East-West vs. South: The New Solar Rules

The Twenty-Year Orthodoxy

If you asked any solar installer between 2000 and 2018 about panel orientation, you'd get the same answer: "South-facing. Maximum annual production. Case closed."

And they weren't wrong—for that era.

A south-facing roof in the Northern Hemisphere catches the sun's arc from morning through afternoon. Panels face the sun directly at solar noon, when solar radiation is most intense. Annual kilowatt-hour production is maximized.

When panels cost $4.00 per watt and every kilowatt-hour counted, maximizing kWh was the only reasonable strategy. You wanted the biggest possible harvest from your expensive equipment.

But two things have changed since then, and they've completely upended the orientation calculus.

First, panels have become absurdly cheap—$0.20-$0.30 per watt at wholesale, down from $4.00 in 2010. Adding more panels costs almost nothing.

Second, and more importantly: the value of electricity now depends on when you generate it, not just how much.

Welcome to the era of Time-of-Use rates.

The Duck Curve: Why Noon Power Is Worthless

California's electrical grid managers noticed something strange starting around 2015. As rooftop solar spread across millions of homes, the middle of the day became saturated with power. The grid didn't need more electricity at noon—it was drowning in it.

But then, around 4 PM, production started crashing as the sun angled toward the horizon. Meanwhile, demand spiked as people came home from work, turned on air conditioners, and started cooking dinner.

When you graph this pattern—low net demand during the day with rapid ramps up in the evening—it looks like a duck. Hence the name: the Duck Curve.

The Utility Response: Time-of-Use Rates

Utilities responded by restructuring electricity pricing to reflect this reality:

Time Period	Typical Rate	Why
Super Off-Peak (11 AM - 4 PM)	$0.12-$0.18/kWh	Solar flood
Shoulder (7-11 AM, 4-7 PM)	$0.25-$0.35/kWh	Transition
Peak (4-9 PM)	$0.45-$0.60/kWh	High demand, low solar

Under these rates, a kilowatt-hour generated at noon is worth $0.15. A kilowatt-hour generated at 5 PM is worth $0.50 or more.

The Implication:

Under the old flat-rate system, south-facing panels producing 1,200 kWh/year beat west-facing panels producing 1,000 kWh/year.

Under TOU rates, west-facing panels generating during expensive evening hours can be worth more money despite generating fewer total kWh.

The game has changed from "maximum energy" to "maximum value."

The East-West Revolution

Instead of putting all panels on a south-facing roof, progressive installers and savvy homeowners are now splitting arrays: some facing east, some facing west.

East-Facing Panels: The Morning Shift

East panels catch the rising sun from 6 AM through noon. By 7-8 AM, they're producing substantial power—right when your household is waking up.

Think about your morning routine: coffee maker, electric stove, hair dryer, shower (if you have a heat pump water heater), EV charging finishing up from overnight. East-facing panels power these loads directly, reducing grid imports when rates are moderate.

West-Facing Panels: The Moneymakers

West panels catch the afternoon and evening sun from noon through 7-8 PM. They're still producing strong at 4 PM, 5 PM, 6 PM—precisely during the expensive peak rate window.

Under TOU rates, west-facing panels generate the most valuable electricity. Each kWh produced during peak hours offsets an import that would cost $0.50+.

The Hybrid Array:

Splitting capacity between east and west creates a flat-topped production curve. Instead of a sharp midday peak (with south), you get sustained production stretching from morning through evening.

This has several benefits:

More hours of production at valuable rates
Better self-consumption (using power as it's generated rather than exporting)
Reduced peak demand charges (for commercial customers)
Smoother inverter operation (no extreme midday peaks)

The Math: South vs. East-West Value Study

Let's compare two systems in California:

Option A: 8 kW South-Facing

Annual production: 12,000 kWh
Production timing: 75% during off-peak/shoulder hours
Weighted value: 12,000 × $0.18 avg = $2,160

Option B: 4 kW East + 4 kW West

Annual production: 10,400 kWh (13% less due to sub-optimal tilt)
Production timing: 50% during peak/shoulder hours
Weighted value: 5,200 × $0.42 + 5,200 × $0.18 = $3,120

Despite generating fewer total kilowatt-hours, the East-West configuration produces 45% more dollar value because a larger fraction occurs during expensive hours.

This is a stylized example—real results depend on your specific roof geometry, local rates, and consumption patterns—but the principle holds: under aggressive TOU rate structures, west-facing panels often outperform south-facing on a dollar basis.

