DIY Solar FAQ: What Are Peak Sun Hours? Posted on 10 Feb 07:30

A DIY solar energy system functions by capturing light energy from the sun and converting it into usable electricity. To provide enough power for your needs, a photovoltaic array must be sized appropriately.

peak sun hours

To accomplish this, you must consider the number of peak sun hours your location receives. What does that mean?

Peak Sun Is not the Same as Available Sunlight

Let’s say the sun rises around 8 a.m. and sets at about 6 p.m. in your area. That adds up to 10 hours of daylight, right?

But this has nothing to do with how your DIY solar system size is calculated. The number of hours of sunlight you see on a daily basis is not the same as the number of peak sun hours for your region of the country.

As the sun moves through the sky, the amount of light varies in intensity over the course of the day. Photovoltaic modules are tested at the maximum intensity, yet your rooftop doesn’t receive that level of sun all day long. So when sizing a DIY solar array, the number of peak sun hours — and not daily sunlight — is what must be taken into account.

This figure is calculated by estimating how much time the maximum intensity or irradiance of the sun reaches an area over the course of a day. This concept is also known as insolation, an acronym for incoming solar radiation.

Why Insolation Matters for a DIY Solar Installation

Insolation levels vary, but even the sunniest climates usually have no more than 6.5 peak hours of sun — far less than the total amount of daylight in these areas.

The lower your insolation level, the larger your photovoltaic system must be to capture enough of the sun’s energy to power your home or business. If your DIY solar array is sized based upon your 10 hours of daily sunlight instead, you may end up with a photovoltaic system that is too small to meet all of your electricity needs.

Determining Peak Sun Hours to Size a DIY Solar System

The National Renewable Energy Laboratory (NREL) has a very helpful map that shows the number of peak hours of sunlight in every region of the country. Take a look and find your state, and you can easily see the insolation for your area.

Technically, you don’t need to know all this, because the easy-to-use Solar GOODs system calculator does all the work to size your photovoltaic system for you. But we find that many of our customers enjoy learning about how photovoltaic design works.

Visit the Solar GOODs site today to learn even more. We are your do-it-yourself online superstore for energy independence. Contact us today for answers to all of your questions about DIY solar power.