South-Facing vs West-Facing Solar Panels: How Much Output Do You Lose?

When Do West-Facing Solar Panels Save More Money Than South-Facing?

West-facing panels can save more when electricity is worth more in the afternoon and evening than at midday. A south-facing array peaks around noon. A west-facing array shifts production toward mid-to-late afternoon, closer to the hours when many utilities charge their highest time-of-use rates (many California plans use a 4–9 PM peak window).

There is hard data on the timing effect. A Pecan Street Research Institute study of Austin, Texas, homes during summer 2013 found that west-facing systems produced 49% more electricity than south-facing systems during peak hours (3–7 PM) and cut household peak demand by 65%, compared with 54% for south-facing systems (GreenBuildingAdvisor). The study sample was small and covered only one summer, and the report itself noted that over a full year south-facing arrays produce more total energy.

Chart summary: In this Austin sample, west-facing systems cut summer 3–7 PM household demand by 65%, compared with 54% for south-facing systems. That supports the timing argument for west-facing panels. It measures peak demand in one summer, not annual bill savings, so it does not show that west-facing wins on total bills.

A simple break-even rule helps. If a west array produces about 86% of a south array’s annual energy, the average kWh it makes must be worth about 16% more (1 ÷ 0.86 ≈ 1.16) just to match the south array’s bill savings. Time-of-use plans with large peak-to-off-peak price gaps can clear that bar. A flat rate cannot.

Three factors usually decide it:

• Rate plan. On a flat rate with full retail net metering, every kWh is worth the same whenever it is produced, so south-facing wins on volume. On time-of-use plans, check how much more peak electricity costs than midday electricity.
• Export credits. California’s NEM 3.0 policy, in effect since April 2023, credits exported solar at an hourly avoided-cost rate instead of the retail rate (Enphase). Where exports earn much less than retail, using your own solar power matters more, which can make later-day production more attractive for households with afternoon and evening loads. Net metering rules differ by state and utility, so confirm yours.
• Batteries. A battery can store midday solar and discharge it in the evening, which reduces the timing advantage of a west-facing array. With storage, the extra total energy from south-facing panels often matters more.

How Do Latitude, Roof Pitch and Climate Change the Gap?

The south-versus-west gap is not one fixed number. It shifts with where you live and how your roof is built.

• Tilt. A nearly flat array faces the sky and is almost indifferent to compass direction. The steeper the tilt, the more the compass direction matters.
• Latitude. The sun’s path and height differ across the country, so the penalty for a west-facing array varies by region. This is why a national average is only a starting point.
• Local weather. If your area gets frequent afternoon clouds or summer storms, west-facing output can fall more than the average suggests. PVWatts uses historical weather data for your location, which captures this.

For a payback estimate that reflects your own rates, use our solar savings calculator and our guides to solar panel costs and payback periods by state. State-specific information is on our state pages.

Bottom Line

South-facing wins on total energy. West-facing costs roughly 10–20% of annual output but can recover some or all of that value where afternoon and evening electricity is worth more, where exports earn low credits, or where your usage is concentrated late in the day. If you have a battery, flat-rate net metering, or a choice between a clean south face and a shaded one, run the numbers for each roof plane before deciding.