How much diesel does a 5 kVA generator use per hour?

A 5 kVA diesel generator at 0.8 power factor makes about 4 kW at full load. At 50% load (2 kW) it burns roughly 0.7 litres/hour; at 75% load (3 kW) about 0.84 litres/hour. Fuel use scales with the actual load, not the nameplate kVA, so a lightly loaded set uses far less.

How do I calculate generator running cost per hour in Sri Lanka?

Multiply litres burned per hour by the fuel price. Litres/hour = kW load × specific fuel consumption (about 0.28–0.40 L/kWh for diesel). For a 2 kW load at 0.35 L/kWh and Rs 382/L diesel: 2 × 0.35 × 382 = Rs 267/hour. This calculator does every step for you.

Is running a generator cheaper than CEB electricity in Sri Lanka?

Almost never. A diesel generator typically costs Rs 100–140 per kWh generated, while CEB domestic tariffs sit far lower per unit. Self-generation is for outages and off-grid sites, not to save money. The tool shows the exact multiplier so you can see how much more you pay.

How much fuel does a generator use at 50% load versus full load?

Per hour, a half-loaded set burns roughly half the fuel of a full-loaded one because it is doing half the work. But per kWh it is slightly less efficient: a diesel engine uses about 0.35 L/kWh at 50% load versus 0.27 L/kWh at full load, since idling and friction losses are spread over less output.

How many litres per hour does a 10 kVA diesel generator consume?

At 0.8 power factor a 10 kVA set makes 8 kW at full load. At 75% load (6 kW) it burns about 6 × 0.28 = 1.68 litres/hour; at full load about 8 × 0.27 = 2.16 litres/hour. Enter your own load level and fuel price above for an exact figure.

What power factor and load level should I use?

Most generators are rated at 0.8 power factor — use that unless the nameplate says otherwise. For load level, a standby set powering a home or shop during an outage usually sits at 40–75% of its rating; 100% is rare and hard on the engine. Pick the band closest to your real usage.

Does this include servicing, oil and generator purchase cost?

No. This tool covers fuel running cost only. Engine oil, filters, servicing, hire and the capital cost of the generator are separate. For the purchase-and-import side, use the Generator Import Tax Calculator linked below; this tool answers what it costs to keep running.

Where do the fuel prices come from?

Fuel-price defaults mirror the Ceylon Petroleum Corporation (CPC) retail prices effective June 29, 2026 — the same figures used across this site's fuel tools. Every price is editable, so if your pump price differs or a new CPC revision lands, type it in and the results update instantly.

Sri Lanka · Finance

Sri Lanka Generator Running Cost Calculator

See what a diesel or petrol generator actually costs to run — fuel burned per hour, cost per day and month, and the real price per kWh versus CEB grid power. Uses current CPC fuel prices. No signup, no ads, sources cited.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated Jul 11, 2026

Generator running cost

CPC price · Jun 29, 2026

Common sizes

Generator rating

kVA

From the nameplate — apparent power in kVA.

Power factor

kW ÷ kVA. Most gensets are rated at 0.8.

Fuel type

Default price is the latest CPC retail figure.

Fuel price

Rs/L

Editable — override with your pump price.

Load level

Hours per day

Running time on a typical day.

Days per month

Days the genset runs each month.

CEB rate

Rs/kWh

Grid tariff to compare against.

Cost per month

Rs 41,714

Cost per day

Rs 1,604

diesel per hour

0.84 L

109.2 L per month

Cost per kWh

Rs 106.96

Verified two ways ✓

Generator vs CEB grid

GeneratorRs 106.96/kWh

CEB gridRs 50.00/kWh

Running this generator costs 2.14× more per kWh than CEB grid power. That is about Rs 22,214 extra a month for the same energy.

Breakdown

Metric	Value
Electrical load	3 kW
Fuel consumption	0.84 L/hr
Cost per hour	Rs 321
Cost per day	Rs 1,604
Fuel per month	109.2 L
Energy per month	390 kWh
Cost per month	Rs 41,714

Fuel running cost only. Excludes servicing, oil, hire and capital cost. Effective Rs/kWh = SFC × fuel price and is independent of load hours.

Sources: CEYPETCO retail fuel prices and the Approximate Diesel Generator Fuel Consumption Chart (SFC band). CEB tariff for the grid comparison only. Full citations below the tool.

