Solar Computation: Size Your Solar Setup From Your Electric Bill

Last checked 20 October 2026 · JH Solar guide

How This Solar Computation Works

A solar computation answers three questions. How much energy do you use in a day? How much panel power makes that energy under Philippine sun? And how much battery and inverter does your goal need? People look for a solar panel calculator because quotes are hard to compare when you do not know the size you need, and brownouts make backup urgent. Knowing your own figures also helps you check a seller’s numbers before you pay.

Send your bill or type it in

Type the kWh used, or the bill amount and rate, yourself. Or send a photo of the bill, account number covered, through the channels on our contact page for quotes and inquiries, and we will do the computation with you. The appliance list works even without a bill, for a new house or a small shop.

A table places your result next to JH Solar Version 1 and Version 2, so you can see whether a ready package covers your need. Copy my estimate copies a short summary you can paste into a message.

How to Read Your Meralco or Electric Cooperative Bill

Every solar computation starts with the bill. Meralco and electric cooperative bills look different but carry the same items, and you need only three: kWh used, billing period and total amount. Look near the meter readings: present minus previous reading is the kWh you used (some meters use a multiplier, so take the kWh figure the bill prints). The billing period shows the start and end dates.

The rate is split into many lines, so divide the total amount by the kWh used to get your effective rate. Charges change every month, so last month’s rate is only a guide. For a wider view, see the Department of Energy’s electricity rate data for the Philippines. In the calculator, always type the rate from your own latest bill, not a figure from the news.

From Bill to kWh: The First Step in Solar Computation

Panels are sized in energy, not pesos, so the first step of any solar computation is to get kWh. If your bill shows kWh, use it. If you only have pesos: monthly kWh = bill ÷ rate per kWh. Divide by 30 for daily kWh, as the calculator does.

Billing periods often run a few days more or less than 30, so for a closer figure divide by the real number of days. Hot months bring more aircon hours, so average two or three bills for the panels, and keep your highest month in mind for the battery and inverter.

The Appliance Method: How to Compute Solar Setup Load by Load

This is how to compute solar setup sizes without a bill, or for backup of only some loads: daily kWh = watts × hours per day ÷ 1,000, added up for every appliance. Take the watts from each label. An inverter-type aircon draws less than its maximum most of the time, so use an average draw. Example from our records: 800 W × 8 h ÷ 1,000 = 6.4 kWh a day.

The list gives two figures. Daily kWh sizes the panels and battery. Peak load, everything that can run at once, sizes the inverter. Unless you type your own peak, the calculator adds up the whole list: here 800 + 150 + 120 + 50 + 100 = 1,220 W.

Peak Sun Hours and System Factor

Two assumptions turn daily kWh into panel size in a solar computation. Both sit under Assumptions in the calculator.

Peak sun hours count hours of full-strength sunlight. Morning and late-afternoon light is weak, so a long day gives far fewer peak sun hours than daylight hours. In the Philippines they are typically about 3.5 to 5 a day, depending on place and season; the calculator starts at 4. Check your city on the Global Solar Atlas map of solar resource.

Panels never deliver their full rating to your sockets. The system factor is the share of panel rating that reaches your loads after heat, dust, cable and inverter losses. The calculator starts at 75%; use less for a shaded or rarely cleaned roof.

Sizing Panels, Inverter and Battery

With daily kWh, peak sun hours and the system factor in hand, the rest of the solar computation is three short formulas. Change the panel size in the calculator to the panel you plan to buy, because the count changes with it.

• Panels: array kWp = daily kWh ÷ (peak sun hours × system factor). Divide by one panel’s kW and round up. The calculator starts with 620 W panels and covers 100% of your use; lower the “share of use to cover” to size a smaller array.
• Inverter (kW, not kWh): the highest load running at once, plus room for start-up surges from aircon compressors, refrigerators and pumps. The calculator adds 25% headroom, which you can change; also check the surge rating in the inverter’s data sheet.
• Battery, nominal vs usable: you cannot use a battery’s full label capacity (you stop before it is empty to protect its life), and some energy is lost on the way to the outlet. Nominal kWh = backup kWh ÷ (usable share × efficiency). LiFePO4 is the common home chemistry and handles deeper cycling than lead-acid.

Three Goals, Three Different Results

The goal you pick changes the battery most; panels follow daily use in all three. Lower my bill needs no battery, but a grid-tied inverter shuts down during a brownout to protect line workers, so it gives no backup. Unused daytime energy earns credit only under net metering: read the Meralco net metering FAQ and check current requirements with your utility.

Backup for brownouts sizes a battery for the loads and hours you choose, such as fans, lights, the refrigerator and Wi-Fi. Off-grid assumes 60% of daily use happens after sunset; if your evenings are lighter or heavier, use the backup option with your own figure. Off-grid also needs extra panel and battery margin for cloudy days, because the calculator sizes for an average day. Example at 10 kWh a day: backup of 500 W × 8 h = 4 kWh needs about 5.56 kWh nominal; off-grid needs 6 kWh, about 8.33 kWh nominal.

How Net Metering Changes Your Solar Computation

With Lower my bill, ask what happens to solar you do not use the moment it is made. Without net metering it is held back by the inverter (zero export) or wasted. With net metering, the surplus goes to Meralco or your cooperative and earns a peso credit, which since the 2025 rule changes can roll over to later bills.

