Solar Panel Shade Analysis 2026: How Shade Affects Output and What to Do

Shade is the single most common reason a solar installation underperforms — and it is also the most frequently misunderstood variable in the pre-installation assessment process. A roof that looks clear from the driveway in July can lose 30–50% of its annual energy potential once a shade analysis accounts for a neighbor's tree in October, the roofline itself blocking morning sun, or a chimney casting a shadow across the center of the array.

This guide explains how shade works in a photovoltaic system, which tools solar professionals and homeowners use to measure it accurately, what the production loss numbers actually look like, and what you can do about it — from inverter choice to tree trimming to site rejection.

Why Shade Is Different for Solar Than for Almost Any Other Electrical System

A solar panel is made up of cells wired in series. In a traditional string inverter system, the cells in one panel are linked in series, and the panels themselves are linked in a string of 8–15 panels running back to the inverter.

The critical physics: current through a series circuit is limited by its weakest link. When one cell is shaded, the current through the entire string drops to that cell's level — potentially cutting the output of 10–14 other perfectly lit panels by 50–90%.

Manufacturers address this partially with bypass diodes, which allow current to route around shaded cells. A standard 60-cell residential panel has 3 bypass diodes, each protecting 20 cells. When a shaded cell triggers its bypass diode, 20 cells (one-third of the panel's capacity) go offline. That means even a shadow from a thin chimney can cut one panel's output by 33% — and in a string system, drag the entire string output down.

The takeaway: in a string inverter system, a little shade causes a lot of production loss. In a microinverter or power optimizer system, shade is mostly contained to the affected panel.

Types of Shade and Their Production Impact

Not all shade is equal. Solar professionals classify shade into four categories:

Shade Type	Example	Typical Annual Production Loss
Transient soft shade	Clouds, fog, light haze	2–8% (location-dependent)
Fixed soft shade	Dust, pollen, bird droppings	1–5% (cleaning-recoverable)
Fixed hard shade	Chimney, roof vent, AC unit, vent pipe	5–20% of affected panels
Seasonal hard shade	Deciduous trees (leaves only in summer); adjacent buildings blocking low winter sun	10–40% annual loss

Seasonal shade is the most underestimated. A homeowner may schedule their site visit in summer when a deciduous tree is blocking very little sun — but from October through March, that same tree may reduce southern-facing panel production by 60–80% during low-angle winter sun hours. Since winter days already produce less energy per hour, losing most of that production during the low-sun months can reduce annual output by 20–35%.

The 20% rule: the solar industry generally considers a site viable if usable roof area receives fewer than 20% of annual hours with greater than 10% shade. Above that threshold, buyers should evaluate shade mitigation (microinverters, tree trimming) before committing.

Shade Analysis Tools: From Free to Professional

PVWatts (Free, NREL)

NREL's PVWatts calculator (pvwatts.nrel.gov) allows users to enter a location, system size, and tilt/azimuth, and receive an estimated annual energy output using historical irradiance data. It includes a "Shading" input as a percentage annual reduction.

PVWatts is accurate for location-based production modeling but requires you to already know your shading percentage — it doesn't calculate it for you. It's most useful for confirming production estimates from installers and checking whether their shading assumptions are realistic.

Best for: validating installer quotes and understanding production by month/hour without paying for a site visit.

Aurora Solar and Scanifly (Installer Tools)

Professional installers commonly use software platforms like Aurora Solar or Scanifly to perform remote shade analysis. These tools import satellite imagery and LiDAR (Light Detection and Ranging) topography data to model sun angles and shade patterns across the roof surface at 15-minute intervals throughout the year.

Aurora Solar generates a TSRF (Total Solar Resource Factor) score for each proposed panel location — expressed as a percentage of maximum potential energy that location actually receives after accounting for shade, tilt, and azimuth. A TSRF of 100% means no shade losses. Most viable residential sites score between 85–100%.

What to ask your installer: Request the TSRF for each panel string in your proposed design. If an installer cannot produce TSRF numbers, they may be relying on a visual assessment rather than a quantitative shade model.

