Solar Fuel Savings Calculator

Calculator Inputs

Enter site demand, solar output, generator and fuel details. Submit to see results above.

Site name

Used on exports and report header.

Daily electrical load (kWh/day)

Average daily site consumption supplied by a generator.

Workdays per year

Use 250–330 for most active projects.

Solar input method

Choose how you want to estimate output.

Solar production (kWh/day)

Average usable energy before availability and curtailment.

Solar availability (%)

Downtime for cleaning, faults, and site moves.

Curtailment and mismatch (%)

Energy lost when solar exceeds demand at times.

Fuel type

Default intensities can be overridden below.

Fuel price (per L)

Use delivered price at the jobsite.

Generator capacity (kW)

Used to estimate runtime hours reduction.

Average load factor (%)

Typical stable operation is 50–80%.

Maintenance cost (per generator hour)

Filters, oil, labor, and service downtime allowance.

Currency symbol

Used for on-screen values and exports.

Fuel intensity override (L/kWh)

Leave blank to use defaults for the selected fuel.

CO₂ factor override (kg/L)

Use your own emissions factor if required.

Solar upfront cost

For simple payback and NPV summary.

Solar O&M (annual)

Cleaning, minor repairs, and monitoring allowance.

Analysis period (years)

Used for projection and discounted value.

Fuel escalation (%/year)

Expected annual price increase in fuel.

Service cost escalation (%/year)

Used for maintenance and solar O&M growth.

Discount rate (%/year)

For discounted savings and NPV estimate.

Tip: If the site runs only seasonally, reduce workdays.

Example Data Table

Use this example to validate your entries or to demonstrate the workflow.

Scenario	Daily Load (kWh)	Solar Effective (kWh)	Fuel Type	Fuel Price	Fuel Saved (per day)	Net Savings (per year)
Baseline example	350	204	Diesel	$1.10/L	55.08 L	$18,400
Higher fuel price	350	204	Diesel	$1.45/L	55.08 L	$26,200
Lower solar availability	350	170	Diesel	$1.10/L	45.90 L	$15,000

Numbers are illustrative; your inputs control final results.

Formula Used

SolarEffective = SolarProduction × (Availability/100) × (1 − Curtailment/100)
SolarUsed = min(SolarEffective, DailyLoad)
GenEnergyWithSolar = DailyLoad − SolarUsed
Fuel = Energy × FuelIntensity, where FuelIntensity is L/kWh
FuelSaved = FuelBaseline − FuelWithSolar
GenHours = Energy ÷ (GenCapacity × LoadFactor)
NetAnnualSavings = (FuelCostSaved + MaintenanceSaved) × Workdays − SolarO&M
CO2Avoided = FuelSaved × CO2Factor

How to Use This Calculator

Estimate or measure your typical daily electrical load in kWh.
Select a solar method: enter daily production, or compute from size and sun hours.
Set availability and curtailment to reflect real site operation.
Pick a fuel type, enter fuel price, and adjust intensity if your generator data differs.
Provide generator capacity and load factor to estimate runtime reductions.
Enter solar upfront and annual O&M for payback and discounted projection.
Press Calculate, then download a CSV or PDF report if needed.

Planning Notes

Fuel intensity and generator loading

Small changes in fuel intensity drive large budget differences. A mid‑load diesel set often falls near 0.25–0.30 L per kWh, while lightly loaded machines trend higher. When you set the load factor, this tool converts daily energy into operating hours using capacity × load factor. If your site uses several sets, use an average capacity and loading to reflect the fleet.

Solar production and usable energy

Daily solar production is rarely fully usable on a construction schedule. Availability captures time lost to moves, dust, shading, or faults. Curtailment covers mismatch when solar output exceeds demand at mid‑day. The calculator caps solar used to daily load, then applies availability and curtailment so savings remain overall realistic. For size‑based estimates, production equals kW × sun hours × performance ratio.

Cost savings components

Fuel savings are only one part of the operational value. Lower runtime reduces service labor, oil and filters, and the chance of unplanned outages. Enter a maintenance cost per hour that reflects your typical service package, including downtime and logistics. The model adds fuel and maintenance savings, then subtracts annual solar O&M to report net annual savings that can be compared to the upfront system cost.

Emissions and reporting

Many projects track carbon performance alongside cost. The calculator multiplies fuel saved by an emissions factor in kilograms per unit of fuel, then scales by workdays per year. If your contract specifies a different factor, override it directly. The PDF export provides a compact audit trail of key inputs and outputs, while the CSV supports monthly reporting and portfolio roll‑ups.

Using projections for decisions

Fuel prices and service costs typically rise over time. The projection escalates these costs annually, discounts future savings, and calculates an NPV that includes the upfront outlay at year zero. Use the analysis period to match your project horizon, and apply a discount rate consistent with your internal hurdle. A positive NPV indicates the solar option is economically favorable under your assumptions.

FAQs

1) What does “fuel intensity” mean in this tool?

Fuel intensity is the amount of fuel needed to produce one kWh of electricity. If you have measured generator data, enter your own value to match site reality and improve savings accuracy.

2) Why is solar “effective” lower than solar production?

Effective output accounts for availability losses and curtailment from mismatch. This prevents overstating savings when solar is offline or when production occurs when the site load is low.

3) How should I choose workdays per year?

Use the expected number of energized site days. For many builds this is 250–330 days. If the site shuts down for long holidays or monsoon periods, reduce workdays accordingly.

4) What if my site uses more than one generator?

Use a representative capacity and average load factor across the fleet, or run separate scenarios and sum annual results. The CSV export makes multi‑set consolidation straightforward.

5) Does this include battery storage benefits?

Not explicitly. Batteries can reduce curtailment and extend solar usage into evening shifts. You can approximate storage impact by lowering curtailment and raising solar used, then documenting the assumption.

6) Why can payback show “N/A”?

Payback is shown only when net annual savings are positive and an upfront cost is provided. If savings are negative, revisit solar assumptions, fuel price, intensity, and O&M settings.