Short answer
A diesel generator burns about 0.25 to 0.31 litres for every kWh it delivers at 75 to 100% load, and more per kWh at light load. Cummins data sheets show a 100 kVA prime set using 6.8 L/h at quarter load and 24.7 L/h at full load: SAR 12 to 44 an hour at SAR 1.79 a litre.
Key takeaways
- kW = kVA × 0.8 on a standard three phase diesel generator: a 100 kVA prime set delivers 80 kW, and fuel charts follow the kW the load really draws.
- From eight manufacturer data sheets, 30 to 1,000 kVA prime sets burn about 0.25 to 0.31 litres per kWh at 75 to 100% load.
- At SAR 1.79 a litre (Aramco, October 2026), a 100 kVA prime set costs about SAR 21 an hour at half load and SAR 44 at full load.
- Light load is the costly load per kWh: the Cummins C900 D5e (820 kVA prime) uses 0.34 L per kWh at quarter load against 0.25 L at full load.
- Use the table to plan, then measure: ENTEK Fuel Tank shows each tank’s litres and daily use, and ENTEK Generator shows whether the set is online and running.
01kVA, kW and the 0.8 power factor: read the nameplate first
Generators are sold in kVA, but the engine burns fuel for kW. kVA is apparent power, the total the alternator can carry. kW is real power, the part that runs motors, chillers and lights. The link between them is the power factor, and the industry convention for three phase diesel sets is 0.8. So kW = kVA × 0.8. Every Cummins data sheet in our table lists its ratings as pairs that follow this rule, such as 110 kVA (88 kW), and its full load current formula divides by 1.73 × voltage × 0.8. The AGG data sheet for a Perkins engined 1,000 kVA set states “PF0.8” outright. Why it matters for fuel: the load percentages on a data sheet are percentages of the kW rating. A 100 kVA prime set at half load is giving about 40 kW. If your site has a poor power factor, the set can reach its kVA limit before its kW limit, but the fuel it burns still follows the kW the load really draws.
02The table: litres per hour from eight manufacturer data sheets
The first table below copies the fuel figures from eight 50 Hz data sheets, from a 30 kVA prime set to a 1,000 kVA one. Seven are Cummins sheets that give litres per hour at quarter, half, three quarter and full load. The eighth is an AGG set with a Perkins 4008-30TAG2 engine, which lists 50%, 75% and 100% prime load only, so its quarter load cell is empty. We show the prime rating because that is the rating for a set that carries a varying load for unlimited hours, which is how most Saudi construction sites, camps and remote yards run. The last column adds full load at the standby rating, which is higher because standby is meant only for outages of a reliable grid. Two cautions. Each number belongs to one model and one engine, so a set of the same kVA from another maker can differ. And the Cummins sheets date from 2012: ask your supplier for the current sheet of the exact model you buy.
03Cost per hour at SAR 1.79 a litre, with a worked month
Aramco lists diesel at SAR 1.79 a litre for October 2026. Multiply any cell in the litres table by 1.79 and you have the fuel cost per running hour; the second table does that for you. Now a worked month for a common site set. A 100 kVA prime generator (Cummins C110 D5) feeds a site office, a small workshop and lighting, and the load sits near half, about 40 kW. The data sheet gives 12.0 L/h at half load. Running 10 hours a day: 12.0 × 10 = 120 litres a day, which is SAR 214.80 a day at 1.79. Over 30 days that is 3,600 litres and SAR 6,444. If the same set ran at full load for the same hours, it would burn 24.7 L/h, 7,410 litres and SAR 13,263.90 a month. Use your own running hours and load, and treat the result as a planning figure: real consumption also depends on engine condition, filters, altitude and heat.
04Light load is the expensive load per kWh
Litres per hour fall as load falls, but not in proportion. An engine needs fuel just to turn at 1,500 rpm, so at light load more of each litre goes into keeping it running and less into electricity. Divide litres per hour by the kW at that load and you get litres per kWh, the true efficiency figure. The Cummins C900 D5e at its 656 kW prime rating uses 55.9 L/h at quarter load, which is 0.34 L per kWh, and 165.2 L/h at full load, which is 0.25 L per kWh. The small C33 D5 goes from 0.40 L per kWh at quarter load to about 0.31 at full load. Across all eight sheets, the range at 75 to 100% load is about 0.25 to 0.31 L per kWh. The lesson for buyers: an oversized set that idles at 20% of its rating pays more for every kWh. Size the generator to the real peak, and for long light-load periods ask your supplier about a smaller second set.
