At what price does LFP storage make it possible to go off-grid?

[Zwy]

I just did



I think that $684/month is 11% cash flow on your net $5872 out of pocket, 6.8% on the $9472 including stimulus check (which you could have put in a frothy stock market or 0.01% passbook account.)

It should be $648/year which is 11.03%.

Put it in the stock market here and you could see it all gone a year from now.

In my case, I can fully fund my IRA's in equities/commodities and still have money left to put somewhere. Already have the toys (too many in fact) and need somewhere to go with it, inflation will eat it away.

If it lasts for ever, that cash flow percentage is as good as an interest rate.
If the system gets torn off your roof in a hurricane one year later, you're out 89% to 93% of your investment.

PV was the cheap part. My system is covered under my homeowner's policy, I'll get a new PV array if a tornado comes by and takes it out. No hurricanes here.

Unlike say a T-bill, you don't get principal returned in the end. So not all of that cash flow is same as interest. Over 20 years, you'll get 220% on out-of-pocket or 137% on the cash you could have had. You get the cash back plus 37% returned, 1.84% per year. Probably about what some interest bearing investments offer? Or maybe not right now. At times in the past decade I've received 2% +/- on 5 year CDs, but they're probably 1% today.

Let's say with batteries and a complete system payback is 10 years.

I think the return long term is much better that 2%, if that was all it returned, you can't get payback in 10 years. Rule of 72 applies, money doubling in 10 years is 7.2%, not counting inflation. That means at 20 years, you not only got your money all back but doubled the initial investment. That's 3.6%, not counting inflation and you still have a system that produces.

Your panels should last 25, maybe 40 years. Inverters may need replacing at some point.

< 2% doesn't seem impressive; somebody please double-check my initial check of 'Tinker's math.

I just did. Rule of 72.

The return after 30 years operation with one inverter replacement probably looks much better.

At your 2% return, it takes 36 years........

72 rule you know.

 

[Zwy]

When you get a cost of living raise it can put you into an even higher tax bracket, so the raise ends up being taxed at a higher rate and the taxman gets a raise too.

They screw you on COLA, the increase is never near the amount of true inflation. That's why in the 80's and 90's they changed the CPI calculation. Otherwise, the government would have been in bankrupt then instead of now......

 

[Hedges]

The total energy a battery is capable of cycling though, and what you actually end up cycling through it are two completely different things.

Back to my question above, how much energy will actually be cycled through the battery over a given period of time?

Agreed, which is why I analyzed cost assuming a Lithium battery sized for 80% to 100% DoD supplying power used during 4:00 PM to 9:00 PM peak rate time.
It would operate to low voltage disconnect each day, and might give 10 years cycle life.
That is only applicable to peak shaving on-grid; you need more capacity for off-grid (unless you can manage loads according to available PV and SoC.)

My AGM would only reach $0.50/kWh if cycled ~ 70% DoD ~ 700 times within decade float life. Because only for occasional power failures, likely to cost me $2.50/kWh or more.
But not all my power goes through the batteries. They would cycle to 70% DoD overnight, recharge at 0.2C during the day while PV powers appliances including A/C and surplus generation is discarded. With PV costing $0.025/kWh over 20 years, cheaper to throw away unused power than to store it in a battery.
The battery is primarily to light up my island grid so GT PV can run the house during grid outages.

 

[Zwy]

I'll give some figures. 32 280Ah cells from Amy. $140 ea x 32 = $4480 shipped. Batrium was CORE and 2 K9's, $1267 shipped. ABB breaker $150. Cabinet for batteries, $200. A few hundred for breakers, cable, cable ends. $35 for 48V to 24V transformer on shunt trip. $6132 total

Figure it out for 3000 and 6000 cycles, per Kw.

 

[upnorthandpersonal]

OK, that's one way to calculate it.

My question though is how much energy will actually be cycled through the battery? Because it is the actual total energy throughput which matters, not the battery's capacity.

