Tesla Wants to Build a Battery for Your House

[Sunking]

What? I thought the main purpose of off-grid solar is to minimize generator run time due to cost. Do you know of a more cost-effective solution for off-grid?

No such thing exist. It is impossible to save any money or offset emissions with an off grid residential system. You are just wasting your money and a heavy polluter doing so. There is nothing Green about the way you live. If you think otherwise you need educated.

[RedDenver]

No such thing exist. It is impossible to save any money or offset emissions with an off grid residential system. You are just wasting your money and a heavy polluter doing so. There is nothing Green about the way you live. If you think otherwise you need educated.

Ok, then answer my question. What's a more cost-effective way to live off-grid than PV-battery to reduce generator run time?

I did not claim it was "green" or less polluting.

[DanKegel]

Assuming you're trying to power a house-sized load (e.g. washer, fridge, A/C, TVs, computers, lights) at night, and you're comparing these two options:
1. running a fossil-fuel-powered generator
2. running off a battery charged by solar panels
option 1 is probably cheaper because batteries are expensive and don't last nearly as long as solar panels.

That may change as battery technology improves. And batteries may already be a win if for some reason fuel is really hard to get, or if there's a huge battery subsidy.

Solar might be economical during the day, though.

[Living Large]

What? I thought the main purpose of off-grid solar is to minimize generator run time due to cost. Do you know of a more cost-effective solution for off-grid?

Simply put - on-grid.

To clarify - when I came here I badly wanted to purchase a nice piece of property that is off grid, and it has an existing cabin. To run power is $94,000.

After going through a design with the assistance of several helpful people here, I came up with an LFP bank, with generator backup system that was about $28,000 on a good day

What to do? Along with all the great advice on battery chemistry and generators and inverters and charge controllers and wiring, came the realization that I was crazy: Yeah, that's right, crazy It's just not for me. You'd have to see the camp and understand more of the economics, but it just wasn't viable to install a system and upgrade the camp and build a garage to have a roof for the SS for my needs. So I started looking for land with power. Point is, I had an option, and chose to exercise it. I got the h&@( out of there. Sunking will say "you need to get out of the 12V box." Well, I got out of the solar box. That would have been some nice living back there, and quiet. I just decided it was too much work and economically sucked either way I looked at it. Everyone is different.

[Living Large]

What? I thought the main purpose of off-grid solar is to minimize generator run time due to cost. Do you know of a more cost-effective solution for off-grid?

From my reply, you can see that when I said "prohibitively expensive," I was referring to living off-grid - not running solar vs running off a genny (which is what the current cabin owner does, and he pollutes the devil out of the area with noise and emissions and the other camp owners wish I'd buy his place and put a real system in). I think that is where the disconnect happened.

[RedDenver]

From my reply, you can see that when I said "prohibitively expensive," I was referring to living off-grid - not running solar vs running off a genny (which is what the current cabin owner does, and he pollutes the devil out of the area with noise and emissions and the other camp owners wish I'd buy his place and put a real system in). I think that is where the disconnect happened.

After I replied, I realized you probably meant on-grid vs off-grid. While off-grid costs are going down, on-grid still costs less unless it's unavailable or only available for a significant cost.

Based on other replies, I'm now curious if using PV-battery to reduce genset use is actually cheaper than just running a genset. I'll doa quick calc once I've gathered some cost numbers.

[DanKegel]

I'm now curious if using PV-battery to reduce genset use is actually cheaper than just running a genset. I'll do a quick calc once I've gathered some cost numbers.

Please do.

http://www.rockymtnsolar.com/Remote.html

implies it does pan out, but in my quick, ignorant google search, I didn't find
a real world example.

[SunEagle]

I bet most readers and posters here support your right to live as you choose about 110+ %. That's probably about 110% more than care what those choices entail.

Opinions vary. Respectfully suggest you consider taking a deep breath and smelling the flowers.

When you live off the grid taking deep breaths and smelling the flowers is about all you can afford.

[Sunking]

Ok, then answer my question. What's a more cost-effective way to live off-grid than PV-battery to reduce generator run time?

I did not claim it was "green" or less polluting.

Oversize both battery and panel wattage.

[Living Large]

Based on other replies, I'm now curious if using PV-battery to reduce genset use is actually cheaper than just running a genset. I'll do a quick calc once I've gathered some cost numbers.

You pay $1300 for an 8000W generator. Lets say you are generating 7000W an hour at 1.5 gallons, and a gallon of gas is $2.50. That's $3.75 for 7kWh, or $.54 per kWh Maybe you drive 20 miles a week hauling 35 gallons of gas back and forth to power 140kWh of energy @ $0.50/mi = $10. That's another $0.07 per kWh, or $0.61.

Now what about the inconvenience? You'll have to live with no power the other 21 hours of the day - sorry.

Now every 100 hours you change the oil and oil filter. 1.5 quarts oil. The oil you collect can be taken for recycling on one of your biweekly trips to get gasoline. Let's say $7, or $.07 per 7 kWh - only a penny per kWh.

