Do I Get Enough Sun? A Guide to Solar Irradiance, Aspect, Latitude, and Shading

Expert analysis: how modern solar technology turns any roof into a power plant — even with shade, north-facing slopes, or northern latitudes.

The three biggest fears homeowners bring to the table: “My roof doesn’t face south,” “I live in a cloudy, northern state,” “My neighbor’s trees block the afternoon sun.” The myth vs. reality: south-facing, unshaded roofs in sunny states are ideal, but they are not the only viable option. Modern solar design accounts for latitude, aspect, and shading to deliver strong returns almost anywhere. This post explains the three pillars of solar potential — latitude, aspect (orientation), and shading — and how professional installers assess them using tools like drones, Project Sunroof, and irradiance modeling.

Part 1: Latitude – How Far North (or South) You Live

What is latitude and why does it matter? Latitude determines solar elevation and daylight hours. Higher latitudes see lower sun angles, especially in winter, affecting annual production.

Location	Latitude	Annual Peak Sun Hours (Avg)	Winter Challenge	Solution
Phoenix, AZ	33° N	6.5–7.0 h	Mild winter; sun remains high	Minimal; south-facing arrays produce exceptionally well
Denver, CO	40° N	5.5–6.0 h	Lower winter sun; snow risk	Tilt racks to optimize winter angle; microinverters for snow shading
Seattle, WA	47° N	3.5–4.0 h	Very low winter sun; frequent clouds	East-west arrays; oversize system; net metering bank summer credits
Minneapolis, MN	45° N	4.0–4.5 h	Extreme winter angle; snow accumulation	Steeper pitch (≥30°) performs better; microinverters for uneven snow melt

What to do about latitude: Optimize tilt angle (ideally ~latitude). In northern states, bifacial panels can boost winter production by 10–15% using reflected light. Accept seasonal curves and leverage net metering.

Part 2: Aspect – Which Direction Your Roof Faces

Production hierarchy relative to south (baseline 100%):

Orientation	Relative Production	Best For / Trade-Offs
South	100%	Max total annual output
West	85–90%	Afternoon peak (TOU rates), ideal for CA, TX
East	80–85%	Morning production, good for morning usage
Southwest / Southeast	90–95%	Balanced production, excellent compromise
North	50–70%	Viable with microinverters & high-efficiency panels

Geographic examples – aspect strategies by region: California (TOU peak 4–9 PM): west-facing often beats south financially. Texas (high cooling loads): south and west maximize AC offset. Northeast: south/southeast balance winter production. Pacific Northwest: east-west split arrays capture limited sun dawn-to-dusk.

What to do about suboptimal aspect: East-west split arrays, ground mounts or carports, and over-paneling (installing larger system) compensate for production losses.

Part 3: Shading – The Obstruction Factor

Old string inverters acted like Christmas lights: one shaded panel dragged down the whole array. Modern Module-Level Power Electronics (MLPE) – microinverters (Enphase) or power optimizers (SolarEdge) – make each panel independent. A chimney shading 2 of 20 panels reduces total output by roughly 10%, not 100%.

How Installers Measure Shade

• Remote Tools: Project Sunroof, LiDAR for initial shading estimates.
• Solar Pathfinder / SunEye: Captures horizon image & calculates Total Solar Resource Factor (TSRF). Benchmarks: ≥80% excellent, 70–79% good, 60–69% viable with MLPE, <60% may need tree trimming or ground mount.
• Drone Survey: High-res 3D modeling maps exact shading patterns hour-by-hour throughout the year.

Scenario	Location	Shade Source	TSRF	Solution
The Oak Tree	Atlanta, GA	Mature deciduous tree south side	72%	Microinverters; panels placed on east/west faces, tree remains
The Chimney	Boston, MA	Large brick chimney	78%	SolarEdge optimizers; shaded panels isolated
Dense Suburb	Los Angeles, CA	Two-story neighbor to south	65%	East-west split array; meets 90% of annual usage
Forested Lot	Asheville, NC	Tall pines	55%	Ground mount in clearing, or selective tree removal

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The Assessment Process: Putting It All Together

Phase 1: Remote desktop analysis using Project Sunroof, LiDAR, local utility rates → initial size & ROI.

Phase 2: On-site drone + Solar Pathfinder, structural assessment, hour-by-hour shading model.

Phase 3: System design with Aurora Solar / Helioscope, production guarantee (90–95% modeled output).

We factor in latitude-adjusted tilt, aspect optimization, and TSRF shading analysis to deliver a custom solution with a performance guarantee.

📌 Case Study: A Complex Home That Still Went Solar

Location: Portland, OR (45° N latitude, high cloud cover). Roof: South face only 30% usable, east partial shade, west limited, north large but north-facing. Solution: East-West split array (12 west, 8 east) with Enphase IQ8 microinverters, oversizing to 9.2 kW, light tree trimming improved east TSRF from 68% to 74%. Result: 9,800 kWh annual production (covers 105% usage), payback 11 years — well within lifespan. “I almost didn’t call because I assumed my roof was wrong for solar.”

Frequently Asked Questions (FAQ)

Q1: My roof faces north. Can I still get solar?

A: Yes, with caveats. North-facing produces 50–70% of south. We can oversize the system or use high-efficiency panels (REC, SunPower) with microinverters.

Q2: Does living in a cloudy state like Washington or Oregon make solar pointless?

A: Not at all. Germany, with less sun than Seattle, leads in solar. Modern panels work on diffuse light, and net metering banks summer credits for winter.

Q3: What if I have a flat roof?

A: Flat roofs are ideal for ballasted racking systems that tilt panels to optimal angle (20–35°) facing south regardless of building orientation.

Q4: How accurate are production estimates?

A: We guarantee production within 5–10% of modeled output using NASA irradiance data, drone shading, and historical weather. Performance guarantees back it.

Q5: Do I have to cut down trees?

A: Rarely. We design around trees unless TSRF <60% and tree is diseased or unstable. We prefer preserving healthy trees.

Ready to Unlock Your Home’s Solar Potential?

Latitude, aspect, and shading are all manageable with modern tools and expertise. A “perfect” south-facing roof isn’t required to achieve serious savings. Stop wondering if your home is “right” for solar — get a data-driven analysis today.

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© Solar Installation Expert — Comprehensive Irradiance & Shading Guide

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