Quick Answer
A diesel generator burns roughly 0.2 litres of diesel per kVA per hour at full load — for example, a 100 kVA set ≈ 20 L/hr (≈5.3 gal/hr), a 125 kVA set ≈ 25 L/hr, and a 200 kVA set ≈ 40 L/hr. At lower loads it uses far less — a 100 kVA unit drops to about 10 L/hr at 50% load and 6 L/hr at 25% load. Fuel consumption scales with the actual electrical load drawn, not just the nameplate size. Use the chart below to find the exact L/hr figure for your kVA and load.
📋 Table of Contents
- Full Fuel Consumption Chart (10–2000 kVA × Load %)
- Fuel Use by Popular Size (100 / 125 / 200 / 250 / 500 / 1000 kVA)
- How to Calculate Diesel Generator Fuel Consumption
- The Formula (L/hr and L/kWh) + Worked Example
- Try the Free Interactive Calculator →
- Specific Fuel Consumption (L/kWh) Explained
- What Affects Fuel Consumption
- The 50–80% Load Sweet Spot
- Fuel Consumption by Brand: Perkins vs Cummins vs Caterpillar
- Fuel Cost per Hour: Calculate Your Operating Expense
- 1 MW Diesel Generator Fuel Consumption (1000 kVA and Above)
- Frequently Asked Questions
- Related Tools and Guides
Diesel Generator Fuel Consumption Chart: 10–2000 kVA × Load %
Figures are typical industry values calculated at ≈0.25 L/kWh at full load, power factor 0.8, ambient 25°C — actual fuel use varies ±10% by engine family, fuel quality, load profile, and site conditions. Gallons shown in parentheses are US gallons.
🌎 Also known in Spanish-language markets as a tabla de consumo de combustible de generadores — this diesel generator fuel consumption chart is widely used in Latin American and Iberian projects for kVA sizing and fuel cost planning.
| kVA | kW | 25% Load L/hr (gal/hr) |
50% Load L/hr (gal/hr) |
75% Load L/hr (gal/hr) |
100% Load L/hr (gal/hr) |
|---|---|---|---|---|---|
| 10 | 8 | 0.6 (0.2) | 1.0 (0.3) | 1.5 (0.4) | 2.0 (0.5) |
| 15 | 12 | 0.9 (0.2) | 1.6 (0.4) | 2.3 (0.6) | 3.0 (0.8) |
| 20 | 16 | 1.2 (0.3) | 2.1 (0.5) | 3.0 (0.8) | 4.0 (1.1) |
| 30 | 24 | 1.8 (0.5) | 3.1 (0.8) | 4.6 (1.2) | 6.0 (1.6) |
| 40 | 32 | 2.4 (0.6) | 4.2 (1.1) | 6.1 (1.6) | 8.0 (2.1) |
| 50 | 40 | 3.0 (0.8) | 5.2 (1.4) | 7.6 (2.0) | 10.0 (2.6) |
| 75 | 60 | 4.5 (1.2) | 7.8 (2.1) | 11.4 (3.0) | 15.0 (4.0) |
| 100 | 80 | 6.0 (1.6) | 10.4 (2.7) | 15.2 (4.0) | 20.0 (5.3) |
| 125 | 100 | 7.5 (2.0) | 13.0 (3.4) | 19.0 (5.0) | 25.0 (6.6) |
| 150 | 120 | 9.0 (2.4) | 15.6 (4.1) | 22.8 (6.0) | 30.0 (7.9) |
| 160 | 128 | 9.6 (2.5) | 16.6 (4.4) | 24.3 (6.4) | 32.0 (8.5) |
| 200 | 160 | 12.0 (3.2) | 20.8 (5.5) | 30.4 (8.0) | 40.0 (10.6) |
| 250 | 200 | 15.0 (4.0) | 26.0 (6.9) | 38.0 (10.0) | 50.0 (13.2) |
| 300 | 240 | 18.0 (4.8) | 31.2 (8.2) | 45.6 (12.0) | 60.0 (15.9) |
| 400 | 320 | 24.0 (6.3) | 41.6 (11.0) | 60.8 (16.1) | 80.0 (21.1) |
| 500 | 400 | 30.0 (7.9) | 52.0 (13.7) | 76.0 (20.1) | 100.0 (26.4) |
| 750 | 600 | 45.0 (11.9) | 78.0 (20.6) | 114.0 (30.1) | 150.0 (39.6) |
| 1000 | 800 | 60.0 (15.9) | 104.0 (27.5) | 152.0 (40.2) | 200.0 (52.8) |
| 1250 | 1000 | 75.0 (19.8) | 130.0 (34.3) | 190.0 (50.2) | 250.0 (66.0) |
| 1500 | 1200 | 90.0 (23.8) | 156.0 (41.2) | 228.0 (60.2) | 300.0 (79.3) |
| 2000 | 1600 | 120.0 (31.7) | 208.0 (54.9) | 304.0 (80.3) | 400.0 (105.7) |
Fuel Consumption by Popular Generator Size (Quick Look-Up)
The six dedicated answers below cover the most frequently searched generator sizes — quick reference if you do not want to read the full table.
