Which direction should solar panels face?
In the US the short answer is south. The useful answer is how much you lose on the roof you actually have.
In the United States, south-facing panels make the most power over a year. Compared with south on a 20° roof in the cities I cover, southwest-facing panels make 2–5% less, southeast 3–5%, west 10–15%, east 13–15% and north 25–31% less over a year (NREL PVWatts).
Yearly output by roof direction
kWh a year from one kW of panels, and the share of south-facing output:
| City | South | Southwest | Southeast | West | East | North |
|---|---|---|---|---|---|---|
| Phoenix, AZ | 1,755 (100%) | 1,677 (96%) | 1,689 (96%) | 1,497 (85%) | 1,514 (86%) | 1,205 (69%) |
| Tucson, AZ | 1,788 (100%) | 1,702 (95%) | 1,732 (97%) | 1,523 (85%) | 1,564 (87%) | 1,243 (70%) |
| San Antonio, TX | 1,503 (100%) | 1,470 (98%) | 1,438 (96%) | 1,355 (90%) | 1,310 (87%) | 1,126 (75%) |
| Austin, TX | 1,483 (100%) | 1,450 (98%) | 1,418 (96%) | 1,336 (90%) | 1,292 (87%) | 1,111 (75%) |
| San Diego, CA | 1,716 (100%) | 1,674 (98%) | 1,628 (95%) | 1,520 (89%) | 1,456 (85%) | 1,206 (70%) |
| Fresno, CA | 1,654 (100%) | 1,589 (96%) | 1,592 (96%) | 1,427 (86%) | 1,431 (87%) | 1,154 (70%) |
NREL PVWatts v8, 1 kW DC, fixed roof mount, tilt 20, losses 14%, standard module; only the direction changes. Collected 2026-09-15.
What it means for a real system
A 7 kW system in Phoenix makes about 12,285 kWh a year facing south, 10,479 facing west and 8,435 facing north. You can make up a smaller loss with an extra panel or two; a large loss changes the payback: is solar worth it.
East, west or both
- If you have no south-facing roof, east and west faces come next, and panels can be split across both.
- West-facing panels produce more in the late afternoon. If your utility plan charges more in those hours, that timing can be worth more than the lost kWh; check the peak hours on your plan.
- North-facing panels lose the most on a sloped roof. Ask the installer to show production for that face separately.
Check the layout in your quote
A quote should list each roof face with its direction, tilt, number of panels and estimated production. Compare each face with the table above, and see production by city for the south-facing baseline.
Run your own numbers
Enter your ZIP and bill: I'll estimate a south-facing system for your ZIP as a baseline.
Keep reading
- How many solar panels you need — Size a system from your electric use and local sunshine, in four steps.
- How much electricity a solar panel produces — Daily, monthly and yearly output per kW and per 400 W panel, city by city.
- Solar on cloudy days, at night and in winter — How much output drops by season in each city, and what happens after dark or in an outage.
Updated 2026-09-15.