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

[Zwy]

I went thru my monitor and added up 18 hours from 3 pm til 10 am. Results were interesting, 11.35 Kwh. I also see the lowest complete 24 hour period was 9 Kwh. It's been cold here, below 0F everynight so that does play into the usage overnight. Average usage is 17.7 Kwh per day.

 

[Ozark Tinkering]

When you can purchase panels at @ less than $0.25 watt it's real hard NOT to look at spending more on batteries.

There is a bit of back-end cost on used panels, though.
That said if I was looking to installing a 5- or 10KWh system I’d probably buy used, and a third or half more than I needed!

What sort of back-end costs are we talking about before I place an order?

I think PV panels can give 25, even 30 or more years of service, amortized cost over life $0.01/kWh (not including SCC, inverter, mounts.)
DIY LiFePO4 might cost $0.05/kWh over anticipated cycle life.

The position that I am beginning to arrive at is that morally and ethically, we if we don't use these to their last good watt then we have no chance of affecting our climate in a positive way. At what point is a solar panel no longer worth the space it takes up? When it hits 80%, 70%, 50%?
I'm asking, I don't know. I'd have to ask the same question about batteries.
The same moral/ethical questions I had to ask myself when I had my grid-tie system installed but used panels without labels weren't an option so everything was new and had warranty.

 

[Zwy]

What sort of back-end costs are we talking about before I place an order?

You can have panels that fail in a short time, panels that need testing before install and of course lifespan over new panels.

The position that I am beginning to arrive at is that morally and ethically, we if we don't use these to their last good watt then we have no chance of affecting our climate in a positive way. At what point is a solar panel no longer worth the space it takes up? When it hits 80%, 70%, 50%?

Good question. For many with rooftop solar and limited space for PV, they may have to replace panels in order to keep generating capacity large enough. Not so important with a ground mount array, one of the reasons I prefer ground mount if given the option.

I'm asking, I don't know. I'd have to ask the same question about batteries.
The same moral/ethical questions I had to ask myself when I had my grid-tie system installed but used panels without labels weren't an option so everything was new and had warranty.

 

[Ozark Tinkering]

You can have panels that fail in a short time, panels that need testing before install and of course lifespan over new panels.



Good question. For many with rooftop solar and limited space for PV, they may have to replace panels in order to keep generating capacity large enough. Not so important with a ground mount array, one of the reasons I prefer ground mount if given the option.

So possibly 10-15 years from now I will want to replace my existing rooftop grid-tie panels for new higher wattage panels and use them in a string for my off-grid setup and still have years left on performance the guaranty but not at the higher wattage rating of a new panel of similar size?
How's that for a run-on sentence? :D

 

[Hedges]

The position that I am beginning to arrive at is that morally and ethically, we if we don't use these to their last good watt then we have no chance of affecting our climate in a positive way. At what point is a solar panel no longer worth the space it takes up? When it hits 80%, 70%, 50%?
I'm asking, I don't know. I'd have to ask the same question about batteries.
The same moral/ethical questions I had to ask myself when I had my grid-tie system installed but used panels without labels weren't an option so everything was new and had warranty.

Over-paneling allow greater avoidance of fossil fuel consumption. A system big enough to not collapse avoids having refrigeration shut down.
Total contribution to environmental damage and other issues is something hard to quantify, and you can be sure if someone purchases a study the results are likely skewed.

"Dollars" can be used as a metric for commodity and labor input. Imperfect, especially with regard to environmental impact, but at least a metric that is easy to measure.
I think you can feel OK spending up to the $$ on PV which don't exceed alternate purchase in $$ of gasoline or lithium batteries over a 25 year system lifespan.

PV panels should deliver 80% of original output for 25 years. Different types vary in expected life. Even if degraded to 50% they may be useful, or swapping panels on existing mounting structure may be best way to restore/boost output. My original system had 130W/m^2 panels. Swapping for 200W/m^2 panels (at 10% the price per watt) boosts output 50% without buying new racking (cost approaches panel cost these days.)

Lithium batteries are considered to be at end of cycle life when 80% of original capacity. Pushing beyond that point may have increased risk of catastrophic failure.
I have 12 year old AGM which were stored, occasionally recharged. I think about 40% of original capacity. Functional in my "test rig" but if I needed the output to run anything at night, probably best to replace. Daytime operation they still supply surge.

So possibly 10-15 years from now I will want to replace my existing rooftop grid-tie panels for new higher wattage panels and use them in a string for my off-grid setup and still have years left on performance the guaranty but not at the higher wattage rating of a new panel of similar size?
How's that for a run-on sentence? :D

'Zacly!

