Tesla Powerwall without solar ?

[NW-Bound]

Electricity in Paradise is the most expensive in the USA. Folks who must use AC to "survive" have electric bills in the multi hundreds of dollars per month. We chose both our locations to allow the trades to blow through. No AC is required though there are occasions it would be nice. Electric bills are $80. YMMV

The summer temperature in Hawaii is not as bad as in the Southwest, and I think it would be economically feasible to have a solar array feeding an AC. Even without a battery for storage for power at night, being able to have air conditioning during the day should help already.

The problem is then to have enough land or roof area for a solar array. Yes, I always want to have lots and lots of land.

 

[Koolau]

The summer temperature in Hawaii is not as bad as in the Southwest, and I think it would be economically feasible to have a solar array feeding an AC. Even without a battery for storage for power at night, being able to have air conditioning during the day should help already.

The problem is then to have enough land or roof area for a solar array. Yes, I always want to have lots and lots of land.

Yes, in a condo building, solar panels are problematic - as are air conditioners. A couple of folks have used the "portable" ACs with the "coaxial" cooling/hot-air venting system. Actual window units are verboten as they can be heard by neighbors in the next egg crate - plus they are considered an eye sore.

There is no central heat/air in most condos though there is an exception we looked at. The building is virtually all glass which gives the luxurious view of the near-by Pacific ocean from as many as 3 directions. The down side is that without air conditioning, it would likely not be habitable because of the sun load - windows open or not. SO, the building has central air (entire building - not per unit.) Of course, when we looked 10 years ago, their HOA dues were over 1K/month. I'm guessing it's closer to 1.5K/month now but have not checked.

I've known several folks who have installed solar panels here (individual homes.) They do work, but I can't recall anyone who has stayed in the house long enough to recoup their investment - it doesn't always translate to higher home price at time of sale either. Short stays in housing has been discussed here (by me) before. Long story, but YMMV.

 

[caninelover]

We installed a 17-panel solar system with 1 Tesla Powerwall in our attached townhouse in SoCal. California law does limit an HOA's ability to disapprove solar installations as long as their is sufficient roof space for all units to have solar on a shared roof. So it may not be feasible in higher density condo developments, but our townhouse only shares a roof with 2 other fairly large units, so we had plenty of roof space available.

Our system went operation in March and we had a PSPS shutdown just last week for 12 hours (we live in a windy area so we expect it to happen quite a bit over the next few years - which partially drove our decision to get the Powerwall with our system). We didn't even know the grid was down as our panels and battery had sufficient juice to power us through the day (though no A/C but we didn't need it). It would have been fine overnight and the next day would have recharged when the sun was out. We think it is worth it but we intend to remain in this home for the foreseeable future.

 

[Koolau]

We installed a 17-panel solar system with 1 Tesla Powerwall in our attached townhouse in SoCal. California law does limit an HOA's ability to disapprove solar installations as long as their is sufficient roof space for all units to have solar on a shared roof. So it may not be feasible in higher density condo developments, but our townhouse only shares a roof with 2 other fairly large units, so we had plenty of roof space available.

Our system went operation in March and we had a PSPS shutdown just last week for 12 hours (we live in a windy area so we expect it to happen quite a bit over the next few years - which partially drove our decision to get the Powerwall with our system). We didn't even know the grid was down as our panels and battery had sufficient juice to power us through the day (though no A/C but we didn't need it). It would have been fine overnight and the next day would have recharged when the sun was out. We think it is worth it but we intend to remain in this home for the foreseeable future.

(Sorry, but imagine me as Col. Jessup dressing down Col. Markinson in A FEW GOOD MEN): "Law, yes, another law. That should do it. That sounds like a good idea. Pass a law. I'm sure that's what we should do."

Here, we have a law that any parking lot over a certain size (I think it's 100 cars) has to have a charging station for electric cars. It has no specifications such as how much does the lot get to charge to use the station, what level of charging must be provided, how to insure folks don't simply park in the slot. Perhaps the worst "oversight" - The law makes no provision for enforcement. So in the several years since the law passed, just about the only lots providing electric car charging stations are in shopping center lots. So far, I've only seen "free" charging which would be a magnet (induction, no doubt, heh, heh ) for shoppers owning EVs, I guess.

