How Many Solar Panels Do I Need?

Last Updated on January 5, 2023 by Jeremy Pearl
Nov 11

If you’re considering installing solar panels on your home, you’re probably wondering how many panels you need.

How many panels should you install if you have a 3,000-square-foot home? What if you live in a smaller space? Deciding how many panels you need is a critical first step in your upcoming project.

Here at Sandbar Solar & Electric, we’ve helped thousands of homeowners in the San Francisco Bay Area and Central Coast determine the ideal array size for their homes. We’re experts in helping people design solar energy systems that help them meet their goals.

In this blog, we’ll discuss how to select the appropriate number of solar panels based on your specific needs.

Let’s dive in.

Before You Calculate How Many Solar Panels You Need, Do This:

Here are three critical considerations to think about before calculating the ideal solar panel system size for your property:

Step 1: Determine your property’s average energy requirements

Before going solar, it’s important to understand the annual energy requirements of your home.

One of the best ways to do this is to consult your past utility bills.

Look for “monthly kilowatt-hours” or “kWh” usage. Usually, these numbers are under headings like “Total Usage” on the Details of Electric Delivery Charges page and are generally represented in lengths of 30 days.

The kWh your home uses per month will vary depending on location and climate. A small house in a relatively mild climate may only use 200 kWh per month, while larger, air-conditioned homes in warmer climates may use 2,000 kWh per month or more.

PG&E customers can access their 12-month electric usage history through their online account or by calling PG&E’s California Solar Hotline at (877) 743-4112.

Remember that solar panels only produce energy during the daytime (when the sun is shining). With this in mind, your solar energy consultant will design a system that produces the energy you expect to use both day and night.

Step 2: Determine how many hours of sunlight your home gets

Now that you understand your home energy usage, you’ll want to understand how much sunlight your home receives daily. Don’t fret! Your Sandbar Solar consultant can guide you through this step.

If you’d like to research this on your own, use the Renewable Resource Data Center, which provides geographical sunlight information. Another clever online tool is Project Sunroof.

Understanding daily hours of sunlight is critical because it impacts how much energy your home’s solar array will eventually produce.

While homeowners in less-sunny areas can certainly install solar panels, their systems won’t produce as much energy as panels in very sunny areas.

Your Energy Consultant will use state-of-the-art solar design tools to model a variety of system sizes at your property, taking into account all of the factors that impact energy production. We even factor in historical weather data.

If you’re considering installing an off-grid system (one that is not connected to the public utility grid), you’ll need more panels than you would for an grid-tied system, and you’ll also need batteries.

Before you get too excited about cutting your connection to the grid, keep in mind that going off-grid can be quite expensive (typical off-grid systems start around $100,000).

Whether you plan to install a grid-tied system, or go entirely off-grid, be sure to talk to a solar energy expert about how many panels and batteries you’ll need to create and store energy for your home.

Step 3: Consider your equipment options

Now, it’s time to learn about the various solar technologies available for residential installations.

As you do this, remember that solar panel quality does make a difference. Higher efficiency panels will produce more energy each day and over their lifetime, and it may be in your best interest to pay the added expense to install higher-end panels.

Today, photovoltaic (PV) solar panels (most common in residential installation) come in wattages ranging from about 300-410 watts per panel. These panels also offer different features.

For example, panels that don’t have grid lines on the front have been shown to absorb more sunlight than conventional cells without being vulnerable to issues like peeling or delamination.

These cells are also more robust and corrosion-resistant.

For best results, we strongly recommend working with experienced solar installers.

An expert solar team can make solar panel recommendations based on your property’s unique specifications, budget, and needs. They’ll also have access to the best quality materials in the industry.

So, How Many Solar Panels do I Need to Power my House?

how many solar panels i need

Once you’ve considered the factors above, we recommend working with a solar provider to calculate precisely how many solar panels you need to cover your home’s energy usage and design the perfect solar panel system for your needs.

Here’s a breakdown of the recommended system sizes for various monthly kilowatt-hour usage profiles in Central California based on monthly electricity usage:

  • 500 kWh per month. For a 500-kWh monthly energy usage, you’d need a typical system size of about 3.6 kW or nine 400W solar panels.
  • 700 kWh per month. For a 700-kWh monthly energy usage, you’d need a typical system size of about 5.0 kW or about twelve 400W solar panels.
  • 1,000 kWh per month. For a 1,000-kWh monthly energy usage, you’d need a typical system size of about 7.2 kW or about eighteen 400W solar panels.
  • 2,000 kWh per month. For a 2,000-kWh monthly energy usage, you’d need a typical system size of about 14.4 kW or about thirty-six 400W solar panels.
  • 2,500 kWh per month. For a 2,500-kWh monthly energy usage, you’d need a typical system size of about 17.92 kW or about forty-five 400W solar panels.
  • 3,000 kWh per month. For a 3,000-kWh monthly energy usage, you’d need a typical system size of about 21.6kW or about fifty-four 400W solar panels.

