Energy

[CrazyRabbit]

5 gallons of propane is equivalent to 146 kWh of electric, so my 8 powerwalls is equivalent to 3.7 gallons of propane.
Just thought this was interesting. I probably would need 11 gallons or more to get the equivalent electric energy, or 100 lbs of propane per day and then I’m trying to find someone open and able to pump propane in three days…

 

[wwhitney]

5 gallons of propane is equivalent to 146 kWh of electric

I get 124 kWh, using 1 gallon of LPG has a heat content of 84,950 BTUs, and 1 kWh = 3412 BTUs.

Miles per gallon gasoline equivalent - Wikipedia

en.wikipedia.org

But that's a theoretical number, you could only make that conversion if you had a fictious 100% efficient LPG generator. If your LPG generator is 30% efficient at making electricity, then you'd only get 37.2 kWh out of your 5 gallons of propane.

Cheers, Wayne

 

[ItsNotAboutTheMoney]

5 gallons of propane is equivalent to 146 kWh of electric, so my 8 powerwalls is equivalent to 3.7 gallons of propane.
Just thought this was interesting. I probably would need 11 gallons or more to get the equivalent electric energy, or 100 lbs of propane per day and then I’m trying to find someone open and able to pump propane in three days…

Well, it's 146kWh energy, not electricity. It's the work you actually care about.

If you have propane and:
- you want to do electrical work, then the low efficiency won't give you much at all.
- you want to heat, the propane will do OK

If you have battery and:
- you want to do electrical work, then battery will be good
- you want to heat, then
- - if it's resistive, your battery is going to run down fast
- - if you can use heat pumps to heat space or water, that will help it last longer
- - if you use induction to cook, that will help it last longer
- you have PV it'll help provide more coverage

Corollary: insulation matters.

 

[CrazyRabbit]

Correct, for theoretical, that is why I multiplied by three to get 11 gallons for generator. I rounded 85kbtu’s up to 100,000, I like simple math. Now a propane space heater is nearly 100% efficient.
So 124kwh x .145 $/kwh = $18 or propane exchange is $22 or more, but propane sell for about $3.80 at tractor supply.
Electric is cheaper, even for resistant heat.

 

[cali8484]

.145 $/kwh

Certainly not in California.

 

[BGbreeder]

5 gallons of propane is equivalent to 146 kWh of electric, so my 8 powerwalls is equivalent to 3.7 gallons of propane.
Just thought this was interesting. I probably would need 11 gallons or more to get the equivalent electric energy, or 100 lbs of propane per day and then I’m trying to find someone open and able to pump propane in three days…

The rather large number of gallons per day needed to support a generator is why you rarely, if ever, see a commercial backup using propane. There is also the issue that propane generators aren't particularly efficient. Amerigas quotes 0.7kWh/lb, or about 3kWh/gal. So, if you are burning your propane to get electrical power, your 8 Powerwalls is equivalent to something closer to 34 gallons of propane. Locally, Amerigas has said that in times of disruptions (storms, etc.) that they will only fill generator tanks when all of the residential (heat/cooking/hot water) customers have been serviced. The last major event had something like a three to four week delay. Diesel generators are significantly more efficient (e.g. 50%).

Generator Cost Per kWh: Diesel, Propane, Natural Gas, Gasoline

The US national average cost of electricity from the grid is about $0.15/kWh. How does the cost per kWh from generators compare? Obviously, the generator cost per kWh will be higher, otherwise everybody would be using generators for electricity. But how much higher? $0.20/kWh? $0.40/kWh? Even...

learnmetrics.com

I think that the primary upside to propane as a backup fuel is that you can put it in a tank, and forget about it until the tank rusts or leaks, which will happen eventually. Diesel takes more work, and gasoline really isn't a viable beyond a year or two without switching to unusual gasoline (e.g. pure alkylate) and special storage tanks.

If there are neighbors close by or you live in a wildfire zone, having a 10,000 gallon propane tank probably isn't in the cards for most people.

Still, eventually there will be episodes of extended overcast and a grid outage, and then...

All the best,

BG