Every Solar PV Feasibility Study MENA looks credible at first glance. The formatting is professional. The Excel model is clean.
The assumptions are presented with two decimal places of precision that suggest a level of accuracy they do not always deserve. The IRR is positive. The payback period is reasonable. The numbers tell a story that justifies the investment.
And then the installation is commissioned — and the real numbers start arriving.
Not dramatically different. Not wrong enough to trigger a conversation. Just consistently, quietly lower than projected — a Performance Ratio that runs a few points below the model, savings that fall short of the monthly target, a payback that is drifting toward seven years instead of six.
The gap is almost never the result of bad faith or incompetence. It is almost always the result of the same set of assumptions — applied consistently across dozens of projects in the MENA region — that were never validated against the actual operating environment of a specific industrial site.
This article is a practical guide to reading a solar PV feasibility study in MENA with enough rigor to identify those assumptions before they become your problem. Not to reject feasibility studies — they are essential tools. But to understand exactly which numbers deserve scrutiny, which questions to ask before signing, and what good actually looks like when a study is done with the care that a multi-million dollar investment deserves.
Disclosure: This article contains affiliate links. If you purchase through these links, I may earn a small commission at no extra cost to you. I only recommend technical resources that I consider genuinely useful for industrial solar professionals working in Africa and the MENA region.
Why Most Feasibility Studies in MENA Follow the Same Pattern
A feasibility study is typically commissioned by a developer or EPC contractor who has a financial interest in the project proceeding. The study is produced under time and cost pressure. The assumptions used are often inherited from a previous project in a similar geography — not independently measured for the specific site. The P50 yield projection is presented as the base case because it produces the most favorable financial metrics.
None of this makes a study fraudulent. It makes it optimistic in predictable, systematic ways that an informed reader can identify.
There is also a knowledge gap that rarely gets discussed openly. The engineers who produce feasibility studies in the MENA region are often working with software tools — PVsyst, Homer, SAM — that produce precise-looking outputs from generic input databases. The soiling figure in the model comes from a regional database, not from a measurement on the specific site. The inverter thermal behavior is modeled at rated conditions, not at the actual ambient temperature of the inverter room in July. The O&M budget comes from a spreadsheet template, not from a conversation with someone who has actually maintained a similar installation in a similar environment.
This is not negligence. It is the natural consequence of producing a study under commercial time pressure, with tools that reward precision of calculation over accuracy of assumption. The numbers look right because the math is correct. The gap emerges because the inputs were not validated against the specific reality of this specific site.
Understanding this dynamic is the beginning of reading a feasibility study critically — not suspiciously, but rigorously.
The 7 Numbers That Actually Matter
Number 1 — The Performance Ratio projection
The projected PR is the single most important number in any solar feasibility study — because every other financial metric flows from it. If the PR assumption is wrong, the IRR is wrong, the payback is wrong, and the savings projection is wrong.
The standard PR projection for industrial solar in Morocco and the wider MENA region in most feasibility studies sits between 80% and 87%. Field data from real industrial installations in Morocco consistently shows actual PR in the range of 77% to 84% — with significant variation driven by soiling management, inverter thermal performance, and maintenance discipline.
What to look for the study should explain exactly how the PR was calculated — which loss factors were included, which were excluded, and what site-specific data was used to calibrate each assumption. A PR projection without a detailed loss cascade breakdown is not a rigorous projection. It is a number chosen to make the model work.
Number 2 — The soiling loss assumption
This is the most systematically underestimated loss in MENA solar feasibility studies. Standard assumptions range from 3% to 5% annually — figures derived from broad regional averages that bear little relationship to the actual soiling behavior of a heavy industrial site.
On industrial sites — cement plants, petrochemical facilities, mining operations — where particulate emissions, vehicle traffic, and proximity to raw material handling create a continuously challenging environment for panel cleanliness, the actual sustained soiling loss is 5% to 8% annually. On particularly challenging sites, it can be higher.
The financial gap between a 3% assumption and a 7% operational reality on a system generating 360,000 USD per year in energy savings is 14,400 USD per year — compounding across a 25-year project lifetime into 360,000 USD in unaccounted losses from a single input that was never validated against site conditions.
What to look for: the study should specify how the soiling assumption was derived. Was it based on satellite data? Regional averages? Actual measurements from a similar nearby site? A soiling assumption of 3% on a cement plant, presented without site-specific justification, is a red flag.
Number 3 — P50 versus P90 yield projections
A P50 yield projection means there is a 50% probability of achieving that output in any given year. By definition, it also means there is a 50% probability of falling short. For a project with a 25-year power purchase agreement, a P50-only base case is not conservative financial modeling — it is optimistic modeling presented as engineering rigor.
To make this concrete: on a project generating 360,000 USD per year at P50, the P90 scenario — accounting for irradiation variability and soiling uncertainty — might deliver between 324,000 and 342,000 USD annually. That gap of 18,000 to 36,000 USD per year represents between 450,000 and 900,000 USD over a 25-year project lifetime. For a project financed with debt, this gap can determine whether annual debt service is covered — or not.