Our Costco lot has two stations - for (SWAG) 600 cars. I don't know my terminology, not owning an EV, but I think the two stations must be level 2. My son who owns the Tesla left me with the impression that these offer maybe 20 miles of range for an hour of charging, but I may not be recalling our conversation correctly.

By the way, even though they are clearly marked and state "for electric vehicle charging only" there is no enforcement if someone simply decides to park in the stall in an ICE car. Oh, and supposedly, you can only charge for one hour. Perhaps the electricity shuts off after an hour - I don't know. In any case, currently, my only options for EV charging would be to travel to a pay charger or take my chances around town in the "free" charger stations.

So if I'm making any point whatsoever that's remotely on topic, it would be that our state currently isn't very friendly toward all this new-fangled solar stuff. Also, our housing situation is likely more skewed toward condo and apartment living by comparison to most other states (land is at a premium to say the least.) Therefore, "doing" solar with or without power walls may be problematic at best. Sad too since we are a state which must be in the top 2 or 3 (think AZ, NV, FL) where solar OUGHT to work. Full disclosure: We do have a lot of solar installations on the Island, but integrating them into the grid has been problematic (and limited.)

So, I'm now returning you to our regularly scheduled discussion as YMMV.

 

[Texas Proud]

Just curious.... anybody with a generator that wants to give the power output and total cost to install?

 

[Offgrid Organic Farmer]

Just curious.... anybody with a generator that wants to give the power output and total cost to install?

Every hour you run a diesel generator to power your house and to recharge a battery, you will lose 20% of that energy just in pushing the charge into the battery. Regardless of all the other losses in converting petroleum into wattage.

That wattage, hours later when you draw it from the battery will be very expensive energy.

It is one thing to have a generator and battery-bank in a house, for areas where the power grid is not routinely available to power homes.

 

[tb001]

Just curious.... anybody with a generator that wants to give the power output and total cost to install?

Bumping this thread, as we just finished a several day stint without power and are looking into options that might power the whole house, or at least a couple of subpanels. Probably wouldn’t need the hvac, though it would be nice.

We may be eligible for the same program skip pro mentioned, but our usage is similar to that of NW bound. A typical day is around 70kW, albeit with a lot running that we wouldn’t necessarily need to use.

Trying to figure out if we should be looking into adding battery capacity (we have two LG batteries now) or a generator.

 

[skipro33]

Every hour you run a diesel generator to power your house and to recharge a battery, you will lose 20% of that energy just in pushing the charge into the battery. Regardless of all the other losses in converting petroleum into wattage.

That wattage, hours later when you draw it from the battery will be very expensive energy.

It is one thing to have a generator and battery-bank in a house, for areas where the power grid is not routinely available to power homes.

I wouldn't be so sure. In PG&E territory of California, TOU rates are above 30 cents a Kwh. A diesel generator that can output 22Kw, minus a 20% loss of efficiency, produces $5.40 an hour in electricity at 30 cents per. The generator will run, on average, 1.6 gph @ full load. Red Dye Diesel is about $2.60 a gallon, so cost for generator fuel is $4.16 an hour.

My home uses between 18 and 20Kwh of electricity a day; about an hour's run time of the generator charging batteries.

 

[NW-Bound]

^^^ Some battery storage systems boast a round-trip efficiency of 95%.

Additionally, having a storage battery means you do not have to run the generator 24 hours. It lets you have some decent sleep.

 

[Sunset]

Yes, this was sort of my idea. Freeze water when electricity is cheap and circulate air over the ice (or circulate the chilled water) and collect the water for refreezing. According to NW Bound, this would be at best a wash from an energy standpoint. I have no ability to check the calculations but I'm guessing they are substantially correct.

