Performance and output

Tilt angle output comparison tool

Enter your latitude-optimal baseline output and latitude. Compare estimated annual output across flat, low-pitch, steep, and vertical tilt angles.

Your baseline system

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your system and location
Use your system's rated annual output assuming tilt equal to your latitude.
Used to show the dollar value of the output difference between tilt angles.
Latitude-optimal tilt approximately equals your latitude in degrees.

How it works

Two steps to a full comparison

Step 1

Start with your latitude-optimal baseline

Use your rated annual output at a tilt roughly equal to your latitude, or run the annual output estimator first if you don't have that figure yet. The array tilt angle optimizer finds the tilt that makes the most of that difference.

Step 2

Enter your latitude

Latitude sets the reference point every other tilt angle is compared against. Check the panel orientation comparison tool too, since orientation and tilt work together.

Understanding tilt angle's effect on output

Why latitude sets the optimal tilt

For maximum annual output, the best tilt angle roughly equals your latitude. A home at 35 degrees latitude sees peak annual output with panels tilted around 35 degrees from horizontal. This rule of thumb positions the panel roughly perpendicular to the sun's average position across the year. A DOE assessment of federal solar systems models tilt and orientation as core inputs to its expected-performance calculations.

Why a flat roof isn't a big handicap

Less than most people expect. A flat, 0 degree tilt produces around 96% of what latitude-optimal tilt produces at 35 degrees latitude. An 11,000 kWh/year optimal-tilt system would still produce roughly 10,500 kWh/year completely flat. This is why flat commercial roofs remain viable for solar without needing steep racking. NLR's PVWatts documentation models tilt as one of the core inputs to its output calculation, and confirms that annual output stays relatively forgiving across a fairly wide range of tilt angles around the latitude-based optimum.

Why the output curve stays so flat near the optimum

The sun's position moves through a wide range of angles across the seasons, so any reasonable tilt captures a similar total amount of light over a full year. The output curve only drops off meaningfully at extreme angles far from the latitude-based optimum, which is why most fixed-tilt rooftop systems perform well across a wide range of actual roof pitches.

Tilting for winter or summer priority

A steeper tilt than latitude-optimal favors winter output, since it faces the lower winter sun more directly, while a flatter tilt favors summer output. This tradeoff matters most for off-grid systems relying on consistent winter production. Check the seasonal output calculator to see how this tradeoff plays out month by month. The off-grid panel tilt for winter sun calculator is built specifically around that winter-priority tilt decision.

What to do with this number next

Compare your best tilt option against the flat roof vs pitched roof comparison if your roof geometry is still an open question.

Questions

Frequently asked

For maximum annual output, the best tilt angle roughly equals your latitude. A home at 35 degrees latitude sees peak annual output with panels tilted around 35 degrees from horizontal.

Less than most people expect. A flat, 0 degree tilt produces around 96% of what latitude-optimal tilt produces at 35 degrees latitude. An 11,000 kWh/year optimal-tilt system would still produce roughly 10,500 kWh/year completely flat.

The sun's position moves through a wide range of angles across the seasons, so any reasonable tilt captures a similar total amount of light over a full year. The output curve only drops off meaningfully at extreme angles far from the latitude-based optimum.

A steeper tilt than latitude-optimal favors winter output, since it faces the lower winter sun more directly, while a flatter tilt favors summer output. This tradeoff matters most for off-grid systems relying on consistent winter production.

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