Looking for Advice on Battery System for off peak savings and outage backup

[schillit]

Hi all - First post here, lots of great info hoping to get some opinions on what I want to build:

Looking to implement a battery solution that utilizes off peak time (10pm-630am) to charge the batteries, then flip to use the batteries to power multiple circuits during the day until the batteries are drained. I do not expect to have a rapid ROI on this, but I will save approximately .11 cents per hour on the difference between peak and offpeak (Currently using about 20,000 kWh per year. The other benefit to me is to have a backup in place for when the power goes out which seems to happen 10-15 times a year. Approximate usage is 50-60kwh per day, but expect that to increase over time as I swap out a few gas appliances for electric (Pool heater, Water heater, dryer, etc..) over time. I don’t need all the circuits to accept the battery power, but ideally would like 12-15 that could. This would be installed indoors in my mechanical room right next to the existing panel but will need to be connected to the off-peak meter that my utility will install.

Have gotten multiple quotes on the Tesla Powerwall 3 system for 1 battery for 20k with installation which just seems ridiculous to me. Have looked at Ecoflow Pro Ultra’s as well which might be an option, also looking at EG4 bundles such as 6000XP or 12KPV. The EG4 seems like the best value and most versatile option to me, but unsure of the complexities of the installation. Would consider the Sol-Ark system as well, but a little harder to find details on that.

Hardest part so far is trying to find local installers (Minneapolis/St Paul area) that have experience with this setup. Most want to push the Tesla Powerwall system in my area.

Would be nice to have the option in the future to have solar inputs, but not required. I also do not need/want to feedback to the grid, but I do want it to work when there is a power outage seamlessly.

Any suggestions on the products I am looking or should be looking at for this type of scenario? Again, not looking to make money here, just offset my costs a bit with off-peak and provide a reliable backup solution that someday in the future could accept solar.

 

[zanydroid]

SolArk’s documentation is comparable to EG4. 12kpv and 18kpv

Delta Flows have traditionally not been code compliant to install for ESS due to lack of listing / lack of the correct listing. 6000XP is not code compliant in my jurisdiction but should be fine for many. Check the version of state/local Residential Code, since that governs the tier of ESS regulation you are under

Really hard to avoid 50-100% markup with turnkey installs. America has a lot of subsidies and a lot of tolerance to cost increases, that combine to magnify prices for solar and ESS. Rarely will there be a local installer that will compete on price. And in my experience, average price installers are already not competent in the U.S., why would you cut money and get even more skill/knowledge risk. Above average price corresponds to a reasonable competence here in the SF area. Average competence and below required micromanaging my first turnkey install so much I just ended up DIYing my second one bc it wasn’t that much more annoying

ESS are all at ground level and only require lifting one (extremely) heavy component to the wall instead of 20-30 panels. So the way to truly save money is to outsource the plans drafting (common service, competitively priced, you can get them for any system), slog through permitting, and self install.

 

[Drunkin Solar]

Your most cost efficient solution for battery storage is DIY batteries built from individually purchasing cells and BMS then assembling them yourself.
It takes moderate mechanical and electrical skills to do but the payoff is huge and very satisfying. You can extend your storage capacity as desired as you go along if expansion is needed later.

I have recently purchased Seplos Mason kits and my own cells and then assembled them. The system I put together runs flawlessly with plenty of storage on the cheap. Something to consider.

 

[zanydroid]

Purchasing cells requires a ton more research (and the reseller side is something that had to be done from scratch due to how variable the market is) than I’m willing to consider personally, and there is a significantly bigger risk of problem from skill issue and more things to go wrong.

IMO the 75% savings of going with a UL1741 off grid inverter, self installed battery — vs that $20K UL9540 turnkey — is already pretty damn good. No need to go to 87.5% savings with the DIY approach.

Granted I do have my bias towards grid tie hybrid which is prohibited from using DIY battery in my jurisdiction

 

[Supervstech]

You have a pool heater you expect to swap for electric?

