When people first think about solar, they look up at the roof. That's natural — but it's the wrong first step. The roof decides whether a system fits; your MERALCO bill decides whether it's worth it, how big it should be, and how quickly it pays for itself. The good news: every number you need is already printed on the bill in your inbox. This guide walks you through it, line by line, in plain language.
The two numbers that drive everything
Strip away the jargon and a solar decision rests on two figures from your bill:
- Your monthly kWh — how many kilowatt-hours of electricity you actually consumed. This is the size of the problem you're solving.
- Your blended rate (₱/kWh) — what you effectively pay for each of those kilowatt-hours, taxes and pass-through charges included. This is the price of every unit solar can offset.
Multiply them and you get roughly your bill. More importantly, together they tell you how much a solar system could save each month — because every kWh your panels produce is a kWh you don't buy at that blended rate. Roof orientation, shading and tilt matter, but they only adjust a number that your usage and your rate have already set.
Finding your kWh: read the meter math, not just the peso total
Look for the section of your bill that shows your present reading minus your previous reading, multiplied by a meter constant (usually 1). The result is your kWh for the billing period — typically printed near the top alongside the number of days covered. A household using around 300 kWh a month is a modest user; 500–800 kWh is common for a family home running air-conditioning; above 1,000 kWh usually points to multiple AC units, a pool pump, or a home office.
Don't anchor on a single month. Philippine usage swings hard with the seasons — the hot, humid stretch from March to June can push consumption far above the December baseline. One bill can mislead you by 30% in either direction.
The blended rate, and why it's higher than you think
Your bill does not charge one tidy rate. It stacks several layers, and it helps to know which is which:
- Generation charge — the cost of producing the electricity. This is usually the single largest slice and the one that moves most with fuel prices.
- Transmission charge — moving power across the grid to your area.
- Distribution, supply and metering — MERALCO's charge for delivering it to your door and reading your meter.
- Taxes and government charges — VAT, universal charges and subsidies layered on top.
Add every charge, divide by your kWh, and you get your blended rate — often around ₱11.50 per kWh for a residential account, though it shifts month to month. This blended figure, not the headline generation rate, is the true value of each kWh solar offsets. People consistently underestimate it, which is why they also underestimate their savings.
The most common mistake we see isn't a bad roof — it's a homeowner judging solar against the generation charge alone, then wondering why the math felt thin. Solar offsets the whole stack.
Why a bigger bill means a faster payback
It feels backwards, but the higher your bill, the better solar usually looks. A larger bill means more kWh at a rate you're already paying, so each panel displaces more pesos every single day. Two homes can install nearly identical systems; the one with the heavier AC habit recovers its investment sooner because it has more expensive electricity to avoid.
In Metro Manila, with roughly 1,817 sun-hours a year of usable irradiance, a well-matched residential system commonly lands a payback of 3 to 5 years — and then keeps producing for two decades. Your exact figure depends on your usage, your rate and your roof, which is precisely why we start from your bill rather than a brochure average.
Sizing a system from your usage
Your usage points to a sensible system size before any installer visits. A rough, honest rule of thumb for Metro Manila: each 1 kW of rooftop solar produces somewhere around 110–130 kWh per month, depending on sun and shading. So a home burning ~600 kWh a month might be well served by roughly a 5 kW system — though you rarely want to cover 100% of usage, because production peaks midday while some of your consumption happens after dark.
This is where the shape of your usage matters. If most of your power is drawn in the afternoon heat, more of your solar is consumed on-site in real time. If your heavy use is at night, you're leaning on net metering to bank daytime surplus against evening draw. The DOE allows residential net-metering systems up to 100 kW, far more headroom than any home needs — so the constraint is almost always your usage and roof, not the rule.
Why we ask for 6–12 months of bills
One bill is a snapshot; a year is the real story. Pulling together six to twelve months of bills lets the estimate capture your seasonality — the summer AC spike, the rainy-season dip, the holiday months — so the system is sized for how you actually live, not for one unrepresentative reading. It's the difference between a number you can plan around and a guess.
- Average, not peak. A full year reveals your true baseline and your real range.
- Rate trends. Multiple bills show how your blended rate has moved, so savings projections aren't built on a single lucky or unlucky month.
- Confidence. More data means a tighter, more honest payback estimate — and fewer surprises later.
How Apolaki turns your bill into an estimate
You don't have to do any of this math by hand. When you start a free assessment, you simply upload a photo or PDF of your bill. Apolaki reads the kWh and charges from it, blends in NASA POWER irradiance and Google Solar rooftop data for your specific address, and produces a clear, bill-backed readiness report: an indicative system size, an estimated payback window, and what your savings could look like. The assessment is free for homeowners, and your details stay private — only anonymised rooftop metrics are ever shared with installers, and only after you choose to connect.
If you'd like more background before you start, our blog covers net metering, choosing an installer, and what a fair quote should include. But the fastest way to a real answer is the bill already sitting in your inbox.