Solmetric SunEye and SunEye App

The Solmetric SunEye is a handheld shade analysis device used by professional solar installers. Placed on the roof or at potential ground-mount locations, it uses a fisheye lens camera to photograph the entire sky hemisphere, then applies sun path data for your latitude to calculate shade obstruction across all sun positions for every day of the year.

SunEye output includes:

• Annual shading factor (how much of available sunlight reaches this location)
• Monthly shading chart (shows which months are worst)
• "Solar window" visualization showing which obstructions matter most

SunEye assessments typically cost $100–$300 as a standalone service from an installer or solar consultant. The data is precise enough to design panel strings around shade problems — for example, putting east-facing panels on one microinverter string and south-facing panels on another.

Best for: complex rooflines, sites with trees, buyers evaluating whether tree removal is worthwhile before committing to installation.

LiDAR-Based Remote Analysis

Several solar design platforms (Nearmap, Vexcel, Google's Solar API) use aerial LiDAR surveys to create 3D models of rooftops and surrounding structures. These analyses are done remotely without a site visit and can identify shade from neighboring buildings, chimneys, and roof features with sub-foot accuracy.

Google's Solar API (the data behind Google's "Project Sunroof") uses LiDAR to estimate both roof solar potential and nearest-neighbor shading. It's free for homeowners to access through the Project Sunroof map. Note that Google's data is updated periodically (not live), so recently added trees or structures may not yet appear.

Limitation: LiDAR-based remote analysis is excellent for identifying fixed structural shade (rooflines, buildings) but may not accurately model vegetation if tree canopies have grown since the last aerial survey.

How Much Does Shade Reduce Annual Solar Production?

Here are realistic production loss estimates for common shade scenarios, assuming a south-facing roof with a 7 kW string inverter system:

Shade Scenario	Affected Panels	Approximate Annual kWh Loss	% of System
Chimney shadow on 2 panels (2 hrs/day)	2 of 18	400–700 kWh	8–12%
Mature oak (60 ft) at 30-ft setback to SW	5–7 of 18	1,200–2,000 kWh	20–35%
Neighboring roofline blocking low winter sun	4–8 of 18 (winter only)	600–1,200 kWh	10–20%
Roof vent (6-inch pipe)	0.5 of 18	100–250 kWh	2–4%
Full south roof, no obstructions	0 of 18	0 kWh	0%

Estimates for Atlanta (4.7 peak sun hours/day) with a 7 kW system. Production loss is higher in states with lower peak sun hours (Pacific Northwest, New England) where each lost hour represents more of total annual production.

A 7 kW system producing 9,000 kWh/year on a clear roof might only produce 7,200–7,500 kWh/year in the oak tree scenario — reducing annual savings from $1,620 to $1,296 at $0.18/kWh. Over 25 years with 4% annual rate escalation, that $324/year difference becomes roughly $13,500 in lost savings.

Microinverters and Power Optimizers: The Shade Mitigation Solution

The technology answer to shade is module-level power electronics (MLPE) — either microinverters or DC power optimizers paired with a string inverter.

Microinverters

Each panel has its own small inverter. Shade on one panel has zero effect on adjacent panels — they continue operating at full power independently. Enphase IQ8M and APsystems EZ1-M are the leading 2026 residential microinverter products.

Shade recovery benefit: In a 7-panel string where 2 panels are shaded, a string inverter may produce 40–60% of what the 5 unshaded panels could produce. Microinverters recover that lost production because each unshaded panel operates at its own maximum power point. Real-world data from multiple studies shows 8–20% annual production gain on moderately shaded roofs when switching from string inverters to microinverters.

2026 cost premium: Microinverters add approximately $0.30–$0.50 per watt to system cost vs. string inverters — about $2,100–$3,500 additional on a 7 kW system. The production recovery of 8–20% typically recoups this cost in 4–8 years in high-electricity-rate states (CA, MA, CT, NY, HI, RI).

DC Power Optimizers (SolarEdge)

DC power optimizers work differently: each panel has a small optimizer that allows it to operate at its own maximum power point, then sends optimized DC to a central string inverter. The result is similar to microinverters for shade mitigation, but with one central inverter rather than individual inverters per panel.