How much diesel does a 100 kVA generator use per hour?
A 100 kVA (80 kW) diesel generator consumes about 20 litres per hour at full load, 15 L/hr at 75% load, 10 L/hr at 50% load, and roughly 6 L/hr at 25% load. Over a 10-hour shift at 50% load that works out to about 100 litres total. For context, a 1,000 litre day tank gives roughly 50 hours of runtime at 50% load — about two days continuous, or roughly a week of typical commercial backup-power operation. (See the full chart above for the kW and gallons-per-hour figures.)
How much fuel does a 125 kVA diesel generator use per hour?
A 125 kVA (100 kW) diesel generator consumes about 25 litres per hour at full load, 19 L/hr at 75%, 13 L/hr at 50%, and about 7.5 L/hr at 25% load. This size is one of the most common construction-site and small-commercial backup ratings — a 1,500 litre belly tank gives roughly 60 hours at 50% load. (Full breakdown in the main chart.)
What is the fuel consumption of a 200 kVA generator per hour?
A 200 kVA (160 kW) diesel generator consumes about 40 litres per hour at full load, 30 L/hr at 75%, 21 L/hr at 50%, and roughly 12 L/hr at 25% load. Common in mid-size commercial buildings, telecom hubs, and prime power applications for remote sites. A typical 2,000 litre auxiliary tank covers about 48 hours at full load or close to 100 hours at 50% load.
How much fuel does a 250 kVA diesel generator consume per hour?
A 250 kVA (200 kW) diesel generator consumes about 50 litres per hour at full load, 38 L/hr at 75%, 26 L/hr at 50%, and roughly 15 L/hr at 25% load. Common in mid-size data center N+1 redundancy and large commercial buildings. Operating cost at 50% load is typically modest per kWh produced compared with grid backup alternatives.
How much diesel does a 500 kVA generator burn per hour?
A 500 kVA (400 kW) diesel generator consumes about 100 litres per hour at full load, 76 L/hr at 75%, 52 L/hr at 50%, and roughly 30 L/hr at 25% load. Typical for large data centers, hospital backup, industrial process sites, and prime power on isolated grids. For engine brand options (Cummins, Perkins, CAT, MAN), N+1 sizing math, and 5-year lifecycle cost planning, see our 500 kVA diesel generator specifications and applications in-depth guide. A 10,000 litre bulk tank gives roughly 100 hours of runtime at full load.
What is the fuel consumption of a 1000 kVA (1 MW) diesel generator per hour?
A 1000 kVA (800 kW) diesel generator consumes about 200 litres per hour at full load, 152 L/hr at 75%, 104 L/hr at 50%, and roughly 60 L/hr at 25% load. Standard size for hyperscale data center power blocks, mining sites, and large hospital campuses. Fuel logistics at this size become a meaningful design factor — many sites use 20,000+ litre bulk storage with weekly truck deliveries on extended outages.
How to Calculate Diesel Generator Fuel Consumption
Estimating diesel generator fuel consumption comes down to three inputs: the electrical load in kW, the engine's specific fuel consumption (SFC) in g/kWh, and the fuel density (approximately 0.832 g/mL for diesel). The chart above already does this calculation across 20 common kVA sizes and 4 load percentages — the sections below explain the underlying formula, so you can compute your own value for any engine spec sheet you have.
Three practical scenarios where you should calculate rather than just look up the chart:
- Custom engine: your genset is not a standard 100/200/500 kVA — use the formula with the OEM SFC value.
- Part-load estimate: chart shows 25/50/75/100%, but you need consumption at 40% or 65% — SFC curve interpolation.