While those are general breakdowns, it’s important to remember that many variables can impact solar panel array sizing (specifically shading and the direction & tilt of your solar panels).

One handy “back of the napkin” calculation you can use is the “kilowatt-hour per kilowatt” formula which notes that 1 kW of solar in Central California produces approximately 1,500 kWh’s per year.

The 1,500 number will be smaller where shading exists and when solar panels are not facing due-south, but this formula will give you a good starting point to size your system.

To use this formula, divide your annual kilowatt-hour usage by 1,500, and that result is the approximate DC system size you’ll need.

For example, if your annual kWh usage is 9,800 kWh/year:

9,800 / 1,500 = 6.5 kW DC (approximately 16 400-watt panels)

With all this in mind, we recommend working with a solar provider to calculate precisely how many solar panels you need to cover your home’s energy usage and design the perfect solar panel system for your needs.

At Sandbar, we offer a Free Initial Consultation that includes an in-person home visit (for most locations in the Central Coast area). Once we complete our initial site evaluation, we can design a custom solar energy system to meet your needs.

Call today to explore your options!

3 Important Tips for Solar Panel System Sizing

These days, the future is moving towards the electrification of everything in our homes.

For this reason, you will want to consider more than just your historical electricity usage when you size your solar energy system.

Follow these professional tips for accurate system sizing:

1. Size for the future

When sizing a PV system, we also recommend “sizing for the future.” You can save money by reducing the need to increase your system size later. With this in mind, factor in your future energy needs.

Are you planning to add:

  • Electric vehicle(s)
  • An Accessory Dwelling Unit (ADU)
  • Pool
  • Air Conditioning
  • Hot tub
  • Sauna
  • Heat pump
  • Induction stove

Will you be transitioning your gas dryer or gas water heater to electric when those appliances need to be replaced?

Make sure to discuss all these topics with your Solar Energy Consultant. At Sandbar Solar & Electric, we are experts in this conversation, and we can approximate energy use for these items and size your solar energy system accordingly.

2. Account for panel degradation

As you think about how much sunlight your home gets and how many panels you’re likely to need, remember that solar panels degrade slowly (approx. 9-15% over 25 years, depending on which solar panel type/brand you purchase).

As they degrade, they produce less energy over time. To accommodate the electrification of everything in the home (gas appliances are being eliminated in new homes, for example), consider adding a couple more panels than you may need today.

Here at Sandbar, the most common feedback we hear from past solar customers is, “I wish I had added more panels from the start.”

3. Consider electric panel safety

Just like anything else in your home, it’s essential to make sure your solar panels and electric panel are all in good working order and that you’re replacing old, worn-out parts that could be dangerous.

As you research solar panels, here’s a side note on electric panel safety: If you have an existing panel that is old or from a brand known to have safety concerns (Zinsco, Sylvania, Federal Pacific), consider upgrading your electric panel when you go solar.

Not only will you benefit from the 30% federal tax credit to offset some of those costs, but most solar companies won’t install solar on those electric panel types.

Ready to Install Your Perfect Solar Array? Sandbar is Here for You

If you want to go solar in the San Francisco Bay Area or Central Coast, contact the solar panel experts at Sandbar Solar & Electric.

We can help you properly size your solar array and account for all your current and future electrical needs.

We service residential and commercial customers throughout the Central Coast, including in San Jose, South San Francisco, Los Gatos, Scotts Valley, Santa Cruz, Monterey, Carmel, and more.

Call Today for a Free Solar Consultation: (831) 469-8888

About the Author

Jeremy has worked in the solar industry since 2006. He has a Bachelor’s Degree from UC Santa Cruz in Environmental Studies. Jeremy has spent most of his solar career in residential sales and Sales Management in both California and Hawaii. He was raised in Santa Cruz County and is passionate about helping local residents make the switch to clean and reliable renewable energy. Jeremy lives on the Westside with his wife and two boys and enjoys music, photography and hiking in his personal time.