How big a pool? How often is it heated?
Average 250kbtu pool heater would require 74kW elements... or about 308A...
A heat pump pool heater could shave down the amps... 1/3 or so... still a ton of power to heat a hole in the ground full of water.

 

[wpns]

Welcome!

Yeah, DIY definitely the way to go, lots of helpful folks here. A couple of random comments:

I really like the EG4 ESS (18Kpv with PowerPro WallMount batteries), and the new inverters and GridBoss might be the answer to all our prayers (ask me next year, when the pioneers have some experience with them).

However, even if you time-shift all your power consumption, you aren't going to make the delta between on-peak and off-peak, as you would have spent off-peak money to cover your night-time needs. And if only half of your consumption is daytime, then you are only going to save 11 cents on 10,000 KWHR, and the PowerPro batteries have a lifetime cost of around 4 cents per KWHR, if that helps.

If you don't have a good idea of how your load looks, get an Emporia Vue and run it for a while (up to a year) to get daily power (KW) and energy (KWHR) numbers so you can size your system appropriately.

Yeah, Tesla PowerWall systems are the Cadillac, and priced appropriately. You can DIY for about 25% of that.

 

[DIYrich]

any electrician should be able to:
1) install 2nd 100a service panel with isolation device between main breaker and top right breaker
2) connect 100a power from main panel to 2nd service panel
3) connect 100a top right breaker to load output of inverter
4) connect 100a from main panel to grid input of inverter
5) move loads from main panel to 2nd panel

You can attach batteties to inverter yourself.

Suggest EG4 12000xp when it comes out, and connect 3 powerpro batteries.

The isolation on the 2nd panel, and breaker on main panel to inverter will allow you to take the inverter out of the circuit if necessary.

If you can't find an electrician (look at eg4 website for installer?) Then go to Sol-arks website and look for an installer. In that instance you will want the 15k, but it will cost more.

 

[GXMnow]

I did my system with a Schneider inverter, but it was not straight forward. While I made it work great, it is hard to recommend.

My brother is looking to add an ESS to his system and it looks like the EG4 8K-PV or 12K-PV is the cost effective option right now.

Pre built 48 volt batteries run about $250 per KWH of storage, give or take. They are getting competitive. I am a bit torn with the planning for my brother's system. I did a DIY using Li NMC EV battery modules. My cost per KWH came out to only $130 per KWH, or about half the price of server rack batteries. The 280 amp hour wall mount units are a little cheaper than the rack mount ones, but you go from 300 AH with 3 100 amp BMS units to a single 200 amp BMS unit. I like the redundancy of having at least two batteries with their own BMS. I originally had a single battery unit and when the BMS had an issue, the whole system shut down. Now I have 2 battery modules and I can take either one off line if needed. And if one fails, the other keeps working.

Plan out how many kilowatt hours you really need to store and get twice as much battery capacity. That way you can cycle from 80% to 30% all the time and have reserve for a power failure. I started with 18 KWHs and double it to 36 KWHs, I cycle 10 to 12 KWHs each day.

If you go with an "All in One" like the EG4 8, 12, or 18K-PV then you will have 2 or 3 MPPT controllers. No rush, but even adding just a couple hundred watts of solar panel can make a big difference. Especially if there is a grid outage. With no solar panels, you just have what is in the battery once. With solar panels, even just 400 watts can give you over a KWH every day while the grid is down. Much more on a clear sunny day, maybe less if it's bad weather. I added 2,000 watts of Dc connected panels to just hlp charge the batteries. In October, they still make over 6 KWHs a day, but I am in So Cal.

 

[schillit]

You have a pool heater you expect to swap for electric?

How big a pool? How often is it heated?
Average 250kbtu pool heater would require 74kW elements... or about 308A...
A heat pump pool heater could shave down the amps... 1/3 or so... still a ton of power to heat a hole in the ground full of water.

Yes, it would be a heat pump setup.

 

[45North]

I've never understood why people would invest $$ thousands of their own money and take on operation of a mini power system to arbitrage a few cents of savings on their power bill.
A hobby, I guess.

