Assumes:60.0% of modeled daytime demand coincides with solar. Solar surplus can charge the 8 kWh battery before any remaining surplus is exported at PHP 9.65/kWh. The default export figure is the September 2026 planning assumption.
Monthly bill savingsPHP 9,056
Investment allowance
PHP 678,900
Bill after solar
PHP 944/mo
Annual net savings
PHP 108,677
Simple payback
6.2 years
First-year net savings / cost
16.0%
Monthly energy breakdown
Generated
725.2 kWh
Direct solar use
208.6 kWh
Battery delivered
175.4 kWh
Exported
321.8 kWh
Unused / curtailed
0.0 kWh
Grid import
248.3 kWh
Export credits generated
PHP 3,105
Modeled unused bill credit
PHP 0
How the numbers are built
Monthly use = (PHP 10,000 - PHP 200 assumed fixed charge) / PHP 15.5 per kWh = 632.3 kWh.
Daytime use = monthly use x 55.0%. Super target = daytime use / (3.8 net yield x 30.4375 days), then round up to whole panels.
Direct solar use = smaller of generation and coincident daytime demand. Except for the ideal case, that demand uses 60.0% overlap. The remaining demand is treated as shiftable for this simplified monthly model.
Battery charging uses solar surplus only: 20% reserve and 90% round-trip efficiency. Storage shifting is limited by usable daily capacity and remaining demand. Battery output power and hourly dispatch are not modeled.
Self-used solar displaces imports at PHP 15.5/kWh. Approved surplus exports receive PHP 9.65/kWh in the selected export scenarios. The modeled bill cannot fall below PHP 200/month; excess modeled credits are not treated as cash savings.
Investment = array kWp x solar allowance + fixed allowance + selected battery and net-metering allowances. Annual net savings = monthly bill savings x 12 - annual maintenance. Simple payback = investment / annual net savings.
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