generator fuel consumption

[JPB3]

Wanting a 20kw Generac or similar.. Trying to get a feel for how much propane it will burn per hour..

Planning on a dedicated 250 gallon tank and want to know the run time ..

Any ideas? Appreciate input..

 

[Mighty Mouse]

The spec sheet on Generac's website lists fuel consumption at half and full load.


250 gallons is the nominal tank capacity, but the safe fill limit is 80% (200 gal) to allow for thermal expansion of the propane. Using Generac's numbers for their 20 kW model, 200 gal of propane would last 84 hrs at half load and 56 hrs at full load. Actual load will depend on what appliances you're running off the generator.

 

[Speaks]

Wanting a 20kw Generac or similar.. Trying to get a feel for how much propane it will burn per hour..

Planning on a dedicated 250 gallon tank and want to know the run time ..

Any ideas? Appreciate input..

I hated the 250 gallon tank on my 11kw, I had to have it filled 3x-4x per year at a cabin I dont use all that much. I had the 500 gallon tank that went to the cabin swapped over to generator since the cabin its self only uses propane for the stove and hot water heater and am much happier with it now.

 

[JPB3]

Great info MM, thank you much.. And from that info I sure see where a 500 gallon tank would be preferable..

Again, thanks!

 

[Weldor]

Don't know how accurate their charts are due to weather conditions. The colder it is the more propane is used. ( liquid pressure vs. gas pressure. All I can add is my Neighbor has a 22kw Genrac and it uses 300 gallons of propane in 3 days at 25 to 35 degrees. I went with diesel at my place for that reason.

 

[JPB3]

Yeah, don't know the current price of propane but the fuel expense would be ridiculous ....

So what brand of diesel generators are used most for this application? Thought about a pto driven gen but hate running a tractor at near full throttle to get 540 rpm's at the shaft.. And fuel consumption for that might be daunting also. I know Miller makes a diesel welder with a 10kw generator .

 

[Mighty Mouse]

Yeah, don't know the current price of propane but the fuel expense would be ridiculous ....

So what brand of diesel generators are used most for this application? Thought about a pto driven gen but hate running a tractor at near full throttle to get 540 rpm's at the shaft.. And fuel consumption for that might be daunting also. I know Miller makes a diesel welder with a 10kw generator .

Cost per kWh from a small scale piston engine generator is going to be high (compared to grid power) regardless of fuel choice. Whatever fuel has the lowest cost per Btu will be your most economical generator fuel. Typically that's natural gas, but obviously only an option if you already have a NG pipeline connection. Propane and off-road diesel are typically pretty similar in terms of $/Btu. Storing enough fuel for extended generator runtime is a challenge for both. Propane requires a large tank that you can't refill yourself. A diesel tank (of the same total Btu content) would be smaller but fuel contamination is more of a concern and diesel engines can be difficult to start in cold weather. If your generator is just for emergency backup purposes, I wouldn't let fuel cost be the primary factor in generator choice; fuel availability/convenience would be the main driver for me.

FYI welder-generators are typically designed to run at full throttle only because they don't have an inverter to allow them to produce 60 Hz electricity at lower engine speeds. In a home backup power application, a welder-generator would be running wide open whether you have one light bulb turned on or everything in the house turned on. A generator designed for extended backup/standby purposes has an integral inverter, which allows the engine to throttle up/down to match the electrical load placed on the generator. The ability to adjust engine speed to electrical load greatly reduces fuel consumption. If you primarily want to use it as a welder, a welder-generator is a good option; if you primarily want to use it as a backup generator, be prepared to stockpile a lot of fuel. That said, a gasoline-powered Hobart 11 kW weld-gen is part of my backup power plan. I figure to use the Hobart intermittently to run my well pump and stockpile water and run my fuel-sipping 3 kW Honda inverter gen continuously for lighting and fridge/freezer. And I'll just do without HVAC until grid power is restored.

 

[Weldor]

Yeah, don't know the current price of propane but the fuel expense would be ridiculous ....

So what brand of diesel generators are used most for this application? Thought about a pto driven gen but hate running a tractor at near full throttle to get 540 rpm's at the shaft.. And fuel consumption for that might be daunting also. I know Miller makes a diesel welder with a 10kw generator .

I use a MQ gen

 

[Weldor]

Cost per kWh from a small scale piston engine generator is going to be high (compared to grid power) regardless of fuel choice. Whatever fuel has the lowest cost per Btu will be your most economical generator fuel. Typically that's natural gas, but obviously only an option if you already have a NG pipeline connection. Propane and off-road diesel are typically pretty similar in terms of $/Btu. Storing enough fuel for extended generator runtime is a challenge for both. Propane requires a large tank that you can't refill yourself. A diesel tank (of the same total Btu content) would be smaller but fuel contamination is more of a concern and diesel engines can be difficult to start in cold weather. If your generator is just for emergency backup purposes, I wouldn't let fuel cost be the primary factor in generator choice; fuel availability/convenience would be the main driver for me.

