Answer
Solar design rework can arise from stale site evidence, inferred geometry, missing obstructions, unverified constraints, wrong equipment, incomplete electrical checks and inconsistent energy or financial inputs. Review those sources before releasing the layout, then reconcile materials and proposals with the controlling project state. Assign unresolved conditions and qualified reviewers; a polished output does not establish feasibility or approval.
A design review should expose the input or handoff failure that needs correcting. A generic approved checkbox does not tell the next person whether the roof geometry, equipment, production estimate and proposal still describe the same project.
The ten patterns below organize that review for installers and EPCs. They are an editorial checklist, not a ranked study of how frequently mistakes occur or how much money they cost. SurgePV publishes this guide and sells the software referenced; no independent performance result is claimed.
1. Using the wrong site or stale evidence
Failure: a plausible layout is tied to the wrong meter, roof revision or dated imagery.
Check: confirm the address, project ID, meter and source dates. Preserve the customer records, survey photographs and measurements behind important inputs. Distinguish confirmed, estimated, pending and changed values.
Action: correct the controlling source before reviewing dependent drawings or calculations. Assign someone to resolve conflicting evidence; do not choose the value that produces the larger system merely because it is attractive.
2. Treating inferred roof geometry as measured
Failure: plane boundaries, pitch, orientation or dimensions inferred from imagery are presented as verified site measurements.
Check: label how each material value was obtained. Compare the model with the relevant survey and investigate discrepancies affecting placement, access or mounting. Stable plane IDs help connect a correction to its photographs and notes.
Action: restrict the layout to the purpose the evidence supports. Route structural capacity, roof condition and attachment suitability to the responsible qualified reviewer. Use the complex roof checklist for plane-by-plane evidence review.
3. Omitting obstruction or shading inputs
Failure: a chimney, parapet, upper roof, tree or neighboring object is missing, wrongly located or represented without a usable height.
Check: record obstruction identity, position, dimensions, height, source date and unresolved questions. Identify the model’s treatment of near objects, the horizon, vegetation and other relevant losses.
Action: update affected geometry and rerun the applicable analysis. Sandia’s shading, soiling and reflection overview treats these as distinct modeling inputs and processes. One generic loss percentage does not establish their treatment for a specific site.
4. Applying an unverified default setback
Failure: a software default is treated as the approved roof-access or clearance rule.
Check: identify the actual jurisdiction, building and fire requirements, local amendments, roof conditions, service-access needs and manufacturer instructions. Record the source and the person responsible for an interpretation.
Action: resolve the requirement before relying on the affected layout. NYC’s design-professional guidance illustrates the coordination of rooftop, structural and electrical review in one jurisdiction. It supplies no global pathway width or approval for projects elsewhere.
5. Selecting the wrong equipment record
Failure: a similar model name, old datasheet or substitute is used without checking its dimensions and electrical characteristics.
Check: reconcile exact model designations, quantities, document revisions and proposed mounting with the commercial scope. Check whether a substitution changes layout, electrical compatibility, operating limits, model assumptions, warranty or price.
Action: retain a substitution decision and review its dependencies. An equipment description generated by an assistant is not a manufacturer specification. DOE’s PV design overview supplies component context rather than compatibility approval.
6. Reviewing strings at only one temperature
Failure: a string is accepted from a nominal voltage or a module count alone.
Check: use the exact module and inverter records, the project’s applicable temperature basis and the required voltage/current checks. For example, the SMA SBSExx-US-50 manual explicitly requires cold-day array open-circuit voltage to remain below that product’s maximum input voltage.
Action: have the responsible designer review the applicable operating range, current limits, protection, connections and grouping. The cited manual is specific to that product; its detailed arrangement is not a universal instruction for other inverters. A voltage check alone does not validate the full electrical design.
7. Comparing energy results with different input bases
Failure: changed production is attributed to a tool improvement when weather, geometry, equipment or losses also changed.
Check: compare the resource source, location, orientation, shading treatment, equipment, losses, operating assumptions and model version. Record which inputs moved between revisions.