Credits are worth less than the power you buy: the DOE says exports are credited at the utility’s blended generation cost, not the full rate per kWh. So keep your solar computation sized to your own daytime use, and treat exports as a bonus. Systems up to 100 kW qualify, and the account must be in your name. For documents, fees and timelines, see our net metering guide for the Philippines.

Worked Examples

These follow the calculator’s solar computation steps with its defaults. Examples only, not quotes.

Example 1, a ₱9,500 bill, lower my bill. ₱9,500 ÷ ₱16.50 (an example rate, not a current one) ≈ 576 kWh a month ≈ 19.2 kWh a day. Array: 19.2 ÷ (4 × 0.75) ≈ 6.40 kWp, or 11 panels of 620 W. That is above Version 1’s 3.72 kWp and within Version 2’s 10.08 kWp (14 × 720 W). No battery is needed for this goal, though you may still want one for brownouts.

Example 2, the appliance list, backup. 9.26 kWh ÷ 3 ≈ 3.09 kWp, or 5 panels of 620 W, inside Version 1’s 6 × 620 W array. To back up the aircon alone for 8 hours: 6.4 ÷ (0.80 × 0.90) ≈ 8.89 kWh nominal; inverter about 1.5 kW for the whole list. Version 1 is rated at 7 kW with a 16 kWh battery, so both fit on paper; we confirm the fit after an assessment.

Example 3, Version 2’s battery. The rated 15.36 kWh × 0.80 × 0.90 ≈ 11.06 kWh to AC loads, about 11 hours at a constant 1 kW. Real loads rise and fall, so actual hours will differ.

What a Solar Computation Cannot Tell You

A solar computation has clear benefits: it shows your real usage, lets you compare quotes on the same kWp, and helps you spot a package that is too small. It cannot check:

• String limits. Each panel string must fit the inverter’s voltage and current limits (cold Voc, hot Vmp, Isc) on each MPPT (maximum power point tracker). Version 2’s 7 panels per MPPT is 5.04 kWp per tracker by power alone.
• Shade from a tree, water tank or neighbor’s wall, which can cut output far more than its size suggests.
• Your roof: direction, tilt, space, and whether the trusses can carry panels and stay put in a typhoon.
• Wiring and permits for your LGU and utility.

Sending Your Bill Safely

For a solar computation we only need the kWh used, the rate or total, the billing period and your city or municipality. We do not need your account number, full name or street address at this stage.

• Cover the account number, name and address with a sticky note before taking the photo.
• Or skip the photo and type the kWh, rate and city in your message.
• Paste your Copy my estimate summary so we see the same numbers you saw.

Next Steps: Quote, Inquiry, Email Updates or DIY

Once your solar computation is done, you have four paths. Pick the one that fits your budget and how hands-on you want to be.

Ask for a quote or send an inquiry

Send your estimate, bill details, city and a few roof photos showing where panels could go. We reply with questions, then arrange a site assessment. The price of a JH Solar package is confirmed after that assessment, because roof, distance and wiring change the parts list.

Get solar updates by email

Email updates are being set up. When sign-up opens, a subscribe link will appear in the calculator.

Do it yourself

If you want to build or manage the project yourself, start with the best solar panel, inverter and battery brands, then compare solar providers in the Philippines or the budget-friendly options. To understand the wiring before you buy anything, open the solar setup diagram hub, then the step-by-step guide with pictures for your system:

• Off-grid setup guideA small battery system you can wire on the DC side.
• Hybrid system guidePanels, battery and grid power together.
• Grid-tied guideDaytime savings and net metering steps.

Portables, and when to step up

A portable power station with a solar panel suits phones, a fan, a laptop and lights. If your computation shows several kWh a day or an aircon, a portable will run out fast. Our step-up is JH Solar Version 1 and Version 2: plug-and-play, floor-standing all-in-one units with the inverter and battery in one cabinet. They can be moved (Version 2 rolls on casters, about 160 kg) and work with a roof array.

Using the Solar Panel Calculator on Your Phone

The calculator is built for phones. A few tips make it easier:

• Open a photo of your bill or your utility’s app in another tab, then switch back to copy the kWh.
• Tap Assumptions to open the hidden settings.
• Turn your phone sideways to see the tables in full.
• Use Copy my estimate, then paste it into your message app.
• Nothing is saved when you close the page, so copy your estimate first.

Philippine Context: Brownouts, Typhoons, Heat and Rain

A solar computation for a Philippine home must fit local conditions. Brownouts are why many families add a battery, so note how long yours last and which loads truly matter. Heat lowers panel output, and the rainy season brings fewer peak sun hours, so run the solar computation again with a lower value if year-round output matters.

Typhoons bring strong winds. PAGASA issues tropical cyclone wind signals; mounting must suit your area’s wind loads, and the array should be inspected after storms. Net-metering and zero-export rules change, so check with your utility (as of October 2026).

Conclusion

A good solar computation turns your bill or appliance list into four numbers: daily kWh, array kWp, battery and inverter size. Keep the assumptions honest for Philippine sun and heat, and pick the goal that matches your real need: a lower bill, brownout backup or off-grid.

Use the estimate to compare packages and quotes on equal terms. Then let a site assessment settle what the numbers cannot: shade, roof, string limits and permits. When you are ready, copy your estimate and reach us for a quote, or follow the DIY path above.