Solar Feasibility Check: A 20-Minute Desktop Method

A solar enquiry often arrives with an address, a target capacity, and almost no evidence. The temptation is to draw modules and quote a number. That sequence hides the questions most likely to stop the project.

A short desktop screen should do something simpler. This solar feasibility check desktop method identifies conflicts, exposes missing information, and decides whether more work is justified. It does not imitate a full feasibility study.

Direct answer. A 20-minute solar feasibility check tests the site, solar resource, electrical path, and commercial evidence. Spend five minutes on each. Finish with one decision: proceed to survey, investigate named gaps, or stop. Do not use the screen as proof of capacity, yield, structural safety, grid approval, or return on investment.

What This Method Is, and What It Is Not

This is a screening method for early opportunity triage. It helps an EPC estimator, developer, or design lead decide what to do next. The timebox forces the reviewer to focus on decision-changing evidence.

It is not a compressed version of a full study. A complete solar feasibility study may need measured survey data, energy modelling, structural assessment, grid engagement, legal review, environmental checks, cost work, and financial analysis. The India feasibility guide covers that broader scope.

The output from this screen is not “feasible” or “unfeasible” in an engineering sense. Use one of these labels instead:

• Proceed to survey: no desktop conflict found, and the next evidence request is clear.
• Investigate: one or more gaps could change the project, but none is yet a confirmed stop.
• Stop: a verified condition conflicts with the stated project basis.

That wording matters. “Proceed” means spend the next unit of effort. It does not mean acquire land, promise capacity, order equipment, or submit an application.

Solar Feasibility Check Desktop Method: Set Up the Record

Open a one-page worksheet before opening a map. Record the project name, reviewer, date, site address, coordinates, project type, target capacity, customer goal, and source links.

Separate every entry into one of three evidence states:

Evidence state	Meaning	Example
Verified	Supported by a current client document or authoritative source	Meter number on a recent bill
Observed	Visible in imagery or public data, but not field-confirmed	Apparent rooftop plant
Assumed	Entered only to continue the screen	Provisional module type

Never leave an important blank looking like a zero. Write “not provided” or “not checked.” That small habit prevents a missing field from becoming an accidental design assumption.

Use current imagery where possible, but record the image date when it is visible. A roof extension, tree line, adjacent building, or land use can change after an image was captured.

Minutes 0 to 5: Check Site Identity and Usable Area

Start by proving that you are looking at the right property. Match the address and coordinates against visible roads, building names, plot shape, or client photographs. Similar industrial roofs can sit beside each other.

Use Google Earth or another lawful mapping source for a visual screen. Do not treat an imagery measurement as a survey measurement. Our satellite design versus site survey guide explains where remote geometry stops being reliable.

For a rooftop, inspect:

• apparent roof form, levels, and orientation.
• parapets, skylights, vents, tanks, and mechanical plant.
• nearby buildings or trees that may cast shadows.
• visible access points and possible maintenance paths.
• signs of additions, damage, or inconsistent roof surfaces.
• a plausible equipment and cable route.

For a ground-mount site, inspect:

• plot shape and apparent land use.
• slope, drainage paths, water bodies, and vegetation.
• road access and nearby settlements.
• transmission lines and substations visible nearby.
• terrain features that divide the usable area.
• evidence that the mapped boundary may not match the legal parcel.

Do not calculate final capacity from a rough polygon. A desktop area can support a first question: is the target obviously larger than the visible opportunity? It cannot confirm setbacks, boundaries, access, structure, row pitch, grading, or equipment layout.

Write a concise note at minute five. The visible roof may fit the target, subject to measurement, access, plant clearance, and structural review.

Immediate site stop signals

A red decision needs verified evidence, not suspicion. One example is a client confirming that the roof is scheduled for replacement. Another is a legal boundary that excludes the proposed land.

Most desktop concerns are amber. Heavy tree cover, steep terrain, crowded rooftop plant, unclear access, or old imagery should create a survey question.

Minutes 5 to 10: Check the Solar Resource

Use a named dataset. Record the site coordinates, output, unit, data period when shown, and retrieval date.

The Global Solar Atlas map provides modelled solar-resource and PV power-potential outputs. Its documentation lists PVOUT, global horizontal irradiation, direct normal irradiation, optimum inclination, temperature, and elevation among the available fields.

