solar battery backup

User Forum Topic
Submitted by moneymaker on December 26, 2017 - 9:40pm

Has anybody installed them and do they make economic sense? I'm going to get a few quotes, solar city, swell, anybody else have recommendations?

Submitted by FlyerInHi on December 27, 2017 - 12:38pm.

Very interesting article on the Tesla system.

I want to build an off grid house near Palm Spring.

https://www.washingtonpost.com/news/the-...

Submitted by gzz on December 27, 2017 - 2:26pm.

They don't even come close to making sense for existing houses. For building a place far from utility lines, they might make sense.

Since commercial buildings have economies of scale and do not get a "base amount" of cheap electricity like houses do, you will know these are ready for prime time when businesses start installing them.

High capacity lithium-ion batteries remain quite expensive.

For emergencies and travel use, and really as a toy, I was lucky to get one of these guys lightly used for half off:

https://www.amazon.com/gp/product/B01CYQ...

It is a really cool product created on kickstarter if you want to dip a toe into solar powered batteries. You can use the phone app to see how fast it is charging and/or how fast it is draining and comes with 100% of what you need to use it in a slick and tough outdoor-proof package.

Submitted by FlyerInHi on December 28, 2017 - 10:09am.

I'm waiting for when solar products are commoditized and easily serviceable.

Cool pack on Amazon.

Submitted by FlyerInHi on December 30, 2017 - 9:48am.

gzz, you sound like a smart engineer type.
What do you think of solar hot water heater? Don’t see too many of those.

I was also wondering... if i have free hot water in a studio apartment can I install a radiator type device for heating? Of course, there would need to be a recirculating type system. But I have not looked into it yet.

My friend who lives in Munich says the municipality provides hot water to everyone, including for heating purposes in their radiant heat. So nice because it’s noise less.

I have condos in Vegas that have hydronic heaters. Air blows through coils heated by water heater. I had to replace 10 year old recirculator cartridges. The repair guy wants $600. Only about $80 on Amazon DIY.

Submitted by Escoguy on December 30, 2017 - 10:59pm.

I did the numbers a dozen times on the residential power wall.

As I have solar and am on EVTOU2 rate, it made no sense.

For a 11-12K investment, I might save $300-$400 best case per year.

Believe me, I really wanted the numbers to work but ended up cancelling my SGiP application. Just decided to add more solar instead.

There may be an additional investment tax credit of $3-4K on top of the SGIP incentive but even then the payback was about 17-18 years vs a 10 year battery life/guarantee.

For commercial users, the math is very different if you can get away from demand charges. I'm looking into a system for the factory I run and the payback may be 5-6 years but need to do more homework.

Submitted by moneymaker on January 1, 2018 - 4:43am.

Thank you everyone that replied, I don't have excessive electricity left over, if I did I would be plugging in an electric car before selling it back to sdge. Even if it could break even I would be tempted in order to avoid power outages. I'm sure it will get to be more enticing eventually.

Submitted by TeCKis300 on January 2, 2018 - 11:32am.

I'm looking into this currently with Tesla directly. Going through initial site survey with them. My goal was to preemptively invest ahead of the peak TOU hour changes. I currently have solar along with EV, and we're just about a wash end of the year for settle-up. With the TOU changes, that will no longer be the case as my PV production is no longer leveraged by producing at peak rates.

In regards to batts, SGIP incentives are practically no longer available. If getting this with solar, or adding it along with existing solar as is my case, the federal ~30% tax incentive still applies.

The cost is still significant and ROI is much longer than I would like.

I'm considering steering my investment back to adding more solar. And making the add on west facing to align with the new TOU peak hours. I believe this would net much better ROI than a battery could.

Submitted by moneymaker on January 5, 2018 - 11:54am.

If the power wall cost $5500 itself then why $11k-$12k to install it? I wonder if solar city would quote a better price? If I could get it installed for $7k or less for a total cost of around $4800 and it would keep my power going during an outage i might consider it. When will all of us solar net meter 1 be forced onto TOU?

