Tesla Powerwall without solar ?

[wanaberetiree]

Hello all,

I see in my neighborhood (San Francisco) more and more houses with Tesla Powerwall batteries.

Wondering - did anyone install batteries only for power storage purposes, e.g. without having installed solar panels?

Please share experience...

Thx

 

[TrvlBug]

Hello all,

I see in my neighborhood (San Francisco) more and more houses with Tesla Powerwall batteries.

Wondering - did anyone install batteries only for power storage purposes, e.g. without having installed solar panels?

Please share experience...

Thx

Was wondering the same. We've lucked out w/o power outages so far but were not as lucky last year and had to throw out lots of food. Other than that our outages have been of short duration. We've done the analysis for solar and it's not worth the cost for us.

 

[Animorph]

My understanding is that without the solar panels there is no federal tax rebate available. That makes it harder to justify Powerwalls without solar.

However, Powerwalls with solar panels are not allowed to charge from the grid unless extreme weather or similar condition is predicted. Without solar panels you should be free to charge a Powerwall with off-peak power and use it during the peak period.

I'd be a little concerned about deep cycling a Powerwall every day in that application. We know that shortens the life of lithium batteries in general. There are lithium battery formulations that can better handle more cycles, but I'm not sure what Powerwalls use.

Even just for backup it would be nice to have solar panels if the grid remained off for multiple days.

Kind of a vague answer, but I haven't seriously looked into solar yet. I've just been reading the solar discussions on the Tesla Motors Club forum. I don't think Powerwall-only installs are very common.

 

[Sunset]

Without solar panels to charge them, it seems a super expensive way to have backup power, which will only last x days.

 

[Koolau]

No expert here, but several power outages as in Cali would make me consider back up power. Our "grid" is pretty fragile (lots of resetting the clocks, etc.) but only one serious black out in 13 years. YMMV

 

[The Cosmic Avenger]

Also, from what I understand the same inverter can be used for both systems, as I understand it, so if you get either solar panels or Powerwall batteries, it's like getting a huge discount (a few thou, IIRC) on the second system, including its installation cost.

 

[Ready-4-ER-at-14]

I was wondering if a person could have a very tiny solar array installed and get the powerwall and inverter if you were primarily looking for a short term back up and still get a rebate based on the entire cost of the system?

I know it is sort of gaming the system but imagine the system could be expanded with more solar cells in the future.

 

[ERD50]

In some places, there may be enough time-of-day price differential to to offset the cost somewhat, or even be profitable if the delta is great enough.

Some people may want them just for black-outs, so if you can also make a little from TOD price deltas, it takes some of the sting out of the price, even if it doesn't pay for them outright.

That's just a theoretical, I don't know if many are actually using them in that way, but it would seem likely in CA?

 

[tb001]

We have two batteries on our system. Not Tesla. They provide battery backup for one circuit on the house, which has been great with some of the outages. We can keep the WiFi up and our kitchen outlets. In SoCA so many people have solar that the electric companies are raising those early evening rates to increase revenue. I don’t know if the cost differential to add the batteries pencils out yet, but it’s a trend I don’t think is going away. And I don’t think twice about turning on the AC at night, which is worth it.

FWIW, there are some pretty strong incentives/rebates for battery backups in CA right now if you have any medical need and live in an area that has had outages. And a cpap is considered a medical need. I am pretty sure DH has sleep apnea and have been pushing him to get dgx.

 

[Masquernom]

I just checked. Tesla recommended 2 powerwalls for our house. $18,000 to power the house for one day.

If you have natural gas available, and a spot for installation, I'd think a Generac gas generator would be a better option.

 

[NoiseBoy]

If you have natural gas available, and a spot for installation, I'd think a Generac gas generator would be a better option.

Here in the Midwest this is the Go To solution for emergency power. Since they run on natural gas, there's no worry about refueling a diesel tank or running out of "gas." They seem to be a popular option for folks who are aging in place too.

 

[aja8888]

I just checked. Tesla recommended 2 powerwalls for our house. $18,000 to power the house for one day.

If you have natural gas available, and a spot for installation, I'd think a Generac gas generator would be a better option.

A Generac (or other brand) on natural gas is what people are installing here in south Texas.

 

[ls99]

18K for powerwall? Let me see, at $3/gal for gasoline, roughly 6000 gallons. Well OK still need to buy a generator. At nearly full load, say 2 gal/hr gas burned, 3000 hours run time.
I'd stick with a generator. But I am not really good with numbers.

 

[The Cosmic Avenger]

18K for powerwall? Let me see, at $3/gal for gasoline, roughly 6000 gallons. Well OK still need to buy a generator. At nearly full load, say 2 gal/hr gas burned, 3000 hours run time.
I'd stick with a generator. But I am not really good with numbers.

Besides the price of the generator itself that would last as long and power a similar number of devices as whatever Powerwall installation you're considering, you'd need to add wiring the generator into your circuit panel, and adding a cutover that automatically turned it on when the power went out...and you still wouldn't have continuous power the way you would with a Powerwall.

