In-House vs Outsourced Solar Design Services for Growing EPCs

Outsourced solar design services convert part of an EPC’s design workload into a contracted deliverable. In-house teams offer direct control and fast collaboration; external teams offer variable capacity and access to specialist skills. The right choice depends on the work being transferred, not a universal annual-project threshold.

Key Takeaways

• Compare the same deliverable and design stage on both sides.
• Model usable capacity, not theoretical designer output.
• Include internal review and revision effort in outsourced cost.
• Verify professional licenses and contractual responsibility by jurisdiction.
• Test an outsourcing provider on paid, representative work before assigning volume.

This page owns the in-house-versus-outsourced staffing decision. For detailed provider selection, use the solar design services buyer’s guide. For permit deliverables, see what a permit-ready plan set includes.

In-House vs Outsourced Solar Design at a Glance

The decision rule is simple: keep work close when it changes quickly or drives customer and construction decisions. Externalize work that can be defined, checked, and handed over without constant context transfer.

Decision factor	In-house design	Outsourced design	What to measure
Cost structure	Salary, benefits, software, management, and overhead	Project, hour, retainer, or capacity fee	Cost per internally accepted deliverable
Capacity	Fixed by team availability	Contracted and potentially variable	Accepted outputs per week at normal and peak load
Collaboration	Direct access to sales, procurement, and field teams	Communication through agreed workflow	Decision and clarification response time
Specialist coverage	Limited to the employed team	Can add disciplines or jurisdictions	Named qualified people and verified licenses
Standards and knowledge	Accumulates inside the EPC	Must be transferred and maintained	Defects caused by missing context or standards drift
Quality control	Direct but still requires independent checking	Defined through inputs, QA evidence, and acceptance	Defect causes, revision quality, and release records
Data control	Held in company systems	Shared with a contracted party	Access, storage, retention, subcontracting, and deletion
Continuity risk	Recruitment, leave, and employee turnover	Provider capacity, concentration, and exit risk	Documented backup and transition plan

Do not award a “winner” from this table alone. Weight each factor for the project mix and business bottleneck.

First Separate the Design Stages

“Solar design” covers several different jobs. An EPC can reasonably keep one stage in-house and outsource another.

Stage	Typical output	Reasons to keep in-house	Reasons to outsource
Site qualification	Constraints, measurements, photographs, and preliminary capacity	Site knowledge affects every later stage	Specialist survey or geotechnical capability is needed
Sales design	Layout, energy estimate, and customer proposal	Speed and customer changes drive conversion	Temporary overflow with a tightly controlled brief
Permit design	AHJ-specific drawings and supporting documents	Concentrated local volume supports internal expertise	Jurisdiction knowledge, variable volume, or licensed review is needed
Detailed engineering	Coordinated construction drawings and calculations	Project-team decisions happen continuously	Specialist electrical, structural, civil, or modelling skills are intermittent
As-built and close-out	Final installed record and handover	Field changes are known internally	Controlled drafting from verified redlines

The US Department of Energy states that rooftop permitting requirements vary by jurisdiction and that inspection and utility connection are separate steps. That variation is one reason permit work may need local or specialist support. See the DOE permitting overview.

Calculate In-House Cost From Company Data

The reliable in-house number is the annual loaded cost divided by accepted production at the quality level you need. Salary alone understates cost; theoretical maximum throughput overstates capacity.

Use:

In-house cost per accepted deliverable = annual loaded team cost ÷ annual accepted deliverables

Annual loaded team cost can include:

• Salary, statutory costs, benefits, insurance, and bonuses
• Design, CAD, modelling, document-control, and collaboration software
• Hardware, office, IT, and security
• Technical management, checking, and professional supervision
• Recruitment, onboarding, training, and expected vacancy cost
• Professional licensing, continuing education, and liability coverage where applicable

Annual accepted deliverables should exclude drafts rejected by your internal QA gate. Separate output by type because one preliminary layout is not equivalent to a commercial construction package.

Worked example using placeholders

Assume an EPC records annual loaded design-team cost as C. The team releases R accepted residential permit sets, S accepted sales designs, and E accepted engineering packages.

A simple blended result, C ÷ (R + S + E), is misleading because the outputs require different effort. Assign each output an internal standard-hour weight, then calculate:

Cost per standard design hour = C ÷ total productive standard hours

Multiply that rate by the standard hours for each deliverable. Use time records and accepted outputs from the last 6–12 months. Do not copy a utilization or productivity benchmark from another company.

