## Forums » Electrical Engineering

### Fuel tank for generator

• • 43 posts
January 16, 2019 10:20 PM PST
Is there any rule of thumb to calculate fuel consumption for a 2.5 MW generator?
• • 8 posts
January 17, 2019 6:35 AM PST

The general rule of thumb for fuel consumption is 7% of the rated generator output

Example: 20 kW x 7% = 1.4 gallon per hour at full load

• • 5 posts
January 17, 2019 7:42 AM PST
Rajish Rakish said:
Is there any rule of thumb to calculate fuel consumption for a 2.5 MW generator?

https://www.generators.joburg/calculator.html

• • 200 posts
January 17, 2019 3:12 PM PST

Rajish Rakish suggested this topic, thanks.

Chris Derek said:

The general rule of thumb for fuel consumption is 7% of the rated generator output

Example: 20 kW x 7% = 1.4 gallon per hour at full load

In the example above, I suppose it is 1.4 gal/hr of DIESEL(???), right?, for backup generators?, because in an EATON updated table for the very same 20 kW has 2.8 gal/hr of LIQUID PROPANE (LP), a less expensive fuel for continuous operation - or 14%, twice the Diesel(?).

If we use the R.o.T. above for the 2.5 MW requested generator, it would be:

2500 kW x 7% = 175 gallon per hour (of Diesel?) at full load - is that right?

Since no detail was given, let's assume it is a MOTOR Generator (driven by a MOTOR), and NOT a TURBO Generator (driven by a Turbine), and LIQUID PROPANE (LP) as fuel.

The Load x Fuel is usually a linear relation for Motors, so it is easy to extrapolate a formula for Load x Fuel correlation from EATON data:

0.151 x Load[kW] + 0.059 = Fuel[gal/hr] of LIQUID PROPANE (LP);

It means a similar R.o.T. as Chris Derek suggested but using a bit more than 15% constant. So for the examples given in this topic:

Chris Derek:    0.151 x 20kW    + 0.059 = 3.1 gal/hr of LIQUID PROPANE (LP);

Rajish Rakish: 0.151 x 2500kW + 0.059 = 378 gal/hr of LIQUID PROPANE (LP);

Does it make some sense? Other opinions are welcome as more details from Rajish Rakish.

• • 43 posts
January 17, 2019 10:15 PM PST
I found below information

Most of the parameters used by manufacturers of diesel generators use G/KW.H, which means how many grams (G) of oil is consumed by one kWh of generators, and then the unit is replaced by liters (L) to know you. Hourly fuel cost. In general, the diesel generator set is 0.21kg/kWh.
• • 71 posts
January 18, 2019 1:02 AM PST

Based on our Schneider experience

Fuel is monitored by a level sensor in the generator fuel tank (calibrated to the bottom of the tank)  that changes readings every 1/2-inch of fuel-level change. From these fixed-level points, the ATS counts the number of gallons of fuel used (based on load over time) and subtracts this amount from
the fixed-level fuel amount to provide an accurate estimate of fuel level. Run time is then calculated based on the fuel-usage rate at  the current load and the remaining fuel in the tank. Once a new fuel-level point is reached, the value of  the calculated fuel used is reset and consumption begins again.

The Fuel Level  and  Run time Estimate  are displayed on the  Generator Status  screen on the ATS  display interface. In addition, the following recorded data • • 156 posts
January 18, 2019 11:47 AM PST
Alex de Moura said:

Rajish Rakish suggested this topic, thanks.

Chris Derek said:

The general rule of thumb for fuel consumption is 7% of the rated generator output

Example: 20 kW x 7% = 1.4 gallon per hour at full load

In the example above, I suppose it is 1.4 gal/hr of DIESEL(???), right?, for backup generators?, because in an EATON updated table for the very same 20 kW has 2.8 gal/hr of LIQUID PROPANE (LP), a less expensive fuel for continuous operation - or 14%, twice the Diesel(?).

If we use the R.o.T. above for the 2.5 MW requested generator, it would be:

2500 kW x 7% = 175 gallon per hour (of Diesel?) at full load - is that right?

Since no detail was given, let's assume it is a MOTOR Generator (driven by a MOTOR), and NOT a TURBO Generator (driven by a Turbine), and LIQUID PROPANE (LP) as fuel.

The Load x Fuel is usually a linear relation for Motors, so it is easy to extrapolate a formula for Load x Fuel correlation from EATON data:

0.151 x Load[kW] + 0.059 = Fuel[gal/hr] of LIQUID PROPANE (LP);

It means a similar R.o.T. as Chris Derek suggested but using a bit more than 15% constant. So for the examples given in this topic:

Chris Derek:    0.151 x 20kW    + 0.059 = 3.1 gal/hr of LIQUID PROPANE (LP);

Rajish Rakish: 0.151 x 2500kW + 0.059 = 378 gal/hr of LIQUID PROPANE (LP);

Does it make some sense? Other opinions are welcome as more details from Rajish Rakish.

