How Many Solar Panels Do I Need? A Philippine Sizing Guide (2026)

Quick Answer

There is no fixed answer per house — but there is a four-step calculation, and you can do it from your Meralco bill in about five minutes. The number that changes everything is not your bill — it's how much of your power you use in daylight. A household with someone home all day needs a system roughly 55% larger to be worth building, because it can consume far more of what it makes. Your roof may overrule the calculation entirely. Plan on about 6.5 m² of usable roof per kWp — and "usable" is a lot less than total roof area.

Rough guide, for a household with typical daytime usage:

Why the honest answer isn't a number

Ask most installers this and you get a package: "for your bill, we recommend 6 kW." That answer skips the three things that actually determine whether the system is worth building.

Two households with identical ₱12,000 bills can need very different systems. One has someone home all day using power while the sun is up. The other is empty until 18:00, so most of what the array makes gets exported — earning the lower generation-only credit rather than displacing the full retail rate.

Same bill. Same roof. Different right answer.

So here is the calculation, rather than a package.

Step 1 — Convert your bill into kilowatt-hours

Take your monthly bill and divide by your rate per kWh.

kWh per month = bill ÷ rate

At ₱15.9500 per kWh — Meralco's August 2026 rate for a household in the higher consumption brackets:

Better still, use the real figure from your bill. Your consumption in kWh is printed on it — no need to work backwards from pesos. And your true rate is your total bill divided by total kWh, which accounts for your bracket and fixed charges.

Step 2 — Work out how much you use in daylight

This is the step that separates a good system from a disappointing one, and almost nobody asks it.

Solar produces between roughly 06:00 and 18:00, peaking around noon. Power you use in that window displaces your full retail rate. Power you export earns roughly the generation component — about ₱9.25, or 42% less.

So the question isn't how much you use. It's when.

Don't overthink it. Walk through a normal day: refrigerator runs regardless, but is the aircon on at 14:00 or only at 22:00? Is laundry done at 10:00 or 20:00? Is anyone home to run anything?

Step 3 — Convert to system size

kWp needed = daily daytime kWh ÷ 3.6

That 3.6 is production per kWp per day in Philippine conditions — 4.5 peak sun hours × 80% system efficiency, after inverter losses, heat derating, wiring and soiling.

At 45% daytime share:

At 70% daytime share — someone home all day:

Look at the difference. The same ₱12,000 bill justifies 3.1 kWp for an empty house and 4.9 kWp for an occupied one — 58% more system, from the same bill.

This is also why the free move is so valuable: shifting laundry, ironing, water pumping and dishwashing into daylight hours raises your daytime share, which raises both the system size that makes sense and the return on every panel.

Step 4 — Convert kWp into actual panels

Modern panels sold in the Philippines are typically 450 W to 620 W. Divide your system size by the panel rating.

Higher-wattage panels mean fewer panels, not more power per square metre. A 620 W panel is physically larger than a 450 W one. The roof area for a given kWp barely changes — what changes is the number of mounting points, connections and labour hours, which is why installers prefer larger panels on bigger systems.

The check that overrules everything: your roof

You can calculate the perfect system size and still not be able to build it.

Plan on roughly 6.5 m² of usable roof per kWp. Usable is the operative word — you lose area to:

• Edge setbacks, typically 300–600 mm all round
• Walkways for access and maintenance
• Water tanks, antennas, vents, aircon condensers
• Any roof plane facing the wrong direction
• Shaded sections

A rough rule: usable area is often 60–70% of total roof area.

If the roof allows less than the calculation suggests, the roof wins. That is not a failure — a smaller system on a good roof plane outperforms a larger one crammed into shade.

Orientation and tilt

Two adjustments that shift the answer.

Orientation. In the Philippines, south-facing arrays produce most. East and west faces produce roughly 10–15% less, which is often perfectly acceptable — and a west-facing array can actually suit a household whose peak use is late afternoon.

Tilt. Most Philippine roofs are between 10° and 20°, which is close enough to optimal. Very low tilt collects more dirt and sheds less rain, so soiling matters more on near-flat roofs.

North-facing planes are the weakest option and are usually left out of the layout entirely.

Four common sizing mistakes

1 · Sizing from one bill. Philippine consumption swings hard between April and December. A system sized off May will be oversized; one sized off January will disappoint every summer. Use twelve months.

2 · Sizing to eliminate the bill. You can't, on a grid-connected system. Fixed charges apply regardless, and most homes still import at night. Chasing zero means buying capacity that exports at the lower rate.

3 · Ignoring the daytime share. The single most common cause of disappointing results. A large array on an empty house exports most of what it makes at 42% less value.

4 · Sizing for August. Wet-season output is roughly 64% of April's. Building for the worst month costs about 25% more capacity that then overshoots for eight months of the year.

Work out your own number

Everything above uses averages. Your bill, your roof and your routine are not average.

Try our appliance calculator — set your own rate, add your actual appliances, and see where your consumption really goes before deciding what to build.

Then send us twelve months of bills and tell us roughly when your household is home. We'll model it against your actual roof — including if the honest answer is a smaller system than you expected.

Frequently asked questions

How many solar panels do I need for a Philippine house?

It depends on your consumption and how much of it falls in daylight hours. As a guide, a household with a ₱12,000 monthly bill and typical daytime usage needs about 3.1 kWp — roughly six 550 W panels — while the same bill with someone home all day justifies about 4.9 kWp, or nine panels.

How many solar panels do I need for a 5 kW system?

Nine 550 W panels, eleven 450 W panels, or eight 620 W panels. Higher-wattage panels reduce the count but not the roof area, because they are physically larger.

How much roof space do solar panels need?

Roughly 6.5 square metres per kWp installed. A 6 kWp system needs about 39 m² of usable roof — after edge setbacks, walkways, water tanks, vents and any shaded or wrongly oriented sections. Usable area is typically 60 to 70 percent of total roof area.

How many solar panels to run a house in the Philippines?

There is no single answer, because households differ enormously in consumption and timing. A modest home using 300 kWh a month may need three or four panels to make a meaningful difference; a home with multiple air conditioners using 1,500 kWh may need twelve or more. The calculation matters more than the rule of thumb.

Should I get more panels than I need?

Generally not. Excess generation is exported at roughly the generation-only rate, about 42% below what you pay for imported power, so extra capacity returns considerably less than the first kilowatt-peak. Size to your daytime consumption and shift what you can into daylight hours instead.

Does panel wattage matter when choosing?

Mainly for panel count and installation labour, not for output per square metre. A 620 W panel is larger than a 450 W one, so the roof area per kWp stays similar. What matters more is the temperature coefficient — how much output the panel loses as it heats up — since Philippine rooftops run far above the 25°C rating condition.

Assumptions