Solar Site Assessment Process in Maryland
A solar site assessment is the structured evaluation performed before any photovoltaic (PV) system is designed, permitted, or installed on a Maryland property. This page covers the definition and scope of site assessments, the step-by-step process installers and engineers follow, the common property scenarios encountered across Maryland's varied building stock, and the decision boundaries that determine whether a site is viable, marginal, or unsuitable. Understanding this process is foundational to every downstream decision about solar energy systems in Maryland.
Definition and scope
A solar site assessment is a systematic field and desk evaluation that determines whether a specific location can support a solar energy system — and under what technical and regulatory conditions. The assessment produces data that feeds directly into system design, structural engineering, interconnection applications, and permit submissions.
The scope of a standard Maryland site assessment encompasses five core domains:
- Solar resource availability — measurement or modeling of insolation at the specific address, accounting for latitude, horizon obstructions, and seasonal sun angles
- Roof or ground-mount structural capacity — evaluation of existing structure to determine load-bearing adequacy for panel and racking weight
- Electrical infrastructure review — inspection of the main service panel, meter base, and wiring to identify upgrade requirements before interconnection
- Shading analysis — quantified assessment of trees, adjacent buildings, chimneys, and HVAC equipment that reduce production
- Regulatory and permitting constraints — identification of zoning overlays, historic district designations, homeowners association rules, and utility-specific requirements
The assessment does not constitute a permit application, a final engineering drawing, or a contract. It is a feasibility and scoping instrument.
Scope boundary — Maryland jurisdiction: This page applies specifically to property within the State of Maryland, governed by the Maryland Public Service Commission (PSC) and local county or municipal building authorities across Maryland's 23 counties and Baltimore City. Federal tax credit eligibility, treated separately in the discussion of the federal Investment Tax Credit for Maryland residents, is not covered here. Properties in neighboring jurisdictions — Virginia, Delaware, Pennsylvania, West Virginia, and the District of Columbia — operate under different regulatory frameworks and fall outside this page's coverage.
How it works
A Maryland solar site assessment typically follows a six-phase sequence. The depth of each phase varies depending on system size — a residential rooftop differs substantially from a commercial solar installation in Maryland or an agricultural solar installation.
Phase 1 — Remote preliminary screening
Using satellite imagery (tools such as NREL's PVWatts Calculator or aerial databases), an assessor estimates annual insolation, roof geometry, and approximate usable area before any site visit occurs. NREL data places Maryland's average annual peak sun hours at approximately 4.5 hours per day, though coastal and western mountain areas deviate from that figure.
Phase 2 — Shading evaluation
On-site shading analysis uses a solar pathfinder, shade analysis app, or 3D modeling software to calculate a shading factor across all hours of the year. The Solar Energy Industries Association (SEIA) identifies shading as the single largest cause of underperforming residential systems. Results feed directly into solar shading and orientation considerations decisions.
Phase 3 — Roof condition and structural review
An assessor inspects roof age, material, pitch, and structural framing. Maryland's International Residential Code (IRC) adoption — administered through the Maryland Department of Labor, Licensing and Regulation (DLLR) — sets minimum structural requirements. Roofs with less than 5 years of remaining service life or deteriorated rafters typically require remediation before installation. A dedicated roof assessment for solar in Maryland covers structural criteria in greater detail.
Phase 4 — Electrical infrastructure inspection
The assessor reviews the existing service panel rating (typically 100A or 200A), available breaker slots, meter socket type, and grounding system. Maryland's adopted National Electrical Code (NEC), currently the 2020 edition per the Maryland Building Performance Standards, governs minimum electrical requirements. Panels rated below 100A frequently require an upgrade to accommodate a grid-tied PV system.