Electricity in Paradise is the most expensive in the USA. Folks who must use AC to "survive" have electric bills in the multi hundreds of dollars per month. We chose both our locations to allow the trades to blow through. No AC is required though there are occasions it would be nice. Electric bills are $80. YMMV

I saw this idea of using ice to cool being run as an experiment in Canada.
They froze a giant block of ice, roughly 10'x10'x20' high. It was insulated with a large roof door.
They filled it with water at the start of winter, and used nature to freeze it solid. Then shut it so it was fully insulated.
Come summer the ice cooled pipes that had be installed in the bottom, probably like a heat pump idea in reverse (cold pump?).

Using nature to make the ice, would mean the cooling cost would be very low.
Ice can survive a surprising long time in summer, I remember playing in an ice house where 100 lb blocks of ice under wood chips made the building nice and cool.
We would buy the ice to use for our refrigerator (ice box).

 

[NW-Bound]

They froze a giant block of ice, roughly 10'x10'x20' high. It was insulated with a large roof door...

Hmm... 2000 cubic feet is 15,000 gallons.

My pool is 25,000 gallons. But how do I keep the expanding ice from breaking the pool?

And I need to figure out how much electricity to freeze that pool water, as we get to freezing at night in the winter only about 1 night a year, if even that, where I am.

And I will need to see how many days of cooling that 25,000 gallons of ice can provide in the 120F summer heat.

 

[skipro33]

Bumping this thread, as we just finished a several day stint without power and are looking into options that might power the whole house, or at least a couple of subpanels. Probably wouldn’t need the hvac, though it would be nice.

We may be eligible for the same program skip pro mentioned, but our usage is similar to that of NW bound. A typical day is around 70kW, albeit with a lot running that we wouldn’t necessarily need to use.

Trying to figure out if we should be looking into adding battery capacity (we have two LG batteries now) or a generator.

It's Ski Pro, not skip pro.
I'm still working my way through the process to get my batteries. I've been approved for funding through PG&E with the funds now in escrow to cover the cost, an engineer from a vendor I selected to do the install has come out and started work on drawings for permits. Once those drawings and plans meet my approval, the permit application will be submitted. I'm told Tesla is back logged months and that I'm likely to be waiting some time before install actually takes place.
In the meantime I did some research. Turns out these batteries are not configured into a system like I thought. I thought this was like a UPS, where an outage would not cause an interruption in power. That was wrong. When AC Mains fails, there is a loss of power before the batteries kick in to make up for it. If my loads are such that they exceed the capacity of the batteries start up current, I won't be powering the house from the batteries AND I won't be switching back to AC Mains once power is restored from the electric company. This might happen if I have more than one of my AC units trying to turn on during a cut over to battery power. If I'm not home to reset the deadman switch after turning off an AC unit, the power remains off until I do.
Also, it turns out that Tesla must be able to log into the batteries every day via wifi. In my area, when an outage occurs that lasts longer than 4 hours, the internet provider's battery back up fails and they don't have a generator. If the outage is extended into the window that Tesla tries to ping my batteries, my batteries have a deadman switch and turn off until a manual reset locally can take place. Yup; loose internet/wifi to the batteries and they will turn off your power within 24 hours with no chance to reset until a person manually does so locally.
On top of that, the TOU rate I have for solar goes away and I'm put on a TOU for electric vehicle rate. (PGE doesn't have a dedicated rate for those with batteries other than Electric Vehicle, so that's what those who go with batteries are lumped under) This rate is over 40 cents a Kwh during all but the wee morning hours of 1am to 5am (or something like that) when they drop to 20 cents a Kwh. Meaning I must be using my batteries every day in order to avoid the price gouging. My solar is not enough to both keep my batteries at 100% at sunset and run my house all day, so I would have to rely on the off peak early AM rates. Right now, I'm able to use PGE as my battery bank with TOU and Net Metering. Under TOU and Net Metering, I do not pay PGE for any power at you end of year true-up. I'm not convinced I won't under Electric Vehicle rates, battery bank size and my loads.
The topper though is that PGE requires I sign an agreement that they will discharge my batteries at 100% of capacity up to 52 times a year. This means that a powerwall II @ 13Kwh is going to back feed their grid every week at some time on my dime. They don't pay me for it. I didn't believe this was true at first, but after careful investigation and many calls, turns out that is what they do and that is why PGE is willing to go forward with 'free' battery installs. They get to use these batteries as a peaking storage without having to cover the cost to purchase them or to even charge them up.
I don't see how I can end up the year without paying PGE compared to my current solar rates.
I guess I'm going to tell the vendor when they want me to sign off and have them install to walk away. They won't be happy, but then I'm not either, having to do the math to figure out what my end cost might be if I switched from solar rates with TOU and Net Metering over to Electric Vehicle rates with up to 52 days a year at 13Kwh per powerwall gifted back to PGE. I roughly calculate 2 powerwalls would cost me $500 in electricity I'd be giving back to PGE per year. Some may argue that $500 is cheaper than the cost of a generator and perhaps the fuel it uses and that may be true. Averaged over 10 years, the life expectancy of the Tesla Powerwalls, it might break even. But I already have a generator so that cost is needs to be weighted in now to the cost of this design. I just do not see how I can save any money going forward with batteries under this program and even more; I can not see how my power becomes any more reliable based on the caveats with wifi, load maximums, manual reset mandate, etc. I was sure hoping I'd never even be aware of an outage without some sort of text or email telling me I"m now on batteries and not AC Mains from the utility. Sure glad I checked it out thoroughly first.