 

[wpns]

I've never understood why people would invest $$ thousands of their own money and take on operation of a mini power system to arbitrage a few cents of savings on their power bill.
A hobby, I guess.

There are certain limited circumstances in which it can work, but then if you add in things like the time value of money, it gets less useful. In addition, putting a lot of capital into something with a multi year payback when the power company could potentially Nerf the deal doesn’t make a lot of sense. Plus, if it is a hobby, you’ll want to add more batteries to deal with blackouts and then more panels to charge your batteries, and then dump loads to get rid of your excess power, rinse, lather, repeat.

 

[schillit]

I've never understood why people would invest $$ thousands of their own money and take on operation of a mini power system to arbitrage a few cents of savings on their power bill.
A hobby, I guess.

Agreed. That's why I stated the primary goal is for backup.

 

[wpns]

Agreed. That's why I stated the primary goal is for backup.

Your original post did not make that very clear.

In that case, get an Emporia Vue or equivalent to do an energy/power survey and check out the EG4 ESS offerings. There are some new products coming around the end of the year, which could be very exciting, so I wouldn’t pull the trigger immediately. If you are able to wait for the Pioneers to check out the new stuff.

 

[schillit]

I did my system with a Schneider inverter, but it was not straight forward. While I made it work great, it is hard to recommend.

My brother is looking to add an ESS to his system and it looks like the EG4 8K-PV or 12K-PV is the cost effective option right now.

Pre built 48 volt batteries run about $250 per KWH of storage, give or take. They are getting competitive. I am a bit torn with the planning for my brother's system. I did a DIY using Li NMC EV battery modules. My cost per KWH came out to only $130 per KWH, or about half the price of server rack batteries. The 280 amp hour wall mount units are a little cheaper than the rack mount ones, but you go from 300 AH with 3 100 amp BMS units to a single 200 amp BMS unit. I like the redundancy of having at least two batteries with their own BMS. I originally had a single battery unit and when the BMS had an issue, the whole system shut down. Now I have 2 battery modules and I can take either one off line if needed. And if one fails, the other keeps working.

Plan out how many kilowatt hours you really need to store and get twice as much battery capacity. That way you can cycle from 80% to 30% all the time and have reserve for a power failure. I started with 18 KWHs and double it to 36 KWHs, I cycle 10 to 12 KWHs each day.

If you go with an "All in One" like the EG4 8, 12, or 18K-PV then you will have 2 or 3 MPPT controllers. No rush, but even adding just a couple hundred watts of solar panel can make a big difference. Especially if there is a grid outage. With no solar panels, you just have what is in the battery once. With solar panels, even just 400 watts can give you over a KWH every day while the grid is down. Much more on a clear sunny day, maybe less if it's bad weather. I added 2,000 watts of Dc connected panels to just hlp charge the batteries. In October, they still make over 6 KWHs a day, but I am in So Cal.

Solar is definitely an option in the future, but with roof that is 20-25 years old it does not make sense at this time unless I was to ground mount them, which I don't have a great option there given the inverter is going in the basement, it would be a long run to where I can ground mount them.

I think the 2 battery option as you stated is the way to go as it gives you better options in case of failure. In terms of output, in Minnesota I am not overly concerned on having the highest output there is, as quite simply the air conditioning I am not going to run during a power outage, and I don't run it that often to begin with. I don't think I would even include it on my circuit if I had to choose. 2 Refrigerators, deep freezer, some lights, Internet equipment, water heaters (gas), furnace (gas), pool pump, and an induction cooktop. I don't need the whole house to be on standby at any point I guess is my point.

 

[schillit]

Welcome!

Yeah, DIY definitely the way to go, lots of helpful folks here. A couple of random comments:

I really like the EG4 ESS (18Kpv with PowerPro WallMount batteries), and the new inverters and GridBoss might be the answer to all our prayers (ask me next year, when the pioneers have some experience with them).

However, even if you time-shift all your power consumption, you aren't going to make the delta between on-peak and off-peak, as you would have spent off-peak money to cover your night-time needs. And if only half of your consumption is daytime, then you are only going to save 11 cents on 10,000 KWHR, and the PowerPro batteries have a lifetime cost of around 4 cents per KWHR, if that helps.

