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Just completing my powerwall 2 install along with my 7.4kw PC system. Here are some.pictures of the powerwall install. No data yet as it will be a few weeks before the inspections are completed and the system becomes functional and I can keep you all posted
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Some pictures -
Could you also share the goal of your energy storage solution? Is it primarily time shifting your consumption to work around your PoCo's TOU plans? What's net metering like in your area? Does the system provide backup power in the event of a PoCo outage? If so, how do you manage load shedding? Did you have to install a second panel board and move circuits into / out of the battery protected load center?
It appears you have two Powerwall batteries. What size is the battery's DC to AC inverter? How many continuous amps can it supply at 240 VAC? for how long?
Thank you! Just curious. I have a lot of experience with large commercial UPS systems (208V & 480V 3-phase, 20kW-250kW) . The UPS systems themselves are generally not too expensive ($20K-$200K) but properly wiring the feeders and loads can be very expensive.
In a residential setting, you'd want to minimize the wiring cost (and the space it takes up) as much as possible. But unlike whole house natural gas generators which are cost effective and large enough (usu 10kW-22kW) to pickup the entire panel board using a simple manual or automatic transfer switch
For example this 22kW 1800-rpm natural gas unit from Generac -- $8800 -- will put out 92 amps @ 240VAC continuously
None of the Solar PV / Storage solutions I've seen have been very large. Meaning that a lot of additional wiring would be necessary to separate out the protected vs non-protected circuits. And run times would be only a few hours -- aka good for a blip and maybe a downed pole. But not for a hurricane, ice storm, etc.
But, if all you want to do is shift your usage later in the evening to work around a TOU plan, then this wouldn't be necessary. Though, at least in the US, I haven't yet seen evidence that using storage for time shifting was cost effective, yet.Comment
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The cost of the install was 17k just for the 2 powerwall installs. State of California sgip rebate was 9400 and with the federal credit of 30% the total out of.pocket is 17k - 5.1k - 9.4k = 2.5k.Comment
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Here's another picture with the wiring diagram. I'll get the additional detail and post. This is the AC powerwall with the built in inverter. One of the first units shipped from the gigafactory in sparks NV.
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And the install is in San Ramon California.Comment
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I dont have any actual numbers but from the calculations and assumptions we made, These 2 units put out enough to power my whole home for 15 hours. As such There's no separate subset of appliances and lights that are powered by these units. And assuming that the sun comes back in 15 hours which is a good bet ? here in norcal my PV system should kick back in power these units and my home. And if I cut my consumption in this scenario, which I don't but I can if needed, I can be off grid indefinitely if needed is the plan.Comment
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Looks like total capacity is 27 kWh so if discharge time is 15 hrs it can handle 1.8 kW which is less than 1 outlet at full power continuously. What is important is the peak power those can produce so even if time is shorter they still can handle something like AC turning on and off during night. At 1.8 kW these won't be able to handle single AC unit, especially its startup current. Hope the peak is at least x5 higher. Another more serious problem as I see it is significant undersize of the PV array- how 7.4 kW number came about? Was it just calculated based on available roof area? These 2 components (array & battery) need to match to provide best performance. Array of that size will produce 6 kW tops under best conditions during 4 hr period. It would be barely enough to charge the battery but then nothing will be left for the house.
Do you have any clouds in San Ramon? Those can easily stretch longer than 15 hrs so I think fully off the grid is still not realistic here but these should help to mitigate TOU rates differences. I'm not sure though if that will worth $2.5k spent on the system which would supposedly need replacement in 5(?) years.
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Yes assumption is that the AC unit is not on. Which works for most of the year here. Mostly cloudless days and sunshine year around.
Bottom line there is no realworld data as these units are brand new. I'll get actuals in the next few months. Everything else is speculation.Comment
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Fwiw Tesla has a 10 year warranty. But the warranty is vague in that it does not guarantee output rate.Comment
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Max load should be somewhere in the specs- how else did they pull permit without supplying those details? For one it would define size of the breaker ... Don't get me wrong, I wish this project complete success despite my reservations against Tesla practices in general, I'm just trying to paint more realistic picture.Comment
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