How it works

A generator's fuel bill comes down to three things: how much power you actually draw, how efficiently the engine turns diesel or petrol into that power, and what the fuel costs. The calculator chains those together in five steps, all shown transparently in the breakdown.

Real power.A generator's nameplate is in kVA (apparent power). Real power in kW = kVA × power factor. Most sets are rated at 0.8, so a 10 kVA set makes 8 kW at full load.
Actual load. Standby sets rarely run flat out. kW load = rated kW × load level% — pick 25/50/75/100% to match how hard yours works.
Fuel consumption. litres/hour = kW load × SFC, where SFC (specific fuel consumption, litres per kWh) is read from the standard diesel-genset consumption chart. Diesel sits in a ~0.27–0.40 L/kWh band — about 0.28 at 75% load, rising to 0.4 at 25% load, because a lightly-loaded engine wastes proportionally more fuel on friction and idling. Petrol runs a higher ~0.40–0.55 band.
Cost. cost/hour = litres/hour × fuel price, then × hours/day and × days/month for the daily and monthly totals. Fuel-price defaults are the latest CPC retail figures and are editable.
Per-kWh cost and grid comparison. The effective cost of each unit generated is cost/hour ÷ kW load = SFC × fuel price — notice the load cancels, so Rs/kWh depends only on efficiency and fuel price, not on how many hours you run. Dividing that by the CEB tariff gives the "× more expensive than the grid" multiplier.

The tool derives Rs/kWh two ways — cost ÷ energy, and the direct SFC × price identity — and flags them as verified when they agree, so you can trust the number. SFC values are approximations from an industry consumption chart; a specific engine may differ by ±10%, so treat the output as a close estimate, not a metered reading.

Worked examples

5 kVA home/shop diesel set · 50% load

4 hrs/day, 30 days, diesel at Rs 350/L

Real power: 5 kVA × 0.8 = 4.0 kW
Load: 4.0 kW × 50% = 2.0 kW
Fuel: 2.0 × 0.35 L/kWh = 0.70 L/hr
Cost/hr: 0.70 × Rs 350 = Rs 245
Cost/day: Rs 245 × 4 = Rs 980
Cost/month: Rs 980 × 30 = Rs 29,400
Per kWh: Rs 980 ÷ 8 kWh = Rs 122.50 → 2.45× the grid at Rs 50

40 kVA office/factory diesel set · 75% load

8 hrs/day, 26 days, diesel at Rs 350/L

Real power: 40 kVA × 0.8 = 32 kW
Load: 32 kW × 75% = 24 kW
Fuel: 24 × 0.28 L/kWh = 6.72 L/hr
Cost/hr: 6.72 × Rs 350 = Rs 2,352
Cost/day: Rs 2,352 × 8 = Rs 18,816
Cost/month: Rs 18,816 × 26 = Rs 489,216
Per kWh: Rs 18,816 ÷ 192 kWh = Rs 98 → 1.96× the grid at Rs 50

7.5 kVA set · full load (edge case)

100% load, Auto Diesel at the CPC default of Rs 382/L

Real power: 7.5 kVA × 0.8 = 6.0 kW
Load: 6.0 kW × 100% = 6.0 kW
Fuel: 6.0 × 0.27 L/kWh = 1.62 L/hr
Cost/hr: 1.62 × Rs 382 = Rs 618.84
Per kWh: 0.27 × Rs 382 = Rs 103.14 (same as Rs 618.84 ÷ 6.0 ✓)
At full load the engine is most efficient, so Rs/kWh is at its lowest.

Frequently asked questions

Sources & references

Fuel-price defaults mirror the CPC retail figures effective June 29, 2026, kept in sync with this site's Fuel Price Today tool. Specific fuel consumption follows the industry-standard diesel-genset consumption chart (SFC ≈ 0.27–0.40 L/kWh for diesel, higher for petrol). Figures last verified on 2026-07-11; prices are editable so you are never tied to a stale number.

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Comments & feedback

Spotted a bug or want an improvement? Tell us — our team reviews every comment, and good ideas get built. Comments are public and anonymous.

Found a bug, edge case, or want to suggest an improvement?

Email me at [email protected] — most fixes ship within 24 hours.