The short version: nine months in, the array is still tracking to a ~3.0-year payback, but August was the weakest month on record. A multi-week monsoon cut generation ~38% to ~15.8 kWh/day and pulled self-sufficiency down to ~51.8% — below December's previous floor. That is weather rather than equipment: the eleven low-generation days all sit inside the flooding that hit Luzon, and the array recovered to ~29.3 kWh on 31 August. The month sharpens the main finding rather than changing it. The money is in the overnight base load — ~3.7 kWh bought at the full rate every night while the battery sits empty, ~₱1,900 in August alone — and when generation collapses, that draw is the one load neither panels nor battery can reach. If you're sizing a system here, the variable that generalizes from this single-site data is the always-on load floor, not panel count. Once it was running I also took it through Meralco net metering — that paperwork is its own story: Net Metering Journey in General Trias.
Headline numbers
Annual bill cut
₱133,476
~66% of pre-solar bill
Simple payback
~3.0 yrs
on ₱400k turnkey
Year-1 generation
~8,153 kWh
~22.3 kWh/day baseline
CO₂ avoided
~5.2 t/yr
≈236 trees · 24,700 km
What the data shows
Self-sufficiency climbed from 54.3% in December to a peak of 76.5% in March, eased through the wet season to 59.9% in June, recovered to 66.5% in July, then fell to 51.8% in August — the dataset low, and the first month below the December baseline. Generation dropped ~38% to ~15.8 kWh/day and grid import rose to ~440 kWh. Household load fell ~19% to ~29.5 kWh/day over the same stretch, with four charging days against July's nine, which cushioned the loss considerably: had load held at July's level, August would have landed nearer 42%.
No equipment fault is visible. Peak PV reached 5.44 kW (68% of inverter capacity), and there is still zero clipping in 273 days. The eleven August days flagged as low generation all fall inside the monsoon — output is suppressed across the whole daylight window rather than cutting off abruptly, and the dips cluster in consecutive runs as weather systems do. August's raw battery round-trip efficiency reads an impossible 105.8%, the mirror of July's depressed 91.9%: the pack opened August at 91% state of charge and closed at 24%. Adjusted for the ~9.5 kWh it carried in and discharged, August reads ~99%, in line with every prior month.
The highest-impact lever is unchanged: an overnight floor of ~700–780 W that draws ~3.7 kWh from the grid through the small hours, after the battery has emptied. Every 100 W trimmed off it is worth ~₱14,700 a year at ₱16.75/kWh, and it repeats whether anyone is home or not. A wet month strengthens the case rather than weakening it. See recommendations →
Monthly bill impact
Month
Bill without solar
Net savings
Dec 2025
₱13,424
₱7,291
Jan 2026
₱11,736
₱7,039
Feb 2026
₱10,609
₱8,420
Mar 2026
₱12,464
₱10,520
Apr 2026
₱17,542
₱12,165
May 2026
₱18,633
₱13,162
Jun 2026
₱18,539
₱11,144
Jul 2026
₱18,001
₱12,129
Aug 2026
₱15,302
₱8,148
Net savings peaked in May at ₱13,162 and fell to ₱8,148 in August, the weakest since January. The fall is larger than it looks: the rate rose to ₱16.75, so the same solar contribution should have been worth more. The saving dropped because the array delivered ~300 kWh less than July while the grid made up the difference at the highest rate yet charged. Each month is billed at the rate that applied then (rates climbed from ₱14.41 in December to ₱16.75 in August); the ~₱133k annual figure is projected at today's rate.
Disclaimer: the report is AI-assisted. While the underlying data comes from the inverter export, the narrative analysis, recommendations, projections, and financial interpretation may contain inaccuracies. Verify critical findings against your own records, manufacturer specs, or a qualified solar professional before acting on them.