- Cost budgeting: convert L/hr to USD/hr using local diesel price to project monthly operating cost.
The three sections below walk through the exact formula, provide a worked example for a 250 kVA Perkins generator at 75% load, and route you to our free interactive calculator for one-off computations.
The Formula: L/hr and L/kWh + Worked Example
The core diesel generator fuel consumption formula is:
Fuel Consumption (L/hr) = kW output × SFC (g/kWh) ÷ Fuel Density (g/L)
where Fuel Density for typical diesel ≈ 832 g/L
Variable definitions:
- kW output: the actual electrical load being served, not the generator's nameplate rating. A 250 kVA generator running at 75% load delivers 250 × 0.8 pf × 0.75 = 150 kW.
- SFC (Specific Fuel Consumption, g/kWh): grams of diesel burned per kilowatt-hour of electrical output. Typical modern diesel gensets: 200–240 g/kWh at 75-100% load, rising to 260–310 g/kWh at 25% load as combustion efficiency drops.
- Fuel Density: 832 g/L for typical automotive diesel at 15 °C. Higher density (winter blends) ≈ 845 g/L; lower density (some biodiesel blends) ≈ 820 g/L.
Worked Example: Perkins 250 kVA at 75% Load
Consider a Perkins 1106D-E70TAG5, common 250 kVA marine and industrial genset:
- Convert kVA to kW at actual load: 250 kVA × 0.8 power factor × 0.75 (load) = 150 kW
- Look up SFC at 75% load (Perkins datasheet): ≈ 205 g/kWh
- Apply the formula: 150 kW × 205 g/kWh ÷ 832 g/L = 36.96 L/hr
Cross-check with the main chart above: 250 kVA at 75% load shows 38 L/hr — a 2.8% difference, well within the ±10% real-world tolerance range. The chart uses a slightly higher industry-average SFC (0.25 L/kWh) as a safe planning number.
The L/kWh Alternative Formula
An equivalent formulation, easier for cost calculations:
Fuel Consumption (L/hr) = kW output × SFC (L/kWh)
where typical SFC in L/kWh = 0.24 to 0.30 L/kWh
To convert between the two units: SFC (L/kWh) = SFC (g/kWh) ÷ 832. So 205 g/kWh = 0.246 L/kWh. The same 150 kW × 0.246 L/kWh = 36.9 L/hr — identical result.
g/kWh to L/h Conversion (Quick Reference)
Given a manufacturer SFC in g/kWh and a specific load, the direct conversion to hourly fuel consumption is:
L/hr = (SFC in g/kWh × kW load) / 832
Quick sanity check: at 200 g/kWh SFC and 100 kW load, L/hr = 200 × 100 / 832 = 24 L/hr. This aligns with the chart's 125 kVA (100 kW) at 100% load = 25 L/hr.
Need an Instant Result? Try the Free Interactive Calculator
For a one-off calculation on your specific generator without opening a spreadsheet, use our free generator fuel consumption calculator — enter kVA, load percentage, and diesel price, and get L/hr, daily litres, and estimated USD cost per hour in seconds.
The calculator uses the same formula as this article, with the option to input a custom SFC value if you have the manufacturer's spec sheet — useful for older engines, specific Perkins/Cummins/CAT models, or non-standard fuel densities.
Specific Fuel Consumption (L/kWh) — What It Means and How It Relates to L/hr
A diesel generator's specific fuel consumption (SFC) is the amount of fuel required to produce one kilowatt-hour of electrical output. Typical modern diesel gensets operate in the range of 0.20–0.30 L/kWh depending on engine family, load, and ambient conditions — equivalent to roughly 3.5–5 kWh per litre of diesel.
SFC is the bridge between the engine spec sheet and the per-hour fuel figure in the chart above:
L/hr = Electrical Load (kW) × SFC (L/kWh)
For example, a 100 kW load running at typical SFC of 0.25 L/kWh consumes 25 L/hr — exactly what the 125 kVA / 100 kW row of the chart shows at full load. At lower loads, SFC tends to creep up (a generator running at 25% load may operate closer to 0.30 L/kWh because combustion efficiency degrades below the engine's design sweet spot — covered in the next section).