In 2 years when the warranty is up, you've put maybe 2000 hours on it, and it is dead. That's 14,000kWh @ $1300, or $0.09 per kWh, for a running total of $0.71 per kwh.

This is probably close to the cost per kWh for an off-grid system with PV, battery and generator costs - but much less convenient and a Class A polluter.

[RedDenver]

Oversize both battery and panel wattage.

Ok, that's in line with what I thought.

You pay $1300 for an 8000W generator. Lets say you are generating 7000W an hour at 1.5 gallons, and a gallon of gas is $2.50. That's $3.75 for 7kWh, or $.54 per kWh Maybe you drive 20 miles a week hauling 35 gallons of gas back and forth to power 140kWh of energy @ $0.50/mi = $10. That's another $0.07 per kWh, or $0.61.

Now what about the inconvenience? You'll have to live with no power the other 21 hours of the day - sorry.

Now every 100 hours you change the oil and oil filter. 1.5 quarts oil. The oil you collect can be taken for recycling on one of your biweekly trips to get gasoline. Let's say $7, or $.07 per 7 kWh - only a penny per kWh.

In 2 years when the warranty is up, you've put maybe 2000 hours on it, and it is dead. That's 14,000kWh @ $1300, or $0.09 per kWh, for a running total of $0.71 per kwh.

This is probably close to the cost per kWh for an off-grid system with PV, battery and generator costs - but much less convenient and a Class A polluter.

Thanks. Only 2 years life for the generator seems short to me, but I don't have better numbers. So for solar to be more cost effective than your example, it needs to cost less than about $0.70/kWh.

If I assume we want 4 days of battery power (so that I can use the published 100 hour rates for convenience) with 7 kWh/day average load with a 48V battery, then we need 7000*4/48 = 583 AH battery. Using these industrial FLA batteries, gives about 604 AH at 100 hr rate and 1500 cycles at 80% DOD, which is roughly 0.8 DOD*604 AH*8=3866 Wh per cycle. At a price of $833*8=$6671 that becomes $6671/(3.866*1500)=$1.15/kWh before even considering the solar panels and equipment. So while there might be a case where a PV-battery system is less than a generator, it's certainly not a sure thing.

I've seen other threads where the price per kWh of FLA batteries is said to be around $0.20/kWh, so I may have made a mistake somewhere.

[Sunking]

I've seen other threads where the price per kWh of FLA batteries is said to be around $0.20/kWh, so I may have made a mistake somewhere.

You made a mistake. Battery cost alone, not anything else included is going to cost you $0.59 to $0.75 per Kwh.

A good 5 year battery to give you 1 usable Kwh per day is going to cost you $1200 and in 5 years delivers 1825 Kwh. $1200/1825 Kwh = $0.657 Kwh. Depending on where you live is 4 to 10 times more than the utility charges you. You want panels, controllers, inverters, generators, fuel tank, wiring, permits, labor, hardware, and equipment to make it work?

[Living Large]

Thanks. Only 2 years life for the generator seems short to me, but I don't have better numbers.

That number is for a generator at the cost quoted - not really intended for long term regular use. You can certainly get better generators, and pay more.

I was looking at a full time house where I'd still have the comforts of home, and not feel like I was camping all the time. In my opinion, that purpose doesn't lend itself to such an intermittent power source, but I thought I put some numbers out there for you to think about if I understood the question. There are several kinds of setup - generator, generator and battery, solar + battery, solar + battery + generator etc and wind and water options.

[RedDenver]

You made a mistake. Battery cost alone, not anything else included is going to cost you $0.59 to $0.75 per Kwh.

A good 5 year battery to give you 1 usable Kwh per day is going to cost you $1200 and in 5 years delivers 1825 Kwh. $1200/1825 Kwh = $0.657 Kwh. Depending on where you live is 4 to 10 times more than the utility charges you. You want panels, controllers, inverters, generators, fuel tank, wiring, permits, labor, hardware, and equipment to make it work?

Thanks. I'll take a look at my math and some other batteries. I'm getting $0.80-1.15/kWh on several batteries I've looked at.

I'm not looking to compare on-grid to off-grid; I'm looking at whether a generator-only off-grid is more cost effective than using a PV-battery system with a generator. I'm just curious how the numbers compare at current prices.

[SunEagle]

Thanks. I'll take a look at my math and some other batteries. I'm getting $0.80-1.15/kWh on several batteries I've looked at.

I'm not looking to compare on-grid to off-grid; I'm looking at whether a generator-only off-grid is more cost effective than using a PV-battery system with a generator. I'm just curious how the numbers compare at current prices.

A more cost effective system would be a grid tie PV system with an emergency generator.

As for the other options it will really depend on where you live and what it costs to run the generator or purchase batteries.

If fuel is really expensive or hard to come by then at some point batteries could be less costly. But in the event of a global upheaval neither fuel nor batteries will be easy to find.