 

[Zwy]

So possibly 10-15 years from now I will want to replace my existing rooftop grid-tie panels for new higher wattage panels and use them in a string for my off-grid setup and still have years left on performance the guaranty but not at the higher wattage rating of a new panel of similar size?
How's that for a run-on sentence? :D

I didn't say higher wattage, the problem is as the panel degrades, output decreases. If available space is taken up, it might not be enough energy produced to cover the usage for the day when this occurs. Take for instance the REC panels https://usa.recgroup.com/sites/defa..._warranty_fact_sheet_usa_web.pdf?t=1643388689 Annual degradation ranging from .25% to .7%

 

[svetz]

Risks

... we still haven't really factored in risk to the calculations, and the risk of grid instability is growing every day....

That's a tough one. Obviously important, but widely different for everyone.
Inflation was easy to put in and can be left as a variable for folks to plug in what they think is appropriate for their locality. Possibly it'll become clearer for the other types of risk as we refine things? Definitely something to think about while reviewing the posts.

Battery for non-daylight case

The thing is that during daylight periods, PV carries that load once you hit full charge.

This is really important especially for loads that can be shifted to solar noon (e.g., running hot water tanks, charging EVs); that is the battery can be smaller as it only powers the nighttime loads. But, it depends on your comfort zone and ability to do without when there's a very gloomy day. Doesn't work well for me as the AC in summer is 24x7. Oddly enough, I could probably bank enough heat in the house during the day to coast through the night as usually there aren't consecutive cold days.

Personally, I'm thinking at least 2d autonomy as a minimum to eliminate the grid because stuff happens and if I do need a full day of backup it would only be a 50% DoD ensuring battery longevity.

...[between] 18 hours from 3 pm til 10 am.... 11.35 Kwh... [of average] 17.7 Kwh per day.

Did I get that right, 64% of your usage is non-solar peak hours? Electric stove?

Used Vs. New
For the numbers I'm thinking the future math can set longevity on the gear, so if new you could plug in the warranty and if used make a stab at it.

Calendar Aged batteries are unsafe

...Lithium batteries are considered to be at end of cycle life when 80% of original capacity. Pushing beyond that point may have increased risk of catastrophic failure.

Well that blows. I've seen a lot of people hypermiling old batteries past 80% because they're cheap... but that just sounds dangerous now.
Pity, I was thinking the second installment of batteries would have a substantial price break as you'd only need to backfill 30% or so (also assuming the issues in Incrementally adding DC batteries would have been solved in a decade).

 

[Zwy]

Risks

That's a tough one. Obviously important, but widely different for everyone.
Inflation was easy to put in and can be left as a variable for folks to plug in what they think is appropriate for their locality. Possibly it'll become clearer for the other types of risk as we refine things? Definitely something to think about while reviewing the posts.

Battery for non-daylight case

This is really important especially for loads that can be shifted to solar noon (e.g., running hot water tanks, charging EVs); that is the battery can be smaller as it only powers the nighttime loads. But, it depends on your comfort zone and ability to do without when there's a very gloomy day. Doesn't work well for me as the AC in summer is 24x7. Oddly enough, I could probably bank enough heat in the house during the day to coast through the night as usually there aren't consecutive cold days.

Personally, I'm thinking at least 2d autonomy as a minimum to eliminate the grid because stuff happens and if I do need a full day of backup it would only be a 50% DoD ensuring battery longevity.

Did I get that right, 64% of your usage is non-solar peak hours? Electric stove?

Gas stove. Microwave would be in there twice. Morning and evening. Water pump ran in the early morning. Wife was home in the morning, I just asked and she ran the washing machine and dryer and now tells me the vacuum cleaner, all before 9 am.

Guess that explains it. I'll dig thru some other nights and see what the baseline I come up with.

Used Vs. New
For the numbers I'm thinking the future math can set longevity on the gear, so if new you could plug in the warranty and if used make a stab at it.

Calendar Aged batteries are unsafe

Well that blows. I've seen a lot of people hypermiling old batteries past 80% because they're cheap... but that just sounds dangerous now.
Pity, I was thinking the second installment of batteries would have a substantial price break as you'd only need to backfill 30% or so (also assuming the issues in Incrementally adding DC batteries would have been solved in a decade).

 

[Hedges]

Well that blows. I've seen a lot of people hypermiling old batteries past 80% because they're cheap... but that just sounds dangerous now.

In this case even more than others, I was just repeating what I read somewhere. So take it with a large grain of ?