What Affects Diesel Generator Fuel Consumption
The chart above assumes typical industry conditions (25 °C ambient, standard No. 2 diesel, well-maintained engine at healthy load). Real-world consumption can vary ±15% or more from those figures. Six factors drive most of the variation:
1. Load Percentage (largest effect: ±20%)
Diesel engines have a fuel efficiency curve, not a flat rate. Specific fuel consumption (SFC in g/kWh) is lowest at 75–90% of rated load — the engine's design sweet spot. Below 30% load, SFC rises 15–30% versus the sweet spot because combustion temperature drops, atomization degrades, and a larger share of injected fuel exits unburned. Above 100% rated load, SFC also rises slightly and internal component stress increases sharply — never a design target. See the next section for the detailed 50–80% sweet spot discussion.
2. Ambient Temperature (±5-10%)
Cold intake air (below 5 °C) is denser and delivers more oxygen per stroke, marginally improving combustion — a 3–5% fuel efficiency gain. Hot intake air (above 35 °C) reduces air density and combustion efficiency, costing 3–7% in fuel consumption. Tropical installations at 40 °C+ ambient may consume 5–10% more fuel than the chart values. Poor engine-room ventilation compounds the effect.
3. Fuel Quality (±5-8%)
Diesel cetane rating (a measure of ignition quality) directly affects combustion completeness. Premium diesel with cetane 51+ delivers 3–5% better efficiency than baseline cetane 45 diesel. Water contamination, sediment, and fuel degradation (fuel stored longer than 12 months without additives) can add another 3–5% fuel penalty from poor atomization and injector fouling. Biodiesel blends (B20 and higher) have slightly lower energy density (~92% of pure diesel) which shows up as ~5-8% higher L/hr for the same electrical output.
4. Engine Maintenance (±5-15%)
A clogged air filter reduces intake airflow and forces the engine to compensate with more fuel — up to 10% penalty. Fouled or worn fuel injectors misatomize fuel, wasting 5–8%. Delayed injection timing (from a slipped belt or worn gear train) reduces combustion efficiency. Poorly maintained engines can drift 10–15% above the chart values over 3–5 years without corrective service; well-maintained engines stay close to specification for the full warranty life.
5. Cooling System Efficiency (±3-7%)
An overheating engine automatically reduces power output (electronic derating) but still burns similar fuel — effectively raising L/kWh. A cooling system running above 95 °C coolant temperature typically costs 3–7% in efficiency, plus accelerated engine wear. Blocked radiator fins, low coolant, or a failing water pump are the common causes. See our diesel generator cooling system design guide for the underlying architecture and diagnostic sequence.
6. Altitude (±3% per 300 m above 1000 m)
Above 1000 m elevation, thinner air reduces oxygen availability and combustion efficiency. Turbocharged engines partially compensate; naturally aspirated engines derate 3–5% per 300 m of additional altitude, and their fuel consumption per kW output rises correspondingly. High-altitude installations (mining sites, mountain telecom) should apply the OEM derating chart when planning fuel budgets.
Combined effect: an under-maintained generator at 25% load in a 42 °C tropical engine room can burn 30–40% more fuel per kW output than the chart values above. Conversely, a well-maintained genset running at 75% load with clean fuel in a temperate climate typically hits chart values within ±5%.
The 50–80% Load Sweet Spot: Where Diesel Generators Are Most Efficient
The single biggest lever on diesel generator fuel consumption per kWh is the steady-state load percentage. Every diesel engine has a well-defined efficiency curve, and the fuel-optimal range runs from roughly 50% to 80% of rated capacity. Understanding this curve is critical for both sizing and operating decisions.
Why the Sweet Spot Exists
At light load (below 30%), combustion chamber temperature drops, fuel atomization degrades, and a larger fraction of injected fuel exits the cylinder unburned. Specific fuel consumption (g/kWh) can rise 20–30% above the design minimum, and the engine slowly accumulates unburned fuel deposits in the exhaust, cylinders, and turbocharger — the condition known as wet stacking. Extended low-load running (many hours per week below 30%) is one of the most damaging operational patterns for a diesel genset.
At heavy load (above 90%), combustion is complete and efficient, but internal component stress — cylinder pressure, exhaust temperature, turbo boost — rises sharply. Sustained operation at 100% rated load shortens engine life without meaningfully improving specific fuel consumption; a small efficiency gain does not offset the accelerated wear.
The 50–80% band is where combustion temperature is high enough for clean, efficient burn, but mechanical stress stays well within the engine's design fatigue envelope. This is the range OEMs use in datasheet SFC figures, and where field-measured consumption most closely matches the chart values above.