If you don't have a good idea of how your load looks, get an Emporia Vue and run it for a while (up to a year) to get daily power (KW) and energy (KWHR) numbers so you can size your system appropriately.

Yeah, Tesla PowerWall systems are the Cadillac, and priced appropriately. You can DIY for about 25% of that.

I probably should have stated that even at some point if I were to go solar, I would not install more than maximum of 12-15 panels, so I am not worried about buying a smaller rating on the Kpv side if I can save money on the inverter.

Definitely will wait based on this GridBoss announcement and more details to come out.

One question I have with my assumptions on charging between 10pm and 630am...would I even have enough time to charge 2 batteries nightly if I ONLY charge during this time? If not, then it probably makes sense to just get the 1 battery system until I can get the solar hooked up.

I am trying to figure out what the difference is between the PowerPro Wall Mount System and the 12k system (besides the obvious). Outside of the output and Kpv ratings, what else am I missing that the Powerpro has? Keep in mind this system will be all indoors, so don't need the all weather ratings. Seems to be for 2 batteries, about a $2000 difference so just trying to understand what the difference/s are.

EG4 PowerPro ESS | 14.3 - 28.6kWh Capacity | EG4-18Kpv & EG4-PowerPro WallMount Battery | UL9540

EG4 PowerPro Energy Storage System: UL9540 Certified, 14.3 - 28.6kWh capacity, includes EG4-18Kpv and WallMount Battery for reliable solar energy storage.

signaturesolar.com

EG4 12kPV Hybrid Inverter | 48V | 12000W Input | 8000W Output | 120/240V Split Phase + EG4-WallMount Indoor Battery 280AH | 51.2V | 14.3kWh [BNDL-E0012]

EG4 12kPV Hybrid Inverter | 48V | 12000W Input | 8000W Output | 120/240V Split Phase + EG4-WallMount Indoor Battery 280AH | 51.2V | 14.3kWh [BNDL-E0012]

signaturesolar.com

 

[Sanwizard]

Hi all - First post here, lots of great info hoping to get some opinions on what I want to build:

Looking to implement a battery solution that utilizes off peak time (10pm-630am) to charge the batteries, then flip to use the batteries to power multiple circuits during the day until the batteries are drained. I do not expect to have a rapid ROI on this, but I will save approximately .11 cents per hour on the difference between peak and offpeak (Currently using about 20,000 kWh per year. The other benefit to me is to have a backup in place for when the power goes out which seems to happen 10-15 times a year. Approximate usage is 50-60kwh per day, but expect that to increase over time as I swap out a few gas appliances for electric (Pool heater, Water heater, dryer, etc..) over time. I don’t need all the circuits to accept the battery power, but ideally would like 12-15 that could. This would be installed indoors in my mechanical room right next to the existing panel but will need to be connected to the off-peak meter that my utility will install.

Have gotten multiple quotes on the Tesla Powerwall 3 system for 1 battery for 20k with installation which just seems ridiculous to me. Have looked at Ecoflow Pro Ultra’s as well which might be an option, also looking at EG4 bundles such as 6000XP or 12KPV. The EG4 seems like the best value and most versatile option to me, but unsure of the complexities of the installation. Would consider the Sol-Ark system as well, but a little harder to find details on that.

Hardest part so far is trying to find local installers (Minneapolis/St Paul area) that have experience with this setup. Most want to push the Tesla Powerwall system in my area.

Would be nice to have the option in the future to have solar inputs, but not required. I also do not need/want to feedback to the grid, but I do want it to work when there is a power outage seamlessly.

Any suggestions on the products I am looking or should be looking at for this type of scenario? Again, not looking to make money here, just offset my costs a bit with off-peak and provide a reliable backup solution that someday in the future could accept solar.

If you just want battery backup, and are not installing panels at this time, then use a local competent electrician to install batteries and inverter, or just buy a generator. SMA makes some good products, including batteries now I believe.
Your use case is the exact reverse of mine. I use solar during the day to run the house ans charge the batteries, and then use the batteries at night. The Grid is my backup, and used during cloudy times.