Action: explain the difference from the actual inputs or leave it open for investigation. PVWatts provides modeled production context, not a project guarantee. Label the estimate’s period, units and limitations before using it in a customer statement.
8. Turning provisional financial inputs into promises
Failure: an old tariff, unconfirmed incentive, generic escalation or financing assumption is presented as an assured saving.
Check: use dated consumption and tariff records; separate import, export, demand-charge and financing assumptions where relevant. Identify eligibility conditions and the provider behind an offer.
Action: label unconfirmed inputs and present a defensible sensitivity discussion. Compare the same scope and cash-flow perspective; do not deduct an incentive twice or treat a modeled annual energy total as a complete bill calculation. Use the financial-assumption audit for the deeper review.
9. Leaving the BOM or proposal on an old design
Failure: the accepted layout changes while procurement or sales continues to use the earlier quantity, equipment or energy estimate.
Check: reconcile project identity, module and inverter counts, mounting approach, system capacity, energy basis, price and scope across the layout, materials record, electrical documents and proposal. Each artifact can have its own version but must link to the controlling project state.
Action: issue corrected versions and notify known recipients of material changes. Mark superseded copies in systems you control and record any downloaded copies that cannot be recovered. The customer-ready proposal framework connects that review to the delivery handoff.
10. Closing an exception without a decision owner
Failure: a drawing looks complete even though a structural, utility, equipment or commercial question remains unassigned.
Check: keep the issue, evidence, affected artifacts, responsible reviewer, next action and due date together. State whether the unresolved condition blocks a concept, proposal, procurement or installation release.
Action: obtain the appropriate review and record the reason for proceeding, holding or revising. A checklist does not turn an internal review into engineering, utility or authority approval.
Keep one review record across the workflow
Retain the useful four-stage sequence: qualification, preliminary design, commercial review and delivery handoff. Define what each gate accepts and the evidence needed for its next use. Early-stage work can carry visible assumptions; later use may require additional measurements, design checks or approvals.
A compact defect register can make the handoff concrete:
| Field | What to record |
|---|---|
| Project and artifact | Controlling project ID and affected output version |
| Finding | The input, condition or inconsistency identified |
| Evidence | Source, date and any conflict |
| Consequence | Which layout, calculation, material or customer statement changes |
| Owner | Who can resolve the issue and who reviews the result |
| Release | Hold, restricted use, revised issue or accepted use with stated conditions |
Track defect categories and recurrence within a defined set of projects. Do not invent an industry rework benchmark or assume every lost sale was caused by design. If a control is unused, investigate whether it remains required or needs clearer implementation before removing it.
Questions about design rework
What should a solar design review check?
Check project identity, source dates, roof geometry, obstructions, applicable access and setbacks, equipment, electrical design basis, production inputs, financial assumptions and downstream document consistency. Assign material exceptions and record the purpose for which the output may be used.
Does a reviewed roof model establish structural suitability?
No. A roof model can organize geometry and placement while leaving condition, capacity and attachment questions unresolved. The project’s required structural evidence and responsible qualified review must address those questions before installation decisions rely on the model.
How should a team handle an equipment substitution?
Identify the exact replacement and source records, then assess its effects on dimensions, layout, electrical compatibility, modeling, mounting, warranty, price and materials. Record the decision and reconcile dependent outputs before the substitute enters procurement or a customer commitment.
How can a team measure rework without inventing a benchmark?
Define the project cohort, count documented correction events and classify their causes and affected artifacts. Separate pending work and later customer changes from design defects. Use the results to improve specific inputs and handoffs rather than claiming a universal improvement percentage.
Evaluate the workflow on a real project
Sources were checked on September 30, 2026. The examples are review prompts, not observed customer results. For a SurgePV demo, bring a representative roof and ask how the design workspace and proposal workflow record sources, equipment changes, exceptions and output versions. Confirm the supported controls before relying on them.
Sources
Primary research and reference material used for this desk-research article.
Where this fits
This article is part of SurgePV's Solar Business & Operations hub, which works through the topic from first principles to the decisions a project team actually has to make.
