Will economics of new Tesla PowerWall product will work for you?

[brianman]

So you think there's a difference beyond the kWh rating?

Powerwall | Tesla Home Battery

Powerwall comes in 10 kWh weekly cycle and 7 kWh daily cycle models. Both are guaranteed for ten years and are sufficient to power most homes during peak evening hours.

Models
10 kWh $3,500
For backup applications
7 kWh $3,000
For daily cycle applications

When Tesla intentionally builds different configurations and uses different language to describe them, I tend to expect there's a material difference.

Sidenote: I understand why they labelled as such, but the units I found amusing:

Flat Screen TV	Lights Per Room	Laptop	Refrigerator	Clothes Washer	Clothes Dryer
0.1 kWh /hr	0.1 kWh /hr	0.05 kWh /hr	4.8 kWh /day	2.3 kWh each use	3.3 kWh each use

 

[woof]

Sidenote: I understand why they labelled as such, but the units I found amusing:

And somehow they forgot to include: "Charge EV: 10-95 kWh each use"

 

[polyphase]

With flat metering (as I have) it the powerwall doesn't make sense other than short term backup. With current off-peak electricity pricing it doesn't make sense either. Off-peak these days means lower pricing only at night. BUT, I suspect as grid-tied solar starts to create more of a headache for utilities, mid-day pricing might fall and that will make batteries sensible.

 

[tga]

Sidenote: I understand why they labelled as such, but the units I found amusing:

Flat Screen TV	Lights Per Room	Laptop	Refrigerator	Clothes Washer	Clothes Dryer
0.1 kWh /hr	0.1 kWh /hr	0.05 kWh /hr	4.8 kWh /day	2.3 kWh each use	3.3 kWh each use

Those numbers seem reasonable, except for the washer - 15A@120V, 30 min would be 900Wh.

Anyway, it doesn't work for me, either. I have 9kW of solar, no net metering (buy @ $0.143 retail, sell @ $0.053 wholesale), and no TOU available.

I don't know what percentage of power I sell vs use in house (I haven't dug out the records), but assume I can shift 7kWh from sell to use in house:

7kWh/day * $0.09/kWh * 365 days/year * 10 years = $2299.50 saved per battery over 10 years.

1 battery probably isn't enough backup/UPS capacity for me (Not sure 2kW output would be enough to run the well pump, definitely not if the refrigerator is running at the time). Since I work from home a lot, all my critical stuff (FIOS box, routers, switches, wifi access point, PC's) are on UPS's, so I can ride out any short outages. Anything extended, and I drag the 7kW gas generator out of the garage and plug into the generator inlet. I need that < once/year.

 

[neroden]

Will economics of new Tesla PowerWall product will work for you?

It would if I could make the economics of solar panels work for me in the first place, but I haven't figured out how to do that yet (shade, minimal roofspace, winter, no company to clean the snow off the panels...) It would be worth it just for backup, but I don't want to do backup just from the grid and then have to rip it out when I put in solar.

 

[cschock]

Won't be economically or technically (as far as I can see) viable for our home use. We already have a grid tied solar system on micro inverters with net metering and no time of use plan available. The net metering and no time of use plan availability make it economically a non-starter and the fact that we have a 32 panel micro inverter array makes it a bad technical fit. I may be missing something on the technical side that would allow it to work as a battery backup power supply however (which honestly where we live would be nice to have.)

 

[nwdiver]

There is one advantage that has been largely overlooked... since the Powerwall is DC coupled it can effectively increase the capacity factor of the the PV array and inverter. As was discussed in Array Oversizing I've found the optimum economic point to be ~1.4 DC/AC. ALL UL1741 inverters are rated to handle ~2x their AC capacity. (They do this by raising DC input voltage, the energy is dissipated on the array not shunted in the inverter)

If you wanted to install 15kW of DC you can now use a 10kW inverter + a Powerwall and you'd be able to capture additional energy with no additional inverter cost. Doesn't shift the economics all that much but it helps...

 

[SageBrush]

Powerwall | Tesla Home Battery

Our home:
Flat screen TV: 4 watts (iPad)
Lights: 5-10 watts per bulb. Between 0 - 5 bulbs on at any one time
Laptop: 7 watts -- either ChromeBook or MacBook Air
Fridge: 800 Wh a day average
Dryer: clothesline

The PW strikes me as a case of conserve first, then count up how much battery to buy

 

[Owner]

Nope....I just ran the numbers.... 18 year payback in an ideal scenario.

here's the write up

Powerwall A Middling Product | TESLA OWNER

 

[omgwtfbyobbq]

Will economics of new Tesla PowerWall product will work for you? 10 kW/h battery pack cost $3500, inverter cost $1000 and installation $500.

If I built my own house it probably would. PV panels + Load Shifting + a PowerWall would probably allow me to get down to ~$.10/kWh off-grid. The only downside is that it would make nighttime EV charging prohibitively expensive, but that's true of any off-grid setup.

 

[Owner]

you'd be better off with more PV panels than a Powerwall. Look at my blog post above.

If I built my own house it probably would. PV panels + Load Shifting + a PowerWall would probably allow me to get down to ~$.10/kWh off-grid. The only downside is that it would make nighttime EV charging prohibitively expensive, but that's true of any off-grid setup.

 

[omgwtfbyobbq]

More PV panels won't help with the energy I would need at night off-grid, and the powerwall seems to be the least expensive form of energy storage unless I had enough room/elevation change for pumped storage.