Per my experience for 2.5 kVA generator, one should check manufacture catalog, there is always given information 50%, 75% and 100% load and fuel consumption. Based on catalog information, one can say, how many gallens/h.

• • 19 posts
January 19, 2019 2:11 AM PST
Alex de Moura said:

Rajish Rakish suggested this topic, thanks.

Chris Derek said:

The general rule of thumb for fuel consumption is 7% of the rated generator output

Example: 20 kW x 7% = 1.4 gallon per hour at full load

In the example above, I suppose it is 1.4 gal/hr of DIESEL(???), right?, for backup generators?, because in an EATON updated table for the very same 20 kW has 2.8 gal/hr of LIQUID PROPANE (LP), a less expensive fuel for continuous operation - or 14%, twice the Diesel(?).

If we use the R.o.T. above for the 2.5 MW requested generator, it would be:

2500 kW x 7% = 175 gallon per hour (of Diesel?) at full load - is that right?

Since no detail was given, let's assume it is a MOTOR Generator (driven by a MOTOR), and NOT a TURBO Generator (driven by a Turbine), and LIQUID PROPANE (LP) as fuel.

The Load x Fuel is usually a linear relation for Motors, so it is easy to extrapolate a formula for Load x Fuel correlation from EATON data:

0.151 x Load[kW] + 0.059 = Fuel[gal/hr] of LIQUID PROPANE (LP);

It means a similar R.o.T. as Chris Derek suggested but using a bit more than 15% constant. So for the examples given in this topic:

Chris Derek:    0.151 x 20kW    + 0.059 = 3.1 gal/hr of LIQUID PROPANE (LP);

Rajish Rakish: 0.151 x 2500kW + 0.059 = 378 gal/hr of LIQUID PROPANE (LP);

Does it make some sense? Other opinions are welcome as more details from Rajish Rakish.

A 2250 KVA  diesel genereator will consume at Full Load  159.5 (gal/Hr). Are you Agree?

• • 5 posts
January 19, 2019 5:39 AM PST

A 2250 KVA  diesel genereator will consume at Full Load  159.5 (gal/Hr). Are you Agree?

See this calculation with reference.

http://www.hardydiesel.com/generator-fuel-consumption-calculator.html • • 200 posts
January 19, 2019 3:46 PM PST

A 2250 KVA diesel genereator will consume at Full Load 159.5 (gal/Hr). Are you Agree?

Calculations would be as this:

Load[kVA] x PF = Load[kW] where the most common Power Factor (PF) is 0.8;

2250 kVA x 0.8 = 1800 kW

If Chris Derek R.o.T. suggestion is used for Diesel (as Mercado Royglenn post):

7% x Load[kW] = Fuel[gal/hr] of DIESEL;

7% x 1800 kW = 126 gal/hr of DIESEL;

Smith Bill said:

See this calculation with reference.
http://www.hardydiesel.com/generator-fuel-consumption-calculator.html

The kW used by Smith Bill was 25000 - that means: 25,000 kW = 25 MW , a very big Diesel Generator - so the site provided 2108.5 gal/hr - that is too HIGH for the purpose of this topic.

If Chris Derek R.o.T. suggestion is used for 25,000 kW Diesel (as tested in Hardydiesel site):

7% x Load[kW] = Fuel[gal/hr] of DIESEL;

7% x 25,000 kW = 1,750 gal/hr of DIESEL - and it becomes too different from Hardydiesel value;

Rajish Rakish said:

Most of the parameters used by manufacturers of diesel generators use G/KW.H, which means how many grams (G) of oil is consumed by one kWh of generators, and then the unit is replaced by liters (L) to know you. Hourly fuel cost. In general, the diesel generator set is 0.21kg/kWh.

Calculations would be as this:

Density of diesel also called HSD (High Speed Diesel) has specific gravity of 0.810–0.850 as per Quality Control Manual followed by Oil Marketing Companies. Let's use the average:

( 0.810 + 0.850 ) / 2 = 0.830 g/cm3 (grams per cubic centimeter - as it is a specific gravity);

And a Liter has 1000 cm3 (cubic centimeters), so a Liter of DIESEL would weight:

0.830 g/cm3 x 1000 cm3 = 830 g (grams) = 0.83 kg

As Rajish Rakish said: "In general, the diesel generator set is 0.21kg/kWh" - that means:

0.210 kg/kWh = 210 g/kWh

210 g/kWh / 0.830 g/cm3 = 253 cm3/kWh = 0.253 L/kWh (Liters per kWh of DIESEL);

Since 1 Liter = 0.264172 Gallon, so let's convert it:

0.253 L/kWh x 0.264172 gal = 0.0668 gal/kWh OR

0.0668 gal/hr for every 1 kW - as 0.0668 is near of 0.07 or 7% the Rajish Rakish data MATCHES with Chris Derek R.o.T.

• • 43 posts
January 20, 2019 9:56 AM PST
Very good explanation