 

[svetz]

Thread Recap: The price-point of ESS to go Off-Grid​

Net-Metering
If you live where there's a good net-metering agreement you'll not want to go off-grid as the bill can be zeroed out with a relatively modest cost of increasing your PV array. But not every place has net-metering and if you do have, it is always under attack. This thread is about figuring out how to find the price-point where it makes sense to go off-grid.

In-between Cases (TOUs)
It's not always necessary to go off-grid, often you only need enough battery to cover a high Time of Use (TOU) rate. This thread isn't about that per se and a number of people (e.g., @GXMnow) have blogged their experiences doing so.

Incentives
Some states (e.g., MA) already offer hefty incentives to installing ESS, it might become a federal tax credit.

Risks
Still working on identifying these and how to include them. Ideally, these are all adjustable parameters as different people will have different ideas as to the value to compensate for the risk.

How Much Storage?
Being off-grid means having a reliable backup power supply (e.g., generator). Ideally, that source only runs a few times per year to over a hump where there's insufficient power from your renewable source (e.g., solar panels).

For LFP, from the graph in the OP we know 3 days of storage gives an average 33% depth of discharge (DoD) which should give 20 years of cycles leaving them at 80% capacity. But, due to calendar aging, they might only last a decade. If a decade is an upper limit then 90% DoD is the minimum based on cycle life.

Ultimately, how much storage is up to you. Generally, 2 to 3 days is the realistic pick for convenience and not being a slave to the generator.

Storage Alternatives
In some cases you can hedge your storage needs by altering power consumption to alter your lifestyle to using the most power while the sun is up or doing without on days you can't provide enough sunshine. You can also oversize your PV array so that sufficient power is available even on gloomy days.

What's the Value of going Off-Grid?
This one is fairly simple assuming consistent usage, it's the sum of the bills over a year. You can use an online inflation calculator to adjust the total for future years and then sum them up for 20 years or the life of the PV array. The PV array's output will degrade over time, you can find the amount from your panel's datahseets.

What's the Cost of Energy Storage?
This is the cost of an installed system plus generator brought out to 20 years (e.g., if you think LFP lasts 10 years double the price to get to 20 years).

Example​

Let's use $0.156/wh as the price of the Energy storage installed and assume:​

• The maximum kWh consumption on record is 70 kWh, but the maximum two consecutive days is only 100 kWh.
• Decide we want 2d autonomy
• The batteries will safely last a decade

Then for two days automony you might decide on 100 kWh. Sure that one day might use more, but the generator can catch the few outlier days. Or not, this is totally up to you. But for this example, we'll use 100 kWh. Then 100 kWh x $156/kWh is $15,600 for the batteries. A ~2 kW inverter generator runs about $1000 and can recharge 48 kWh of battery/d. For this example, we'll assume you already have an inverter properly sized for your off-grid needs (but otherwise you'd add the costs in).​

So, $15,600 * 20 years needed/10 year-calender-life + $1000 generator = $32,200 investment.​

​

What's the value?
Let's say your grid bill totals $1500 per year. Over 20 years with 2% inflation that's ~$39,000. From the example above the cost is $32,200, so is it good deal? The payback period is positive, but if you invested that at 1.25%, it would return $41,000 over 20 years.

Other Unknowns

• What happens if the feds offer a 25% incentive on ESS? Then that $32,200 system in the example above costs $24,150.
• LTO has a cycle life of over 50 years, if the calendar life is over two decades the economics look very positive (see #39)
• Solid-state batteries are expected to start being mass-manufactured in 5 years and in common use in 10. They may have both long cycle and calendar lives at lower prices and higher densities.
• Rather than invest in a battery, if your driving patterns permit, it might soon be possible to use your EV battery for 2nd or 3rd day emergency use, reducing the size of the main ESS.
• The argument most commonly used by those trying to get rid of net-metering is the burden it places on those without net-metering (as if they weren't charging for grid-access or that there was no value in the energy residential DERs provided), what happens when people who can leave the grid? What new legislation would need to be enacted?

 

[12VoltInstalls]

The argument most commonly used by those trying to get rid of net-metering is the burden it places on those without net-metering (as if they weren't charging for grid-access or that there was no value in the energy residential DERs provided), what happens when people who can leave the grid? What new legislation would need to be enacted?

This idea troubles me from an Adam-Smith-Natural-Price-of-Things perspective.
Competition for providing power resources to the residential market from the solar sector should both drive efficiency moves in the grid business model and serve to drive solar prices downward. Conversely, cost increases of grid power to consumers to ‘offset’ a loss in revenue - or perhaps shareholder profits- merely serve to sustain the over-lucrative cash grabs built into installed sales. (I have some relationships that give me a window into this; if there’s three layers of individuals making well over six figures before you buy equipment or pay the installers there’s a lot of undisciplined cash running around)

In some cases you can hedge your storage needs by altering power consumption to alter your lifestyle to using the most power while the sun is up or doing without on days you can't provide enough sunshine. You can also oversize your PV array so that sufficient power is available even on gloomy days.

