Tesla Solar Battery

[BajaScout]

Has anyone added one to their solar system?

Got a quote and was surprised the solar battery system will cost more than the solar system (10 panels) I had installed two years ago.

Before the 30% tax credit I am looking at $13,400. With the 30% and the $3,000 state rebate I will pay $6,380.

Don't necessarily need it now since I over produce each month with my current system. I plan on retiring this October so I will be in the garage much more running the tools and lights. Also the electrical provider (SDG&E) is changing their rate structure for time of use.

Any thoughts if the above cost seems reasonable.

If you are in the business and want to provide me a quote, please PM me. I am located in San Diego.

 

[dcg9381]

Baja,
What are you after by adding this battery?


I've installed a fair number of solar systems (not my profession) and I've looked at the Tesla deal for several people.

A few things to note - the Tesla deal ONLY makes sense for under one of three conditions:

1) You live somewhere with no "net metering" - meaning that you're charged more for buying electricity from the grid than you get when you sell it back to the grid. In this case, it's (perhaps) better to store it.

2) You want some "off grid" capability.

3) Your grid has variable (demand based) pricing and you can "buy cheap" in non-demand hours, store it, and use it later. In this case, it can "save" money.


Note, for #2, a powerwall 1 is only capable of 2KW sustained. That's about the power output of a Honda 2K generator that you can carry with one arm - it'll run some stuff, but not a lot. A powerwall 2 can do 5kw, about a mid-sized generator. At full output, both will last a bit over 2 hours. I haven't installed one - or read the install manual, so I'm unsure if it is connected to specific breakers or is a "whole house" deal. If whole house, I assume it load-sheds and would drop out if the house pulls more than it is capable of producing.


It's covered by warranty (70% output) to 10 years. A fair number have already been replaced. Sure, it might last longer than that, but it is a giant constantly-cycling battery.


So I think we're talking about $10k (installed) for a few hours worth of off-grid power - lights, refrigerator, basic appliances. Not water heaters and air conditions.

To me, it's a relatively small, $10,000, no-moving-parts generator. It's very unlikely to "pay" for itself (ever) under most circumstances and I feel - in most economic cases where utilities "net meter" that you're better off with a traditional solar system sized "at" your current electricity use.

I see it as a supplement in a true off-grid situation where you also have a stand-by generator.... Maybe...

 

[BajaScout]

Appreciate the insight.

My existing solar system already over produces so I most likely don’t need a battery system.

Reasons I want one are (1) tax savings and (2) to front load the tiered rate structure starting next year. With retirement I will also be using more electricity.

Any other options for barter storage you would recommend? I guess I could always look into additional panels too.


Sent from my iPhone using The Garage Journal mobile app

 

[dcg9381]

Spending $13.4k with a net cost of $6.38k - unless you think it adds more than $6.38k of value to the home, that's a net loss to me... If there is some other more complicated tax reason, I'll leave it to your CPA.

If your rate structure is hourly "on demand" tiered, the battery can help. I'd be very surprised if spending $6.38k EVER pays back in the next 10 years... But with over production, don't you have a "net bill" of $0? If so, the tiered structure doesn't really matter... Assuming I'm understanding right.

You're in CA. I assume that high energy use times are also high solar production times? The option that I recommend for "barter storage" is net metering - you either have it or you dont. If you guys have that (seems some of CA does at least) and you're over producing, you should do NOTHING until you're under producing... Even then, I seriously doubt the economics of adding this battery will be in your favor, at least in your lifetime, but it depends on how much more power you use in retirement.

For grid connected homes, I won't (will not) install batteries or wind power (needs batteries) - as the sheer economics of storing that power and the costs of servicing it for the consumer do not make sense.

 

[Ray-CA]

When did you install the solar system?

We have one also and don't have to switch to "time of use" as we're grandfathered in to our rate structure. Solar City (Tesla) was here last week for the same reason. The dollars didn't work out for us to drop that much on a battery. I could just a really great emergency generator and still have money left over.