I'm not saying that a Powerwall is definitely better; they originally marketed them mostly in Australia, where the rates vary greatly depending on the time of day, and you can actually save a fair amount every year by charging the batteries overnight and running off them during the day. But if you're going to compare a Powerwall and a generator, you should include all the pros and cons.

 

[aja8888]

Besides the price of the generator itself that would last as long and power a similar number of devices as whatever Powerwall installation you're considering, you'd need to add wiring the generator into your circuit panel, and adding a cutover that automatically turned it on when the power went out...and you still wouldn't have continuous power the way you would with a Powerwall.

I'm not saying that a Powerwall is definitely better; they originally marketed them mostly in Australia, where the rates vary greatly depending on the time of day, and you can actually save a fair amount every year by charging the batteries overnight and running off them during the day. But if you're going to compare a Powerwall and a generator, you should include all the pros and cons.

My neighbor just this summer installed a natural gas fired Generac for whole house power with automatic transfer switch, installation, wiring, etc for $12,000. Already has been tested and been used! (south Texas)

 

[The Cosmic Avenger]

My neighbor just this summer installed a natural gas fired Generac for whole house power with automatic transfer switch, installation, wiring, etc for $12,000. Already has been tested and been used! (south Texas)

Thank you, that's helpful. That's probably as much as a slightly smaller Powerwall installation, or only a little less than the installation recommended for Masquernom if they already had solar.

IMO, if you have a lot of short interruptions, Powerwall might be preferable, as it will always provide completely uninterrupted power with no blips or brownouts; if you have particularly long outages, a generator that has a supply of natural gas might be better. But then I run home servers and DVRs, devices that get cranky when power is interrupted.

 

[skipro33]

I have been approved through PGE for 2 tesla power walls through CPUC for free. Called the SGIP resiliency program or something like that. I live in and have experienced PSPS outages and am on a medical baseline rate to qualify. The money comes from cap-n-trade carbon credits purchases. Waiting for my tesla order to come through now, they are back logged.

 

[Offgrid Organic Farmer]

We have solar panels and a large household battery-bank.

 

[NW-Bound]

In some places, there may be enough time-of-day price differential to to offset the cost somewhat, or even be profitable if the delta is great enough.

Some people may want them just for black-outs, so if you can also make a little from TOD price deltas, it takes some of the sting out of the price, even if it doesn't pay for them outright.

That's just a theoretical, I don't know if many are actually using them in that way, but it would seem likely in CA?

On the Web, I found that some Californians do use their units to save money with the TOD differential.


Here in Phoenix, I chose a time-of-day rate structure that charges 24.09c/kWh during the peak summer hours of 2-8PM, and 7.3c/kWh outside that peak period. Or I could choose a fixed rate of 11.57c/kWh all day.

Even before I installed a DIY solar+storage, the TOD rate saved me a bit of money already, simply by programming my pool pump to avoid the peak period, plus installing a timer to cut out the water heater between 2-8PM (and avoiding using a lot of hot water during that period).

I looked on the Web and found the following rate by Southern Cal Edison: 41c/kWh for 4-9PM, and 26c/kWh for off peak. But for people with a residential energy storage system, the rates are 43c and 16c.

With an energy storage system, you want to arbitrage between the 2 rates, and that's 43c minus 16c, or 27c/kWh. But daily cycling of the battery will shorten its life, so that must be taken into consideration.

Now, Tesla guarantees that the Powerwall 2 will retain at least 70% of its initial storage capacity after 10 years or 37.8 MWh of throughput, whichever occurs first.

That 37.8 MWh or 37,800 kWh multiplied by $0.27 is $10,206. That's roughly the installed cost of a Powerwall 2 with 13.5-kWh capacity. The unit pays for itself after 10 years, and of course it will still has 70% of capacity left, so there's a significant residual value.

References:

1) https://www.sce.com/residential/rates/Time-Of-Use-Residential-Rate-Plans

2) https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_us_1-4.pdf

 

[Offgrid Organic Farmer]

Here in Maine, there is no 'time-of-day rate structure'. All grid power rates remain the same every hour of the day.

As a farmer my solar power system depreciates over 7 years. So every year I can use a tax write-off of 1/7th of the total expense.

The prime benefit of using solar power is to compensate for all the times when the power grid here goes down.

 

[Koolau]

A Generac (or other brand) on natural gas is what people are installing here in south Texas.

I know 2 folks (back home) who have these. Their only disappointment has been that they've not really needed them. Power there is quite stable and black outs are only severe-weather related - uh, generation is primarily coal with a trace of wind No need to worry about endless supplies of NatGas, so virtually no time limit on backup availability. Not sure a Tesla Powerwall with or without solar would keep the power on for very long. With NatGas generator, you have uninterrupted power until you fail to pay your gas bill. I guess my only question would be which is cheaper to install/maintain/operate so YMMV.