Yeah, this depends a lot on how people are set up, and it's a lot harder to calculate since there are so many variables. For example, in winter I cycle from full to empty and back every week. In summer it's cycled much less, but once I have an EV (eventually) it goes up - do we count transport related costs in context of the original question? I'm paying 2€/Litre for gasoline here.

 

[Ozark Tinkering]

It should be $648/year which is 11.03%.

Put it in the stock market here and you could see it all gone a year from now.

In my case, I can fully fund my IRA's in equities/commodities and still have money left to put somewhere. Already have the toys (too many in fact) and need somewhere to go with it, inflation will eat it away.


PV was the cheap part. My system is covered under my homeowner's policy, I'll get a new PV array if a tornado comes by and takes it out. No hurricanes here.



Let's say with batteries and a complete system payback is 10 years.

I think the return long term is much better that 2%, if that was all it returned, you can't get payback in 10 years. Rule of 72 applies, money doubling in 10 years is 7.2%, not counting inflation. That means at 20 years, you not only got your money all back but doubled the initial investment. That's 3.6%, not counting inflation and you still have a system that produces.




I just did. Rule of 72.



At your 2% return, it takes 36 years........

72 rule you know.

I don't know anything about rule 72...0r 73 for that matter but going forward I do expect my production to exceed the 1st year and dividends to go up, since in part way into the year I had those trees removed giving me a perfect hump on my graph on a sunny day. In the beginning there was a big hunk taken out just past peak production.

 

[Zwy]

The Rule of 72: Definition, Usefulness, and How to Use It

The Rule of 72 is a shortcut or rule of thumb used to estimate the number of years required to double your money at a given annual rate of return and vice versa.

www.investopedia.com

Calculator: https://www.calculatorsoup.com/calculators/financial/rule-of-72-calculator.php

 

[Hedges]

It should be $648/year which is 11.03%.

Dyslexia strikes again.

I just did. Rule of 72.



At your 2% return, it takes 36 years........

72 rule you know.

If I'm not mistaken, Rule of 72 determines how long before compound interest equals principal, doubling your investment.
(harvesting income in the mean time by diverting cashflow probably doesn't invalidate the analysis.)
But, if I'm not mistaken it assumes "return OF my money". That is what we hope for when buying bonds or whatever, but know we won't get when buying PV.
So seems to me Rule of 72 for PV only says when I see return of principal.

Am I correct? If so, please use your eraser and sharpen your pencil.

Rule of 72 - Wikipedia

en.wikipedia.org

 

[Ozark Tinkering]

The Rule of 72: Definition, Usefulness, and How to Use It

The Rule of 72 is a shortcut or rule of thumb used to estimate the number of years required to double your money at a given annual rate of return and vice versa.

www.investopedia.com

Calculator: https://www.calculatorsoup.com/calculators/financial/rule-of-72-calculator.php

Whew! I was afraid I was missing an important off-grid battery term.

Dad just taught that as "The Magic of Compounding". when BofA actually paid kids interest on their savings account.

 

[DaGoose13]

Lithium-titanate battery - Wikipedia https://en.wikipedia.org/wiki/Lithium-titanate_battery​

The calculations after the OP generally use 3 days autonomy and a generator. So, four is three?


Never say never is also an old mantra.


The value of backup is different for everyone, so it wasn't included in the calculations as to what the ESS price point was to where it made more sense to be off-grid than on-grid.

It's more the thought if the solar power system goes down, then you don't have anything. Whereas if you kept the grid tie, you might still have power.

 

[MrM1]

Man that's a lot of words in this thread today. My head hurts.

 

[Zwy]

Dyslexia strikes again.




If I'm not mistaken, Rule of 72 determines how long before compound interest equals principal, doubling your investment.

Rule of 72 applies also to income and the compound interest on that principal. After 10 years, I'll still have PV and batteries and the income that would normally have been paid to the power company.