 

[tb001]

Ha! I’m blaming auto correct for skip pro

That’s really helpful information. Appreciate you taking time to post it as it’s likely we would have similar issues. Was Tesla your only option? We have lg batteries installed now, based on almost no research at the time, but they’re lower capacity. I didn’t realize part of the deal was the constant charging and discharging—I would think that lowers battery life considerably depending on how it’s done.

It seems like long term solar is the better option but I wonder about a generator until the technology gets there in terms of battery life and output. My initial thought was solar is less in maintenance and replacement costs.

 

[mpeirce]

...

OMG

I thank my luck stars that I flip the switch and get power reliably with only the odd short outage every couple of years!

 

[skipro33]

OMG

I thank my luck stars that I flip the switch and get power reliably with only the odd short outage every couple of years!

PG&E just announced that they will have a PSPS (public safety power shutoff) starting as soon as Sunday night until Tuesday. High winds and low humidity resulting in increased fire danger and downed power lines.
The strange thing is that outdoor burn permits are now allowed. So PGE says fire danger, Cal-Fire says go ahead and burn your outdoor brush. So which is it?
In any case, I'll fire up my generator today and make sure it's all in operational order. I've had to keep the mice out of it, they chew wires. I don't want to discover that again after dark.
California is darn near a third world country any more when it comes to critical infrastructure like power, water, healthcare, roads, etc.

 

[NW-Bound]

Skipro, it's too bad things don't work out as you thought. In a way, it makes sense that PG&E is not doing this out of the goodness of their heart.

Perhaps you can look into doing a DIY storage system. There are some companies now offering simple components that anyone with a bit of technical knowhow can wire together. They are off-grid and will not feed into the grid, and this simplifies matter. And being off-grid, it does not require the permission of the power company. I don't know if the local ordinance requires inspection or permit, but many places do not care or know about these "experimental" systems.

Such a DIY system would be best installed in a shed away from your main house, for obvious safety reasons. And one needs to study all safety issues with lithium batteries before tackling this, although many storage systems now come with BMS (Battery Management System) pre-installed.

A power storage or solar system can be dangerous. But careless people have also been hurt working on their cars, or running power tools.

... On top of that, the TOU rate I have for solar goes away and I'm put on a TOU for electric vehicle rate. (PGE doesn't have a dedicated rate for those with batteries other than Electric Vehicle, so that's what those who go with batteries are lumped under) This rate is over 40 cents a Kwh during all but the wee morning hours of 1am to 5am (or something like that) when they drop to 20 cents a Kwh...

YIKES!

Here in Phoenix, the rate for EV owners is 24c/kWh for 2PM-8PM. During off-peak hours, it's 6.14c at night, and 7.7c in the morning.

If I were in CA, I would pave my lot with solar panels, and cover the entire roof. Can't afford that 40c/kWh price. Wowza!