Ray

 

[BajaScout]

dcg9381,
Your advice is appreciated. I think I will pass on the purchase.
GJ saves another guy from making stupid mistakes!


Sent from my iPhone using The Garage Journal mobile app

 

[BajaScout]

When did you install the solar system?

We have one also and don't have to switch to "time of use" as we're grandfathered in to our rate structure. Solar City (Tesla) was here last week for the same reason. The dollars didn't work out for us to drop that much on a battery. I could just a really great emergency generator and still have money left over.

Ray

Ray,
March 2017. Understand I will go to a tier structure in 2021?




Sent from my iPhone using The Garage Journal mobile app

 

[BajaScout]

When did you install the solar system?

We have one also and don't have to switch to "time of use" as we're grandfathered in to our rate structure. Solar City (Tesla) was here last week for the same reason. The dollars didn't work out for us to drop that much on a battery. I could just a really great emergency generator and still have money left over.

Ray

I was also thinking about the generator option. Thanks!


Sent from my iPhone using The Garage Journal mobile app

 

[dcg9381]

Not trying to tell people what to do / not do, just want to talk about the "real" economics of it. Damn Tesla "solar roof" is just as nutty - costs are crazy and they'll still tell you that "costs about the same" as a re-roof.

I looked at the Power Cell. I imagine there are a only a very few circumstances where it makes financial sense, but not many...

And in the off-grid cases, you're either to design for it up front (10K buys a lot of battery) OR accept that you need a real-whole house 20KW+ backup system for your home.

 

[99LeCouch]

What are the new TOU rates going to be, and when in the day do they kick in? How are you currently billed? It might make sense for a 4-8 PM TOU rate if it is really expensive, and your solar can charge it enough during the day. Make some money on the arbitrage between your low cost to charge it during late morning through early afternoon, and having it reduce imports during the late afternoon and early evening.

 

[BajaScout]

What are the new TOU rates going to be, and when in the day do they kick in? How are you currently billed? It might make sense for a 4-8 PM TOU rate if it is really expensive, and your solar can charge it enough during the day. Make some money on the arbitrage between your low cost to charge it during late morning through early afternoon, and having it reduce imports during the late afternoon and early evening.

The peak hours are 4-9 PM. I am still generating with my panels until it gets dark. Plan on retiring this October so I can avoid the peak hours easily. I live close enough to the coast that I seldom have to run the AC.


Sent from my iPhone using The Garage Journal mobile app

 

[Git]

I looked into it 2 years ago, and it was too expensive for me.

It makes sense on paper - not only would you have some 'backup power' available in case of power outages (pretty rare for us) but they are also able to tap into your battery system during peak demand to help supply electricity to your neighbors

We have a pretty large system - 12.48 kWh DC which produces 19,000 kWh annually. To qualify for the incentives (it's called SGIP) we would be required to purchase TWO Power wall batteries. The initial cost was quoted at $20k and we would end up paying out of pocket about $9K IF the SGIP (Self-Generation Incentive Program) funding held up. (The program is first come, first serve and as more people get involved, the incentives are reduced)

So $9K to avoid a rare power outage didn't seem like a really good deal to me. And, the batteries would eventually need to be replaced

I was just looking at electrical rates - S Cal Edison sent me a rate comparison. We are grandfathered in under Net Metering 1.0 so we can still get the Tiered Rate, but they are indicating that if I switch to TOU - with peak hours between 5PM to 8PM, we would save $347 per year. It looks like this year we may actually have to pay around $200 on our annual true-up, so I will probably switch

https://www.cpuc.ca.gov/sgip/

 

[Git]

What are the new TOU rates going to be, and when in the day do they kick in? How are you currently billed? It might make sense for a 4-8 PM TOU rate if it is really expensive, and your solar can charge it enough during the day. Make some money on the arbitrage between your low cost to charge it during late morning through early afternoon, and having it reduce imports during the late afternoon and early evening.

