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Diesel Generator Savings

Fuel and money saved by displacing DG with solar.

Financial

Inputs (SI units)

Nameplate rating of the diesel generator.

Average loading of the DG while running; affects specific fuel consumption.

DG fuel burn per kWh delivered — rises sharply below ~40% load factor; enter the value for the actual operating load, not the datasheet full-load figure.

Local diesel fuel price.

Maintenance, filters, oil and wear cost per kWh of DG operation.

Total PV energy generated per year.

Fraction of PV generation that actually occurs while the DG would otherwise be running — solar does not automatically replace all DG runtime (e.g. DG often runs at night or during grid outages).

Total hours the DG operates annually before solar.

Editable — typical diesel combustion factor is 2.6–2.7 kg CO₂/L.

Installed cost of the PV system used for the simple payback calculation.

Results

Total annual savings
510,400
Fuel saved
5,120 L/yr
Fuel cost savings
486,400
Maintenance savings
24,000
Avoided DG energy
16,000 kWh/yr
DG cost per kWh (baseline)
32/kWh
CO₂ reduction
13,722 kg/yr
Simple payback on solar CAPEX
3.5 years
✓ PASS — Avoided DG energy does not exceed the DG's own annual output.
✓ PASS — Payback period is within a typical bankable range for diesel-offset solar.

Engineering Recommendations

  • →Size the coincidence factor from actual load and DG-runtime profiles — assuming 100% PV-to-DG displacement systematically overstates savings.
  • →Re-derive the specific fuel consumption at the DG's typical partial-load operating point, not the datasheet full-load figure.
  • →Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.

Detailed Calculation Log

Note: Solar does not automatically displace all DG runtime — displacement is capped by both the coincidence factor and the DG's own annual energy output.
DG annual energy available: 97,500 kWh
Solar generation coincident with DG hours: 16,000 kWh
Avoided DG energy (the binding constraint): 16,000 kWh

Save & Load Project

Designs are stored privately in this browser — nothing is uploaded.

Engineering Formula

  • Fuel saved = Gen × SFC [L]
  • Money saved = Fuel × Price
  • CO₂ avoided ≈ Fuel × 2.68 kg/L

Typical DG SFC is 0.28–0.35 L/kWh at 75% load. Below 40% load SFC balloons past 0.5 L/kWh — solar makes even more sense.

Step-by-step Calculation

  1. 1.DG annual energy output (pre-solar)Rated kW × load factor × hours/yr97,500 kWh
  2. 2.DG cost per kWhSFC × fuel price + maintenance/kWh32/kWh
  3. 3.Solar energy coincident with DG hoursSolar generation × coincidence factor16,000 kWh
  4. 4.Avoided DG energymin(coincident solar, DG annual energy)16,000 kWh
  5. 5.Fuel savedAvoided energy × SFC5,120 L
  6. 6.Fuel cost savingsFuel saved × price486,400
  7. 7.Maintenance savingsAvoided energy × maint. cost/kWh24,000
  8. 8.Total annual savingsFuel + maintenance510,400
  9. 9.CO₂ reductionFuel saved × diesel EF13,722 kg/yr
  10. 10.Simple paybackSolar CAPEX / annual savings3.5 yr

How to use this calculator: Diesel Generator Savings

Fuel and money saved by displacing DG with solar. The example below is calculated by this page's real engine from the displayed inputs.

  1. 1Confirm that the Diesel Generator Savings matches the quantity or design check you need.
  2. 2Enter DG rated output, Average DG load factor, and Specific fuel consumption at this load using the units printed beside each field.
  3. 3Check every value before calculating, especially decimal points and measurement units.
  4. 4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
  5. 5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.

Input guide and example values

Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.

InputExample valueWhy it matters
DG rated output100 kWNameplate rating of the diesel generator.
Average DG load factor65 %Average loading of the DG while running; affects specific fuel consumption.
Specific fuel consumption at this load0.32 L/kWhDG fuel burn per kWh delivered — rises sharply below ~40% load factor; enter the value for the actual operating load, not the datasheet full-load figure.
Diesel price95 currency/LLocal diesel fuel price.
DG maintenance cost1.5 currency/kWhMaintenance, filters, oil and wear cost per kWh of DG operation.
Annual solar generation40000 kWh/yrTotal PV energy generated per year.
Coincidence factor (PV output during DG hours)40 %Fraction of PV generation that actually occurs while the DG would otherwise be running — solar does not automatically replace all DG runtime (e.g. DG often runs at night or during grid outages).
DG running hours per year1500 h/yrTotal hours the DG operates annually before solar.
Diesel CO₂ emission factor2.68 kg CO₂/LEditable — typical diesel combustion factor is 2.6–2.7 kg CO₂/L.
Solar system CAPEX1800000 currencyInstalled cost of the PV system used for the simple payback calculation.