The NASA POWER Data Access Viewer provides solar and meteorological data based on satellite observations and models. Its daily API documentation states that daily point data extend from 1981 to near real time. It also documents a 0.5 degree by 0.5 degree global grid.

For a rapid screen, capture no more than you can explain:

• the resource or PV-output metric used.
• its unit.
• the assumed array orientation, if the tool asks for one.
• the model or dataset name.
• a screenshot or exported result.
• any visible uncertainty or limitation note.

Do not combine outputs from different tools without checking definitions. GHI, plane-of-array irradiation, PVOUT, and specific yield are not interchangeable.

The Atlas accuracy guidance explains that satellite-model uncertainty varies by climate and location. It identifies northern India among aerosol-affected regions where uncertainty can be higher. The same principle applies elsewhere: a neat map value is still a model result.

Use the number as a reasonableness input, not a guaranteed production figure. A bankable or investment-grade result needs a defined weather source, system design, losses, uncertainty treatment, and review standard.

Resource questions that change the next step

Ask whether the site appears broadly consistent with nearby projects or another trusted dataset. A large unexplained difference is an amber flag. Wrong coordinates, wrong units, unusual terrain, coastal effects, snow, aerosols, or dataset coverage can all matter.

Do not spend the timebox tuning losses. Record the resource evidence and move on. Detailed modelling comes after the site and project basis survive the screen.

Minutes 10 to 15: Check Load, Meter, and Grid Path

A good roof without a defined electrical path is only a layout opportunity. The third five-minute block asks who will use the energy and where the system could connect.

For behind-the-meter commercial solar, request:

• a recent electricity bill with customer and meter identity.
• at least the available monthly consumption history.
• interval data when demand shape affects sizing.
• service voltage and sanctioned or contracted demand.
• the existing single-line diagram, when available.
• transformer and main-switchboard details.
• operating schedule and planned load changes.

For export, open-access, or utility-connected work, record the utility, proposed point of interconnection, likely voltage, nearest known substation, and any application already filed. Do not infer spare grid capacity from a visible line or substation.

Match the project goal to the evidence. A self-consumption project needs load shape, not only roof area. An export project needs an interconnection and offtake path. A backup project needs critical-load and outage information. A capacity target without its operating purpose is an amber flag.

Check names and dates. A bill for a different meter or an SLD that predates an electrical upgrade can misdirect the entire design.

Use this minute-fifteen statement format:

Electrical screen: The project goal is [self-consumption, export, backup, or mixed]. The current evidence includes [documents]. The missing decision items are [items]. No grid or connection approval is implied.

Grid and load stop signals

A confirmed customer refusal to share any load or service information may stop a consumption-led proposal. A written utility rejection can stop the current connection concept. It may not stop every revised project.

Missing interval data, transformer details, grid capacity, or a current SLD usually creates an investigation task. It should not be replaced with a familiar value from another site.

Minutes 15 to 20: Test the Commercial Inputs

The last block does not build a full financial model. It checks whether a meaningful model can be built.

Record the project delivery model and identify the owner of each key input.

Input	Minimum screen question	Evidence needed next
Energy price	Which units of energy create value?	Current tariff or agreed offtake basis
Export value	Is export allowed and compensated?	Utility or contract source
Project cost	Is there a dated cost basis?	Budget quote or cost plan
Operating cost	Who maintains the system and at what scope?	O&M basis
Incentive or tax item	Does it apply to this owner and date?	Current official or professional advice
Financing	Who supplies capital and on what terms?	Indicative or approved term sheet
Schedule	Which date changes value or eligibility?	Documented deadline and owner

Do not calculate payback from an unverified tariff, annual energy guess, and generic project cost. A precise spreadsheet output can still be unsupported.

For early screening, state the commercial conclusion in words. “The value case can be tested after interval data and a current tariff are received” is honest. “Four-year payback” is not, unless the supporting model exists and has been reviewed.

The full feasibility phase can add scenario analysis, cash flow, financing, tax treatment, degradation, replacement assumptions, curtailment, escalation, and uncertainty. The desktop screen only proves that the required inputs have owners.

Score the Result: Green, Amber, or Red

Use the matrix after minute twenty. Do not average a red issue away with several green ones.