05From the data sheet to your own tank
A data sheet is measured under set conditions. The AGG sheet, for example, states its ratings at 25 °C inlet air, 100 kPa and 30% humidity, far from a Riyadh afternoon in August, so ask for the derate sheet of your model before you size for summer. After the set is running, the honest number is the one your tank gives you. ENTEK Fuel Tank, a built-in solution on ENTEK IoT, shows the level of each tank in litres and percent, hourly and daily consumption, refuel and drop events, and marks a tank Low below 35% and Critical below 20%. Compare its daily litres with the data sheet line for your load: a large gap is a reason to check the load, the engine or an unexplained drop. ENTEK Generator shows whether each set is online and running on a site map. Rules are checked every 30 seconds and alerts reach named people by email, SMS or WhatsApp, usually within about a minute. Sensors and installation come through the ENTEK marketplace and RFQ at entek.ai.
| Model | Prime kVA (kW) | Standby kVA (kW) | 25% load | 50% load | 75% load | 100% load | 100% standby |
|---|---|---|---|---|---|---|---|
| Cummins C33 D5 | 30 (24) | 33 (26.4) | 2.4 | 3.7 | 5.3 | 7.4 | 9.0 |
| Cummins C66 D5 | 60 (48) | 66 (52.8) | 4.5 | 7.4 | 11.0 | 14.7 | 16.1 |
| Cummins C110 D5 | 100 (80) | 110 (88) | 6.8 | 12.0 | 18.0 | 24.7 | 27.2 |
| Cummins C220 D5e | 200 (160) | 220 (176) | 15.2 | 27.5 | 36.8 | 45.6 | 48.8 |
| Cummins C275 D5 | 250 (200) | 275 (220) | 14.2 | 25.8 | 38.3 | 52.5 | 62.5 |
| Cummins C500 D5 | 455 (364) | 500 (400) | 32.9 | 51.6 | 71.9 | 94.3 | 103.6 |
| Cummins C900 D5e | 820 (656) | 900 (720) | 55.9 | 92.8 | 126.0 | 165.2 | 185.1 |
| AGG P1100D5 (Perkins 4008-30TAG2) | 1,000 (800) | 1,100 (880) | not listed | 108 | 160 | 213 | 234 |
| Prime size | 25% load | 50% load | 75% load | 100% load |
|---|---|---|---|---|
| 30 kVA (C33 D5) | SAR 4.30 | SAR 6.62 | SAR 9.49 | SAR 13.25 |
| 60 kVA (C66 D5) | SAR 8.06 | SAR 13.25 | SAR 19.69 | SAR 26.31 |
| 100 kVA (C110 D5) | SAR 12.17 | SAR 21.48 | SAR 32.22 | SAR 44.21 |
| 200 kVA (C220 D5e) | SAR 27.21 | SAR 49.23 | SAR 65.87 | SAR 81.62 |
| 250 kVA (C275 D5) | SAR 25.42 | SAR 46.18 | SAR 68.56 | SAR 93.98 |
| 455 kVA (C500 D5) | SAR 58.89 | SAR 92.36 | SAR 128.70 | SAR 168.80 |
| 820 kVA (C900 D5e) | SAR 100.06 | SAR 166.11 | SAR 225.54 | SAR 295.71 |
| 1,000 kVA (AGG P1100D5) | not listed | SAR 193.32 | SAR 286.40 | SAR 381.27 |
Fuel cost per hour at 75% prime load, by generator size
Litres per hour from Cummins and AGG data sheets, multiplied by SAR 1.79 a litre (Aramco, October 2026).
Cummins C900 D5e: litres per kWh by load (prime 656 kW)
Data sheet litres per hour (55.9, 92.8, 126, 165.2) divided by the kW at each load; worked in this article.