Practical Implications for Sizing
A generator sized to run at 50–80% of its rating during normal operation will consume less fuel per kW delivered than an oversized generator running at 20–30% for the same electrical load. Two common sizing mistakes that hurt fuel efficiency:
- Oversizing "for future growth": a 500 kVA generator running a 100 kW average load (20%) burns 5–10% more fuel per kWh than a right-sized 250 kVA unit running the same 100 kW load at 50%.
- Undersizing to save on CAPEX: a 100 kVA generator running a 90 kW continuous load (>110% of continuous rating) wastes fuel through inefficient boost and reduces engine life.
Operational Best Practice
For sites with variable load, the target is to keep the generator loaded above 40% for most operating hours. Where a single genset cannot achieve this, options include: paralleling smaller units and sequencing them (bring second unit online only when first exceeds 80%); adding a load bank exercise cycle to burn off wet-stacking risk quarterly; or specifying a smaller "trim" generator for typical loads with a larger unit as backup.
For a deeper treatment of low-load and wet-stacking risk in continuous-duty applications, see our wet stacking prevention guide.
Fuel Consumption by Brand: Perkins vs Cummins vs Caterpillar
The chart values above use an industry-average specific fuel consumption (SFC) around 0.25 L/kWh at full load. In practice, published OEM data varies by brand and engine family — differences of 5–10% between manufacturers at the same kVA size are common, driven by engine technology (mechanical vs common-rail), turbocharging strategy, and compression ratio.
Typical SFC by Brand (100–500 kVA Range)
| Brand | Engine Series (Example) | Typical SFC at 75% Load | Strengths |
|---|---|---|---|
| Perkins | 1103A / 1104C / 1106D / 2506J | 200–215 g/kWh | Compact, low CAPEX, strong 30–500 kVA sweet spot, wide global parts network |
| Cummins | QSB / QSL / QSX / QSK | 195–210 g/kWh | Slightly lower SFC on high-hour continuous duty, robust for 100 kVA to multi-MW |
| Caterpillar | C4.4 / C7.1 / C13 / C18 | 200–215 g/kWh | Premium build quality, strong resale value, dominant in large mission-critical and mining |
| Volvo Penta | TAD532 / TAD942 / TAD1642 | 200–210 g/kWh | Marine and industrial standby, strong European service network |
| Mitsubishi | S6 / S12 / S16 | 195–210 g/kWh | High reliability, common in Asian shipping and telecom |
Comparison at 250 kVA (75% Load)
Applying the formula for a specific example — 250 kVA at 75% load = 150 kW electrical output — across three common brands:
- Perkins 1106D-E70TAG5: 150 kW × 210 g/kWh ÷ 832 = 37.9 L/hr
- Cummins QSL9-G7: 150 kW × 202 g/kWh ÷ 832 = 36.4 L/hr
- Caterpillar C9: 150 kW × 208 g/kWh ÷ 832 = 37.5 L/hr
All three fall within the chart's typical range of 38 L/hr at 250 kVA / 75% load. Real-world differences of 1–2 L/hr per genset at the same size are normal.
For Perkins-specific values sourced directly from published OEM ElectropaK datasheets across 8 common genset models (1104C-44TAG2, 1106D-E70TAG5, 1706A-E93TAG1, 2206C-E13TAG3 and others) with L/hr at 25/50/75/100% Prime load, see our Perkins fuel consumption by model and L/hr data guide.
When to Choose Each Brand
Perkins is the value leader in the 30–500 kVA range — lower CAPEX, competitive fuel efficiency, and the widest global parts network make it the default for cost-sensitive small-to-medium projects. Cummins tends to lead on continuous-duty fuel efficiency and offers the broadest kVA range (below 20 kVA up to multi-MW), suiting hyperscale data centers, telecom, and process industries. Caterpillar commands a CAPEX premium (typically 10–15% above Perkins) but delivers strong resale value and dominates large mission-critical and mining applications. Volvo Penta and Mitsubishi are competitive in their regional strengths (Europe/marine and Asia respectively).
Fuel efficiency alone rarely drives brand selection — parts availability, service network coverage, and total lifecycle cost (5–10 year TCO) matter more. See the manufacturer's own datasheet for exact SFC curves at all load points before finalizing procurement decisions.