Area	Green	Amber	Red
Site identity	Address, coordinates, and visible property agree	One reference is missing or old	Verified wrong site or unavailable property
Usable area	Target appears plausible, subject to survey	Obstructions, access, slope, or boundaries could change it	Verified constraint conflicts with stated target
Solar resource	Named source and units recorded	Sources disagree or uncertainty needs review	Wrong location or unusable source basis
Load and meter	Goal, meter, and useful load evidence align	Consumption detail or current SLD missing	Confirmed load basis conflicts with project goal
Grid path	Utility and likely path identified	Capacity or connection evidence missing	Written rejection of the current connection concept
Commercial inputs	Tariff, cost, ownership, and schedule sources exist	One or more decision inputs lack evidence	Verified rule or contract removes the value case

Apply these decision rules:

• Proceed to survey when there is no red item and each amber item has a named owner and next action.
• Investigate when an amber item can change capacity, connection, cost, schedule, or value.
• Stop when verified evidence defeats the stated project basis. Record what would need to change for reconsideration.

The decision must include its date. Public data, tariffs, policies, site conditions, and project assumptions can change.

The One-Page Output

End the review with a one-page record. It should let another person reproduce your decision.

Include:

1. Project identity, coordinates, client, reviewer, and date.
2. Project goal and target capacity supplied by the client.
3. Site evidence with image date and source.
4. Resource output with dataset, unit, and retrieval date.
5. Meter, load, utility, voltage, and connection evidence.
6. Commercial inputs received and still missing.
7. Green, amber, or red rating for each area.
8. Overall decision and the next three actions.
9. A clear desktop-only limitation statement.

The next action should be specific. “Get more information” is weak. “Client to provide twelve months of bills and the latest SLD by 2 October” is useful.

Keep source screenshots or exports with the worksheet. Links and public interfaces change. The record should show what the reviewer saw at the time.

Two Worked Desktop Screens

These examples are fictional. They demonstrate decision logic without claiming results from real projects.

Example A: Commercial rooftop with missing electrical evidence

An installer receives an enquiry for a factory roof. The client provides the correct address, a recent bill, and a target capacity. Satellite imagery shows one large roof with several plant rooms.

The first five minutes produce an amber site rating. The target appears possible, but the roof dimensions come only from imagery. Plant heights and maintenance clearances remain unknown. No current roof plan is available.

The resource check produces a green rating for further study. The reviewer records a Global Solar Atlas output, its unit, the coordinates, and the retrieval date. The result is not converted into annual system production.

The electrical check produces amber. The bill confirms the meter and contracted demand. It does not show interval consumption, transformer details, or spare switchboard capacity. The client has not supplied a current SLD.

The commercial check also produces amber. The current tariff is available, but project cost and export treatment remain open. No payback is calculated.

The overall result is investigate, not proceed. The next actions are precise:

1. Obtain a measured roof plan and current rooftop equipment schedule.
2. Request interval data and the latest electrical SLD.
3. Confirm structural-review responsibility and roof age.

The opportunity remains alive. The team has avoided promising capacity or savings before the controlling evidence arrives.

Example B: Ground site with a confirmed boundary conflict

A developer submits coordinates and a target for a ground-mount plant. The map pin opens on the expected parcel. The visible area appears large enough for more study.

The client then provides a current legal boundary file. Much of the area used in the original target sits outside that boundary. A watercourse also divides the remaining parcel.

The boundary conflict is verified, so the site-area row becomes red. There is no reason to spend the remaining time improving yield or financial inputs for the original basis.

The result is stop the current concept. That does not mean the wider opportunity is dead. The record should state what would permit reconsideration: a revised capacity, added land rights, or another parcel.

This is the value of a fast screen. It directs effort toward the condition that controls the decision.

Data Hygiene for Repeatable Screening

A desktop screen becomes useful at scale only when another reviewer can repeat it. Use the same small set of controls on every opportunity.

Pin the coordinates. Store latitude and longitude, not only a typed address. Record how the coordinates were confirmed.

Date every changing source. Imagery, tariffs, utility documents, bills, policies, and client drawings can become stale.

Keep units beside values. Write kWh/m², kWh/kWp, kW, kVA, acres, hectares, metres, or feet as applicable. Never rely on a column heading that may disappear during export.

Preserve source identity. “Online map” is not enough. Name the platform, page, dataset, file revision, and retrieval date.

Separate observation from interpretation. “Two rooftop units are visible” is an observation. “They make the roof unusable” is an interpretation that needs dimensions and rules.