 

[wpns]

I probably should have stated that even at some point if I were to go solar, I would not install more than maximum of 12-15 panels, so I am not worried about buying a smaller rating on the Kpv side if I can save money on the inverter.

"I'm so glad I didn't get the bigger inverter". No-one ever. 8*)

Seriously, you can get the smaller one and upgrade later if you decide you need to. Or wait for the new inverter and GridBoss.

One question I have with my assumptions on charging between 10pm and 630am...would I even have enough time to charge 2 batteries nightly if I ONLY charge during this time? If not, then it probably makes sense to just get the 1 battery system until I can get the solar hooked up.

You've got 560AH of battery, and 200A (167A with the 12Kpv) of charge current, I think you'll get them charged and balanced every day without a problem. If you get more than <lessee> five batteries with the smaller inverter it'll be tight, but do-able. {Long digression into bigger inverter, new inverter, ChargeVerter, etc. Is there a common acronym for "Too Long: Didn't Write"? }

I am trying to figure out what the difference is between the PowerPro Wall Mount System and the 12k system (besides the obvious). Outside of the output and Kpv ratings, what else am I missing that the Powerpro has? Keep in mind this system will be all indoors, so don't need the all weather ratings. Seems to be for 2 batteries, about a $2000 difference so just trying to understand what the difference/s are.

That's pretty much it, the batteries are essentially identical, but the indoor ones are less expensive. The 12Kpv inverter is lower power and less expensive, but the new inverter and GridBoss are AFAICT even less expensive.

BTW: Each of the batteries can generate about 10KW of DC, so you'll need at least two of them to drive the 18Kpv to its full 12KW output. One should be fine for the 12Kpv, but 14KWHR of battery won't run very long if your load is significant. I guess it depends what your maximum power outage time will be...

 

[GXMnow]

Each day, you only need to charge back in the amount you discharged out. I have 36 KWHs of battery, but typically cycle less than 15 KWHs each day. The short cycles extend the battery life, and when the grid does go down, you can run twice as long. If it takes 2 days to charge up when the grid comes back, it's not a big deal.

 

[Hedges]

I do not expect to have a rapid ROI on this, but I will save approximately .11 cents per hour on the difference between peak and offpeak (Currently using about 20,000 kWh per year.

An EG4 PowerPro or the Midnight battery will amortize out to $0.05/kWh over its lifetime. Maybe 16 year of daily cycling.
"Amortize" meaning ignore interest, time value of money. Maybe $0.10/kWh with that factored it.

DIY about 1/3 that price.

Then you need an inverter as well, increasing cost.

The other benefit to me is to have a backup in place for when the power goes out which seems to happen 10-15 times a year.

This can be worthwhile, judiciously sized, with some PV. PV panels are a fraction the cost of batteries.

Approximate usage is 50-60kwh per day

About 4x Power Pro, so the cost of 18kPV only adds maybe $0.03/kWh to the cost. Call it $0.13/kWh. Excluding all material and labor costs outside of those two major components.

Hardest part so far is trying to find local installers (Minneapolis/St Paul area) that have experience with this setup. Most want to push the Tesla Powerwall system in my area.

Don't count on finding anyone who will install your hardware. Companies will sell and install.

I don't know the cost for turnkey battery/inverter systems. PV/inverter cost 3x what hardware does. Applying that the total would be $0.40/kWh

Would be nice to have the option in the future to have solar inputs, but not required. I also do not need/want to feedback to the grid, but I do want it to work when there is a power outage seamlessly.

If your spread is $0.11, what is the total price?

Turnkey PV should cost you $0.10/kWh (amortized over 20 years) or $0.025/kWh DIY.

With PV during the day, battery doesn't need to be as big. Close to zero battery required if most loads are A/C.

 

[wpns]

An EG4 PowerPro or the Midnight battery will amortize out to $0.05/kWh over its lifetime. Maybe 16 year of daily cycling.
"Amortize" meaning ignore interest, time value of money. Maybe $0.10/kWh with that factored it.