Fuel Cost per Hour: How to Calculate Your Diesel Generator Operating Expense
Fuel is typically 60–80% of a diesel generator's lifecycle operating cost. Translating the L/hr figures above into USD per hour and per year is a critical planning step for backup, prime, or continuous applications. The math is straightforward:
Operating Cost (USD/hr) = L/hr × Diesel Price (USD/L)
Diesel prices vary significantly by country and region — from about USD 0.80/L in low-tax markets (Middle East, some Asian countries) to USD 2.00/L+ in high-tax European markets. The tables below use three reference prices to bracket typical global scenarios.
Cost per Hour Reference Table (75% Load)
| Generator Size | L/hr at 75% Load | @ $1.20/L | @ $1.50/L | @ $2.00/L |
|---|---|---|---|---|
| 100 kVA | 15.2 L/hr | $18.24/hr | $22.80/hr | $30.40/hr |
| 250 kVA | 38.0 L/hr | $45.60/hr | $57.00/hr | $76.00/hr |
| 500 kVA | 76.0 L/hr | $91.20/hr | $114.00/hr | $152.00/hr |
| 1000 kVA (1 MW) | 152.0 L/hr | $182.40/hr | $228.00/hr | $304.00/hr |
| 2000 kVA (2 MW) | 304.0 L/hr | $364.80/hr | $456.00/hr | $608.00/hr |
Annual Operating Cost Scenarios
Total annual fuel cost depends heavily on operational profile. Three common patterns:
- Standby / emergency backup: ~100 hours/year of actual runtime (monthly testing + occasional utility outages). A 500 kVA site at $1.50/L: 100 hr × $114/hr = $11,400/year.
- Prime power (rural / grid-poor site): 3,000–4,000 hours/year. A 500 kVA prime at $1.50/L: 3,500 hr × $114/hr = $399,000/year.
- Continuous (24/7 operation, e.g. remote industrial site): 8,760 hours/year (subtract 100–200 hr for maintenance). A 500 kVA continuous at $1.50/L: 8,600 hr × $114/hr = $980,400/year.
Cost per kWh Calculation
For comparing diesel generator power against grid electricity, LNG, solar+battery, or other sources, convert to USD per kWh delivered:
Cost per kWh = (L/hr × Diesel Price) ÷ kW Output
For a 500 kVA generator at 75% load = 300 kW output, burning 76 L/hr at $1.50/L: cost per kWh = (76 × 1.50) / 300 = $0.38/kWh. At typical prime-power efficiency, diesel generation costs $0.30–0.50/kWh in fuel alone (before maintenance, capital amortization, or labor).
Fuel-Cost Optimization Levers
Three practical ways to reduce fuel cost per kWh delivered:
- Right-size the generator: run at 50–80% load (see Sweet Spot section) rather than oversizing "for future growth" — saves 5–10% fuel per kWh.
- Hybrid with solar or battery: reduces generator run-hours by 30–60% on daytime-heavy loads, cutting annual fuel spend proportionally.
- Bulk fuel procurement: negotiated bulk delivery contracts can save $0.05–0.15/L versus retail pump prices, cutting operating cost 3–10%.
Always cross-check calculated figures against actual metered fuel consumption after commissioning — real-world variance of ±10% versus theoretical values is normal.
1 MW Diesel Generator Fuel Consumption (1000 kVA and Above)
Industrial-scale diesel generators in the 1 MW to 2 MW range (1000–2500 kVA) are common in large data centers, hospital campuses, mining operations, offshore platforms, and prime-power grid-poor sites. Fuel logistics at this size become a significant design factor — a 1 MW generator running continuously burns roughly one 20,000-litre bulk delivery every 5 days.
Fuel Consumption at 1 MW Range
| Size | kW Output (pf 0.8) | 25% Load L/hr | 50% Load L/hr | 75% Load L/hr | 100% Load L/hr |
|---|---|---|---|---|---|
| 1000 kVA (1 MW) | 800 kW | 60 L/hr | 104 L/hr | 152 L/hr | 200 L/hr |
| 1250 kVA (1.25 MW) | 1000 kW | 75 L/hr | 130 L/hr | 190 L/hr | 250 L/hr |
| 1500 kVA (1.5 MW) | 1200 kW | 90 L/hr | 156 L/hr | 228 L/hr | 300 L/hr |
| 2000 kVA (2 MW) | 1600 kW | 120 L/hr | 208 L/hr | 304 L/hr | 400 L/hr |
1 MW Fuel Storage Sizing (Industrial Rule of Thumb)
Common applications at 1 MW and above typically specify on-site fuel storage matched to expected outage duration:
- Data center Tier III: minimum 12 hours at full load = ~2,400 L (1 MW) to 4,800 L (2 MW) day tank + bulk delivery.
