How this calculator works
Monthly generation (kWh) = system size (kWp) × peak sun hours × performance ratio × 365 ÷ 12
Used at home (kWh) = generation × self-consumption % (capped at your monthly use)
Exported (kWh) = generation − used at home
Monthly savings (₱) = used at home × your rate + exported × export credit rate
Simple payback (years) = system cost ÷ (monthly savings × 12)Export credits are only counted up to the size of your remaining energy bill. Excess credits are usually carried forward to later bills, not paid out in cash, so counting them as savings would overstate the benefit.
Worked example
Example (estimate). A 3 kWp system, 4.7 peak sun hours, an 78% performance ratio, a home using 300 kWh a month, 70% self-consumption, no export credit, and an example rate of ₱15.06/kWh:
- Generation: 3 × 4.7 × 0.78 × 30.4 ≈ 335 kWh a month
- Used at home: 70% ≈ 234 kWh; exported ≈ 100 kWh
- Savings: 234 kWh × ₱15.06 ≈ ₱3,526.54 a month, or ₱42,318 a year
With an export credit, the exported kWh would add to the savings. All inputs here are assumptions, not a prediction for any particular home.
Choosing your inputs
Peak sun hours
“Peak sun hours” express a location’s average daily solar energy as the number of hours of full-strength sunlight (1,000 W per m²). It changes with location, season and weather, and the rainy season brings lower output. World Bank / ESMAP country data prepared by Solargis put the Philippines’ average daily global horizontal irradiation at about 4.73 kWh/m² — roughly 4.7 peak sun hours — with most of the country between about 4.25 and 5.17 (10th–90th percentile). The calculator starts at 4.7 hours. Look up your own location on the Global Solar Atlas for a better figure.
Sources: World Bank / ESMAP — Global Photovoltaic Power Potential by Country, country data (Solargis, 2020) ; Global Solar Atlas (World Bank Group / ESMAP) ; IEA PVPS Task 13 — Performance of New Photovoltaic System Designs (2021) .
Performance ratio
Real systems produce less than their nameplate rating × sun hours because of heat (panels lose output when hot), wiring and inverter losses, dust, mismatch and shading. The performance ratio captures all of these. An IEA PVPS study of rooftop systems in tropical Singapore reports typical performance ratios of about 75–80%, so the calculator starts at 78%. Installers’ simulation reports usually state their own figure — ask for it.
Self-consumption
Solar produces most around midday. Every kWh you use as it is produced saves the full retail rate; every kWh exported earns only the export credit (or nothing without net metering). Shifting laundry, ironing, water pumping and pre-cooling into daytime hours raises self-consumption.
Your electricity rate
The calculator starts with an example rate of ₱15.06 per kWh. That is Meralco’s announced overall rate for a typical household using 200 kWh a month in October 2026 (₱15.0615/kWh), as reported by The Philippine Star on 14 October 2026.
Limitations
- This is a first-year, monthly-average estimate. It ignores seasonal variation, panel degradation, tariff changes and maintenance — use the solar payback calculator for a multi-year view.
- Shading, roof orientation and tilt can reduce output significantly and are only captured if you lower the performance ratio or sun hours.
- Net-metering eligibility, export credit value and bill treatment depend on your utility, your system and current ERC rules. Confirm with your utility before relying on export savings.
- It is not a quote. A qualified installer should assess your roof, wiring and usage pattern.
Want to understand the decision more broadly? Read is residential solar worth it in the Philippines and how many solar panels a Philippine home needs.