It's no different than purchasing a piece of property and making improvements on it such as my shop building. Is the property worth more when I'm done? Of course it is. Solar systems are the same way.

It seems you think after 10 years the solar system is worth nothing, not even salvage which isn't true. As long as it can produce income or reduce expenditures, it still holds value.

(harvesting income in the mean time by diverting cashflow probably doesn't invalidate the analysis.)

I look at it this way, my money is earning something daily and 24 hours a day while I sleep. In other words, I don't have to work for it.

Otherwise, it's just cash buried in jar in my backyard or under my mattress with less end value everyday due to inflation. I don't have any other investments I currently am interested in other than some commercial property I will expand on but not at the current prices for materials to do it.

But, if I'm not mistaken it assumes "return OF my money". That is what we hope for when buying bonds or whatever, but know we won't get when buying PV.

I have news for you, you may never see the return of principal with some investments. You could buy real estate today and watch as the value drops when it is discovered to have Chinese drywall or built on a nuclear dump site.

If you think you can't lose with bonds or even money market, then I have a bridge to sell you. I had money in a money market back in 2008, way more than what my system cost me today. Government locked it up and devalued the principal. Eventually, the government made it whole, but I also lost use of that money for about a year plus no interest. Don't think it won't happen again. Many forget or are unaware of the 1994 Bond Crisis either. Good luck in this market with rising inflation and stagflation on it's way when it comes to bonds.

So seems to me Rule of 72 for PV only says when I see return of principal.

What is payback? Return of the principal. After that, it is interest on the investment.

Am I correct? If so, please use your eraser and sharpen your pencil.

Rule of 72 - Wikipedia

en.wikipedia.org

You come from a different background than what I do, I've been thru the 80's and as I live in the Midwest, saw the Farm Crisis then. Saw land sell for $800/acre then, now it sells for $14K/acre. Went thru a pretty big depression in flyover country but gov won't admit it. I've seen high inflation, I've seen the Dot Com bust, I've been thru the GFC. I paid more in interest in the early 90's than I earned in a year, I had money in equities and investments since the early 90's. Biggest joke I ever saw were banks telling people to borrow against the equity in their homes and invest in equities because real estate will never go down, and the market always goes up too.

I'll take risk for a decent return. I also know when things don't look good because of past experience. I'll invest mine where I know I'll still have something in the end.

And yes, Rule of 72 applies.

 

[eXodus]

Germany?

Yep, Natural gas only doubled

Agree, I didn't put much weight on the payback from savings when I purchased my system.
It's priceless when the grid is down, and America is very vulnerable to an attack on the grid.

I'm environmental minded, so I usually plow forward with those kind of ideas (Solar Thermal in 2000, Build a Electric car in 2008, Solar PV in 2011, EV Scooter in 2012) and ten years later the market proofed that I'm just a early adopter, and so far I always got a great return on my invest on all of those Ideas. Where everybody told me at that time that's a bad deal.

When you get a cost of living raise it can put you into an even higher tax bracket, so the raise ends up being taxed at a higher rate and the taxman gets a raise too.

not paying money on a service like energy is cheaper then getting a raise on your job.

 

[Zwy]

Whew! I was afraid I was missing an important off-grid battery term.

Dad just taught that as "The Magic of Compounding". when BofA actually paid kids interest on their savings account.

It still applies. I've run a business for 35 years as of Jan 1st. Everything is figured up/down sideways and what interest would cost if I was to borrow or earn on anything.

My father taught me all about such things early in life, he needed to know it in order to survive farming. He did learn it well I must say.

Some look at battery systems as an unnecessary expense as they grid tie and net meter. The problem is, the rules keep changing to keep the jingle in the pockets of power companies. When I saw the generating coal plants in this area shut down, I could see rates rising and they certainly are.

 

[Hedges]

not paying money on a service like energy is cheaper then getting a raise on your job.

Until somebody figure out how to tax photons.
I take it you don't live in California?