Calculate Outsourced Cost on the Same Basis

The supplier fee is only one part of outsourced cost. Add the EPC’s intake, review, coordination, correction, and transition effort.

Use:

Outsourced cost per accepted deliverable = provider fee + EPC intake and review + excluded work + expected revisions + risk allowance

Request itemized quotes covering:

• Exact drawings, calculations, reports, and native files
• Project-size and complexity boundaries
• Required professional review and seals
• Included revision rounds and AHJ comment response
• Expedited work and service hours
• Site, jurisdiction, utility, or client research
• Equipment changes and customer scope changes
• Taxes, currency, payment milestones, and quote validity
• Survey, application filing, fees, and other excluded services

The buyer’s solar scope of work template can be adapted into the request. Compare quotes only after every provider returns a compliance matrix against the same list.

Find the Break-Even Point Without Inventing a Threshold

Break-even depends on fixed cost, available capacity, outsource price, project mix, and internal review effort. A universal “hire at X projects” rule ignores all 5.

For one standardized deliverable:

Break-even annual volume = avoidable annual in-house fixed cost ÷ (outsourced accepted cost − in-house variable cost)

Use this formula only when the deliverables are truly comparable. If the internal employee also supports sales, field questions, standards, or procurement, allocate that work separately rather than charging it all to plan sets.

Run at least 3 scenarios:

Scenario	Inputs to stress
Base	Trailing project mix, normal revision rate, current staffing
Peak	Highest credible monthly volume, provider surge capacity, overtime
Downside	Lower sales, employee vacancy, provider delay, higher revision effort

The break-even output is a planning estimate, not a promise. Recalculate it when the project mix, geography, software stack, or service scope changes.

Compare Turnaround With One Clock

Advertised turnaround is meaningless until the start and finish are defined. An internal team may start when the survey arrives; a provider may start only after its intake team accepts every input.

Measure:

Accepted turnaround = timestamp of internal acceptance − timestamp of complete-input acceptance

Your service level should define:

• Complete-input criteria and who accepts them
• Business hours, holidays, and time zones
• Milestones by deliverable type
• What pauses the clock
• Internal and client review windows
• Revision and urgent-response targets
• Escalation contacts and remedies

Compare the internal team and supplier using the same accepted-turnaround measure. Track missing input, design error, scope change, AHJ or client change, and reviewer interpretation separately.

Compare Quality With Evidence

Neither employment model guarantees accuracy. Quality comes from controlled inputs, competent designers, independent checks, clear standards, and a release process.

Use a scorecard such as:

Measure	Definition
Completeness	Contracted deliverables present at first internal review
Technical defect	Confirmed error in calculation, drawing, data, or requirement application
Coordination defect	Conflict between sheets, schedules, models, or applications
Revision effectiveness	Closed comments that remain closed without introducing conflicts
Accepted turnaround	Time from complete input to internal acceptance
External comment cause	Provider error, EPC input, changed rule, scope change, or interpretation

Do not treat first-pass approval as a pure designer score. AHJ or client comments can have several causes. Record the cause and corrective action for each comment.

Our solar design QA checklist provides a starting framework. Qualified people must adapt and approve electrical, structural, safety, and jurisdiction-specific checks.

Professional Responsibility Does Not Disappear

Outsourcing drafting does not automatically transfer the EPC’s contractual, construction, or acceptance duties. The agreement should name the design author, checker, approving professional, deliverable status, reliance limits, insurance, and responsibility for corrections.

When a professional signature or seal is required:

• Confirm the required discipline and jurisdiction with the authority
• Verify the person’s active license with the relevant regulator
• Confirm the professional reviewed the final project-specific work
• Keep the signed calculation and release records
• Do not assume a partner network covers every project location

Have counsel and qualified engineering leadership review liability terms. This article is an operational comparison, not legal advice.

When the Hybrid Model Works

A hybrid model retains work that needs business context and externalizes controlled production or specialist scope. It often suits an EPC whose pipeline is growing faster than a permanent engineering team.

One practical split is:

• Internal: site-data ownership, customer-facing layout, proposal, equipment standards, design basis, project decisions, and final acceptance.
• External: controlled drafting, jurisdiction-specific permit packages, overflow, specialist calculations, or professional review within an agreed scope.