Submitted by livinincali on January 5, 2018 - 1:32pm.

A gas or diesel generator is far more effective for the occasional power outage. It might not be as green but it's hell of a lot cheaper and better suited for occasional infrequent use. Generally complete off grid power use deep cycle lead acid batteries because there are just better suited for the work load requirements. Lithium ion's biggest strength is weight to power density which matters in cell phones, cars and planes but not so much in a house. That doesn't stop Tesla from marketing Powerwall but it really doesn't make much sense to do that over deep cycle marine battery storage.

Submitted by flu on August 4, 2019 - 1:31am.

Anyone try Tesla's battery backup? Is so, thoughts?

Submitted by Hobie on August 4, 2019 - 1:44am.

Prepping?? Say it ain't so flu!

Seriously, do you have problems of power outages? I thinking not, so why a battery? Unless for a rural situation. Why not a generator?

Submitted by flu on August 4, 2019 - 7:16pm.

Was thinking more of storage when usage is low

Submitted by Hobie on August 5, 2019 - 11:11am.

I've been on Time of Use billing for several months now. I also have consciously switched to using the higher wattage items during non-peak hours and opting out of consuming during peak.

Result- damn near the same as prior residential bill!! Granted, the rates during summer are only a few pennies difference peak vs off peak. So we will see how it shakes out during the winter.

Guessing during the summer at least, using a battery during peak hours will be a quite long ROI. Unless you have to use lots of power on-peak.

Submitted by flu on August 5, 2019 - 11:15am.

Hobie wrote:
I've been on Time of Use billing for several months now. I also have consciously switched to using the higher wattage items during non-peak hours and opting out of consuming during peak.

Result- damn near the same as prior residential bill!! Granted, the rates during summer are only a few pennies difference peak vs off peak. So we will see how it shakes out during the winter.

Guessing during the summer at least, using a battery during peak hours will be a quite long ROI. Unless you have to use lots of power on-peak.

Gotcha.... Next question. I think the answer is no... but... Do you drive an EV? I am wondering how that will work out with TOU.... Just doing some planning and thinking. Nothing concrete yet...

Submitted by Hobie on August 5, 2019 - 7:30pm.

No EV yet. However was thinking for one just for in town errands.

Summer TOU rates not that attractive but winter maybe. I don't know if SDGE offers better than off peak for EV now. If not, then maybe better in winter vs. summer. But... in long run... just buy gas and drive normal car and plan trips a bit better. Not a real money saver, me thinks. Unless you need to impress neighbor with your 'green' agenda. ha.

Maybe other piggs with EV can weigh in.

Gut feeling, just add more solar to below Tier 1 might be more cost effective. But again, I'm on TOU so I haven't got that far yet. Me thinks, just put your additional new solar capacity in the bank for now.

Lomg story short... just watching and thinking.

Submitted by OwnerOfCalifornia on August 7, 2019 - 12:18pm.

I think there is a very long answer to this. SDG&E offers several EV-TOU rates, but I'm not well versed in many of them. I know the best one for someone with a small solar system (net consumer) or no system at all, is EV-TOU-5. It has a super-off-peak rate of $0.09 / kW-h, but comes with a fixed $16 / month fee (that's not a minimum use--you pay it no matter what).

I have a small east-facing solar system and a Tesla model S, and I'm a net consumer. My sweet spot is TOU-DR-P. On peak rate isn't too bad, and a modest discount for super-off-peak. The trade-off is those reduce-your-use days (of which there are only a few per year, obviously during super hot weather): My rate from 2pm-6pm is crazy high, like $1.40 / kW-h. Whenever that happens I'll just stay a work late.

Also, I don't have a Tesla home battery or anything, but I think one could really game the TOU rates, especially the EV-TOU-5. Load up super-off-peak, and dump on-peak.

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