Formula inputs & variables for Diesel Generator Savings

These are the named quantities used by this calculator. When the source formula does not define a mathematical symbol, OneCalcApp keeps the real input label instead of inventing one.

Variable / inputUnitMeaning in this calculation
DG rated outputkWNameplate rating of the diesel generator.
Average DG load factor%Average loading of the DG while running; affects specific fuel consumption.
Specific fuel consumption at this loadL/kWhDG fuel burn per kWh delivered — rises sharply below ~40% load factor; enter the value for the actual operating load, not the datasheet full-load figure.
Diesel pricecurrency/LLocal diesel fuel price.
DG maintenance costcurrency/kWhMaintenance, filters, oil and wear cost per kWh of DG operation.
Annual solar generationkWh/yrTotal PV energy generated per year.
Coincidence factor (PV output during DG hours)%Fraction of PV generation that actually occurs while the DG would otherwise be running — solar does not automatically replace all DG runtime (e.g. DG often runs at night or during grid outages).
DG running hours per yearh/yrTotal hours the DG operates annually before solar.

How the Diesel Generator Savings works

The Diesel Generator Savings uses DG rated output, Average DG load factor, Specific fuel consumption at this load, Diesel price, DG maintenance cost, Annual solar generation, Coincidence factor (PV output during DG hours), DG running hours per year, Diesel CO₂ emission factor, and Solar system CAPEX to calculate Total annual savings, Fuel saved, Fuel cost savings, Maintenance savings, Avoided DG energy, DG cost per kWh (baseline), CO₂ reduction, and Simple payback on solar CAPEX. Its engine applies Fuel saved = Gen × SFC [L]; the worked values below come from that same live calculation rather than a separately typed example.

With DG rated output 100 kW, Average DG load factor 65 %, Specific fuel consumption at this load 0.32 L/kWh, Diesel price 95 currency/L, DG maintenance cost 1.5 currency/kWh, Annual solar generation 40000 kWh/yr, Coincidence factor (PV output during DG hours) 40 %, DG running hours per year 1500 h/yr, Diesel CO₂ emission factor 2.68 kg CO₂/L, and Solar system CAPEX 1800000 currency, the main worked-example result is Total annual savings = 510,400.

How each Diesel Generator Savings input is used

DG rated output

The Diesel Generator Savings worked example uses DG rated output = 100 kW. This value is passed directly into the calculation, with an allowed minimum 0.1. Nameplate rating of the diesel generator.

Average DG load factor

The Diesel Generator Savings worked example uses Average DG load factor = 65 %. This value is passed directly into the calculation, with an allowed minimum 5 and maximum 100. Average loading of the DG while running; affects specific fuel consumption.

Specific fuel consumption at this load

The Diesel Generator Savings worked example uses Specific fuel consumption at this load = 0.32 L/kWh. This value is passed directly into the calculation, with an allowed minimum 0.15 and maximum 0.8. DG fuel burn per kWh delivered — rises sharply below ~40% load factor; enter the value for the actual operating load, not the datasheet full-load figure.

Diesel price

The Diesel Generator Savings worked example uses Diesel price = 95 currency/L. This value is passed directly into the calculation, with an allowed minimum 0.01. Local diesel fuel price.

DG maintenance cost

The Diesel Generator Savings worked example uses DG maintenance cost = 1.5 currency/kWh. This value is passed directly into the calculation, with an allowed minimum 0. Maintenance, filters, oil and wear cost per kWh of DG operation.

Annual solar generation

The Diesel Generator Savings worked example uses Annual solar generation = 40000 kWh/yr. This value is passed directly into the calculation, with an allowed minimum 0. Total PV energy generated per year.

Coincidence factor (PV output during DG hours)

The Diesel Generator Savings worked example uses Coincidence factor (PV output during DG hours) = 40 %. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 100. Fraction of PV generation that actually occurs while the DG would otherwise be running — solar does not automatically replace all DG runtime (e.g. DG often runs at night or during grid outages).

DG running hours per year

The Diesel Generator Savings worked example uses DG running hours per year = 1500 h/yr. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 8760. Total hours the DG operates annually before solar.

Diesel CO₂ emission factor

The Diesel Generator Savings worked example uses Diesel CO₂ emission factor = 2.68 kg CO₂/L. This value is passed directly into the calculation, with an allowed minimum 1 and maximum 4. Editable — typical diesel combustion factor is 2.6–2.7 kg CO₂/L.