For us, we are on an annual billing plan. After every 12 months, you settle up (they call it a 'true up) and then you start over from a clean slate. If you used more electricity than you generated, you have to pay your bill. If you over generated, you can either roll it over into the next year as a credit or you can get paid for it, but it's at the wholesale rate, which is around $.02 per kWh. No one is going to make money from over generating

 

[BajaScout]

Just running some simple numbers with final out of pocket at $6,380 I would have to have an electric bill over $53/month to break even at 10 years.

Sine I have a surplus every month I doubt that I will be in that situation unless once I retire I am running the power tools or welder a lot.


Sent from my iPhone using The Garage Journal mobile app

 

[Git]

By the way - My Solar Contractor was from San Diego. Baker Electric. We were extremely pleased with them. Fair price, outstanding workmanship and did what they said they were going to do. Anyone in S Cal - if your looking for solar, I would highly recommend Baker Electric

https://www.baker-electric.com/

https://www.bakerhomeenergy.com/

 

[BajaScout]

By the way - My Solar Contractor was from San Diego. Baker Electric. We were extremely pleased with them. Fair price, outstanding workmanship and did what they said they were going to do. Anyone in S Cal - if your looking for solar, I would highly recommend Baker Electric

https://www.baker-electric.com/

https://www.bakerhomeenergy.com/

I had a great experience with Semper Solaris.

Two places to get quotes from in San Diego.


Sent from my iPhone using The Garage Journal mobile app

 

[ard]

Ive been looking at two powerwalls....but cannot get past the whole 'need to pay some yahoo to install it'. Seriously, just ******* away a TON of money. Sell me the hardware, Im down tomorrow.

 

[Git]

With PGE going bankrupt over all the wildfires, I would imagine your area is going to be in for a lot of power outages as soon as the wind starts kicking up

 

[99LeCouch]

That structure is very different from my utility's solar billing. I am net metered and on a fixed rate per kWh. It's the same for every homeowner around here. A battery doesn't make sense with the net metering since the grid itself is my "battery". Count the kWh exported, count the kWh imported, get billed on the difference. Any extra production gets rolled onto the next month's bill, in perpetuity until it's used up. So, without the need to offset a higher rate that kicks in when the solar is ramping down for the day, it makes no sense.

 

[ard]

With PGE going bankrupt over all the wildfires, I would imagine your area is going to be in for a lot of power outages as soon as the wind starts kicking up

Just had another shutdown warning yesterday....High winds from 2-6PM in the afternoon.

In case peole don't know.... When temps get high, AND they predict high winds, PGE may 'proactively' shut off power to large areas. This reduces the odds of wind driven power line damage then triggering a fire.

But it means they must first inspect every mile of line, PRIOR to retuning power. Can take days. Entire swaths of the region can be without power- schools shut; commercial refrigeration down, etc etc.

We, as ratepayers, paid and paid for them to install and maintain lines- apparently poorly engineered for the job at hand.....arrrgggghhh,

 

[tyme2par4]

Just a note, Tesla isn't the only game in home battery systems. LG I believe sells as many if not more batteries than Tesla does. They also have options on different sizes.

 

[checkthisout]

That's crazy. My house is full electric and our total bill for the year is around $2000.00 (10 cents per KWh.

I could gain efficiency by going to a heat pump as well.

What rates are you guys paying for power that makes solar make any sort of financial sense?

From my perspective, it only makes sense if you DIY and have high cooling loads?

 

[slow]

all depends on where you live, and if you have TOD (time of day) metering, and kw cost. I am in FL so cheap electric (just under $0.10 kwh delivered) no TOD and very similar in total cost per year.

Friends in CA said they pay up to mid 0.3x a kwh, but looking at so cal edisons' prices, some plans are up to $0.51 kwh. Making solar and batteries far easier to justify.

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

 

[dcg9381]

That's crazy. My house is full electric and our total bill for the year is around $2000.00 (10 cents per KWh.