 

[eXodus]

ome look at battery systems as an unnecessary expense as they grid tie and net meter. The problem is, the rules keep changing to keep the jingle in the pockets of power companies. When I saw the generating coal plants in this area shut down, I could see rates rising and they certainly are.

At this point an Off-grid system is cheaper then going through the permit and engineering headache of a On-Grid System. (Future money + Risk)

Keep the Grid as backup so that you don't need a battery for 5+days.

Until somebody figure out how to tax photons.
I take it you don't live in California?

No, I don't, I want to go on Vacation there in the Nature at some day.

Photons are still free here.

But I'm still trying to diversify my energy portfolio. Currently:
Solar + small Battery, Natural Gas Furnace, Gasoline Generator.

Want to add a Biogas Digester, Large batteries, and a Heatpump. So I would be able to shift my usage around to whatever energy source is the most efficient / cheapest.

 

[Ozark Tinkering]

Otherwise, it's just cash buried in jar in my backyard or under my mattress with less end value everyday due to inflation. I don't have any other investments I currently am interested in other than some commercial property I will expand on but not at the current prices for materials to do it.

A fella told me last year when I was having my system installed that he preferred to keep his xtra money in the form of silver bullion in his safe because the dollar was worth-less everyday. I told him if he'd go grid-tie solar he could store his silver on the roof where it would actually do something instead of just take up space in an expensive safe. Since then silver has gone down by about $3 oz.

 

[Hedges]

A way to store summer photons for winter combustion would be useful.
Biofuels are one way. Your biogas could be good. Maybe biodiesel. Firewood is basic.
But if hydrolysis and hydrogenation let spare photons boost energy content of biodiesel (not to the point of "grease car" which apparently cokes up the engine), that could add to the mix.

 

[eXodus]

A way to store summer photons for winter combustion would be useful.
Biofuels are one way. Your biogas could be good. Maybe biodiesel. Firewood is basic.
But if hydrolysis and hydrogenation let spare photons boost energy content of biodiesel (not to the point of "grease car" which apparently cokes up the engine), that could add to the mix.

Lol, I actually got a Vegetable Oil Burning Diesel in my Garage. A good old Volvo 850 TDI.

Converted in 2004 - still going strong. You need to preheat the Grease and adjust engine timing to very early, otherwise you get unburned fuel on your exhaust valves until they don't close anymore. Drove about 200.000 km without paying for fuel by picking up frying oil from restaurants in my youth. Now I mostly drive diesel and store bought oil because of the mess the filtering of WVO (Waste veggie oil) makes behind the house.

Biodiesel is hydrophilic toxic waste destroys every seal in a engine which can be stored maybe for a 2-3 months. Veggie Oil can be stored for almost indefinite. I've bought 10 year expired oil by the IBC Container Pallet. No issues whatsoever.

 

[Ozark Tinkering]

It still applies. I've run a business for 35 years as of Jan 1st. Everything is figured up/down sideways and what interest would cost if I was to borrow or earn on anything.

My father taught me all about such things early in life, he needed to know it in order to survive farming. He did learn it well I must say.

Some look at battery systems as an unnecessary expense as they grid tie and net meter. The problem is, the rules keep changing to keep the jingle in the pockets of power companies. When I saw the generating coal plants in this area shut down, I could see rates rising and they certainly are.

Dad was no a farmer. He left grandpa's farm at 15 and headed for California by way of Yakima Wa. and a season of picking apples, where young businessmen could thrive! Eventually made his way to Berkley for a business degree. Arkie done good. There he became a financial planner and the magic of compound interest became part of his religion.
Never really had much interest in a suit and tie so I became an electrician instead.

So far here in Entergy country the rates have held pretty steady until now, but I will be surprised if they don't start going up soon. It seems like I saw they have ask for a 4% increase over the next couple of years but I'm not sure about that. Natural gas is up something like 45% here this year. My response to that will be to increase the size of my system. It'll only pay for itself quicker.