The payback period is the time it takes for your cumulative energy savings to equal your system cost. The formula sounds simple — system cost divided by annual savings — but the annual savings figure is where most calculators get it wrong.
Calabarzon receives approximately 4.9 peak sun hours per day. A properly sized 5 kWp system will generate roughly 585 kWh per month (5 × 4.9 × 30 × 0.78 system efficiency). Of that, how much you self-consume vs export matters enormously — self-consumed kWh saves at the full Meralco rate (₱12.50/kWh) while exported kWh only earns a credit at the generation charge rate (approximately ₱5.50/kWh).
For a household with a ₱10,000/month Meralco bill and someone home during the day (70% self-consumption), annual savings at Year 1 are approximately ₱73,000. At that rate, a ₱232,000 Standard tier system pays back in about 3.2 years.
For a household where nobody is home during the day (30% self-consumption), annual savings drop significantly — the same system might take 5+ years to pay back. This is why your installer should be asking about your daily schedule, not just your bill.