How to Estimate Solar System Size From Your Electric Bill

If you are thinking about solar, the best starting point is not a random package size. It is your actual electric bill.

Your bill shows how much electricity your home used for the month, usually in kilowatt-hours, or kWh. That number gives a better first estimate than guessing based on the number of appliances or the size of the house.

Quick answer

Start with the monthly kWh on your electric bill, divide it by about 30 days, then compare that daily usage with the expected daily production of a solar system.

Example:

• Monthly usage: 450 kWh
• Approximate daily usage: 450 ÷ 30 = 15 kWh per day
• Planning direction: a solar system should be checked against that daily energy need, your daytime usage, roof space, and whether you want batteries

This is still only a planning estimate. Final sizing depends on roof fit, shading, inverter selection, battery goal, net-metering path, and actual usage pattern.

Step 1: Find the monthly kWh on your bill

Look for the part of your electric bill that shows monthly consumption in kWh. For Meralco customers, the bill layout includes consumption and billing details that help show how much electricity was used during the billing period.

The peso amount is useful, but the kWh is more important for solar sizing because solar panels produce electricity, not pesos. Rates can change, but kWh tells us the amount of energy your home actually used.

Step 2: Convert monthly usage into daily usage

Use this simple planning formula:

```text Monthly kWh ÷ 30 = approximate daily kWh ```

Examples:

This helps identify the rough energy target. It does not automatically mean the solar system must cover 100 percent of that usage.

Step 3: Separate daytime and nighttime usage

Solar panels produce power during the day. That means your daytime usage matters.

A home with heavy daytime loads, such as air-conditioning, refrigerators, pumps, computers, and business equipment, can often use more solar power directly while the sun is available.

A home with mostly nighttime usage may still benefit from solar, but the design question changes:

• Grid-tied solar can reduce daytime grid consumption and may use net-metering for exported excess energy when approved by the distribution utility.
• Hybrid solar adds a battery path for selected loads and nighttime or brownout support.
• A stronger backup or near-zero-import target usually needs a bigger system and more battery capacity.

Step 4: Match the system direction to your goal

The right system size depends on what you want the system to do.

If your goal is lower bill

A grid-tied or hybrid bill-reduction setup may be the starting point. The estimate should look at how much of your usage happens during the day and how net-metering may apply.

If your goal is brownout backup

The important question is not only monthly kWh. You also need to choose priority loads, such as refrigerator, lights, internet, fans, selected outlets, or a small air-conditioning load. Battery size and backup wiring become important.

If your goal is near-zero import

This is a stronger target. It usually needs a larger solar array, a carefully designed inverter and battery setup, and realistic expectations about rainy days, seasonal production, and high-load appliances.

Solar can reduce your dependence on the grid, but no installer should promise a guaranteed zero bill without checking the full site and utility conditions.

Step 5: Check the roof and system assumptions

After the bill-based estimate, the next checks are practical:

• Is there enough roof space for the target panel count?
• Is the roof shaded by trees, walls, or nearby buildings?
• What direction and tilt will the panels have?
• Where can the inverter and battery be safely located?
• Does the electrical panel support the proposed setup?
• Is the project going grid-tied, hybrid, or selected-load backup?
• Will the distribution utility require net-metering documents or interconnection review?

These checks turn a rough estimate into a real proposal.

A simple example

Suppose your home uses around 450 kWh per month.

That is about 15 kWh per day.

A planning estimate would ask:

1. How much of that 15 kWh happens during the day?
2. Do you mainly want lower bill, backup, or both?
3. Do you want a lower-upfront system now or a stronger battery-backed setup?
4. Does your roof fit the needed panels?

From there, a solar provider can prepare a more useful proposal than simply saying, "You need a 5kW package" or "You need an 8kW package" without showing the basis.

What to send for a better estimate

For a fast preliminary solar estimate, send:

• Latest electric bill
• General city or area
• Monthly kWh, if visible
• Main goal: lower bill, backup, or both
• Usual daytime versus nighttime usage pattern
• Priority loads if you want battery backup

You do not need to know the perfect system size before asking. A good solar estimate should help you find that size using your actual bill and goals.

Sources and planning basis

• Meralco explains the structure of the residential electric bill and where billing and consumption details appear: https://www.meralco.com.ph/residential/billing-payment/understanding-your-bill
• NREL PVWatts is a public tool used to estimate solar photovoltaic energy production for grid-connected systems: https://pvwatts.nrel.gov/
• Global Solar Atlas provides solar resource and photovoltaic potential information by country, including the Philippines: https://globalsolaratlas.info/download/philippines

Want a bill-based estimate?

Send Naxo Solar your latest electric bill and your general location. We can prepare a preliminary solar direction based on your monthly kWh, usage pattern, and goal before moving to a more detailed proposal.