 

[tb001]

On the Web, I found that some Californians do use their units to save money with the TOD differential.


Here in Phoenix, I chose a time-of-day rate structure that charges 24.09c/kWh during the peak summer hours of 2-8PM, and 7.3c/kWh outside that peak period. Or I could choose a fixed rate of 11.57c/kWh all day.

Even before I installed a DIY solar+storage, the TOD rate saved me a bit of money already, simply by programming my pool pump to avoid the peak period, plus installing a timer to cut out the water heater between 2-8PM (and avoiding using a lot of hot water during that period).

I looked on the Web and found the following rate by Southern Cal Edison: 41c/kWh for 4-9PM, and 26c/kWh for off peak. But for people with a residential energy storage system, the rates are 43c and 16c.

With an energy storage system, you want to arbitrage between the 2 rates, and that's 43c minus 16c, or 27c/kWh. But daily cycling of the battery will shorten its life, so that must be taken into consideration.

Now, Tesla guarantees that the Powerwall 2 will retain at least 70% of its initial storage capacity after 10 years or 37.8 MWh of throughput, whichever occurs first.

That 37.8 MWh or 37,800 kWh multiplied by $0.27 is $10,206. That's roughly the installed cost of a Powerwall 2 with 13.5-kWh capacity. The unit pays for itself after 10 years, and of course it will still has 70% of capacity left, so there's a significant residual value.

References:

1) https://www.sce.com/residential/rates/Time-Of-Use-Residential-Rate-Plans

2) https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_us_1-4.pdf

That’s interesting, thanks for posting. When I did the calculations for our system I think the payback rate was about 10 yrs, but I assumed pretty minimal price hikes in electricity, which hasn’t been the case. When we looked into the Tesla system, the cost to install was very expensive vs traditional batteries, but I’ll admit we just wanted to get our system in ASAP, so we didn’t spend as much time as I would have liked researching options.

 

[Alan]

In some places, there may be enough time-of-day price differential to to offset the cost somewhat, or even be profitable if the delta is great enough.

Some people may want them just for black-outs, so if you can also make a little from TOD price deltas, it takes some of the sting out of the price, even if it doesn't pay for them outright.

That's just a theoretical, I don't know if many are actually using them in that way, but it would seem likely in CA?

That would work.

For several hours last night our price was less than 1c/kWh and between 4 and 7 this afternoon the prices will be between 25 and 30c/kWh. I have our batteries scheduled to charge at low rates so we never use any electricity during the peak period which is always between 4 and 7pm.

 

[The Cosmic Avenger]

I know 2 folks (back home) who have these. Their only disappointment has been that they've not really needed them. Power there is quite stable and black outs are only severe-weather related - uh, generation is primarily coal with a trace of wind No need to worry about endless supplies of NatGas, so virtually no time limit on backup availability. Not sure a Tesla Powerwall with or without solar would keep the power on for very long. With NatGas generator, you have uninterrupted power until you fail to pay your gas bill. I guess my only question would be which is cheaper to install/maintain/operate so YMMV.

An installation with 2 Powerwall units would probably keep our house going for 6 days, according to Tesla:

6 Days Backup Duration
Includes plugs, lights, 120V appliances, and some 240V appliances

Even if you think that's overly optimistic, it would probably do for at least 2-3 with mostly normal usage, or maybe closer to 24 hours if it was ridiculously hot and we were running the whole house AC compressor. That's not too bad, IMO. As I said, a generator might be best for those who experience long outages, like those at the end of the infrastructure. A battery system would probably be optimal for those who have frequent but brief interruptions or dips in power.

 

[NW-Bound]

An installation with 2 Powerwall units would probably keep our house going for 6 days, according to Tesla:

6 Days Backup Duration
Includes plugs, lights, 120V appliances, and some 240V appliances

Even if you think that's overly optimistic, it would probably do for at least 2-3 with mostly normal usage, or maybe closer to 24 hours if it was ridiculously hot and we were running the whole house AC compressor. That's not too bad, IMO. As I said, a generator might be best for those who experience long outages, like those at the end of the infrastructure. A battery system would probably be optimal for those who have frequent but brief interruptions or dips in power.

It is best to know exactly how much energy you use.

My utility company has a Web site where I can look up my exact daily usage, going back 3 years. It even has the hourly usage, but going back only 1 year.

Prior to having my DIY solar+storage system, my minimal usage was 24 kWh/day, in fall and late spring when there was no need to run air conditioning nor heating. That seems high, but I have a large pool to filter, and two large fridges, and the house is all electric with cooking and water heating all done with electric.

In the summer when it gets to 120F, my highest daily usage was 100 KWh/day. Thanks goodness it got that high only about 10 days each summer. The average usage in August was about 90 kWh/day.

In comparison, 2 Powerwall units have the combined capacity of 27 kWh. They do not last long for me under the normal usage, although in the case of electric outage, I may cut back enough so they last 2 days. More on this later.