Solar calculator: what it produces, what it costs, when it pays back
Enter the site load and the project duration. The calculator uses the real solar irradiation of the selected county, works out the photovoltaic output month by month, sizes the right unit and shows the difference in total cost against a diesel generator, the litres of diesel avoided and the payback point. Every assumption is shown, so you can redo the maths.
Investment not yet recovered
31,297 EUR
after 12 months; the unit stays yours and keeps producing
Diesel avoided
4,564 l
≈ 12.2 tonnes of CO₂ not emitted
Payback
47.8 months
from fuel savings
Recommended model: VOLTRAIL T15
For 45 kWh per day in București county, where one kWp yields 1330 kWh per year, you need 14.4 kWp. VOLTRAIL T15 produces 52 kWh per day on average and covers 87% of the annual load, calculated month by month. The rest stays on a backup genset or on the grid.
Mind the winter. In January the same unit produces only 23 kWh per day on average, that is 52% of your load. If the project runs through the winter months, we either size up or plan a backup genset for the peaks. The annual average alone leads to undersizing.
Specifications of T15 →| Cost over 12 months | Diesel generator | VOLTRAIL |
|---|---|---|
| Fuel | 7,880 EUR | 1,034 EUR |
| Maintenance and wear | 3,657 EUR | covered by warranty |
| Unit purchase | existing generator | 41,800 EUR |
| Total | 11,537 EUR | 42,834 EUR |
Want the calculation checked by an engineer?
We send the full sizing, with your hourly load profile and the monthly output estimated for the exact location.
Calculation assumptions
- Specific genset consumption: 0.32 litres per kWh produced, a typical value at partial load.
- Genset maintenance and wear: 0.89 EUR per running hour.
- Emissions: 2.68 kg CO₂ per litre of diesel burnt.
- Photovoltaic yield: 1330 kWh per year per kWp installed in București county, provisional until PVGIS data is integrated.
- Rates are derived from Romanian list prices at a reference rate of 5.05 RON/EUR.
- The calculation excludes the cost of hauling fuel to site, which in practice tilts the balance further.
Starting points
Typical loads by project type
If you do not know the exact load, start from the values below and adjust. They come from real projects, not from catalogue sheets.
The detailed report, by email
We send the full sizing as a PDF: load profile, monthly output estimated for the exact location, fuel avoided and CO₂ for your environmental reporting.