I could gain efficiency by going to a heat pump as well.

What rates are you guys paying for power that makes solar make any sort of financial sense?

From my perspective, it only makes sense if you DIY and have high cooling loads?

We are charged .107 per KWH, give or take, with a flat "delivery fee" of $20 for the honor of being tied to the grid.

My cost (self installed) - 6KW solar system, about $9000 up front. After the federal rebate, lets call it $7000.

My system is not at perfect tilt, so it really peaks at about 5.7KW.

Payback is probably inside 10 years, maybe a little better if power costs increase.

Payback can be better in other areas that supplement the federal rebate... But most of these will not allow self-install.

 

[anythingyoucanimagine]

Elon is like Steve Jobs. You have to buy into the whole package or it won't work. Other thing you have to look at is the fine print. Last time we looked, technically you get "credits" back --just like how you give the IRS an interest free loan, you get "rollover credits" so if next month you use more, it'll be "free". What you don't know is they have giant energy trading desks profiting from your rollover credits.

We are 100% DIY grid tie with bank of 48x 12v batteries and 24 panels. New house we are building will be bigger system, 3 phase from grid, grid tie, professional install, LG batteries... and shes gonna have to deal with the dryer plug to charge her X. I like burning gasoline.

 

[dcg9381]

Last time we looked, technically you get "credits" back --just like how you give the IRS an interest free loan, you get "rollover credits" so if next month you use more, it'll be "free".

I think you're talking about net metering which is going to be very location/provider specific.

Elon is like Steve Jobs.

Jobs never put a car in space "just because". I suppose that if social media was around back in the day, Jobs might have matched Elon's "twitter habit" - but I doubt it...

Not sure that Apple, cept for some time in the 80s or 90s ran on pure market speculation rather than profit.. but I stand to be corrected.

Note, love Tesla's products and bleeding edge technology. If I was going to buy a car right now, I'd be a 3P. But Elon is a little nutty and may sink that company eventually.

We are 100% DIY grid tie with bank of 48x 12v batteries and 24 panels. New house we are building will be bigger system, 3 phase from grid, grid tie, professional install, LG batteries... and shes gonna have to deal with the dryer plug to charge her X. I like burning gasoline.
.

Love it!

 

[tyme2par4]

That's crazy. My house is full electric and our total bill for the year is around $2000.00 (10 cents per KWh.

I could gain efficiency by going to a heat pump as well.

What rates are you guys paying for power that makes solar make any sort of financial sense?

From my perspective, it only makes sense if you DIY and have high cooling loads?

Here in the northeast prices are nearly double what you pay. In NH I'm at about $.17/kWh, with a lower price, third party supplier.
I would love to do a DIY system on my house, but I live in one of the few towns that doesn't have a property tax exemption for solar. And assessor has decided each panel adds $800 in value to your property. So I'd be paying an extra $400/year in property taxes.

 

[anythingyoucanimagine]

I think you're talking about net metering which is going to be very location/provider specific.

I don't know all the laws and rules. My comments about Elon, Jobs and metering were more that Elon/Tesla seem to be an "all or nothing" type guy, similar to how Jobs was "seamless integration of hardware and software", Jobs was very "all apple or nothing".

Elon wants you to have his panels (or roof shingles), his batteries, his car, his chargers, etc.

In terms of metering or net metering with the Elon system, we didn't get that far. We looked at it pre-powerwall. Back then, if the grid wend down, you also went down. That was a deal breaker for me/us. I refused to buy into the whole package just to be put on a battery wait list. (and also we have 3ph residential and they wanted us to switch over to split phase 120/240v)

From what I remember back when we looked, it was a bunch of big, convoluted contracts. Essentially you didn't get a check back from your PoCo every month, anything you over-produced came back to the homeowner as "credits" (not dollars) and the actual energy credits (the things that are worth the dollars) went back to Elon/Solar City. The homeowner credits were handled almost like cell phone rollover minutes. Use less than you produce this month and you carry forward "credits". Next month if you use more than you produced... no biggie... you can apply your rollover minutes.

