Tesla Wants to Build a Battery for Your House

[donald]

These packs wont be warrantied for off grid either. But that not the point. The point is the cost of lithium based battery systems. I can order a sophisticated 30 kwh of battery system from a credible company for $10K. This is finally a fundamental change in the economics and practicality of home scale storage.

Plenty of companies will build inverters for 350v DC. Is there any reason these inverters will be more expesive to build than todays standard inverters?

What voltage does tesla's dc motor use?

[J.P.M.]

Being an early adoptor comes with risks. I'd wait at least 2-3 years after serious roll out and see what develops.

[SunEagle]

So what? Ten years of off grid for $10K with no maintenance batteries would be a godsend.

I seriously think they will not last in an "off grid" application for ten years.

[donald]

That type of inverter will put the "system" cost a lot higher then using FLA batteries with a standard inverter making the cost/kWh much higher.

So what? Ten years of off grid for $10K with no maintenance batteries would be a godsend.

[SunEagle]

The Voltage alone should tell you that it wasn't designed for Off-Grid.

That 350 to 450 range must be the DC voltage which means you still need some type of inverter to get your 120/240AC home power. That type of inverter will put the "system" cost a lot higher then using FLA batteries with a standard inverter making the cost/kWh much higher.

[Willy T]

Before you start to push for that new battery you really need to get more details then just the price, kWh rating and warranty period.

Cycle count based on DOD % will give you a better idea on how long it will really last. Can it be used for deep cycling applications or is it really designed for brief discharge periods a few times a week. Big difference in the way it would be used by off grid people.

The Voltage alone should tell you that it wasn't designed for Off-Grid.

[SunEagle]

Or you could just buy the Tesla Powerwall, 7kWh costs you $3K.
Ref:

http://www.teslamotors.com/powerwall

The price of battery power for solar installations just dropped by >2x today.

Before you start to push for that new battery you really need to get more details then just the price, kWh rating and warranty period.

Cycle count based on DOD % will give you a better idea on how long it will really last. Can it be used for deep cycling applications or is it really designed for brief discharge periods a few times a week. Big difference in the way it would be used by off grid people.

[SmartElectric]

A good 5 year battery to give you 1 usable Kwh per day is going to cost you $1200

Or you could just buy the Tesla Powerwall, 7kWh costs you $3K.
Ref:

http://www.teslamotors.com/powerwall

The price of battery power for solar installations just dropped by >2x today.

[donald]

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.

I wonder about this too. But I expect for this to work requires an expensive low rpm diesel that is amortized over many years. So large upfront costs. What they do in Alaska is always a good place to look at off grid without solar.

I wouldn't want to maintain and repair a Honda generator that runs four hours a day. "Cost Effective" can quickly become an undesirable situation. Batteries have undesirable characteristics. But moving parts (engines and windmills) are often worse.

[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.

[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.

[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.

[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?

[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.

[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.