"How many solar panels do I need?" is the most common question we get. Getting the size right is critical. If your system is too small, you'll still have a high electric bill. If it's too large, you'll overpay for equipment and generate excess power you can't use.

This guide will teach you how to properly size a solar system in the Philippines using your current electric bill, taking into account Philippine peak sun hours and real-world system inefficiencies.

Want the fast answer? Use our interactive solar ROI calculator to automatically determine your system size based on your monthly bill.

Quick Reference: Bill to System Size

If you just want a rough estimate, you can size your system based on your average monthly Meralco or VECO bill. The table below assumes you want to eliminate 70% to 100% of your daytime usage.

Average Monthly BillRecommended System SizeEst. Number of Panels (550W)Target Savings
P4,000 — P6,0003KW6 PanelsP3,500/mo
P7,000 — P11,0005KW9 to 10 PanelsP6,000/mo
P12,000 — P16,0008KW14 to 15 PanelsP10,000/mo
P17,000 — P25,00010KW18 to 20 PanelsP15,000/mo
P30,000+15KW - 20KW28 to 36 PanelsP25,000+/mo

*Assumes an average electricity rate of P12 per KWh.

How to Calculate Your Exact System Size

If you want to do the math yourself like a professional engineer, you need to look at your actual KWh consumption, not just the peso amount on your bill.

Step-by-Step Sizing Calculation

1
Find your Daily KWh Consumption

Look at your electric bill and find your total monthly KWh usage. Let's say it's 600 KWh per month. Divide this by 30 days.

600 KWh ÷ 30 days = 20 KWh per day
2
Determine your Daytime Target

Solar panels only produce power during the day. If you don't have a massive battery, you only want to size your system to cover your daytime usage (usually about 60% of total usage for a standard home).

20 KWh × 0.60 (Daytime) = 12 KWh target per day
3
Divide by Peak Sun Hours (PSH)

In the Philippines, we get an average of 4.5 "Peak Sun Hours" per day. This is the equivalent of 4.5 hours of 100% maximum sunshine.

12 KWh ÷ 4.5 PSH = 2.66 KW required size
4
Account for System Losses (80% Efficiency)

Solar systems lose power through heat, wiring resistance, and inverter conversion. To get the final size, divide by 0.8 (80% efficiency).

2.66 KW ÷ 0.8 = 3.32 KW ➔ Round to a 3KW or 5KW system

Sizing Solar for Air Conditioners

Many homeowners in the Philippines install solar specifically to run their aircon during the hot daytime hours without guilt. Aircons are the biggest power draw in your house.

  • 1.0 HP Inverter Aircon: Draws ~600W to 800W. Requires at least 3 solar panels (1.6KW) to run smoothly.
  • 1.5 HP Inverter Aircon: Draws ~1,000W to 1,200W. Requires at least 4 solar panels (2.2KW).
  • 2.0 HP Inverter Aircon: Draws ~1,500W to 1,800W. Requires at least 6 solar panels (3.3KW).

If you want to run two 1.5HP aircons all day long, you will need a 5KW system. Read our deep dive on solar panels for aircons for more specific load calculations.

How to Size Your Battery (For Hybrid Systems)

If you are installing a hybrid system, you also need to size the battery. The battery's job is not to run your whole house overnight (that would be extremely expensive); its job is to keep essential loads running during a brownout.

A standard 5KWh LiFePO4 battery (the most common size in the PH) can power the following simultaneously for about 8 hours during a brownout:

  • 1 Inverter Refrigerator (150W)
  • 4 Electric Fans (240W total)
  • 10 LED Lights (90W total)
  • WiFi Router & Phone Chargers (30W total)

Total continuous load: ~510W.
5,000Wh battery ÷ 510W load = ~9.8 Hours of Backup Time.

Warning: Attempting to run an air conditioner on a single 5KWh battery during a brownout will drain it completely in less than 4 hours, and may void the battery's warranty if the surge current is too high. If you want AC during a brownout, you need at least a 10KWh battery bank.

Philippine Peak Sun Hours (PSH) Explained

You might wonder why a 5KW system doesn't generate 5KW for 12 hours a day (60 KWh). The sun's intensity changes throughout the day. Early morning and late afternoon sun is weak. Passing clouds block sunlight.

Engineers use a metric called Peak Sun Hours (PSH). In the Philippines, the average PSH is 4.5 hours. This means a 5KW system will generate roughly:

5KW × 4.5 PSH = 22.5 KWh per day

During summer (March to May), you might hit 5.5 PSH (27.5 KWh/day). During rainy season (July to September), it might drop to 3.5 PSH (17.5 KWh/day).

Peak Sun Hours by Philippine Region

Region / CityAnnual Avg PSHBest MonthWorst Month
Cebu, Central Visayas4.7 hrs/dayApril (5.6 hrs)December (3.7 hrs)
Metro Manila / Luzon4.5 hrs/dayApril (5.4 hrs)January (3.2 hrs)
Davao, Mindanao4.4 hrs/dayMarch (5.2 hrs)December (3.4 hrs)
Iloilo / Bacolod4.6 hrs/dayApril (5.5 hrs)December (3.5 hrs)
Palawan / Island Areas5.1 hrs/dayApril (6.0 hrs)January (3.9 hrs)

*Based on NASA POWER / PVGIS irradiance averages. Island areas consistently receive the highest solar irradiance in the Philippines.

Frequently Asked Questions

For a typical 3-bedroom Filipino home running 2 aircons, a fridge, and basic appliances, a 5KW system (roughly 10 panels) is the sweet spot. For larger homes with 3-5 aircons, a 10KW system (20 panels) is required.
You should pair 5KW worth of solar panels with a 5KW inverter. It is common and safe practice to slightly 'oversize' the panels (e.g., putting 6KW of panels on a 5KW inverter) to ensure the inverter reaches maximum capacity even on slightly cloudy days.
No. In fact, we don't recommend it unless you apply for Net Metering. If you don't have Net Metering, any excess power generated during the day that you don't use is thrown away. Sizing your system to cover 60-70% of your bill (your daytime usage) gives you the fastest ROI.
Yes, but with caveats. You can only add panels up to the maximum capacity of your inverter. If you buy a 3KW inverter, you can't upgrade to 5KW later without throwing away the 3KW inverter. It's often better to buy a 5KW inverter now, install 3KW of panels, and add more panels later.
A 5KW system in the Philippines generates approximately 22.5 KWh per day on average (5KW x 4.5 PSH). Over 30 days, that is roughly 675 KWh per month. At a Meralco rate of P12 per KWh, this translates to about P8,100 in monthly electricity savings.
A small sari-sari store or carinderia typically consumes 150 to 400 KWh per month. A 3KW grid-tie system is sufficient. For a small restaurant with a commercial refrigerator and air conditioning running daytime, a 5KW to 8KW system is more appropriate.
Yes, a 3KW system can power a small home (1-2 bedrooms) running lights, fans, a refrigerator, a TV, and a laptop. It cannot reliably run an air conditioner during the day without exceeding system capacity. For homes with an aircon, a minimum of 5KW is recommended.

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Related Guides: Solar Panel Price List · Turnkey Packages · Solar for Aircon Guide