Quick answer
Yes. East- and west-facing panels typically produce about 15% less than south-facing ones, so you need a few more panels to cover the same bill. For a $150 ComEd bill, we estimate payback rises from about 8.3 to 11.3 years. North-facing roofs lose about 30% and are usually the weakest choice.
How much less power do east- and west-facing panels make?
| Roof faces | Output vs. south | System to cover the bill | Net cost | Payback |
|---|---|---|---|---|
| South | None (the baseline) | 8 kW (20 panels) | $10,800 | 8.3 years |
| East or west | About 15% less | 9.2 kW (23 panels) | $14,300 | 11.3 years |
| North | About 30% less | 11.2 kW (28 panels) | $19,900 | 15.7 years |
The losses are typical figures from SolarReviews; the exact number depends on your roof's pitch. The estimates use our savings calculator assumptions, sizing a bigger system to make up the lower output, and include the ComEd rebate and Illinois Shines.
Illinois Shines' own analysis puts the ideal for Illinois at true south, tilted 33 to 37 degrees. Real systems vary a lot: the program's systems average a 22-degree tilt and face 174 degrees, just east of south, and the program notes that many well-designed systems don't face true south.
Is a west-facing roof better than an east-facing one?
West-facing panels make more of their power in the late afternoon, when air conditioners run and grid demand peaks. In an Austin, Texas study by Pecan Street, west-facing systems produced 49% more power than south-facing ones from 3 to 7 p.m. in summer.
Under Illinois' standard rates, that timing doesn't change your bill credits much. It can matter on ComEd's Hourly Pricing or Ameren's Power Smart Pricing, where afternoon power often costs more. See solar with hourly pricing.
Does Illinois Shines pay less for an east- or west-facing roof?
Indirectly. There's no rule against east- or west-facing arrays, but the Illinois Shines payment is based on how much power your system is expected to produce over 15 years, so a system that produces less earns less. The program flags arrays that face north of east or west (an azimuth under 90 or over 270 degrees) for a closer look, and installers include a short explanation.
Should I put panels on a north-facing roof?
Usually only as a last resort. North-facing panels produce about 30% less than south-facing ones, more on steep roofs. If your south, east and west faces are small or shaded, a ground-mounted system aimed south may be the better option on a larger lot.
What should I ask installers about my roof's direction?
- 1
What's the production estimate for each roof face?
Ask for the expected kWh per year, not just system size.
- 2
How many panels go on each face?
Splitting panels across east and west roofs is common and works well.
- 3
Which inverter fits a multi-face roof?
Microinverters or optimizers handle panels facing different directions.
See microinverters vs. string inverters and how many solar panels you need.
Sources
- SolarReviews: Best direction and orientation for solar panels
- Illinois Shines: System design best practices and considerations
- Illinois Shines: Arrays facing outside of installation best practices
- Pecan Street (via U.S. DOE): West-facing solar and peak demand in Austin, Texas
- Illinois Shines: Consumer FAQs
- ComEd Hourly Pricing: Solar customers
This guide is general information, not tax, legal or financial advice. Incentive programs change, so confirm current terms with your installer, your utility and a tax professional.