How Big of a Solar System Do You Need to Run a House?

How Big of a Solar System Do You Need to Run a House?
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    With the cost of living seemingly rising everywhere, a lot of people have a growing interest in solar power. The prospect can feel daunting as they don't necessarily know how big of a solar system they need to run their entire home.


The answer to this question depends on a few different factors, including the size of the home, average energy usage, and the climate the home is in. Here are some steps for figuring it all out!

Get a Baseline for Energy Usage

The first thing you need to do is calculate your home’s average energy usage. This can be done by looking at your past energy bills and finding the average amount of kilowatt-hours (kWh) you use per month.

Energy usage will typically be higher in the summer months due to air conditioning usage and lower in the winter months. This isn’t always the case though, and depending on the age of your home, your insulation – or lack of it – and your heating methods, it could be the opposite.


Once you have your monthly average, you need to find out how much of that energy usage is from appliances that can run on solar power. This includes things like refrigerators, washers and dryers, dishwashers, and lights.

These are typically referred to as "base load" appliances, as they are always running or need to be run regularly.

For appliances that are plugged into an outlet, you can usually find out how many watts they use by looking at the appliance label or owner’s manual. If you can’t find this information, there are online calculators that can help you estimate wattage usage.

Once you have a list of all the base load appliances in your home and an estimate of the wattage each one uses, you can start to figure out how big of a solar system you’ll need.

Determine the Size of Solar Panel Needed

The size of the solar panel is determined by the amount of power it produces in watts. A standard solar panel produces between 250 and 400 watts of power.

To find out how many solar panels you need to run your home, you first need to calculate the total wattage of all your base load appliances. Once you have that number, you can divide it by the number of watts produced by a standard solar panel. This will give you a rough estimate of how many panels you’ll need to install.

For example, if your total appliance wattage is 1,500 watts, you would need at least four solar panels to run your home. Don’t forget to include in your calculations the need to power any other electrical devices you might have, such as computers, TVs, and stereos.

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Efficiency and Installation

You also need to factor in the efficiency of the solar panels you’re using. Solar panel efficiency is the amount of sunlight that hits the panel that is converted into usable electricity.

Solar panels typically have an efficiency rating between 15% and 20%. This means that for every 100 watts of sunlight that hits the panel, between 15 and 20 watts of electricity are produced.

Another thing to consider is the installation method you’ll be using. Solar panels can either be installed on your roof or on the ground. Ground-mounted systems tend to be more efficient as they can be oriented to maximize exposure to the sun.

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Roof-mounted systems are typically less efficient as they can be shaded by trees or other objects. Experts at Harmon Solar can help you make your decision to ensure you get the right system for your needs.

Now that you know how to determine the size of the solar system you need to run your home, you can start planning your installation. Be sure to factor in the cost of the inverters, batteries, and other equipment needed to get you up and running!

Reach out to your local solar pros if you have questions or need help.

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