Record who owns the gap. Assign each open item to the client, surveyor, designer, utility, lawyer, structural engineer, or commercial lead.

Version the decision. When new evidence arrives, issue a new screen date. Do not overwrite the earlier basis without an audit trail.

These controls take little time. They prevent a preliminary screenshot from becoming an undocumented project fact.

What the Desktop Check Cannot Verify

Remote work cannot confirm every decision-changing condition.

Measured geometry. Imagery does not establish legal boundaries, exact roof dimensions, levels, slopes, or obstruction heights.

Physical condition. A map cannot inspect a roof membrane, corrosion, drainage, soil, vegetation, or access restriction.

Structural capacity. Visible roof area says nothing conclusive about deck, framing, connections, foundations, wind, snow, or seismic resistance.

Electrical capacity. Imagery cannot establish switchboard ratings, fault current, protection, transformer capacity, conductor routes, or power quality.

Grid approval. Distance to a substation does not prove hosting capacity, acceptable protection, or an approved connection.

Legal and environmental status. A desktop map is not title review, zoning approval, land conversion, environmental clearance, or stakeholder consent.

Final yield and economics. Public resource data are inputs. They are not a reviewed system model, cost plan, tariff analysis, or investment case.

The next step is often a measured site survey and land feasibility scope. A rooftop concept may also move into solar 3D pre-design after the required inputs arrive.

Common Mistakes in a Fast Screen

Drawing modules before defining the decision

The reviewer improves a layout before checking whether load or grid evidence matters more.

Treating map measurements as verified dimensions

The values move from a screenshot into a proposal without a source label. Later teams mistake them for survey data.

Copying a resource number without its unit

GHI, PVOUT, and specific yield become mixed in the same worksheet. The commercial model then uses the wrong quantity.

Calling missing grid evidence a pass

No visible issue is not the same as available capacity. Unknown belongs in amber, with an owner.

Producing a payback number to complete the page

Time pressure does not improve weak inputs. If tariff, load, export, cost, or financing evidence is missing, record the gap.

Using one score for unrelated risks

A strong solar resource cannot cancel a failed title review or rejected grid concept. Keep the decision areas separate.

When to Commission the Full Study

Move beyond desktop screening when the opportunity survives triage. The next decision may concern land, budget, design, financing, procurement, or approval.

A full scope may need:

• boundary, topographic, drone, or measured roof survey.
• geotechnical and earth-resistivity work.
• structural investigation and calculations.
• detailed shading and energy-yield modelling.
• load analysis and electrical studies.
• utility engagement and connection study.
• legal, permitting, and environmental review.
• cost plan, schedule, risk register, and financial scenarios.

The full scope should reflect the decision at hand. A lease option, EPC bid, lender review, and construction release do not require the same evidence.

You can compare the expected deliverables with our design sample pack. For a scoped discussion, use the contact page and send the coordinates, project goal, target capacity, available bills, drawings, and survey data.

FAQ

Can a solar feasibility check really be done in 20 minutes?

A preliminary screen can. The timebox is enough to organize available evidence, identify obvious conflicts, and define next actions. It is not enough for engineering feasibility.

Can I estimate system capacity from satellite imagery?

You can test whether a target appears broadly plausible. Label the result as imagery-based. Final capacity needs verified dimensions, setbacks, access, structure, layout, and equipment decisions.

Which solar-resource tool should I use?

Use a named source with documented outputs and limitations. Global Solar Atlas and NASA POWER can support early screening. Project requirements may demand another source or method later.

What makes a desktop result red instead of amber?

Red needs verified evidence that conflicts with the stated project basis. Uncertainty, missing information, or suspicious imagery usually belongs in amber.

Does a green screen mean the site is feasible?

No. It means no desktop stop was found and the next evidence request is defined. Survey, structural, electrical, grid, legal, and commercial checks remain open.

What should I ask the client for first?

Ask for coordinates, project goal, current bills, site drawings, target capacity, utility details, and schedule constraints.

Should rooftop and ground-mount projects use the same worksheet?

They can share the four decision areas. Their evidence differs. Rooftops need building, roof, and service data. Ground sites need boundaries, terrain, access, soil, and evacuation evidence.

How long is a desktop check valid?

There is no universal validity period. Date the result and repeat affected checks after changes to the site, tariff, utility rules, equipment basis, client goal, or public data.