SolarEdge is the dominant optimizer platform; the SolarEdge HD-Wave inverter is the most common pairing for residential systems. Production advantage over string-only: approximately 5–15% in shaded conditions (slightly less than microinverters because the string inverter still influences output at the system level).

2026 cost: SolarEdge optimizer systems typically run $0.15–$0.30/watt more than string-only systems — less than the microinverter premium. If your site has moderate shade on 2–3 panels and a straightforward roof, a SolarEdge system may be the best cost-performance balance.

String Inverters Only: When Are They Still Appropriate?

String inverters without MLPE are still the right choice for completely unshaded sites. They are:

• Less expensive ($0.30–$0.50/watt savings vs. microinverters)
• Simpler to maintain (one inverter, not 18–20 microinverters)
• Adequate for uniform, south-facing arrays with TSRF > 98%

If your SunEye or Aurora analysis shows a TSRF above 95% for all panels, the production benefit of microinverters may not justify their added cost.

The Tree Decision: Trim, Remove, or Reroute?

Trees adjacent to solar panels create some of the most difficult pre-installation decisions. The analysis requires weighing:

Tree trimming costs: Professional tree trimming for a mature tree to remove shade-causing branches typically costs $500–$2,000 per tree. Trimming generally needs to be repeated every 3–5 years.

Tree removal costs: Full tree removal for a medium-to-large mature tree (40–70 ft): $2,000–$8,000, depending on proximity to structures, access, and disposal.

Production value of the recovered sunlight: Calculate annual production loss from the tree shadow (using SunEye data or Aurora TSRF), then multiply by your electricity rate. Example: a mature oak costing 2,000 kWh/year of production, at $0.22/kWh, = $440/year in lost savings.

25-year NPV calculation:

• $440/year × 25 years = $11,000 in lost savings at flat rates
• With 4% annual rate escalation: closer to $18,000 in lost savings
• Tree removal cost: $4,000 one-time

In this example, tree removal (even at $4,000) is clearly financially justified — but only if the tree can be removed and the resulting roof area actually has adequate TSRF after removal. A second SunEye assessment post-trimming is advisable before full commitment.

When to leave the tree: Some homeowners place high value on mature trees for privacy, cooling, and aesthetics. In that case, microinverters or power optimizers can partially mitigate the shade loss — recovering 8–15% of production even when the tree remains. The combination of tree retention + microinverter upgrade may save $2,000–$5,000 vs. tree removal, at the cost of some ongoing production loss.

Panel Placement Strategies for Shaded Roofs

When shade is unavoidable, strategic panel placement can minimize its impact:

Avoid placing panels directly in the shadow path: Use the installer's Aurora TSRF heatmap to identify the highest-TSRF areas of your roof and concentrate panels there. A roof with 80% TSRF on the south-south-west section and 60% on the south-south-east section should have more panels on the higher-TSRF side.

Avoid mixing shaded and unshaded panels on the same string: In a string inverter system, even one shaded panel drags the entire string down. Ask your installer to keep shaded panels on separate strings (or use MLPE to make this a non-issue).

Consider east/west facing roofs: A split east-west array eliminates the "all panels peak at noon" profile of a south-facing array. East panels produce in the morning; west panels produce in the afternoon. This flatter, longer production curve can actually increase self-consumption in TOU states (like CA) where morning and evening power is more valuable than midday export.

Ground-mount as an alternative to rooftop: If your roof is heavily shaded but your property has clear open space, a ground-mount array eliminates all rooftop shade constraints. Ground-mount systems cost approximately $0.30–$0.70/watt more than rooftop systems due to racking, foundation, and trenching costs — but recover it in production by achieving near-optimal tilt and azimuth without shade constraints. See our guide on roof vs. ground-mount solar systems for a full comparison.

When to Reject a Site: The Minimum Viable Shade Threshold

Some sites simply have too much shade for solar to be economically viable. General industry thresholds:

• TSRF < 70%: Most installers will recommend against installation. The production loss is severe enough that payback periods extend beyond 20 years in most markets.
• TSRF 70–80%: Marginal viability. Only appropriate for high-electricity-rate states (CA, HI, MA, CT, NY, RI) where even a shaded system can achieve sub-15-year payback.
• TSRF 80–90%: Viable with MLPE (microinverters or optimizers). Standard string inverter systems are not recommended.
• TSRF > 90%: Viable with either string inverter or MLPE. Consider MLPE only if shade is concentrated on 2–3 panels and string isolation is not possible.