DIY about 1/3 that price.

Then you need an inverter as well, increasing cost.



This can be worthwhile, judiciously sized, with some PV. PV panels are a fraction the cost of batteries.



About 4x Power Pro, so the cost of 18kPV only adds maybe $0.03/kWh to the cost. Call it $0.13/kWh. Excluding all material and labor costs outside of those two major components.



Don't count on finding anyone who will install your hardware. Companies will sell and install.

I don't know the cost for turnkey battery/inverter systems. PV/inverter cost 3x what hardware does. Applying that the total would be $0.40/kWh



If your spread is $0.11, what is the total price?

Turnkey PV should cost you $0.10/kWh (amortized over 20 years) or $0.025/kWh DIY.

With PV during the day, battery doesn't need to be as big. Close to zero battery required if most loads are A/C.

Also, as above, you don't save the delta between on-peak and off-peak on the power that you would have used off-peak anyway.

 

[schillit]

Also, as above, you don't save the delta between on-peak and off-peak on the power that you would have used off-peak anyway.

Not sure I understand that? How would I have used off peak anyway?

 

[schillit]

"I'm so glad I didn't get the bigger inverter". No-one ever. 8*)

Seriously, you can get the smaller one and upgrade later if you decide you need to. Or wait for the new inverter and GridBoss.

You've got 560AH of battery, and 200A (167A with the 12Kpv) of charge current, I think you'll get them charged and balanced every day without a problem. If you get more than <lessee> five batteries with the smaller inverter it'll be tight, but do-able. {Long digression into bigger inverter, new inverter, ChargeVerter, etc. Is there a common acronym for "Too Long: Didn't Write"? }

That's pretty much it, the batteries are essentially identical, but the indoor ones are less expensive. The 12Kpv inverter is lower power and less expensive, but the new inverter and GridBoss are AFAICT even less expensive.

BTW: Each of the batteries can generate about 10KW of DC, so you'll need at least two of them to drive the 18Kpv to its full 12KW output. One should be fine for the 12Kpv, but 14KWHR of battery won't run very long if your load is significant. I guess it depends what your maximum power outage time will be...

All good points. What I really like about the EG4 option/s is that it's very modular, and relatively easy to swap out should I get into this in a few years and realized I undersized it.

 

[schillit]

Each day, you only need to charge back in the amount you discharged out. I have 36 KWHs of battery, but typically cycle less than 15 KWHs each day. The short cycles extend the battery life, and when the grid does go down, you can run twice as long. If it takes 2 days to charge up when the grid comes back, it's not a big deal.

Yeah, that's a good point.

 

[wpns]

All good points. What I really like about the EG4 option/s is that it's very modular, and relatively easy to swap out should I get into this in a few years and realized I undersized it.

Indeed, I could add a pair to mine within about an hour of them arriving (plus or minus firmware updates and voltage equalization). Slide them into place, connect the parallel data cable from the last battery in the string, set the Battery ID to the next number, connect the DC parallel cables, turn on the BMS, flip the breaker, and Bob's Your Uncle!
The _next_ pair would be a tight fit, so I might have to put them on the other side of the wall, so cut a 2" sleeve into the wall, etc, but that's not anytime soon. #I'llBurnThatBridgeWhenIComeToIt.

 

[zanydroid]

Indeed, I could add a pair to mine within about an hour of them arriving (plus or minus firmware updates and voltage equalization). Slide them into place, connect the parallel data cable from the last battery in the string, set the Battery ID to the next number, connect the DC parallel cables, turn on the BMS, flip the breaker, and Bob's Your Uncle!
The _next_ pair would be a tight fit, so I might have to put them on the other side of the wall, so cut a 2" sleeve into the wall, etc, but that's not anytime soon. #I'llBurnThatBridgeWhenIComeToIt.

What about cross battery balance if the pack voltage are too far apart? That could be a high charge current, causing the new battery BMS to repeatedly cut out charging path