 

[skipro33]

I want to make a correction on the EV rates that PGE uses for anyone with back up batteries.

Here's a chart that shows the current rate called EV-B;

They have an older version that only those grandfathered into still have. It's called EV-2A;

 

[Freedom56]

We have a grid connected solar system. We looked into the Tesla wall but found that it was not really worth it. We have on average one power failure/shutdown per year. There is no way to justify the cost of batteries under that scenario. We looked into adding a generator connection to our main breaker and buying a generator. That would cost about $1200-1500 for the generator and the connection. Without a battery back-up we would have to keep the solar system shutdown while the generator is operating.

 

[bonusboxalley]

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...powerwall.pdf/

The payback may actually be faster. SCE is proposing a 14.4% rate hike for 2021. Plus with more options for batteries, the costs should hopefully be even lower in the near future. I think it only makes sense that every home has some kind of battery in the future.

 

[Ready]

I saw these Duracell battery powered generators at Costco today. They are of course much smaller than a Tesla power wall but at $500 each you can buy close to 20 of them for the price of one power wall. And apparently they can be daisy chained together. It might be a cheaper solution for someone wanting battery powered backup without the full expense of the Tesla solution.

https://www.costco.com/duracell-pow...tTVu4Ms/D40XSb86JJecFEv0fT4U+IdVS3iZ+5NC5oYIi

 

[travelover]

I saw these Duracell battery powered generators at Costco today. They are of course much smaller than a Tesla power wall but at $500 each you can buy close to 20 of them for the price of one power wall. And apparently they can be daisy chained together. It might be a cheaper solution for someone wanting battery powered backup without the full expense of the Tesla solution.

https://www.costco.com/duracell-pow...tTVu4Ms/D40XSb86JJecFEv0fT4U+IdVS3iZ+5NC5oYIi

Reading the reviews this is not a lithium battery, it is AGM and like any lead acid battery, you can't really use the full advertised capacity.

 

[NW-Bound]

I saw these Duracell battery powered generators at Costco today. They are of course much smaller than a Tesla power wall but at $500 each you can buy close to 20 of them for the price of one power wall. And apparently they can be daisy chained together. It might be a cheaper solution for someone wanting battery powered backup without the full expense of the Tesla solution.

https://www.costco.com/duracell-pow...tTVu4Ms/D40XSb86JJecFEv0fT4U+IdVS3iZ+5NC5oYIi

Reading the reviews this is not a lithium battery, it is AGM and like any lead acid battery, you can't really use the full advertised capacity.

What travelover said.

I also do not see that you can parallel multiple units for more power. What it says is you can wire additional external lead-acid batteries to extend the run time. A marine 12V battery of the same capacity as the internal battery can be bought at Costco for about $75, I think.

The spec on Costco Web site is incomplete. On Amazon, the listing for the same DR660PSS unit says 12V-55Ah battery (for 660Wh battery capacity, which is not all usable without shortening the life of the battery).

The important spec that Costco site does not mention is that the inverter is rated at 1440W continuous, and 1800W surge. This means that this inverter should be capable of running a residential fridge, although not for very long with just one battery. My 30-c.f. fridge draws 5kWh/day. It would consume the 660Wh battery in (660/5000)*24 hr = 3 hours.

PS. This device will accept a solar panel to use it to recharge the battery. However, I cannot find the power rating of this internal solar charger.

 

[Texas Proud]

Read an article that you will NOT be able to just buy a powerwall going forward... you can only get them if you buy a solar system from them...


(let the puns begin lol)...

 

[braumeister]

you can only get them if you buy a solar system from them...

Kinda gives new meaning to the term "megacorp".

Maybe "exacorp"? (10^18)

 

[The Cosmic Avenger]

I saw that when I went to price out a system, and I was very annoyed. I already have solar panels, from Tesla (well, SolarCity), and I can't seem to qualify for installation! If I cared more I might call or email them, but even logged in to my solar account, it doesn't show a pathway to add Powerwall to my current system. That's annoying.

Has anyone heard whether they will install it for existing solar installations?