How to Interpret Solar Power Graphs

Solar power graphs are a depiction of how much power (or, in a related format, energy) a solar energy system produces over time. Graphs that show a full day or many days usually show one or more peaks, which correspond to power collected during daylight hours. Learning to interpret solar power graphs can help you if you're interested in understanding or buying a solar power system.

Difficulty: Moderately Easy

Instructions

1. Determine the type of information measured on each axis of the graph. Usually, solar power graphs depict time on the horizontal axis and power (or energy) on the vertical axis.

2. Examine the tick marks and associated units on each axis. The horizontal (time) axis may use units of days, hours or another increment. The vertical (power or energy) axis typically uses kilowatts for power or kilowatt-hours for energy.

3. Look at the overall shape of the graph. For power graphs, the curve should generally increase and peak in the middle of the day and then decrease toward zero as darkness falls; there should be no power at night. For energy graphs, the curve should increase during daylight hours and remain flat at night.

4. Study the smaller fluctuations of the graph. These small changes indicate the effect that passing clouds and other such phenomena have on the power collection of the system.

Tips & Warnings

• A kilowatt-hour is the amount of energy required to power ten 100-watt light bulbs for 1 hour.
• A sharper overall plot of solar power indicates the system is not good at steadily collecting power over a long period of time during the day. A broader curve indicates the opposite. For example, a system that changes the orientation of solar panels to align with the sun throughout the day will have a curve that's less sharp than a system that has fixed panels.