# What is the best solar panel tilt?

Computes the best fixed tilt for solar panels from latitude, the tilt that faces the noon sun on any date from the sun’s declination, and which way the panels should face.

- Page: https://www.acalculator.org/construction/solar-panel-tilt-calculator
- JSON spec: https://www.acalculator.org/construction/solar-panel-tilt-calculator.json
- Version: 199d78a3c17f

## Default answer

Example with the default inputs (Latitude 40, Date October 19, 2026) on the example date Monday, October 19, 2026: For the year, tilt them 40° facing south; on this date, tilt them 51° facing south.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| lat | Latitude | Your latitude in degrees: positive north of the equator, negative south. |
| date | Date | The day to angle the panels for. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| yearTilt | Year-round tilt | The best fixed tilt for the whole year: the latitude, ignoring its sign. |
| yearFacing | Face the panels | Toward the equator: south in the north, north in the south. |
| dayTilt | Tilt for this date | The tilt that faces the panel square to the sun at solar noon on the date: \|latitude − declination\|. |
| dayFacing | Face them on this date | Toward the noon sun on the date; none when the sun stays below the horizon at noon. |
| yearAdvice | For the year | The year-round tilt and direction, in words. |
| dayAdvice | On this date | The tilt and direction for the date, in words. |
| declination | Sun’s declination | How far north (+) or south (−) of the equator the sun is overhead at noon on the date, in degrees. |
| elevation | Noon sun height | The sun’s angle above the horizon at solar noon: 90° − \|latitude − declination\|; below 0, the sun does not rise at noon. |

## Method

δ = −23.45° × cos(360/365 × (d + 10)); tilt for the date = |latitude − δ|; year-round tilt = |latitude|; noon sun height = 90° − |latitude − δ|; no date tilt when that height is below 0.

## Assumptions

- The panels are fixed and face the equator (true south in the northern hemisphere, true north in the southern).
- The date tilt points the panel at the sun at solar noon; the year-round tilt is the yearly average of that tilt. Cloud, snow and shade can move the best angle a few degrees.

## Worked examples

1. lat = 40, date = 2026-06-21 gives yearTilt = 40, yearFacing = south, declination = 23.449131, dayTilt = 16.550869, dayFacing = south, elevation = 73.449131. Source: PVEducation (Honsberg and Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), d the day of the year with 1 January as d = 1, https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18); PVEducation, Elevation Angle: the sun’s elevation at solar noon from latitude and declination, https://www.pveducation.org/pvcdrom/properties-of-sunlight/elevation-angle (retrieved 2026-10-18); PVEducation, Solar Radiation on a Tilted Surface: a fixed panel gets the most power over a year at a tilt equal to the latitude, https://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-radiation-on-a-tilted-surface (retrieved 2026-10-18).
2. lat = 40, date = 2026-12-21 gives declination = -23.45, dayTilt = 63.45, elevation = 26.55. Source: PVEducation (Honsberg and Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), d the day of the year with 1 January as d = 1, https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18).
3. lat = -33.9, date = 2026-03-20 gives yearTilt = 33.9, yearFacing = north, declination = -0.908037, dayTilt = 32.991963, dayFacing = north. Source: PVEducation (Honsberg and Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), d the day of the year with 1 January as d = 1, https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18).
4. lat = 10, date = 2026-06-21 gives dayTilt = 13.449131, dayFacing = north, dayAdvice = tilt them 13.4° facing north. Source: PVEducation (Honsberg and Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), d the day of the year with 1 January as d = 1, https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18).
5. lat = 70, date = 2026-12-21 gives elevation = -3.45, dayFacing = none (no sun at noon), dayAdvice = the sun stays below the horizon at noon, yearAdvice = tilt them 70° facing south. Source: PVEducation (Honsberg and Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), d the day of the year with 1 January as d = 1, https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18).

## FAQ

### What angle should solar panels be at?

For fixed panels used all year, a tilt about equal to your latitude is the usual starting point: about 40° at latitude 40° N, facing true south. That angle is the average over the year of the tilt that points the panel straight at the noon sun.

### How do I work out the best tilt for a given day?

Find the sun’s declination for the date, then take the latitude minus the declination, ignoring the sign. On 21 June the sun is 23.45° north of the equator, so at latitude 40° N the tilt is 40 − 23.45 = 16.55°.

### Should solar panels be steeper in winter?

Yes. The winter sun is lower, so a steeper panel faces it better. At latitude 40° N the noon tilt is about 63° in late December and about 17° in late June. Panels you can adjust a few times a year collect more than one fixed angle.

### Which direction should solar panels face?

Toward the equator: true south in the northern hemisphere and true north in the southern hemisphere. In the tropics the noon sun is on the other side for part of the year, so the date result can say north while the year-round result says south.

### What is solar declination?

The latitude where the sun is straight overhead at noon. It moves from 23.45° N in late June to 23.45° S in late December and is close to 0° at the equinoxes in March and September.

### Does a few degrees of tilt matter much?

Less than you might think. Output changes slowly near the best angle, so panels set at your roof pitch a little off the ideal still collect most of the energy. Shade and the direction the panels face also matter.

## Sources

- PVEducation (C. Honsberg and S. Bowden), Declination Angle: δ = −23.45° × cos(360/365 × (d + 10)), with d the day of the year and 1 January as d = 1. https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle (retrieved 2026-10-18)
- PVEducation (C. Honsberg and S. Bowden), Elevation Angle: the sun’s elevation at solar noon from latitude and declination. https://www.pveducation.org/pvcdrom/properties-of-sunlight/elevation-angle (retrieved 2026-10-18)
- PVEducation (C. Honsberg and S. Bowden), Solar Radiation on a Tilted Surface: a fixed panel gets the most power over a year when its tilt equals the latitude. https://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-radiation-on-a-tilted-surface (retrieved 2026-10-18)