Not arguing with you at all, so don’t take this wrong: How likely is it that the culture can be educated to change lifestyle or ‘do without’ in the soft, not-pioneer culture we’ve become over the last, say, thirty years? It’s not just millennials and gen-x, either; many contemporary generations scrimp on vehicle maintenance, neglect home maintenance, and don’t take second jobs- but they have the latest phone, new easy chairs, fitbits, surround sound, buy 50% discounted food from welfare recipients, and buy vehicles that consume 30% + of their incomes. All to not feel any discomfort.

Does residential autonomous solar have a mainstream chance?
Long-term, I have trouble envisioning grid-distributed solar model. But I have more trouble envisioning an individually self-responsible model. The recent thread on transmitting 5 bajillion mega volts 500 ft in Alaska may be an outlier in architecture and pocket depth, but the underlying attitude/dichotomy is not an outlier.

Obviously I’m all for solar and hope for an individually sustainable model. Pre-installation profits and battery costs create the two major barriers. Your summaries make the issue concise and more readily understood

 

[Zwy]

One thing is the tax credit for solar has not yet been renewed after this year. If you install batteries with your system now, you will get the tax credit with the batteries included in the system. You may not get the credit on adding batteries in later years.

 

[svetz]

How likely is it that the culture can be educated to change lifestyle or ‘do without’

From the thread's point of view, changing your lifestyle is just an option that can affect economics. People can live and do as they please in my book as long as it doesn't hurt others.

I realize with climate change there's an argument that anyone consuming 400 kWh/d for a private residence is doing more harm than someone consuming 40 kWh/d, but IMO that can be fixed with carbon offsets rather than telling them they can't. That is I don't see the need for austerity with renewables. As long as it's sustainable and net-zero live like a king if you want. But that's discussed in other threads.

Long-term, I have trouble envisioning grid-distributed solar model.

At some point the cost to maintain the physical wires just won't be economical. At that point I could see everyone having power plants (fuel cells with PV solar to regenerate the fuel) in their homes (similar to air conditioners today). You'd hire a "power company" to do maintenance on it if you didn't want to bother with it yourself.

Or possibly someone will perfect wireless power transmission and change the economics again and we'll get power from space at rates too cheap to meter. ; -)

Folks being responsible and having solar on their roof... or mega solar farms with capitalists making money for doing so. I've no problem with either, both models work... I just want to see them treated fairly under the law and not have the "big farms" trying to oust the little DERs or new taxes to support monopolies at the expense of the DERs.

The energy landscape in 2050 will be so vastly different. There shouldn't be any coal or natural gas consumed in the U.S. and EVs the norm. Most governments are both supporting DERs (e.g., the solar tax credit) and the utility monopolies conversion to renewables. Being a DER isn't going to be for everyone, but I'd like to see more energy freedom rather than monopoly control. In any time of change the organized win, and we aren't that organized.

In a perfect world, as we consumers pay the hikes of our monoply utilities to switch to solar/wind then our bills should steadily decrease (because the maintenance costs are decreased, capex is decreased, and fuel costs are eliminated). But I suspect we'll pay the hikes and never see the rewards unless we DIY.

But I have more trouble envisioning an individually self-responsible model.

I don't know, seems like everyone on the forums is already responsible for their system. But yeah, DIYers are a small segment of the population... overall I agree the far larger segment is the throw-it-away-and-buy-new or it's-so-complicated-you-can't-do-it-yourself.

 

[12VoltInstalls]

new taxes to support monopolies

You understand the issues quite well

possibly someone will perfect wireless power transmission and change the economics again and we'll get power from space at rates too cheap to meter. ; -)

Tesla knew some things that he didn’t get to the point of understanding. He made experiments showing stuff was going on but hadn’t conquered it before he died. Einstein knew some things and figured them out along with others. And developments continued after he died.
Nothing significant has been done with Tesla’s ideas after he died.
(Off topic but while “the world” is talking about greenhouse effect and global warming there is no major attention being given to the actual production of heat we have generated and are generating in the production of energy.
The energy / heat load factor of simple things like structure environmental controls (heating, aircon), manufacturing, nuclear plant cooling, transportation, and yes even EV get missed in the public eye. Nothing in energy is really free)

seems like everyone on the forums is already responsible for their system. But yeah, DIYers are a small segment of the population... overall I agree the far larger segment is the throw-it-away-and-buy-new or it's-so-complicated-you-can't-do-it-yourself.

ya

So are you going to assemble the form and calcs and hack some Java to have a $4.99 universal tool available for download in the “app stores” sometime later next week?

