Solar savings calculator
Estimate system size, installation range, savings, and payback for a Philippine property.
Updated 2026-07-17 · Formula version appears with every result.
Preparing the calculator…
This should only take a moment. You can retry if it does not finish.
Data confidence
Early estimate
Evidence used
Uses your bill, rate, target offset, daytime use, shading, system type, and degradation allowance.
What can vary
Roof orientation, local weather, export rules, equipment losses, and installer design must be verified.
Planning use
Educational estimate only. Confirm the final design and quotation with qualified professionals.
How this estimate works
Calculations are versioned, reviewed, and reproducible. Inputs are validated and planning ranges are used instead of false precision.
Results support early decisions. Confirm utility rates, equipment specifications, site conditions, and professional requirements before committing money. Review the methodology and source policy before treating any estimate as decision-ready.
Worked example
A home with a PHP 8,000 monthly bill at PHP 11.50/kWh uses about 696 kWh per month. With a 70% target reduction, 65% daytime use, 10% shading, and a grid-tied system, the calculator produces a planning size, installed-cost range, savings range, and payback. An installer must still verify roof structure, panel layout, inverter design, permits, and net-metering scope.
Why the inputs matter
- Monthly bill and rate estimate your current kWh use.
- Daytime use matters because solar used immediately normally saves more.
- Shading reduces generation and can change the final electrical design.
- Grid-tied, hybrid, and off-grid systems have different backup and battery costs.
Common input mistakes
- Using one unusually high or low bill instead of a 3–6 month average.
- Forgetting future loads such as air-conditioners, pumps, or EV charging.
- Assuming battery backup is included in every solar quote.
- Comparing quotes that exclude permits, net metering, or roof work.
Frequently asked questions
Why can the estimate differ from an installer design?
Installer designs include exact roof layout, structural checks, inverter limits, utility requirements, brand availability, and site access.
Does grid-tied solar work during brownouts?
Usually no. Backup needs compatible hybrid or backup equipment, safe isolation, and selected critical circuits.
Are these calculator results a quotation?
No. These are educational planning estimates. Use the quote-comparison tool to normalize written installer quotations.
Related calculators
Before using the calculator
What this calculator estimates
Estimate a planning range for solar size, production, savings, and payback using electricity use, daytime consumption, shading, and system type.
Who it is for
Philippine homeowners and small businesses building a preliminary solar brief before requesting comparable quotations.
Inputs and methodology
The model converts the entered bill and electricity rate into estimated consumption, applies the target reduction and daytime-use assumptions, then uses documented solar-yield, shading, loss, degradation, maintenance, and system-type factors to produce planning ranges.
Required inputs
- Average monthly bill and actual electricity rate
- Daytime use, target reduction, and roof shading
- System type, panel wattage, rate growth, degradation, and maintenance allowance
Philippine planning assumptions
- The entered bill is representative and not dominated by arrears or one-time charges.
- The selected regional reference and user-entered rate are current enough for preliminary planning.
Worked example
A ₱6,000 monthly bill at an entered ₱11.50/kWh implies roughly 522 kWh before considering non-energy charges. The final size and savings depend on daytime use, target offset, shading, and the selected system type.
How to interpret the result
Treat the output as a brief for questions and quotations. Compare conservative, expected, and optimistic results, then check whether installer assumptions use the same bill, rate, shading, daytime-use, and production basis.
Use the result as a comparison baseline: change one assumption at a time, keep the original inputs, and ask installers to explain why their written estimate differs.
Common mistakes
- Using one unusual bill as the annual baseline
- Treating all generated electricity as bill savings
- Ignoring roof, electrical, permit, and quotation scope
Related questions
Is the result a quotation?
No. It is a transparent planning estimate designed to help you ask better questions and compare written proposals.
Why does daytime use affect savings?
Electricity used while solar is producing can replace imported electricity directly. Exported electricity may be treated differently under applicable utility arrangements.
Limitations and disclaimer
- The result is an educational planning estimate, not a quotation, site survey, electrical design, or engineering approval.
- Verify current rates, equipment, roof conditions, utility rules, and written installer assumptions before spending.
Last reviewed 2026-07-20