- Data center Tier IV / hyperscale: 72–96 hours at full IT load = 14,400–19,200 L (1 MW) or 28,800–38,400 L (2 MW), typically bulk storage tank with polishing loop.
- Hospital campus: 96 hours per NFPA 110 Level 1 or local health authority requirement.
- Mining / offshore prime power: 7-14 days at expected load, matched to logistics supply cycle.
For the underlying redundancy topology and Uptime Tier compliance framework at 1 MW+ mission-critical sites, see our data center generator redundancy design guide.
Turnkey vs Modular at 1 MW+
At the 1 MW threshold, project owners often face a design choice: a single 1 MW genset (lower CAPEX, simpler control) vs two paralleled 500 kVA units (N+1 redundancy, wider load-sweet-spot coverage, easier maintenance without dropping load). For continuous or mission-critical duty, paralleled units almost always win the lifecycle economics despite ~15% CAPEX premium.
Frequently Asked Questions
How much fuel does a diesel generator use per hour?
A diesel generator burns approximately 0.2 litres per kVA per hour at full load, which works out to roughly 0.25 litres per kWh of electrical output. A 100 kVA generator uses about 20 L/hr at full load, 10 L/hr at 50% load, and 6 L/hr at 25% load. Actual consumption varies ±10% by engine family, fuel quality, ambient conditions, and load profile.
How much diesel does a 200 kVA generator use per hour?
A 200 kVA (160 kW) diesel generator consumes about 40 litres per hour at full load, 30 L/hr at 75% load, 21 L/hr at 50% load, and roughly 12 L/hr at 25% load. Over a 24-hour day at 50% load that totals about 500 litres. See the main chart above for kW and US gallons-per-hour figures.
How long do 100 litres of diesel last in a generator?
It depends on generator size and load. In a 50 kVA (40 kW) generator at full load (10 L/hr), 100 litres lasts about 10 hours. In a 100 kVA unit at 50% load (10 L/hr), it also lasts roughly 10 hours. In a 200 kVA generator at full load (40 L/hr), 100 litres lasts about 2.5 hours. Always size the day tank around realistic load profile, not just nameplate capacity.
How much fuel does a generator use at 50% load?
A diesel generator at 50% load typically consumes about 0.13 litres per kVA per hour — roughly half of the full-load figure but slightly more than half because specific fuel consumption rises modestly at part load. Example values: 50 kVA → 5.2 L/hr; 100 kVA → 10.4 L/hr; 200 kVA → 20.8 L/hr; 500 kVA → 52 L/hr. Operating in the 50–80% load band is the efficiency sweet spot for most diesel engines.
How many litres of diesel does a generator use per hour?
Per-hour diesel consumption scales with the actual electrical load drawn, not just the nameplate kVA. At full load, a generator burns roughly 0.2 L/kVA/hr; at 50% load, about 0.13 L/kVA/hr; at 25% load, about 0.075 L/kVA/hr. For exact figures across 10–2000 kVA at every load level, see the chart above.
Why does my generator burn more fuel at low load than expected?
Diesel engines are most efficient at 50–80% of rated load. Below approximately 30% load, specific fuel consumption increases because combustion temperature drops, atomization quality degrades, and a small fraction of injected fuel exits unburned. Extended operation below 30% load also causes wet stacking — a long-term engine damage pattern separate from the fuel waste. Sizing the generator closer to the actual continuous load (rather than chasing maximum peak) almost always reduces lifetime fuel cost.
How do I calculate the fuel cost per kWh for a diesel generator?
To calculate fuel cost per kWh, use: Cost per kWh = (Fuel consumption in L/hr × Diesel price per L) ÷ Electrical output in kW. Example: a 500 kVA generator at 75% load burns 76 L/hr; at diesel price $1.50/L, delivering 300 kW output: (76 × $1.50) ÷ 300 = $0.38/kWh. Typical diesel generator fuel-only cost ranges $0.30–0.50/kWh depending on generator size, load percentage, and local diesel price. Add capital amortization, maintenance labor, and lubricants for total operating cost, which typically adds another $0.05–0.15/kWh. See the Fuel Cost per Hour section above for a full 3-diesel-price scenario table across common generator sizes from 100 kVA to 2000 kVA.
