Live Demo — Solar vs Diesel TCO Calculator
Enter both solutions' costs, energy demand and economic parameters to compare discounted total cost of ownership and payback instantly.
Solar vs Diesel TCO Calculator
Free professional total cost of ownership calculator for off-grid lighting projects. Input the solar solution's initial investment, annual O&M and battery replacement cycle and cost, together with the diesel solution's generator costs, annual energy requirement, fuel consumption rate, fuel price and O&M, then choose a discount rate and service life to compare both solutions' discounted NPV-based TCO and the solar payback period.
Key Features
Solar Solution Costs
Enter the solar system's initial investment (panels, battery, pole, installation) and annual O&M cost.
Battery Replacement Modelling
Set the battery replacement cycle (lithium 5-8 years, lead-acid 2-3 years) and cost per replacement so replacements are discounted into the TCO.
Diesel Solution Costs
Capture the generator, tank and pole investment, annual energy requirement, diesel consumption rate, fuel price and annual O&M.
Fuel Cost Calculation
Estimate annual fuel spend with C_fuel = E_year × rate × P_fuel, defaulting to a typical 0.079 gal/kWh and US EIA 2026 fuel prices.
NPV Discounting
Convert every year's expenditure into today's value with your discount rate (5-8% typical) over the chosen life cycle.
TCO Comparison & Payback
Compare total solar vs diesel TCO, read the absolute cost saving and the solar payback period against annual fuel and O&M savings.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | C_fuel = E_year × 0.079 gal/kWh × P_fuel; TCO = Σ C_t / (1 + r)^t; Payback = C0_solar / (annual fuel savings + annual O&M savings) |
| Solar Initial Investment | USD (0 and up) |
| Annual Solar O&M | USD/year |
| Battery Replacement | Cycle 2 - 10 years (Li 5-8, lead-acid 2-3) | Cost USD/replacement |
| Diesel Initial Investment | USD (0 and up) |
| Annual Energy Requirement | kWh/year (luminaires × W × h/night × 365) |
| Diesel Consumption Rate | 0.066 - 0.092 gal/kWh (typical 0.079) |
| Diesel Fuel Price | USD/gal (US EIA Aug 2026 ≈ $5.26) |
| Discount Rate | 0% - 30% (5% - 8% typical) |
| Service Life | 1+ years (10 - 25 typical) |
| Industry Standards | ISO 15686-5, ASTM E833, NREL / IEA PVPS T12, IPCC Guidelines |
| Output | Solar TCO (USD), diesel TCO (USD), 20-year cost saving (USD), solar payback period (years) |
Frequently Asked Questions
What is total cost of ownership (TCO)?
TCO captures every cost over the system's life cycle — initial investment, annual maintenance, fuel or electricity, and battery replacements — discounted to today's value with a net-present-value formula. Comparing full TCO is fairer than comparing purchase prices alone, because diesel trades a cheap upfront cost for expensive, ongoing fuel.
How is the annual diesel fuel cost computed?
The calculator multiplies the annual energy requirement by a diesel consumption rate (typically 0.079 gal/kWh, range 0.066-0.092) and the fuel price: C_fuel = E_year × 0.079 × P_fuel. With 8,030 kWh/year and $5.26/gal this equals about $3,337 per year.
Why discount future costs with NPV?
Money spent later is worth less than money spent today, so each future payment is divided by (1 + r)^t. Discounting at a realistic rate (e.g. 6%) lets you fairly compare a big solar investment now against diesel's repeated fuel and maintenance spending over 20 years.
Why must E_year be based on actual lighting hours?
E_year must reflect the true duty cycle — e.g. 20 luminaires × 0.1 kW × 11 h/night × 365 days = 8,030 kWh/year. Using 24h × 365 continuous supply instead would inflate diesel fuel cost about 2.2 times and wrongly conclude that "solar is far better." Realistic inputs keep the comparison honest.
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