Solar system CAPEX

The Diesel Generator Savings worked example uses Solar system CAPEX = 1800000 currency. This value is passed directly into the calculation, with an allowed minimum 1. Installed cost of the PV system used for the simple payback calculation.

Diesel Generator Savings formulas and result interpretation

Formula 1: relationship used

In the Diesel Generator Savings, Fuel saved = Gen × SFC [L]. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 2: relationship used

In the Diesel Generator Savings, Money saved = Fuel × Price. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 3: relationship used

In the Diesel Generator Savings, CO₂ avoided ≈ Fuel × 2.68 kg/L. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Total annual savings

For the displayed Diesel Generator Savings worked example, Total annual savings is 510,400. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Fuel saved

For the displayed Diesel Generator Savings worked example, Fuel saved is 5,120 L/yr. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Fuel cost savings

For the displayed Diesel Generator Savings worked example, Fuel cost savings is 486,400. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Maintenance savings

For the displayed Diesel Generator Savings worked example, Maintenance savings is 24,000. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Avoided DG energy

For the displayed Diesel Generator Savings worked example, Avoided DG energy is 16,000 kWh/yr. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

DG cost per kWh (baseline)

For the displayed Diesel Generator Savings worked example, DG cost per kWh (baseline) is 32/kWh. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

CO₂ reduction

For the displayed Diesel Generator Savings worked example, CO₂ reduction is 13,722 kg/yr. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Simple payback on solar CAPEX

For the displayed Diesel Generator Savings worked example, Simple payback on solar CAPEX is 3.5 years. Verify DG rated output, Average DG load factor, and Specific fuel consumption at this load and their units before relying on this output.

Diesel Generator Savings accuracy, checks and limitations

  • Diesel Generator Savings units check: confirm DG rated output (kW), Average DG load factor (%), Specific fuel consumption at this load (L/kWh), Diesel price (currency/L), DG maintenance cost (currency/kWh), Annual solar generation (kWh/yr), Coincidence factor (PV output during DG hours) (%), DG running hours per year (h/yr), Diesel CO₂ emission factor (kg CO₂/L), and Solar system CAPEX (currency) before calculating.
  • Diesel Generator Savings result check: compare Total annual savings, Fuel saved, Fuel cost savings, Maintenance savings, Avoided DG energy, DG cost per kWh (baseline), CO₂ reduction, and Simple payback on solar CAPEX with the substituted formula steps and the displayed rounding precision.
  • Diesel Generator Savings: This is an estimate, not a lender offer. Verify fees, taxes, rate changes, eligibility and repayment terms in the official product documents.

Understanding the result

Read the main result together with supporting checks, assumptions, limits and intermediate values.

For a manual check, repeat the first equation, confirm the units and change one input at a time.

Common mistakes when using Diesel Generator Savings

  • Do not mix units for DG rated output (kW), Average DG load factor (%), Specific fuel consumption at this load (L/kWh). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
  • Do not replace the displayed Fuel saved = Gen × SFC [L] relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
  • Do not treat Total annual savings = 510,400 from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.

When the Diesel Generator Savings is useful

Diesel Generator Savings is designed for cases where DG rated output, Average DG load factor, Specific fuel consumption at this load, Diesel price are known and you need Total annual savings, Fuel saved, Fuel cost savings. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.

Use the calculator for the scope described by its inputs and notes. The displayed method is Fuel saved = Gen × SFC [L]. If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.

DG rated output and Average DG load factor: what changes the answer

The worked example uses DG rated output = 100 kW, Average DG load factor = 65 %, Specific fuel consumption at this load = 0.32 L/kWh, Diesel price = 95 currency/L. With those values, Total annual savings is 510,400. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.

For this calculator, the main input roles are: DG rated output (kW): Nameplate rating of the diesel generator. Average DG load factor (%): Average loading of the DG while running; affects specific fuel consumption. Specific fuel consumption at this load (L/kWh): DG fuel burn per kWh delivered — rises sharply below ~40% load factor; enter the value for the actual operating load, not the datasheet full-load figure. Diesel price (currency/L): Local diesel fuel price.

How to sanity-check a Diesel Generator Savings result

Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Total annual savings, because it is the first worked-example output shown by the live engine.

Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.

Next logical calculator

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AC Cable Sizing Calculator covers the same practical workflow from a related calculation angle, making it a useful cross-check after Diesel Generator Savings.

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Standards, source trail and limitations

References show the method used. Check the current local edition, amendments and project specification before a regulated decision.

Design Assumptions

  • • 100% solar generation displaces DG runtime.

Engineering Tips

  • ◆Add DG maintenance saving of ~₹1.5/kWh.

Warnings

  • ▲Peak-lopping needs hybrid inverter for seamless transfer.

Standards & References

CPCB DG normsBEE benchmarks

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