What to look for: any bankable feasibility study should present both P50 and P90 scenarios with a clear explanation of the uncertainty inputs driving the gap between them. If only P50 is presented, ask explicitly for the P90 sensitivity case before making any financial commitment.
Number 4 — The degradation rate assumption
Solar panels degrade over time — their output declines year after year as cell materials age, micro-cracks propagate, and encapsulant materials deteriorate. The rate of this degradation is a critical input to any 25-year financial model.
Most feasibility studies in MENA use a standard degradation rate of 0.5% to 0.7% per year — consistent with manufacturer warranties and broadly accepted industry benchmarks for monocrystalline technology in moderate climates. In the high-irradiance, high-temperature environment of the MENA region — where panels are exposed to significantly higher UV and thermal stress than in European or North American test conditions — actual degradation rates may be at the higher end of this range, or occasionally above it.
What to look for: the study should specify the degradation rate used, cite the source of that assumption, and provide a sensitivity analysis showing the impact on IRR of degradation rates at 0.5%, 0.7%, and 1.0% per year.
Number 5 — The O&M budget
The Operations and Maintenance budget determines what resources will be available to keep the installation performing at its projected level for 25 years. It is also the line item most likely to be underestimated — because a lower O&M budget produces a more attractive IRR.
Real O&M costs on an industrial solar installation in Morocco — including cleaning at the frequency actually required to manage soiling, preventive maintenance of inverters and electrical connections, periodic thermal imaging inspections, and the physical inspection program needed to detect string-level losses — are significantly higher than the generic benchmarks most studies apply.
A cleaning program calibrated to real soiling behavior on a heavy industrial site costs between 15,000 and 40,000 USD per year per MWp. A physical inspection program that actually finds the losses monitoring misses costs 3,000 to 8,000 USD per year. These figures should appear in any honest O&M budget for an industrial site in MENA.
What to look for: the study should itemize O&M costs by category — cleaning, preventive maintenance, inspections, inverter replacement reserve — and justify each figure with site-specific data. A single O&M line item expressed as a percentage of capital cost, without breakdown or site justification, deserves scrutiny.
Number 6 — The IRR sensitivity analysis
The base case IRR in a solar feasibility study is almost always calculated at P50 yield, standard degradation, and budgeted O&M costs. This produces the most favorable return figure — and is also the scenario least likely to fully materialize in practice.
A rigorous sensitivity analysis shows how the IRR changes under combinations of adverse assumptions: P90 yield rather than P50, soiling at 7% rather than 3%, O&M costs 30% above budget, degradation at 0.7% rather than 0.5%. The difference between the base case IRR and the stress-tested IRR tells you how much margin the project has against real-world variability.
For a project reviewed independently in Morocco — a development exceeding 5 million USD — the base case IRR looked attractive. The stress-tested scenario, with realistic soiling assumptions and actual O&M costs, produced an IRR that was meaningfully lower and changed the risk conversation considerably.
What to look for: request a sensitivity table showing IRR under at least three scenarios — base case, realistic assumptions, and stress case. If the developer resists providing this, that resistance is itself informative.
Number 7 — The inverter thermal derating assumption
This is the loss that appears in almost no MENA feasibility study — and that has direct financial consequences on every installation operating in a hot climate.
When ambient temperature in the inverter room exceeds 40°C to 45°C — the derating threshold for most string and central inverters — output automatically reduces by 6% to 12% to protect the equipment. In Morocco, inverter room temperatures of 50°C to 55°C are routine during summer months. In Saudi Arabia and the Gulf, they are frequently higher.
The financial impact on a 2 MWp system — 9,600 USD per year in avoidable losses, representing 240,000 USD over a 25-year lifetime — comes from a cause that is entirely predictable, entirely measurable, and almost entirely ignored in feasibility modeling.
What to look for: the study should either include inverter thermal derating as an explicit loss factor in the energy yield model, or provide a written justification for why it was excluded. Silence on this topic is not an acceptable answer for an installation in a hot climate.
What the Real Numbers Look Like — Field Data vs Study Assumptions
This table summarizes the gap between standard MENA feasibility study assumptions and measured operational reality — with the financial consequence of each gap made explicit:
| Parameter | Standard Study Assumption | Real Field Data — Morocco | Annual Financial Impact |
|---|---|---|---|
| Performance Ratio | 80% to 87% | 77% to 84% | Up to 25,000 USD/year gap |
| Soiling loss | 3% to 5% | 5% to 8% | 14,400 USD/year unbudgeted |
| Inverter thermal derating | Not modeled | 6% to 12% in summer | 9,600 USD/year lost silently |
| O&M cost — cleaning | Generic benchmark | 3x per month minimum | Systematically underbudgeted |
| String loss detection | Assumed via monitoring | 15%+ missed by monitoring | 5,340 USD/year unrecovered |
| P90 scenario | Often absent | 5% to 10% below P50 | 18,000 to 36,000 USD/year gap |
| Degradation rate | 0.5% standard | 0.5% to 0.7% in MENA | Cumulative impact over 25 years |
Every row in this table represents a real, measurable, and predictable gap — not exceptional bad luck, not equipment failure, but assumptions that were never validated against the specific operating environment they were supposed to represent.