Phase 5 — Utility and interconnection screening
The assessor identifies the serving utility — BGE, Pepco, Delmarva Power, Potomac Edison, or SMECO — and reviews that utility's specific interconnection application requirements. The Maryland PSC's net metering rules under COMAR 20.50.11 set the statewide framework, but each utility maintains its own technical screens. Maryland utility interconnection requirements detail those utility-specific thresholds.
Phase 6 — Assessment report
The assessor compiles findings into a written report that includes a production estimate, identified constraints, recommended system size, and a list of pre-installation work items. This report becomes the basis for the permit package submitted to the local building authority.
Common scenarios
Scenario A — Standard suburban residential roof (unshaded, 200A service)
This is the least complex scenario. A south- or west-facing roof with a pitch between 15° and 40°, no significant shading, and a 200A main panel typically clears all six assessment phases with no remediation requirements. The assessment can be completed in a single 2–3 hour site visit. Most residential solar installations in Maryland fall into this category.
Scenario B — Older urban rowhouse with partial shading and 100A service
Common in Baltimore City and older suburban municipalities, this scenario introduces 2 to 3 complicating factors simultaneously: limited usable roof area (often under 300 square feet of unobstructed south-facing surface), shading from adjacent structures, and an undersized service panel. Assessment outcomes here frequently recommend microinverters or DC optimizers to mitigate shading losses, plus a panel upgrade cost estimate.
Scenario C — Rural property with ground-mount potential
When the primary structure has a suboptimal roof, a ground-mounted array may be assessed separately. Ground-mount assessments add a soil evaluation, setback measurement against local zoning ordinances, and stormwater management considerations under Maryland Department of the Environment (MDE) regulations. Agricultural properties may qualify for specific rate structures reviewed under agricultural solar installation guidelines.
Scenario D — Historic district or HOA-governed property
Properties in Maryland's designated historic districts — governed by the Maryland Historical Trust under Maryland Code, State Finance and Procurement § 5A-325 — require additional review before visible solar installations are approved. HOA-governed properties are subject to the Maryland Homeowners Association Act, which limits (but does not eliminate) an HOA's ability to prohibit solar. The Maryland HOA rules and solar installations page addresses those limitations.
Decision boundaries
A site assessment produces one of three disposition categories:
| Disposition | Criteria | Typical next step |
|---|---|---|
| Viable | Insolation ≥ 4.0 peak hours/day, shading factor ≤ 20%, structure sound, electrical adequate | Proceed to system design and permitting |
| Conditionally viable | One or two remediable barriers (panel upgrade, tree trimming, minor roof repair) | Remediate, then reassess |
| Not viable | Irremediable constraints: structural failure, insolation below 3.5 peak hours/day, zoning prohibition | Alternative options (community solar, off-site purchase) |
The 3.5 peak hours/day floor is derived from NREL's minimum economic viability threshold for grid-tied residential systems without substantial battery storage. Properties falling below this threshold may still benefit from Maryland community solar programs as an alternative to on-site generation.
Battery storage interaction: Assessments for systems incorporating battery storage require an additional load analysis and may trigger separate permitting requirements under the Maryland State Fire Marshal's office guidance on lithium-ion battery installation. Solar battery storage in Maryland covers those additional requirements.
For a broader understanding of how assessment findings connect to system design and production modeling, the conceptual overview of how Maryland solar energy systems work provides the foundational framework. The full regulatory environment governing every phase of this process — from PSC oversight to building code adoption — is documented in the regulatory context for Maryland solar energy systems.
References
- Maryland Public Service Commission (PSC)
- COMAR 20.50.11 — Net Energy Metering, Maryland Division of State Documents
- National Renewable Energy Laboratory (NREL) — PVWatts Calculator
- Solar Energy Industries Association (SEIA)
- Maryland Department of the Environment (MDE)
- Maryland Department of Labor, Licensing and Regulation (DLLR)
- [Maryland Historical Trust — Maryland Code, State Finance and Procurement § 5A-325](https://mgaleg.maryland.gov/mgawebsite/Laws/StatuteText?article=gsf