Figures and sources
- In-Kingdom retail diesel price listed by Aramco for October 2026: SAR 1.79 per litre (Source: Aramco, Retail fuels (Prices for the month of October 2026), as of 2026-10-19)
- Power factor used in the three phase full load current formula of the Cummins generator set data sheets: 0.8 (Source: Cummins Power Generation, C110 D5 generator set data sheet (DS381-CPGK-RevA), as of 2026-10-19)
- Cummins C33 D5 (prime 30 kVA, 24 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 2.4 / 3.7 / 5.3 / 7.4 L/hr (Source: Cummins Power Generation, C33 D5 generator set data sheet (DS93-CPGK-RevE), as of 2026-10-19)
- Cummins C66 D5 (prime 60 kVA, 48 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 4.5 / 7.4 / 11.0 / 14.7 L/hr (Source: Cummins Power Generation, C66 D5 generator set data sheet (DS376-CPGK-RevA), as of 2026-10-19)
- Cummins C110 D5 (prime 100 kVA, 80 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 6.8 / 12.0 / 18.0 / 24.7 L/hr (Source: Cummins Power Generation, C110 D5 generator set data sheet (DS381-CPGK-RevA), as of 2026-10-19)
- Cummins C220 D5e (prime 200 kVA, 160 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 15.2 / 27.5 / 36.8 / 45.6 L/hr (Source: Cummins Power Generation, C220 D5e generator set data sheet (DS331-CPGK-RevD), as of 2026-10-19)
- Cummins C275 D5 (prime 250 kVA, 200 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 14.2 / 25.8 / 38.3 / 52.5 L/hr (Source: Cummins Power Generation, C275 D5 generator set data sheet (DS22-CPGK-RevD), as of 2026-10-19)
- Cummins C500 D5 (prime 455 kVA, 364 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 32.9 / 51.6 / 71.9 / 94.3 L/hr (Source: Cummins Power Generation, C500 D5 generator set data sheet (spec sheet EMERS-5888-EN), as of 2026-10-19)
- Cummins C900 D5e (prime 820 kVA, 656 kW) fuel use at 1/4, 1/2, 3/4 and full prime load: 55.9 / 92.8 / 126 / 165.2 L/hr (Source: Cummins C900D5(e) genset data sheet D-6551, in a Cummins technical submittal published by the UK Environment Agency, as of 2026-10-19)
- AGG P1100D5 with Perkins 4008-30TAG2 (prime 1,000 kVA, 800 kW) fuel use at 50%, 75% and 100% prime load: 108 / 160 / 213 L/h (Source: AGG Power, P1100D5 generator specification (Perkins 4008-30TAG2), as of 2026-10-19)
- Frequency, phase and power factor stated on the AGG P1100D5 specification: 50 Hz / 3 phase / PF 0.8 (Source: AGG Power, P1100D5 generator specification (Perkins 4008-30TAG2), as of 2026-10-19)
- Site conditions for the AGG P1100D5 ratings: 25 °C inlet air, 100 kPa, 30% relative humidity (Source: AGG Power, P1100D5 generator specification (Perkins 4008-30TAG2), as of 2026-10-19)
Questions
How many litres of diesel does a 100 kVA generator use per hour?
It depends on the load. The Cummins C110 D5 data sheet, prime 100 kVA (80 kW), lists 6.8 L/h at quarter load, 12.0 at half, 18.0 at three quarters and 24.7 at full load. Another maker’s 100 kVA set can differ a little, so check its own sheet.
How do I convert kVA to kW for a generator?
Multiply by the power factor, which is 0.8 for standard three phase diesel sets. A 500 kVA set is 400 kW, and a 1,000 kVA set is 800 kW. Fuel charts and load percentages follow the kW figure.
What does a generator cost in diesel per hour in Saudi Arabia?
Multiply litres per hour by SAR 1.79, the October 2026 Aramco price. A 100 kVA prime set costs about SAR 12 an hour at quarter load and SAR 44 at full load; a 1,000 kVA set at full prime load costs about SAR 381 an hour.
Why does my generator use more diesel than the table says?
Common reasons are a higher real load than you think, summer heat and dust, worn injectors or clogged filters, or fuel leaving the tank without being burned. Measure the tank’s daily litres and the load at the same time, then compare with the data sheet line for that load.
Is it cheaper to run a big generator at low load?
Per hour it burns less, but per kWh it costs more. The Cummins C900 D5e uses 0.34 L per kWh at quarter load and 0.25 L at full load. Size the set to your real peak instead of a large margin.
Sources
- Aramco, Retail fuels: in-Kingdom prices for the month of October 2026
- Cummins Power Generation, C110 D5 generator set data sheet: fuel use by load, 0.8 power factor, ISO 8528 rating definitions
- Cummins Power Generation, C500 D5 generator set data sheet
- Cummins C900D5(e) genset data sheet D-6551 (in a technical submittal on the UK Environment Agency consultation site)
- AGG Power, P1100D5 generator specification with Perkins 4008-30TAG2 engine