Solar & battery
Solar Tilt Angle Calculator
Works tilt against seasonal production, where the choice depends on which season matters.
Result
Roof-mounted panels almost always follow the roof, because tilting them up costs money, catches wind and often needs planning approval. The loss from a suboptimal pitch is usually small enough that adding one more panel is the cheaper fix.
Get a Free Business AuditHow the calculation works
Production at a given tilt compared across seasons, with the annual total and the seasonal split shown. A tilt near latitude maximises the annual figure; a steeper tilt shifts production toward winter at the cost of summer, and a shallower one does the reverse. Which is better depends entirely on what the production is worth when it occurs.
What moves the number
- Latitude and the tilt chosen.
- Which season's production is more valuable.
- Whether the tariff credits exports at retail.
- Snow and self-cleaning considerations.
Where this one goes wrong
Under a tariff that credits exports at full retail value, maximising annual energy is the right objective and tilt follows latitude. Under a tariff that credits exports poorly, production that coincides with consumption is worth far more than production that is exported, which can favour a different tilt and orientation entirely. Decide what you are optimising for before optimising, because the two objectives point different ways.
Before you quote
- Decide whether annual energy or self-consumption is the objective.
- Read the export credit terms before optimising tilt.
- Weigh winter production if heating load is electric.
Where the rules come from
Questions
About this calculator
Should I tilt for summer or winter?
It depends on what production is worth when it happens. Under full retail export credit, maximise annual energy. Under poor export credit, production that coincides with your own consumption is worth much more, which can point to a different tilt entirely.
How much does a steeper tilt cost in annual energy?
Less than the seasonal shift it produces, over a moderate range. Steepening from the annual optimum sacrifices some summer production for winter gain, and whether that trade is worthwhile is an economics question rather than an engineering one.
Does tilt help panels stay clean?
A steeper tilt sheds rain, dust and snow better, which reduces soiling losses and matters in dusty or snowy locations. On a very shallow array soiling accumulates and the annual loss can exceed the tilt advantage on paper.
The formula
tilt in degrees = arctangent(rise / 12)
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
How to use this calculator
- Roof pitch. Enter your own figure; the page starts at 6:12 (26.6 degrees).
- Latitude (degrees). Enter your own figure; the page starts at 39.
- System size (kW DC). Enter your own figure; the page starts at 7.2.
- Peak sun hours per day. Enter your own figure; the page starts at Mid-Atlantic, Ohio Valley (4.5).
The result updates as you type, so you can try a figure, see what it does to roof tilt, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Roof pitch | 6:12 (26.6 degrees) |
| Latitude (degrees) | 39 |
| System size (kW DC) | 7.2 |
| Peak sun hours per day | Mid-Atlantic, Ohio Valley (4.5) |
What comes out
| Result | Value |
|---|---|
| Roof tilt main result | 26.6 |
| Optimal tilt | 39.0 |
| Difference | 12.4 |
| Estimated loss | 1.91% |
| Annual production at this tilt | 9,280 |
A 6:12 roof sits at 26.6 degrees, 12.4 degrees from the optimum here, costing about 1.91% of production.
How sensitive the answer is
Holding everything else steady and changing only latitude (degrees), this is what happens to roof tilt. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Latitude (degrees) | Roof tilt |
|---|---|
| 19.5 | 26.6 |
| 29.25 | 26.6 |
| 39 example above | 26.6 |
| 58.5 | 26.6 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Roof pitch
- Choose from 2:12 (9.5 degrees), 3:12 (14 degrees), 4:12 (18.4 degrees), 5:12 (22.6 degrees), 6:12 (26.6 degrees), 8:12 (33.7 degrees), 10:12 (39.8 degrees), 12:12 (45 degrees).
- Latitude (degrees)
- A number, between 0 and 70, starting at 39.
- System size (kW DC)
- A number, between 0 and 5000, starting at 7.2.
- Peak sun hours per day
- Choose from Pacific Northwest, northern UK (3.5), Northeast, Midwest (4.0), Mid-Atlantic, Ohio Valley (4.5), Southeast, coastal California (5.0), Texas, inland California (5.5), Arizona, Nevada, New Mexico (6.0).
What the results tell you
| Result | What it is |
|---|---|
| Roof tilt | The headline result. A decimal figure. |
| Optimal tilt | A decimal figure. |
| Difference | A decimal figure. |
| Estimated loss | A percentage. |
| Annual production at this tilt | A number. |
A design still needs a site visit
Output and sizing figures use the assumptions you enter, not measured irradiance, shading or roof orientation at your address. Real production depends on all three, plus inverter behaviour and local interconnection rules.
Keep going
Related calculators
Estimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.