The Over-Paneling Strategy

Here's where the economics get even more interesting.

Solar panels have become so cheap that the cost structure has inverted. The panels themselves are a small fraction of system cost. The expensive components are:

Inverters ($1,000-$3,000)
Electrical upgrade (if needed, $1,000-$5,000)
Permitting and inspection ($500-$1,500)
Labor (largely fixed regardless of panel count)

Adding extra panels has a marginal cost of only $100-$200 each at the installer level.

The Insight:

If panels are cheap but inverters are expensive, it makes sense to "over-panel"—install more panels than your inverter can theoretically handle at peak output.

Example: Install a 10 kW panel array (5 kW east, 5 kW west) on a 7.6 kW inverter.

Why This Works:

East and west panels never reach peak output simultaneously. The east panels peak at 9-10 AM when west panels are producing almost nothing. The west panels peak at 3-4 PM when east panels are fading.

The combined output looks like a flat-topped curve hovering around 6-7 kW for many more hours than a south-facing system achieves, instead of spiking to 8 kW briefly at solar noon.

The inverter runs near capacity for 6-8 hours instead of 2-3 hours. You extract more total energy from limited inverter capacity. The "extra" panels pay for themselves through extended production hours.

Aesthetic and Geometric Benefits

Beyond economics, East-West orientation often works better with real-world roof geometry.

Hip Roofs:

Classic hip roofs have minimal south-facing area. The south face is either small or contains dormers, vents, and other obstructions. East and west faces are often larger and cleaner.

A south-only approach on a hip roof might yield only 8 panels. Using east and west faces might yield 24 panels.

Street Aesthetics:

In many neighborhoods, the south face of a house is the front facade facing the street. Some homeowners (and some HOAs) prefer not to have visible solar panels on the street-facing roof.

East and west roofs are typically side faces, less visible from the street.

Denser Installations:

Because east and west panels don't shade each other at midday (the way south-facing low-tilt panels can), you can often achieve higher panel density on the available roof area.

When South Still Wins

East-West is not universally superior. South remains optimal in specific scenarios:

1. Net Metering 1.0/2.0 Grandfathered Plans:

If your utility allows true 1:1 net metering—exporting at the same rate you import—then total kWh production is what matters. South maximizes production.

2. Flat Rate Structures:

If your electricity rate is flat regardless of time of day, the value of each kWh is equal. Maximize kWh = maximize value. South wins.

3. Battery Systems:

With home battery storage, you can store midday surplus and discharge during evening peak hours. A south-facing array paired with batteries achieves the best of both worlds: maximum production AND time-shifting to valuable hours.

If you're installing batteries anyway, south-facing with storage often beats east-west without storage.

4. Extreme Latitude:

At high latitudes (northern US, Canada), the sun angle is low year-round. South-facing optimization becomes more important as east-west mounting catches less energy in winter months.

The Design Process

How should you approach system design in 2026?

Step 1: Understand Your Rate Structure

Get your utility rate tariff. Identify peak, shoulder, and off-peak periods with their rates. Calculate the rate differential between noon and 5 PM.

If peak rates are 2x+ off-peak rates, East-West deserves serious consideration.

Step 2: Model Your Roof

Use a tool like PVWatts (NREL) or HelioScope to model production from each available roof face. Get annual kWh estimates for south, east, and west orientations.

Step 3: Calculate Value, Not Just Production

Multiply each orientation's production by the hour-weighted average rate. An installer focused only on kWh may push you toward south; you need to push back with value calculations.

Step 4: Consider Future Rate Evolution

TOU rate structures are spreading nationwide. Even if you're on flat rates today, you may be on TOU in five years. Design for the future.

Conclusion: Generate When It Matters

The old dogma—"South or nothing"—was correct for its era. Panels were expensive. Net metering was generous. Every kWh counted equally.

That era is over.

In the world of Time-of-Use rates, cheap panels, and Duck Curve economics, the question is no longer "How much do you generate?" but "When do you generate?"

West-facing panels generate during the most expensive hours. East-facing panels cover your morning loads. Combining them creates a broader production window that better matches usage patterns.

For new installations in TOU territories, request a value analysis, not just a production analysis. Your installer should understand the difference. If they don't, find one who does.

The sun rises in the east, sets in the west. Finally, solar economics are starting to match solar reality.