Important: TSRF numbers should be verified by SunEye measurement or Aurora LiDAR analysis, not by visual inspection. A roof that "looks clear" in summer can score TSRF of 75% once winter sun angles are factored in.

State-Specific Shade Considerations

Shade analysis is especially critical in certain markets:

California (NEM 3.0): Under NEM 3.0's low export rates ($0.05–$0.08/kWh for export), maximizing self-consumption is paramount. Shade that reduces midday production also reduces self-consumption (unused energy flows back to the grid at the now-low export rate). In California, shade that previously cost $0.12/kWh in lost credits now costs the same $0.12/kWh in lost self-consumption — the economics are identical. A microinverter or hybrid inverter with battery storage is strongly recommended for any shaded California site. See the California solar incentives guide.

Hawaii: Hawaii's HECO Smart Export tariff pays $0.14–$0.20/kWh for export (far better than CA's NEM 3.0) but still below the retail rate of $0.40–$0.46/kWh. Self-consumption maximization is critical. Any shade loss in Hawaii costs $0.40–$0.46/kWh — among the highest in the nation. See the Hawaii solar incentives guide.

Performance-Based Incentive (PBI) states (MA, CT, MN, IL): In states where solar incentives pay on a per-kWh-produced basis (MA SMART: $0.15–$0.22/kWh; CT RSIP: $0.20–$0.26/kWh; MN Solar*Rewards: $0.020–$0.035/kWh), every kWh of shade loss costs double: lost electricity savings AND lost incentive income. A 10% shade loss in Massachusetts costs roughly $480/year (electricity savings lost + SMART income lost) vs. $90/year in a state with poor incentives and low rates.

Pacific Northwest (WA, OR): Pacific Northwest sites already operate at lower peak sun hours (3.8–4.5 hours/day). Shade loss that might be acceptable in Phoenix (5.8 peak hours) can be devastating in Seattle. A site with TSRF of 80% in Phoenix produces about the same as a site with TSRF of 90% in Seattle, because the absolute kWh loss per shaded hour is higher when there are fewer unshaded hours to compensate. See the Washington state solar guide and Oregon solar guide.

Shade Analysis in the Installation Process

When to expect shade analysis:

1. Initial consultation: Many installers perform a preliminary shade assessment (often via Google Solar API or satellite imagery) before your first site visit to confirm viability.

2. Site visit: A professional site assessment includes rooftop shade evaluation. Ensure the visit is scheduled to observe early-morning and late-afternoon sun conditions (not just a midday visit), and that the installer documents the shade analysis in writing.

3. System design review: Before signing a contract, ask for the Aurora TSRF numbers or SunEye analysis for your proposed array layout. Request that TSRF data appears on the final quote.

4. Production guarantee: Some installers offer production guarantees tied to the TSRF analysis. If your installer guarantees 9,000 kWh/year based on a TSRF of 87%, that number should be verifiable in the monitoring system after installation.

How to Use Shade Data When Comparing Quotes

When comparing multiple installer quotes:

• Ask each installer their assumed annual shading percentage — if Installer A assumes 5% shade loss and Installer B assumes 15% shade loss for the same roof, their production estimates will differ by ~10% even with identical systems.

• Request TSRF data for each panel location — TSRF is a standardized metric that lets you compare apples-to-apples.

• Verify production estimates in PVWatts — enter the installer's stated shading percentage and compare the PVWatts output to the installer's projected production estimate. If they diverge by more than 10%, ask for clarification.

• Tie the production estimate to your payback calculation — use our Solar ROI Calculator to see how a 10% shade adjustment changes your payback period and 25-year savings.

See our Solar Quote Comparison Guide for the full checklist of what to verify in every proposal.