 

[svetz]

...So are you going to assemble the form and calcs and hack some Java to have a $4.99 universal tool available for download in the “app stores” sometime later next week?

As only DIYers could probably get benefit at this point, figured they'd want to do it themselves...
It probably wouldn't be hard to set it up in a spreadsheet, but is there really interest? If so, I could post one for what we have so far.

 

[eXodus]

What's the Value of going Off-Grid?
This one is fairly simple assuming consistent usage, it's the sum of the bills over a year. You can use an online inflation calculator to adjust the total for future years and then sum them up for 20 years or the life of the PV array. The PV array's output will degrade over time, you can find the amount from your panel's datahseets.

My grid tied PV system is by now 12 years old. Best year of production was year 8. second best was year 2.
Year 12 wasn't much different from year 4.

So far the panels are not degrading as fast as on the spec sheet. (cold Germany) with that rate I'm going to be at 90% by year 20. I can live with that.
I've designed the system that it produces 200% of what I need in 2008. Since then - thanks to improved appliances - my energy needs went down. At this point I'm producing 250% of my total needs. Just need battery - to cover the night time use.

 

[justgary]

is there really interest?

Yes, please.

 

[12VoltInstalls]

is there really interest

I think it would be something in high demand for a lot of folks. Not applicable to me but I’d probably pass it on to others.

I think a calculator format tool in the app stores could make a lot money, btw. I could be wrong?
The only stuff out there I’ve seen are set up for selling not wise decision making.

 

[NPhil]

I just happened upon this thread, and, after glancing through, I nominate it as the best thread ever! Even though I have disliked arithmetic since I was a small boy, and consequently only do it when it seems necessary (which it is, annoyingly often), and, does not appear to apply to me, since I don't own property. I will attempt to contribute anyway:

I'm in the SF Bay Area, which is in California (you know, the "as goes" state), so I have a perspective others may lack, on:

1. The price of energy (it's probably going up. A lot).
2. The reliability of energy supply (it's looking shaky, and could get worse. A lot).
3. Your political acceptability, if you are not extremely adept at Newspeak, and that's a lifestyle you can live with (don't count on retaining it).

A couple of years ago, I started building what I call my mobile solar power testbed (solar panels and batteries, in the van I use for service calls), because:

1. I don't know how long I'm going to be able to afford to live here, and if I have to move, what circumstances I will find.
2. I don't know what, if anything, is actually happening with AGW, but, I'm pretty sure it's either somewhat real, or, a self-fulfilling prophecy, perhaps driven by manufactured mass hysteria, the immediate consequences of which, on my ability to get enough electricity to keep a few computers up and running, get a cup of hot tea in the morning, and such, seem likely to be very similar.
3. Apparently, the population around me are becoming twitchy, which is not a state which gives me reason to suppose it wise to rely on them to meet (what used to be) normal expectations regarding civil treatment of their neighbors (me, for example).


My mobile solar power testbed is not much, and it cost too much (by my standards), even at the best bargain prices I could find, but, I'm doing it anyway.

How much is "not much"? Well, about 1.5 KWH battery, mixed LiFePO4 and LCA (Tesla 2170) at 24V, and (nominal) 600 watts of solar panels. That's enough to squeak by, using a test load of mobile refrigeration (about 30 qt. of fridge and 30 qt. of freezer), making tea with a 1000W electric kettle, and a meal or two, most days, with a 700W microwave, 1000W hotplate, or both (not at the same time), plus a security camera, trickle charge of the starter battery, and maybe this or that I'm forgetting, in the SF Bay Area climate (very forgiving, I don't even have heaters for the LiFePO4 battery in yet, and other such things). My plan is to about double the battery capacity, and then about triple both battery capacity and solar power output, with stuff I've already purchased, but is not in the van yet (it's just a testbed), before I consider it in shape to hit the road, if necessary. If it's not necessary, then it's around 7KWH (usable) of mobile power, for backup, or whatever, at a price I can (sort of) afford.

How much is "too much"? I guess under $5000, counting all the odds and ends, but not the vehicle, which I have to have anyway.

 

[Hedges]

A self-powered van system is a reasonable thing to have, especially if you're not anchored to a piece of real estate.

LCA Tesla 2170 battery, and to a much lesser extent LiFePO4 - people have seen their vans and houses incinerated by battery packs. Some sort of fire containment and an ejection system might be a good idea, to protect your "home". Metal box, smoke detector, Anderson plug and a chain to yank it out of the vehicle?