The part I don't know is whether that has changed since tesla bought first solar, if that varies from state-to-state, etc. But that was my takeaway: the homeowner gets fake "credits", elon got an interest free loan and didn't share the profits with the homeowner.

My experience: I've spent some time working in the energy trading space. I used to know how much the cost of electricity rises for nyc customers when it rains and I still do some hosting and low-latency connectivity work for trading groups and hedge funds. I know a lot about stuff like how gasoline companies trade energy futures against the gas they haven't sold at the pumps yet, airplane manufacturers trade metals futures against the airplanes they have not sold yet, commercial airlines trade energy futures to offset the cost of the fuel they burn... Then there are speculators like what Enron was/did. Again, my takeaway was that Elon had an energy trading desk and was probably monitoring usage, building databases... and then trading and massively profiting from customer's "rollover minutes"... But I could be totally wrong.


Our solar & batteries:
Doing solar ourselves was really fun. I have such an awesome/amazing wife. We bought panels in bulk for stupid cheap from a guy on Craigslist, I fabricated my own brackets (then dealt with a year of ******** with the town getting my brackets approved for our wind load ratings), then accumulating the batteries, putting it all together, I wrote a ton of custom code and modified open source programs to make it do exactly what we wanted. She taught herself several programming languages (C, Python, sql, R) so we could write the code together (and if I get hit by a bus tomorrow she'll be totally fine managing the system on her own). Working with her to make it all happen was the best part.

Our power currently comes from the batteries. Technically we are 100% off the grid (in a residential neighborhood). The solar charges the batteries first then we wrote an algorithm... algo is fancy word, we wrote a small piece of code that has defined logic to decide whether to auto-start the generator or switch over to the grid. It looks at stupid stuff like what circuits are on (whether or not the oven/stove is on or if I'm welding), how close are we to the weekly generator auto-run, how close is the generator to it's maintenance schedule, etc. So house runs on batteries, solar charges batteries first, then if solar doesn't work the brain decides whether the generator or the grid charges the batteries next... Lots of old school stuff like programmable logic controllers because the town/city didn't trust fancy modern computers. Was fun... About $12k and we get a check for about $100 every month from the PoCo.

 

[Git]

all depends on where you live, and if you have TOD (time of day) metering, and kw cost. I am in FL so cheap electric (just under $0.10 kwh delivered) no TOD and very similar in total cost per year.

Friends in CA said they pay up to mid 0.3x a kwh, but looking at so cal edisons' prices, some plans are up to $0.51 kwh. Making solar and batteries far easier to justify.

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

I am a S Cal Edison customer and just switched to a Time of Use Plan from a traditional tiered plan because they indicated it would save me money and they are guaranteeing it for the first year.

The TOU window is from 5 to 8 pm and during the summer hours, we will be paying the $.051 per kWh rate during weekdays

Still can't justify batteries - we hardly ever have a power outage and I bought a small dual fuel generator recently 'just in case'.

Our solar panels are made by LG and LG does have it's own battery system - called the LG chem RESU. I don't care who makes the battery - when you look at the specs, it is really hard to justify the price unless you have an off grid system. The LG battery for example, is warrantied for 10 years and the warranty only kicks in if the battery capacity drops below 60% (losing 39% of your storage is a lot)

 

[dcg9381]

he solar charges the batteries first then we wrote an algorithm... algo is fancy word, we wrote a small piece of code that has defined logic to decide whether to auto-start the generator or switch over to the grid. It looks at stupid stuff like what circuits are on (whether or not the oven/stove is on or if I'm welding), how close are we to the weekly generator auto-run, how close is the generator to it's maintenance schedule, etc.

That's pretty sophisticated. I understand the software development. You're controlling a 3-way ATS that does "battery", "grid", or generator?
What's the hardware for that?