The 10 Questions to Ask Before You Sign
These are the questions that a rigorous technical due diligence process should answer before any financial commitment on an industrial solar project in MENA — with an indication of what a good answer looks like versus a red flag:
1. What is the source of the soiling assumption?
Good answer: “We conducted a dust deposition study on this specific site over 30 days.”
Red flag: “We used regional MENA averages.”
2. Has inverter thermal derating been modeled as an explicit loss factor?
Good answer: “Yes — we modeled derating at measured summer ambient temperatures for this location.”
Red flag: “Inverters operate within rated specifications.”
3. Is a P90 yield scenario available, and what inputs drive the gap with P50?
Good answer: “Yes — here is the P90 case with the uncertainty inputs documented.”
Red flag: “We use P50 as our base case.”
4. What cleaning frequency does the O&M budget assume, and is it validated for this specific site type?
Good answer: “We budgeted for three cleaning cycles per month based on comparable industrial sites in the region.”
Red flag: “We use a standard 1% annual O&M cost assumption.”
5. What degradation rate is used, and what is the IRR sensitivity to a degradation rate of 0.7%?
Good answer: “We used 0.6% with a sensitivity case at 0.7% — here is the IRR impact.”
Red flag: “We used 0.5% — it is within warranty specifications.”
6. Does the O&M budget include a provision for physical inspection beyond dashboard monitoring?
Good answer: “Yes — we budgeted for annual thermal imaging and biannual string current measurements.”
Red flag: “The monitoring system will flag any performance issues.”
7. What is the IRR under a stress scenario combining P90 yield, realistic soiling, and O&M costs 30% above budget?
Good answer: A specific IRR figure with documented inputs.
Red flag: “We are confident in our base case assumptions.”
8. Has the inverter room been thermally assessed for summer ambient temperature conditions at this specific location?
Good answer: “Yes — we measured peak summer temperatures and designed the ventilation accordingly.”
Red flag: “The inverters are rated for ambient temperatures up to 50°C.”
9. What is the basis for the grid curtailment assumption, if any?
Good answer: “We reviewed the local grid operator’s curtailment history for this connection point.”
Red flag: Silence, or “curtailment is not applicable in this market.”
10. Has the study been independently reviewed by a technical advisor with no financial interest in the project proceeding?
Good answer: “Yes — here is the independent engineer’s report.”
Red flag: “We are happy to provide references from previous clients.”
A developer or EPC contractor who is confident in their analysis will answer these questions directly and provide supporting documentation. Resistance to any of these questions is a signal worth taking seriously before committing capital.
What a Bankable Feasibility Study Actually Looks Like
A rigorous feasibility study for an industrial solar project in MENA is not one that produces the most attractive IRR. It is one that produces the most defensible IRR — a projection that a sophisticated investor, a development finance institution, or an independent technical advisor can review and validate with confidence.
That means site-specific soiling data rather than regional averages. It means inverter thermal derating included in the energy yield model. It means a P90 scenario presented alongside P50. It means an O&M budget that reflects actual cleaning requirements and includes a physical inspection program.
It also means a developer who is willing to have that conversation — who treats technical rigor as a competitive advantage rather than a negotiating obstacle.
For investors and project developers who want to build the analytical foundation needed to evaluate feasibility studies with genuine rigor — understanding yield modeling, loss cascade analysis, and financial sensitivity frameworks — Renewable Energy Finance: Funding the Future of Energy by Charles Donovan provides one of the most practical treatments available of how technical assumptions translate into bankable financial models. It is particularly valuable for anyone navigating the gap between what a feasibility study projects and what an investment committee needs to see before committing capital.
A solar PV feasibility study is not a guarantee. It is a model — built on assumptions, calibrated to data that may or may not reflect the specific conditions of your site, and structured to tell a story that justifies the investment it is evaluating.
The 7 numbers in this article are not the only numbers that matter in a feasibility study. But they are the ones where the gap between assumption and reality is most predictable, most consistent, and most financially consequential for industrial solar projects in MENA.
The cumulative financial impact of these 7 assumption gaps — soiling at 7% instead of 3%, thermal derating at 9,600 USD per year, string losses at 5,340 USD per year, P90 shortfall at 18,000 USD per year — on a single 2 MWp installation over 25 years exceeds 1,000,000 USD. Not from equipment failure. Not from bad luck. From assumptions that were never validated against the specific site they were supposed to represent.
That is the financial case for asking 10 questions before signing. Every one of them costs nothing to ask.
The plants that deliver what their financial models promised are the ones where someone asked these questions before the first panel was installed.
The ones that quietly underperform for 25 years are the ones where nobody did.
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The first 8 pages of the MENA Industrial Solar Data Guide — real Performance Ratio data, soiling measurements, and thermal derating figures from an industrial installation— No spam, just real data.
Disclosure: This article contains affiliate links. If you purchase through these links, I may earn a small commission at no extra cost to you. I only recommend technical resources that I consider genuinely useful for industrial solar professionals working in Africa and the MENA region.
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Solar PV MENA Expert