Practical Shade Assessment Checklist Before Installation

Work through this checklist at your own home before scheduling an installer site visit:

Visual inspection (ground level):

• Walk the south, southeast, and southwest perimeter of your home. Note all trees, buildings, and structures visible above your roofline.
• Note the height and distance of each shade source. A 40-ft tree at a 40-ft setback has a very different shadow impact than a 40-ft tree at a 15-ft setback.
• Check for roof-mounted obstructions: chimneys, skylights, HVAC units, vent pipes, satellite dishes.

Online preliminary check:

• Use Google's Project Sunroof or Project Sunroof-equivalent (available from installers) to get a preliminary shade estimate. Note that this is directional, not design-grade.
• Run a preliminary PVWatts estimate with your roof's orientation, pitch, and a shading assumption of 10–20% to see how production varies.

Professional assessment:

• Request a SunEye measurement or equivalent at your site visit if you have identified any shade sources.
• Request TSRF per panel position in the proposed system design.
• Ask the installer to show you the production estimate month-by-month — large drops in winter (below 40% of July production) may indicate seasonal shade problems.

Decision questions:

• Does the proposed system achieve TSRF > 80% for all panels?
• If TSRF < 90%, is MLPE (microinverters or optimizers) included in the quote?
• Is tree trimming or removal economically justified given the 25-year production value calculation?
• Is a ground-mount location available if the rooftop is heavily shaded?

The Bottom Line on Solar Shade Analysis

Shade is the most frequently underestimated variable in residential solar economics — and the most recoverable once identified. A professional shade analysis using SunEye or Aurora TSRF data typically costs nothing (it's included in the site visit from reputable installers) and can save buyers from installing a system that will underperform by 20–35% for its entire 25-year life.

Key principles:

1. Demand a TSRF analysis from every installer you consider, not just a visual assessment.
2. Use microinverters or power optimizers for any roof with TSRF < 90% on any panel position.
3. Run the 25-year NPV math on tree removal before deciding to leave shade sources in place.
4. Check seasonal shade — schedule your site visit to include early-morning and late-afternoon assessments, not just midday when shade is minimized.
5. Reject any site with TSRF < 70% unless you are in a very high electricity rate state and willing to accept a 15+ year payback.

Use our Solar ROI Calculator to see exactly how shade percentage affects your system's 25-year economics in your state, and our Solar System Designer to size your system based on actual expected production rather than unshaded nameplate capacity.

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Frequently Asked Questions About Solar Panel Shade

How much does shade reduce solar panel output? Shade impact depends heavily on your inverter type. In a traditional string inverter system, shade on just 1–2 panels can reduce the entire string's output by 20–40%. In a microinverter or power optimizer system, shade is contained to the affected panel(s), limiting system-wide loss to 3–7% even with 3–4 shaded panels.

What is TSRF and what score is good for solar? TSRF (Total Solar Resource Factor) is the percentage of maximum possible solar energy a given panel location receives, accounting for shade, tilt, and azimuth losses combined. A TSRF of 100% means no losses. Most viable residential sites score TSRF of 85–98%. Sites below 70% TSRF are generally not economically viable for solar without significant shade mitigation.

Do microinverters fully eliminate shade problems? Microinverters significantly reduce shade-related production loss — typically recovering 8–20% of annual production compared to string inverters on a moderately shaded roof. However, they do not fully eliminate shade problems: a panel that is 70% shaded still only produces 30% of its capacity with microinverters. Full shade mitigation requires either removing the shade source or repositioning panels out of the shadow path.

Should I remove the tree or install microinverters? Run the 25-year NPV comparison for both options. If the annual production loss from the tree shade exceeds $400–$500/year (common for large deciduous trees adjacent to south-facing roofs), and tree removal costs under $5,000, removal is almost always the better economic choice. If tree removal is impractical, microinverters can recover 8–15% of the shaded production and are a good second-best solution.

Can I do a shade analysis myself without paying for a professional tool? Yes, at a preliminary level. Google Project Sunroof provides free shade estimates for most U.S. addresses based on satellite and LiDAR data. However, for design-grade shade analysis before signing a contract, request a SunEye measurement or Aurora TSRF assessment from your installer — these are included in professional site assessments at no extra cost from reputable companies.