Performance and output

Output loss from tree shading calculator

Enter your annual output, the tree's height and distance, canopy type, and a growth projection. See today's loss and how it might grow over time.

Your system and the tree

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your system
Use your system's rated annual output with no tree shading applied.
Find this on a recent utility bill.
3 The tree
Estimate using nearby reference points, or ask an arborist for a precise measurement.
Closer trees cast a bigger relative shadow than distant ones of the same height.
Deciduous trees cut their own shading impact for part of the year automatically.
Use 0 for today's loss only, or a longer horizon to see how growth affects output.
Fast-growing species like poplar or pine can exceed 2 ft/yr, while oaks grow much slower.

How it works

Three steps to today's loss and tomorrow's

Step 1

Measure the tree's height and distance

These two figures set the shadow-casting geometry. Check the general shading loss estimator too if you have multiple shade sources beyond just this one tree.

Step 2

Identify the canopy type

Deciduous trees cut their own impact for part of the year, while evergreens shade consistently across all four seasons.

Step 3

Project the tree's growth

Trees keep growing, unlike buildings or chimneys, so this step matters more here than for other shading sources like the ones in the chimney shading calculator. Under a tree, the inverter choice decides how much of the array the shade drags down, and the microinverter vs string inverter output tool compares the options.

Understanding your tree shading loss

What a typical nearby tree costs today

A 40 foot deciduous tree standing 60 feet from the array costs around 5.9% of annual output today. An 10,800 kWh/year system would lose roughly 634 kWh a year under those conditions, growing as the tree matures. Height and distance together determine how far the tree's shadow reaches across your array during low-sun-angle hours. A NREL study on shaded PV arrays found that shadows from external obstructions can reduce power by over 30 times their physical size, a dynamic relevant to any growing tree canopy.

Why deciduous and evergreen trees behave so differently

Deciduous trees lose their leaves for part of the year, cutting their shading impact significantly during that season, while evergreen trees cast a consistent shadow year-round. A deciduous tree typically costs roughly half the annual output loss of an equally sized evergreen in the same spot, since bare winter branches let far more light through than a full evergreen canopy. That seasonal gap is the main reason the same tree can look harmless in January and costly in July, and the Department of Energy's review of federal solar performance lists shading among the standard loss factors that separate modeled output from measured output.

Why growth projection matters for trees specifically

Trees can grow a foot or more per year depending on species and age, so a shadow that barely touches your array today can grow into a serious problem within five to ten years if the tree isn't trimmed or removed. Fast-growing species like poplar or willow pose a bigger long-term risk than slow-growing oaks or maples, even starting from the same height.

Weighing removal or trimming against the output loss

Compare the recovered annual output value against the cost of professional tree trimming or removal, factoring in the tree's projected growth over the next several years, not just its current height. A tree that's a minor issue today but projected to become a major one in five years often justifies earlier action than waiting until the loss becomes obvious. The morning vs afternoon shading tool can help pinpoint exactly which hours are most affected before you decide. The vegetation trimming maintenance cost tool can help put an actual number on the trimming side of that comparison.

What to do with this number next

If the tree shares roof space with other shade sources, run the general shading loss estimator too for a combined picture, or check partial shading if the tree only clips a thin edge of your panels rather than covering them broadly.

Questions

Frequently asked

A 40 foot deciduous tree standing 60 feet from the array costs around 5.9% of annual output today. An 10,800 kWh/year system would lose roughly 634 kWh a year under those conditions, growing as the tree matures.

Deciduous trees lose their leaves for part of the year, cutting their shading impact significantly during that season, while evergreen trees cast a consistent shadow year-round. A deciduous tree typically costs roughly half the annual output loss of an equally sized evergreen in the same spot.

Trees can grow a foot or more per year depending on species and age, so a shadow that barely touches your array today can grow into a serious problem within five to ten years if the tree isn't trimmed or removed.

Compare the recovered annual output value against the cost of professional tree trimming or removal, factoring in the tree's projected growth over the next several years, not just its current height.

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