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3kW vs. 8kW vs. 20kW of Solar: What Will It Power?

Solar 101/
how much power do 3kw, 8kw and 20kw solar systems produce

An essential part of installing a renewable energy system is deciding what size it should be. Determining solar panel system size depends on numerous factors, and you’ll need to carefully consider what your energy needs are.

This article will walk you through everything you need to know about the differences in solar panel system sizes and their applications.

The Difference Between Power and Energy

The formal definitions state that energy is the capacity to do work, and power is the rate at which work is done.

The best way to explain those definitions is to use a lightbulb as an example. Let’s start by saying that you have a 100-watt lightbulb that you leave on for 10 hours. You’ll use 1,000 watt-hours.

The lightbulb uses 100 watts of power (the rate), and in 10 hours, it would use 1,000 watt-hours of energy (the amount of work done).

When we talk about electric bills and solar panel systems, we usually mention “kWh” which stands for kilowatt-hours. A kilowatt-hour is 1,000 watt-hours, so in our example, the lightbulb used 1 kWh.

Solar Power and Solar Energy

Solar panel systems don’t use power, but instead generate power. However, the same math (from the lightbulb example) still applies. A 100-watt solar panel with 10 hours of peak sun will generate 1,000 watt-hours of energy or 1 kWh.

Note that when we talk about how much energy a solar system generates, we use the term “peak sun hours.” The sun may be up for 12 hours a day (more in the summer and less in the winter), but the sun is not at full strength for the whole day. The number of peak sun hours is equivalent to how many hours the sun is out at full force.

Location is critical. After you factor in average weather conditions, southwestern states get 5.5 peak sun hours while northeastern states (think the Seattle area) only get 3.5.

How Much Energy Does a 3kW System Produce?

If you install a 3kW solar power system, you can expect it to generate around 375 kWh or 12 kWh daily. That is enough energy to run a 55-gallon water heater with average household use.

How Much Energy Does a 5kW System Produce?

A 5kW system would generate around 625 kWh per month which is enough energy to keep one room cool with a 9,000 BTU window air conditioner in  August in a hot climate.

How Much Energy Does an 8kW System Produce?

8kW solar systems are popular among consumers. These systems generate close to 1,000 kWh per month, enough to cover the average electric usage of a small house with all gas appliances in a temperate climate.

How Much Energy Does a 10kW System Produce?

10kW solar systems will provide enough energy for the small home described above, plus an electric vehicle that averages 25 miles per day.

How Much Energy Does a 15 to 20kW System Produce?

A 20kW solar system will generate more energy than the average home uses. But, if you are in a large home or live in a hot climate that requires constant air conditioning use, a 15kW or 20kW solar panel system might make sense for you.

Take our Solar Quiz to determine which solar panel kit you need.

5 Tips to Size a Solar Panel System for Your Home

Calculate Your Average Energy Usage

To size a solar energy system for your home, you first need to calculate your energy usage in a year. Look at the past 12 months of electric bills to determine the average amount of energy you use. Then, look at what size system will offset the desired percentage of your electric usage. Check out our easy calculator here.

Look at Your Available Roof Space

In sizing your solar system, there are other factors to consider, like how much roof space you have. If you decide that a 15kW solar system is right for you, but your roof only has room for 12 solar panels on your roof, you might have to compromise.

In this scenario, you could use higher-watt solar panels to maximize energy from your limited space. Reach out to us for a free system design, and we’ll show you what kind of solar panel configurations are possible for your home.

Assess Your Roof Orientation

The orientation of your roof also matters. In all the previous examples, we assume the solar panels face south. If your roof faces east or west, your solar system will generate less power, so you’d need a bigger system to get the kWh you want.

Calculate the Full Cost of Solar

Another factor to consider is payback on the solar energy system. You should compare the cost of electricity from your utility company with the cost of your solar panel system. For example, an 8kW solar system costs more per watt than a 20kW solar system, which means that the larger your system is, the lower the average cost per kWh generated.

Lastly, don’t forget to calculate the costs and savings from your solar installation. The federal tax credit is currently 26% for systems installed before December 31, 2022, and 22% for systems installed in 2023. There may also be local rebates or tax credits that can offer you additional savings.

Read: What is the Cost of Solar Panels?

Ask the Experts

Sizing the right solar panel system can be challenging, as you have to consider several factors. So don’t go it alone! Contact the experts at GoGreenSolar — a team of experienced DIY solar veterans who can walk you through the system design and installation process, end to end. We’ll help you at every step of the way.

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