Energy Efficiency

How Many Watts Should My Solar Panel System Be?

solar panels on home in fl

Solar panels can play a significant role in reducing your carbon footprint. Better yet, this efficient energy source takes a chunk out of any homeowner’s energy bill. Whether you want to fight against the many environmental crises afflicting the world or battle against your own budget, solar panels are likely the choice for you. More and more people keep making the change because solar power continues to prove it’s for real and can make a lasting positive impact.

However, equipping your home with a solar panel isn’t as simple as a quick impulse-buy after performing a bit of online research. Nor will it take a couple of minutes at a given hardware store. Instead, you must ensure you’re purchasing the solar panel that will suit your needs and is powerful enough for your home’s size and structure.

With all this said, what goes into determining the ideal power levels of a solar panel for your home? What must you measure? And is power the only factor you should consider? Keep in mind, if you don’t have the correct answers, you could end up with the wrong type of solar panel. Then, you won’t reap the benefits that should come with such an investment.

This article will answer the above questions, helping you decide how large of a system you need for your home, so you can enjoy all the advantages of solar energy.

What Is A Watt? What Is A KiloWatt?

One of the most common questions we hear is “what’s the difference between a watt and a kiloWatt?”. In reality, the differences are pretty simple.

Watts: A unit of radiant flux or power, the watt (W) is a derived unit of 1 joule per second, used to quantify energy transfer rates.

Here’s how watts are commonly applied:

  • A 100 kg person who takes 5 seconds to climb a 3-meter-high ladder works at a 600-watt rate:
    • In this instance, you multiply the person’s mass by the acceleration due to gravity times height divided by how long it takes to lift the object to the given height.
    • From there, you have the rate of power or doing work.
  • To further illustrate, the average laborer maintains a 75-watt average output during an 8-hour day. And athletes can reach even higher power levels for shorter intervals.

Kilowatts: Equal to 1,000 watts, the kilowatt (kW) is used as the unit of measurement for the power output of electric motors, tools, heaters, and other machines.

It’s estimated that a kilowatt equals 1.34 horsepower and that a small electric heater with one element can use 1.0 kilowatt. Also, a one-square-meter surface area usually receives 1 kilowatt of sunlight on a clear day near the equator.

Most often, solar energy is measured in kilowatt-hours (kWh). Though more substantial systems get measured in megawatts (MW), which is 1,000 kilowatts.

How Much Of Your Energy Usage Do You Intend To Replace?

Before deciding how many kWh your solar panel should be, you need to figure out how much energy you want to replace. Below, we’ll break down the factors that go into these calculations:

Fully Power Your Home With Solar

The US Solar Technologies Office explains how it only takes an hour and a half for the sunlight that strikes the earth’s surface to handle the world’s total yearly energy consumption. So, yes, solar energy is completely capable of powering your entire home.

However, many factors dictate whether your home (and your energy goals) make you a prime candidate for a 100% solar-powered home. First, each home is built differently. And each house needs a specific number of solar panels to convert the sun’s energy into something that can power your home.

Other factors include:

  • Your home’s monthly energy consumption rate
  • The hours of sunlight your house receives
  • The type of solar panels your home needs

Partially Power Or Supplement Your Energy Consumption With Solar

While fully solar-powering your home can take a massive chunk out of your energy bill, the installation and maintenance costs can seriously set you back financially. Plus, some homes aren’t ideally built or located to leverage full solar power, requiring more panels than is economically feasible.

As such, it might be wise to partially solar power your home, supplementing your energy consumption. This way, it won’t take as much work and planning to solar power your home, and you have other energy sources as fail-safes. Furthermore, you’ll still be doing your part in cutting down on your energy consumption and reducing your carbon footprint. Every effort you make helps, even if it’s not full-on adoption.

How Much Power Does Your Home Use Now?

A critical consideration for your ideal system is how much power you tend to use, which we will help you figure out below:

Average Power Use

Recent statistics show a 10,649 kWh annual average annual electricity consumption for a U.S.residential utility customer. Per month, that’s equal to an average of 877 kWh. Of course, the higher your average, the more solar panels you might need.

