How to Size a Solar Panel System in the Philippines
Solar panel system sizing determines how many kilowatts of solar capacity you need to meaningfully reduce your Meralco bill. Size too small and your savings are limited. Size too large and you overpay for capacity your roof cannot maximally use. This guide explains the three-step sizing process SolarPro Install uses for every property in Metro Manila, Cavite, Laguna, and Bulacan.
Based on Metro Manila solar irradiance of 5.1 kWh/m²/day · Using actual Meralco billing data · Per ERC Net Metering capacity limits
DOE-Accredited
Solar Installer
Meralco-Accredited
Solar Installer
ERC Net Metering
Accredited
PRC-Licensed
Electrical Engineer
Serving:
Metro Manila
Cavite
Laguna
Bulacan
What Does Solar System Sizing Mean?
Solar system sizing refers to determining the correct kilowatt-peak (kWp) capacity of solar panels for a specific property and consumption profile. The kWp rating indicates the maximum power output of the system under ideal conditions. In the Philippines, a correctly sized system generates enough electricity to offset 60 to 100 percent of daytime consumption and export surplus to Meralco for net metering credits.
System sizing is not simply “bigger is always better.” A system larger than your consumption, roof area, or transformer hosting capacity can result in unused capacity, wasted investment, or technical complications with Meralco registration.
The Three-Step System Sizing Process
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Step 1 — Determine Your Monthly kWh Consumption
Find your monthly kWh consumption on your Meralco bill. Review 12 months of bills to get your average monthly consumption. Example: ₱8,000 bill ÷ ₱12 per kWh = approximately 667 kWh per month.
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Step 2 — Calculate the Required System Size
Divide your average monthly kWh consumption by 150 kWh to get the approximate kWp system size. Example: 667 kWh ÷ 150 = 4.4 kWp. Round up to the nearest standard size (5 kWp). The system size also determines your inverter capacity — see our
solar inverter Philippines guide for how inverter sizing relates to your system.
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Step 3 — Verify Against Roof Area and Hosting Capacity
Each kWp requires approximately 5.5 to 6.5 square meters of unshaded roof area. A 5 kWp system needs approximately 28 to 32 sqm. SolarPro Install checks hosting capacity during every site assessment.
Quick Sizing Reference: Meralco Bill to Recommended System Size
| Monthly Meralco Bill |
Est. Monthly kWh |
Recommended Size |
Roof Area Needed |
Panel Count |
| ₱3,000–₱5,000 |
250–420 kWh |
3 kWp |
18–20 sqm |
8–10 panels |
| ₱5,000–₱8,000 |
420–670 kWh |
5 kWp |
28–32 sqm |
12–14 panels |
| ₱8,000–₱12,000 |
670–1,000 kWh |
8 kWp |
44–52 sqm |
18–22 panels |
| ₱12,000–₱20,000 |
1,000–1,670 kWh |
10 kWp |
54–65 sqm |
22–26 panels |
Based on Metro Manila irradiance of 5.1 kWh/m²/day, 150 kWh per kWp per month, and Meralco rate of ₱12/kWh.
The Most Accurate System Size Comes from a Site Assessment, Not a Formula.
Factors That Affect Your Ideal System Size
1
When You Use Electricity
If your household uses most electricity during the day, a larger system is more valuable because more solar generation goes directly to consumption.
2
Roof Orientation and Tilt
South-facing roofs in the Philippines produce the highest output. East or west-facing roofs produce approximately 15 to 20 percent less.
3
Shading
Trees, adjacent buildings, water tanks, or antennae that shade panels during peak hours reduce actual generation below the formula-based estimate.
4
Transformer Hosting Capacity
Meralco limits total solar capacity per distribution transformer. SolarPro Install checks hosting capacity for every property before finalizing a system size recommendation.
Meralco hosting capacity and transformer limits for solar installations →
How Inverter Type Affects Your System Size →
Frequently Asked Questions About Solar System Sizing
How many solar panels do I need for a typical Filipino home?
A typical Filipino home paying ₱5,000 to ₱8,000 per month to Meralco needs approximately 12 to 14 solar panels (5 kWp system). Homes paying ₱3,000 to ₱5,000 per month typically need 8 to 10 panels (3 kWp).
What is kWp and how is it different from kW?
kWp stands for kilowatt-peak and refers to the maximum power output of a solar panel system under Standard Test Conditions. kW is a measure of power at any given moment; kWp is the rated peak power of the system.
How much roof space does a solar system need?
Each kWp of solar capacity requires approximately 5.5 to 6.5 square meters of unshaded roof area. A 5 kWp system needs approximately 28 to 32 sqm.
Get a Precise System Size Recommendation for Your Property
Formulas give estimates. An actual site assessment gives the precise system size that maximizes your savings based on your roof, your consumption, and your Meralco bill. Request a free assessment from SolarPro Install.