FYI welder-generators are typically designed to run at full throttle only because they don't have an inverter to allow them to produce 60 Hz electricity at lower engine speeds. In a home backup power application, a welder-generator would be running wide open whether you have one light bulb turned on or everything in the house turned on. A generator designed for extended backup/standby purposes has an integral inverter, which allows the engine to throttle up/down to match the electrical load placed on the generator. The ability to adjust engine speed to electrical load greatly reduces fuel consumption. If you primarily want to use it as a welder, a welder-generator is a good option; if you primarily want to use it as a backup generator, be prepared to stockpile a lot of fuel. That said, a gasoline-powered Hobart 11 kW weld-gen is part of my backup power plan. I figure to use the Hobart intermittently to run my well pump and stockpile water and run my fuel-sipping 3 kW Honda inverter gen continuously for lighting and fridge/freezer. And I'll just do without HVAC until grid power is restored.

My MQ at full throttle as a gen uses on average 9-11 gallons of diesel in 48 hrs. Depends on the fuel Bio-diesel or regularl diesel. so it's around 40 bucks for fuel. Propane is over $4.00 a gallon where I live plus I can get diesel myself were as you have wait for a delivery for large LP . Not reliable for delivery here either. Plus freezing weather des not effect it's fuel preformance. If I ever find a solid MQ rental gen at auction I would snag it for sure and save the hours on my welder/gen.

 

[Mighty Mouse]

My MQ at full throttle as a gen uses on average 9-11 gallons of diesel in 48 hrs. Depends on the fuel Bio-diesel or regularl diesel. so it's around 40 bucks for fuel. Propane is over $4.00 a gallon where I live plus I can get diesel myself were as you have wait for a delivery for large LP . Not reliable for delivery here either. Plus freezing weather des not effect it's fuel preformance. If I ever find a solid MQ rental gen at auction I would snag it for sure and save the hours on my welder/gen.

Propane vs. diesel economics vary by region (and season). In my neck of the woods (Ozarks), bulk propane is currently around $2.00/gal and offroad (red-dyed) diesel is around $3.20/gal. Normalized by energy content, that's approximately $22/MMBtu for propane and $23/MMBtu for diesel.

I'm not sure I buy the claim that a propane-driven engine consumes more Btu of fuel in colder weather. The propane in the storage tank exists as a mixture of liquid and gas at whatever vapor pressure happens to be at the ambient temperature (around 20 psi when it's really cold, 100+ psi when it's hot). Pressure at point of use is much lower (0.5 psi or less), so the propane will fully vaporize (regardless of ambient temperature) as it flows out of the tank across the pressure regulator.

 

[NRA4LIFE]

Can I ask what you need that much power for? When the power goes out here I run our 2400 that powers most everything we need in the house (no hot tub). But our appliances are all propane. We generally do not lose power when we need the heat pump running for A/C.

 

[JPB3]

Good point.. I have run the house in past outages with a 8500 watt generator.. Have to pick and choose what to run and NO a/c although can run a window unit in the bedroom at night if needed. Could probably get by with 15K set up.. Of course the sole reason for wanting something else is convenience. Not have to refuel every 6-8 hours..

 

[Mighty Mouse]

Can I ask what you need that much power for? When the power goes out here I run our 2400 that powers most everything we need in the house (no hot tub). But our appliances are all propane. We generally do not lose power when we need the heat pump running for A/C.

A small 120V generator is workable for home backup if you're not on well water and have mostly propane appliances. In my case, I need to run a 3/4 hp pump to have water and all my appliances are electric.

 

[NRA4LIFE]

That's a good point MM. We are also not on a well.

 

[JPB3]

l too live in the country and am on well water.

 

[JPB3]

BTW, MM your knowledge on this is admirable. Thank you for your input.

 

[Weldor]

Propane vs. diesel economics vary by region (and season). In my neck of the woods (Ozarks), bulk propane is currently around $2.00/gal and offroad (red-dyed) diesel is around $3.20/gal. Normalized by energy content, that's approximately $22/MMBtu for propane and $23/MMBtu for diesel.

I'm not sure I buy the claim that a propane-driven engine consumes more Btu of fuel in colder weather. The propane in the storage tank exists as a mixture of liquid and gas at whatever vapor pressure happens to be at the ambient temperature (around 20 psi when it's really cold, 100+ psi when it's hot). Pressure at point of use is much lower (0.5 psi or less), so the propane will fully vaporize (regardless of ambient temperature) as it flows out of the tank across the pressure regulator.

Not to make a arguement, but my propane regulator has frozen and line before. We keep a halligen light under the tank at the cabin for that reason. Down here I run the Deisel on the main house no worries about freezing. pressure is greatly effected by tempature and pressure . So if pressure drops it is less efficiant.

 

[TripleJ]

We have a Generac 24k fueled by a 250g propane tank. We had a nasty ice storm last year and lost power for 9 days. We made it 6 days running the generator 24/7 before we needed a re-fill. I checked the gauge on the tank every day to try and make sure we didn't run too low. We had our heat pump turned off and ran our wood stove upstairs and a plug-in heater downstairs for heat. We tried to be conscious of turning lights off when not in the room and such, but there is only so much you can do of that in a 2,600 square foot house with 5 people living there. Between the garage and the house, we had 3 fridges and 2 freezers going all the time, and we were able to shower every day. We plugged our old school DVD player into the TV and watched movies every night since the internet was down. In 8 years of living there, this is the third time we have had an extended outage that long. 2 for snow/ice, and for the other one, we were evacuated for a fire. Normally we are only out for half a day or so, maybe 1-2 days at the worst, one to two times a year. Someday down the road, I may look at getting a 500-gal tank, but for where we live and the frequency/duration we normally lose power, we are pretty good with a 250.