Peak Power Use

The average power consumption will weigh every hour of the day, not considering the daily ebbs and flows of energy usage. Peak power usage accounts for the times of the day where you use the most power and just how much power you’re using during that time. While your overall consumption might be low, your peak hours might still be substantial. This could mean you require a more robust setup despite not using that much total energy on average.

Your peak hours will be when everyone who lives in your home is there, so likely in the early mornings and after school/work.

What Determines The Power Output Of A Solar Panel?

Here are all the factors that will dictate the power output of your solar panel (spoiler: it goes far beyond kilowatts).

Solar Panel Efficiency

First, it’s important to note that the average efficiency of a solar panel is between 15% and 22%. When solar panels are more efficient, they produce more energy per light that hits the cell, meeting your requirements with less output. It’s worth keeping in mind that wattage and power output aren’t the only factors that define a panel’s performance. For instance, a 250-watt and 300-watt panel might both have 15% efficiency.

Solar Panel Ratings Explained

A solar panel’s rating is based on its generated watts. Higher wattage ratings mean your solar panel will produce more power. Typically, residential solar panels have 250 to 400-watt power output ratings. It’s based on the size of the installation and how successfully it produces energy from the sunlight.

As was just touched upon, higher power ratings are not the only way to weigh a panel’s performance.

Solar Panel Size

Technologies have improved so that solar panels can be designed in smaller sizes while absorbing more sunlight and creating more power than their larger counterparts. So, you could have physically smaller panels that out-produce a group of larger ones.

Of course, physical size matters depending on the space you have on your roof (or on the ground). But efficiency is a far more critical factor. Though, if you can find a panel that produces more energy at a smaller size for a price that makes sense, jump all over it.

Type Of Solar Panel: Mono Vs Poly Vs Amorphous

The panel type in question is another factor you must mull over besides wattage or kilowattage for your ideal solar panel system. Here are the panel types you have to choose from:

Monocrystalline Solar Panels

These panels are made up of monocrystalline solar cells, which consist of a cylindrical silicon ingot. Like semiconductors, the ingot is grown from a single, high-purity silicon crystal. They’re sliced into wafers to form cells. With 17% to 22% efficiency ratings, monocrystalline solar panels are seen as the most efficient on the market.

Polycrystalline Solar Panels

With blue cells comprised of multiple silicon crystals, polycrystalline panels are less efficient than monocrystalline panels. But they’re the far more affordable option of the two.

Amorphous Solar Panels

Amorphous solar panels don’t contain actual cells. Instead, they’re created by a deposition process that forms silicon directly on the glass substrate. A film gets produced by the amount of silicon. It’s typically around 100-times less than a polycrystalline cell’s thickness. These cells are efficient, but they need twice as much surface area to equal a monocrystalline panel’s output. However, amorphous cells perform better in low light conditions compared to your top monocrystalline models on the market.


You can mount your solar panel on the roof or on the ground. Both options have their advantages and disadvantages, but you want direct access to the sunlight either way.

Direction & Angle

Since you’re living in the northern hemisphere, the best practice is mounting your solar panel so that it’s south-facing. This way, your panel captures the maximum amount of sunlight since the sun is along the southern part of the sky.

South-facing panels should be tilted at 30-40-degree angles, changing based on the latitude of your home. Getting your angle right ensures the sunlight hits the panel perpendicularly to generate the most energy. Also, this angle allows for snow to slide off during the winter in northern latitudes.

Battery Storage Increases Energy Freedom

Battery storage maximizes how much electricity your solar panel retains. It allows you to take more control of your energy, providing surplus electricity that’s stored in the battery until needed. You’ll find that battery storage pays massive dividends during an outage, sunsets, or any other time you need extra power.

Make The Decision Easier With Our Solar Energy Calculator

All the information provided in this article should offer plenty of value and insights to guide your search for the ideal solar panel. You can also make your decision even better informed by using our solar energy calculator. Furthermore, by submitting your information to us, you’ll have the expertise of a local installer on your side. This will further inform your purchasing decision while providing an exact quote on the installation.