One party must own the master equipment schedule, document register, revision status, and construction release. Without that ownership, the proposal, permit, procurement, and field package can drift apart.

Solar design software can keep the preliminary layout, selected equipment, and string basis in one project record. Solar proposal software keeps the customer document tied to that design. Software supports coordination; it does not replace professional review.

Test Outsourced Solar Design Services With a Paid Pilot

A pilot should resemble production. Use representative projects, real deadlines, your normal data quality, and written acceptance criteria.

1. Select projects covering the most common scope plus one realistic exception.
2. Send the same controlled input pack you expect in production.
3. Record questions, assumptions, milestones, and escalations.
4. Review against the contract, technical checklist, and native-file requirement.
5. Score accepted turnaround, completeness, defect causes, revision quality, and communication.
6. Confirm data return or deletion and transition capability.

Do not commit recurring volume until the pilot passes. Keep a qualified backup for capacity-sensitive work.

When Heaven Designs May Fit

Heaven Designs may fit EPCs that want external capacity across preliminary design, rooftop or ground-mount engineering, civil and structural work, site feasibility, or North American permit packages. Its current service catalogue lists a 50+ engineer team, 300+ EPC clients, work across 15+ countries, and 102+ MW designed. These are company-published figures, not independently audited metrics.

The company says typical project delivery is 5–7 business days depending on complexity. Buyers should verify the exact scope, complete-input rule, relevant professional coverage, capacity, revision terms, and accepted-turnaround commitment in a project proposal.

Limitation: Heaven Designs provides design and engineering services. It does not replace the EPC’s site verification, customer contract, construction control, or final acceptance unless a signed scope expressly assigns those duties.

Disclosure: SurgePV is promoting Heaven Designs through a commercial relationship. Apply the same cost model, sample review, license verification, paid pilot, and QA criteria described above.

Review the current Heaven Designs service catalogue, then request samples matched to your project type before asking for a quote.

Decision Checklist for Growing EPCs

Choose a model only after confirming:

• Design stages and deliverables are separated.
• Internal loaded cost uses accepted production and real company data.
• External quotes include EPC review, revisions, exclusions, and risk.
• Base, peak, and downside capacity scenarios have been tested.
• Turnaround uses one start condition and one acceptance condition.
• Technical defects and external comments are classified by cause.
• Professional authority and liability are verified per jurisdiction.
• Standards, equipment, files, data, and revision ownership are defined.
• A representative paid pilot has passed.
• An exit and continuity plan exists for either model.

Frequently Asked Questions

Is it cheaper to outsource solar design or hire in-house?

Neither model is always cheaper. Compare the annual loaded cost and usable capacity of an internal team with itemized external quotes for the same deliverables. Include internal review, revisions, professional stamps, idle capacity, recruitment, software, and schedule risk. Use your own trailing project data rather than a universal project-volume threshold.

What solar design work is easiest to outsource?

Repeatable drafting, permit plan sets, specialist calculations, and jurisdiction-specific professional review can be good outsourcing candidates when the scope and inputs are controlled. Customer-facing sales design and work requiring frequent project-team decisions often benefit from remaining in-house.

How should an EPC compare outsourcing turnaround?

Define when the clock starts, the required output, business hours, review pauses, revision targets, and escalation rules. Then compare accepted turnaround on a paid pilot, not advertised delivery alone. Measure time to an internally accepted deliverable and classify every delay by cause.

Does outsourcing solar design remove the EPC’s engineering responsibility?

No. Contractual and professional responsibility depends on the scope and jurisdiction, but the EPC should still control project inputs, design basis, equipment, acceptance, and construction release. Verify every required professional license and have qualified people review safety-critical electrical and structural work.

When does a hybrid solar design model work?

A hybrid model works when the EPC keeps rapid sales layouts, customer changes, standards, and final acceptance in-house while an external team handles controlled drafting, permit packages, overflow, or specialist engineering. One party must own the design basis, equipment schedule, revision register, and release status.

How do I test an outsourced solar design provider?

Run a paid pilot on representative projects. Use the same input pack, scope, acceptance checklist, and deadline you expect in production. Score completeness, technical accuracy, requirement fit, communication, accepted turnaround, revision quality, and native-file handover before assigning recurring volume.