How much fuel does a 1 MW (1000 kVA) diesel generator use per hour?
A 1 MW (1000 kVA / 800 kW) diesel generator consumes approximately 200 litres per hour at full load, 152 L/hr at 75% load, 104 L/hr at 50% load, and roughly 60 L/hr at 25% load. Standard size for hyperscale data center power blocks, mining operations, and large hospital campuses. Fuel logistics become a significant design factor at 1 MW — a continuous 1 MW site burns through a 20,000-litre bulk delivery in roughly 5 days at 50% load, or about 100 hours at full load. Common practice is to specify on-site bulk storage matched to expected outage duration: 12-hour minimum for Tier III data centers, 72–96 hours for Tier IV, and 7–14 days for remote prime-power sites.
What is the fuel consumption of a Perkins 250 kVA generator?
A Perkins 250 kVA generator (typically 1106D-E70TAG5, 200 kW electrical output) consumes approximately 50 litres per hour at full load, 38 L/hr at 75% load, 26 L/hr at 50% load, and roughly 15 L/hr at 25% load. Perkins engines in the 1106D and 2506J series typically have a specific fuel consumption (SFC) of 200–215 g/kWh at 75% load — competitive with Cummins and Caterpillar in the same size class. For exact SFC values at every load point, consult the Perkins ElectropaK datasheet for your specific model, and see the Brand Comparison section above for how Perkins compares against other major OEMs at 100, 250, and 500 kVA sizes.
How do I convert g/kWh to L/h for a diesel generator?
To convert specific fuel consumption (SFC) in g/kWh to hourly consumption in L/h, use: L/h = (SFC in g/kWh × Load in kW) ÷ 832. The number 832 is the density of typical diesel fuel in grams per litre (at 15 °C). Example: a 200 kW load with SFC 200 g/kWh consumes (200 × 200) ÷ 832 = 48 L/h. Alternatively, first convert SFC to L/kWh: SFC in L/kWh = SFC in g/kWh ÷ 832, then multiply by load in kW. For the same example: 200 / 832 = 0.240 L/kWh, then 0.240 × 200 = 48 L/h — identical result. Note that fuel density varies slightly by blend (winter diesel: ~845 g/L; summer diesel: ~832 g/L; biodiesel blends: ~820 g/L), so use the density from your fuel specification sheet for precise calculations.
What is the diesel generator fuel consumption formula?
The diesel generator fuel consumption formula is: Fuel Consumption (L/hr) = kW output × SFC (g/kWh) ÷ 832, where kW output is the actual electrical load (not the nameplate rating), SFC is the specific fuel consumption from the engine datasheet (typically 200–240 g/kWh at 75–100% load), and 832 is the density of typical diesel fuel in grams per litre. An equivalent formulation for cost calculations: L/hr = kW × SFC in L/kWh, where SFC in L/kWh = SFC in g/kWh ÷ 832 (typically 0.24–0.30 L/kWh). Worked example: a 250 kVA generator at 75% load (150 kW output) with 205 g/kWh SFC: 150 × 205 ÷ 832 = 37 L/hr — matching the chart's typical 38 L/hr at 250 kVA / 75% load within 3%.
Related Tools and Guides
Bookmark this chart for quick reference, or use the calculator above for project-specific calculations.
Methodology
Fuel consumption figures in the chart are calculated from engine nameplate ratings using a typical specific fuel consumption of 0.25 L/kWh at full load and a power factor of 0.8. Actual values in field service vary ±10% depending on engine family, fuel grade, ambient temperature, altitude, generator age, and load profile. Always cross-check against the OEM specification sheet for your specific genset before sizing fuel tanks or budgeting operating cost.
Sources & References
- Engine manufacturer specification sheets (Cummins, Caterpillar, Perkins, Volvo Penta, Mitsubishi) — typical SFC published curves
- ISO 3046-1:2002 — Reciprocating internal combustion engines — performance ratings
- Anonymized field service data from ASO Genset commissioning records across data center, marine, and industrial deployments
Reviewed by Smith Parkson
Power Systems Engineer · ASO Genset · 15+ years in diesel generator commissioning and sizing
Last reviewed and updated: June 2026
