Solar Savings and Payback Calculator for Sites
Is solar worth it at your site, and how fast does it pay back?
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Solar Savings and Payback Calculator for Sites by TheCalcTools
How the Solar Savings and Payback Calculator for Sites works
Enter the system size, expected yield and installed cost.
Choose whether the solar energy replaces grid or diesel energy and enter its cost per kWh.
Savings are energy value minus O&M; payback is cost ÷ yearly savings. The 25-year gain includes degradation.
The formula
Worked example
Using the default values shown in the calculator:
| System size (kWp) | 10 |
|---|---|
| Yield (kWh per kWp per day) | 4.2 |
| Installed cost (PKR) | Rs1.8e+06 |
| Energy displaced | Grid electricity |
| Grid tariff (PKR per kWh) | Rs62 |
| Diesel energy cost (PKR per kWh) | Rs86 |
| O&M per year (PKR) | Rs30000 |
| Annual degradation (%) | 0.5 % |
- Energy = 10 × 4.2 × 365 = 15,330 kWh a year.
- Savings at Rs 62 per kWh, less O&M, = $920,460; payback 2.0 years; 25-year net gain $19,838,990.
Result:
| Energy per year (kWh) | 15,330 |
|---|---|
| Savings per year (PKR) | Rs 920,460 |
| Simple payback (years) | 2.0 |
| Net 25-year gain (PKR) | Rs 19,838,990 |
Frequently asked questions
Does this include batteries?
No. Add battery cost and replacement to the installed cost and O&M if the system includes storage.
What about net-metering income?
Export credits are not modelled. Add them to the displaced price if applicable.
Sources and further reading
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This calculator gives estimates for planning only. Electrical installations must be designed, checked and carried out by qualified personnel following local codes and the equipment manufacturer's data. Never rely on this result alone for safety-critical decisions. See our disclaimer.