that low in the summer. Lots of insulation, high r rating hurricane glass. Solar operated fans ventilating the attic. High efficiency multi speed compressor AC unit. Each room is individually zoned with motion sensors and temperature sensors that know when the room is occupied and opens and closes the ac ducts in that room. The house knows when it’s not occupied and automatically resets AC temperature. It geo locates my phone to know I’m about re-enter the neighborhood and cools down again by the time I open the door. LED lights also on smart home automation system.etc, etc, etc...

That 2 kWhs figure arose from someone else’s assumptions and calculations.

So I read quit a bit about Powerwall before they were installed the end of last month. I’m learning even more from monitoring them, and the most yet from the collective insights and helpful remarks of the very intelligent members of this forum. Thank you!

Ok, I see, that makes more sense.

 

[Ampster]

My Powerwall installation messed up the Envoy consumption monitoring I had relied on, but I’m using about 1700 kWhs per month this time of year.

You can move or have an electrician move the CT on the Envoy to measure your consumption more accurately. It sounds like you have done a great job making your home more energy efficient.

The issue I would be concerned about if I had your system is whether you are getting the optimium economic benefit. I assume your production does not cover your consumption but you are on a TOU rate so can you at least reduce your bill by changing to a different mode for the Powerwalls.

 

[NuShrike]

Great information. Mine are inside the garage, but in the summer it can stay hotter in there for longer, but maybe the overall daily temperature is closer to an average than the high/lows of being outside.

@NuShrike - when you're seeing ~647 Wh of drain for 2 PWs, do you have an a general idea of how much you're putting in, and taking out on those days? i.e. are you completely filling them to 100%, and draining them to 0% each day, for instance? When less is pulled from the PWs, do they have the same losses, more, or less? Just curious, a lot of questions I know.

Just wondering if the level of cycling also comes in to play, and has to be calculated. I.e. if NuShrike puts 3x amount of energy in, and takes 3x out on average, as compared to you (GenSao) that might also be a factor that has to be accounted for in addition to temperature.

Thanks, some really good points there. I haven't been specifically tracking to/from PW although now the app will let me go back and get the numbers.

I do go from 100% to reserve every day (midnight reserve is 65%, before dawn reserve is 55%). However, it would be very difficult for me to account beyond the app numbers if the PWs are draining above and beyond unless I put independent CT monitoring on it.

I have TP-Link monitoring on most appliances but not all. There's a hole where the PWs, HVAC, lights, floor/ceiling fans, etc fall into where I can't really tell which is the vampire.

 

[NuShrike]

Quite a difference from my units that are outside and your that are inside (assumed from profile pic).

Yes, they're in the garage where the temperature averages 80F due to various other computing devices dumping heat ambiently. I do have some minor venting, but that doesn't drop the temperature much even late at night.

 

[Shygar]

Yea, if your electricity costs different amounts at different times of the day, you should not be using backup only mode.

 

[Alto Nimbus]

You can move or have an electrician move the CT on the Envoy to measure your consumption more accurately. It sounds like you have done a great job making your home more energy efficient.

The issue I would be concerned about if I had your system is whether you are getting the optimium economic benefit. I assume your production does not cover your consumption but you are on a TOU rate so can you at least reduce your bill by changing to a different mode for the Powerwalls.

I’m on my utilities residential standard rate plan. Last year the PV array met 100% of my energy and resulted in an end of year credit being applied to my account. Even if I never draw power from the Powerwalls, it’s looking like the parasitic energy use for conditioning the batteries will result in charges from the utility for the first time in 2 years. If that happens and I’m unable to find ways to be more energy efficient I’ll be exploring TOU billing. I would have preferred to expand the array in beyond 12 kw, but to do so will require buying an insurance policy for one million dollars in liability coverage for the electric utility and paying a fee to the utility for doing it.

My Tesla installers placed the Consumption CTs on the mains entering the Tesla Gateway. Before my Powerwall installation the Enphase app accurately recorded my array’s production, what was imported and exported from the grid and my home’s energy use. Now at night, the Consumption CTs accurately record my home use, and the app doesn’t display an error message. But when the sun’s up the app reports an error, says the readings are negative, I should check CT orientation and wiring. So far, I’ve had no solution. I don’t know where to move the Consumption CTs to. Supposedly they should have been placed in the Main Panel, not the Gateway. But it could be as simple as L1 and L2 being reversed on the new breaker to the Envoy. I don’t think the Tesla electrician is ever coming back. I still don’t have a copy of the building permit or notice of commencement for the project. Even though the batteries were hung the end of last month, the city’s inspection and hopefully closing out the permit isn’t scheduled until next week.

The installation was scheduled to be a one day deal. But only one worker showed up for the install at the appointed time. After I contacted Tesla to protest the expected delay...again of the project, a second truck showed up to park on my sprinklers near the end of the day. Because they started so late, they didn’t finish. They the extra crew came back the day after tomorrow. I don’t think they were licensed electricians. They added a master breaker to my distribution panel. When they did so, it was loose and a light press on it would cause all the lights in the house to flicker. When the panel cover was replaced one circuit’s breaker was dislodged from the buss bar. This resulted in a spark, subsequently the washing machine that on that circuit started throwing a variety of error codes, and I had to buy a new one.

The Powerwalls when they flip on are quick but not instantaneous. The delay is long enough that all the smart lights and switches default to on status. When the batteries are fully charged and the panels are generating power, the Powerwalls turn off the panel inverts by delivering power at 66Hz instead of 60Hz. My microwave oven won’t even turn on with this off spec power. All my UPCs turn and drain the internal batteries then shut down whatever is attached to them.

 

[Ampster]

I’m on my utilities residential standard rate plan. Last year the PV array met 100% of my energy and resulted in an end of year credit being applied to my account. Even if I never draw power from the Powerwalls, it’s looking like the parasitic energy use for conditioning the batteries will result in charges from the utility for the first time in 2 years. If that happens and I’m unable to find ways to be more energy efficient I’ll be exploring TOU billing.

I misunderstood an earlier post which I thought you said you were on TOU. The Time Based Control mode in your PowerWall could get you back to a credit on your billing cycle. Load shifting with a PowerWall can get you more dollar credits even though your consumption doesn't change. It also might help leverage your existing solar without needing to consider more generation.

 

[Alto Nimbus]

I misunderstood an earlier post which I thought you said you were on TOU. The Time Based Control mode in your PowerWall could get you back to a credit on your billing cycle. Load shifting with a PowerWall can get you more dollar credits even though your consumption doesn't change. It also might help leverage your existing solar without needing to consider more generation.

In FL the State’s Constitution was amended with a “Solar Bill of Rights”. Part of this are the Net Metering Rules. Energy sent to the grid is returned as energy from the grid. A credit only comes into play, if a surplus exists at the end of the year. The reimbursement rate is the utility’s wholesale cost. It’s less then any customer rate.

 

[Ampster]

Energy sent to the grid is returned as energy from the grid. A credit only comes into play, if a surplus exists at the end of the year. The reimbursement rate is the utility’s wholesale cost. It’s less then any customer rate.

Yes that is similar to how it works in California. Not much incentive to develope a big credit at the end of the year. I was referring to your goal of not wanting to pay for energy during the year. Does your power company allow rolling credits over from month to month?

 

[Alto Nimbus]

Yes that is similar to how it works in California. Not much incentive to develope a big credit at the end of the year. I was referring to your goal of not wanting to pay for energy during the year. Does your power company allow rolling credits over from month to month?

Yes, monthly credits roll over month to month, starting with zero January 1st, each year.