What's your total amp capacity on the battery setup - how many KW can you draw peak?

 

[anythingyoucanimagine]

That's pretty sophisticated. I understand the software development. You're controlling a 3-way ATS that does "battery", "grid", or generator?
What's the hardware for that?

You forgot the panels. Think five total parts: house, batteries, panels, grid, generator. The home runs off the batteries and the only job of the ats is to select what charges the batteries. If the grid goes down at night and I'm out of diesel, we are screwed once the batteries are done.

Hardware is homebrew. Mostly allen bradley 8-pin stuff. I'd like to make it orders of magnitude smaller but that's probably a pipe dream. It's more complicated than that, we have residential 208Y.

What's your total amp capacity on the battery setup - how many KW can you draw peak?

We currently have a dynamically controlled bank of 53 12v batteries providing 48vdc. I need to get that back up to 55 batteries so the email alarms stop harassing me. (battery bank is a pain in the ***)

Peak we are probably 12-13, maybe 8-9 stored. Probably 20kwh. We got most of the batteries for "fell off the back of the truck" prices so they weren't perfect. If I spent some time optimizing the bank/array it would help a bunch but a screaming baby at 3am makes you lazy.

Most of what I have in the real hardware is allen bradley. That was all straightforward textbook stuff. The rest is all local bsd OS redundant to cloud. Also a local raspberry pi as a GUI. We use that same pi to http broadcast our bbq smoker temp controller so I can run and get more beer mid-cook.

 

[dcg9381]

> (battery bank is a pain in the ***)

Which is why I've refused to install them.

I assume your batteries are big... I like projects and your installation is probably one of the more interesting / complex that I've heard about. Massive capacity for 20kwh - you basically can match a "whole house" generator.


I'll look at allen bradley. I always wondered what hardware would support home-brew control of power systems...

Thanks for your reply.

 

[anythingyoucanimagine]

> (battery bank is a pain in the ***)

Which is why I've refused to install them.

I assume your batteries are big... I like projects and your installation is probably one of the more interesting / complex that I've heard about. Massive capacity for 20kwh - you basically can match a "whole house" generator.


I'll look at allen bradley. I always wondered what hardware would support home-brew control of power systems...

Thanks for your reply.

I know GJ is pretty good with people's privacy but I'm a little cautious posting details/public info about our setup because we have more on our roof than we are permitted for and much of the hardware we got "fell off the back of a truck" (we got hooked up from family).

Send me a PM if you want, or start a new thread if you want to talk generally. There are LOTS of people getting rid of solid state PLC's that would work. It really depends on your budget, if you have the budget and the wherewithal, you could build something very small with mosfets, breadboards and an arduino/pi combo. You can build it on a breadboard and then have a custom board made for stupid cheap these days. Or just old school it for free. If I had excess I'd give them to you. I have a TON of relays and switches but no PLC's. Look at government auctions. I'll gladly give you several milk crates full of 8-pin stuff.

Our house generator is a diesel Kohler (marine division) 19kW 3ph so yes, you are very much in the ballpark. I can weld (gtaw) and throw extension cords over the fence when the neighborhood grid is out.


In orders of magnitude, we were able to buy 85-90% good lead acid batteries for about 25% of scrap value so it is what it is. It *****, they take up space, I probably spent $400 building (fabricating/welding) a storage rack for the batteries. But they are a constant maintenance nightmare. I wish I never taught her how to write scripts or cron jobs because she now manages the batteries and rides my *** about them daily. Spend up and buy good batteries.


When we did install we applied for a permit with x number of lower wattage panels. Permit was approved then we bought higher wattage panels than we stated on the permit. Not to make money selling back to the grid, simply to never have a month when we owed. Our jurisdiction only allows 100% of average of last six months. We kept the lights on, tried to bump everything up, then installed bigger panels than stated.

Start a thread or PM me and I'm happy to talk about the controllers. It wasn't hard at all.