6 Ways to Interpret the Numerical Values Used in Proposal Documents in the PVSyst Manual

Table of Contents

• Key points to consider before using PVSyst figures in proposal materials

• Annual power generation should be viewed not as a standalone number but together with the assumptions behind it.

• Specific power generation is used to compare by normalizing differences in facility size.

• Read PR as an auxiliary metric for describing design quality

• The loss diagram breaks down and explains the reasons for decreased power output.

• Monthly results are used to explain seasonal differences and risks.

• In the proposal materials, place the basis for the numbers and any points to note on the same page.

• Summary

Points to Keep in Mind Before Using PVSyst Figures in Proposal Documents

In photovoltaic proposal documents, many figures are listed, such as annual energy production, PR, specific yield, loss rates, monthly generation, and solar irradiance. When creating proposal materials while referring to the PVSyst manual, what is important is not simply copying each figure as-is, but organizing and using them according to what they are intended to explain. Even if you make the generation numbers look large, what customers and internal approvers want to know is under what conditions those values were calculated, how reliable they are, and where the remaining risks lie.

The official PVSyst documentation explains that the software can handle a large number of variables as simulation outputs, and that values can be displayed and used externally on a monthly, daily, hourly, and even finer time-step basis. It also explains that for each simulation an engineering report including the parameters and key results can be generated. In other words, the figures used in proposal documents should be regarded not merely as result tables but as material for explaining design conditions, input data, loss factors, and seasonal variations.

A common mistake in proposal documents is including too many numbers, which prevents the reader from making a clear judgment. PVSyst reports contain many technical items—solar irradiation, array-plane irradiance, temperature losses, mismatch losses, inverter losses, shading losses, wiring losses, and so on—that are important to engineers. However, what the proposal recipient wants to know are the factors for making a decision: how much power will be generated in the end, why that amount will be generated, and which parts are most likely to fluctuate when conditions change.

Therefore, when preparing proposal materials with reference to the PVSyst manual, it becomes easier to read if you first separate the roles of the numerical values. Annual energy production is the main figure used to explain project viability and the effects of installation. Specific yield is the figure used to compare proposals with different capacities. PR is an auxiliary indicator used to explain the validity of the design and losses. The loss diagram provides the rationale for why actual values fall short of the ideal. Monthly results serve as material to explain seasonal differences and generation imbalances. And the assumptions are the foundation that supports the reliability of all figures.

In proposal documents, it is more important to arrange these items in the order the reader will understand them than to cram them all onto a single page. First show the annual power generation, then show the specific yield (generation per unit of capacity) derived from that figure, next supplement the validity with PR and loss diagrams, and finally explain the risks using monthly results and the assumptions. Following this flow makes it easier to incorporate the technical figures into sales materials and internal approval documents.

The purpose of checking numbers in the PVSyst manual is not just to memorize the field names on the screen or in reports. It is to decide which figures to include in proposal documents, which to move to supplementary materials, and which should have a cautionary note. Hereafter, I will organize six ways of interpreting numbers that are easy to use in proposal documents, aligned with practical workflow.

Annual power generation should be viewed not as a standalone number but together with its underlying assumptions

The most prominent figure in proposal materials is the annual energy production. Because it indicates how much electricity can be expected after installation, it is an important item both for customers and for those making investment decisions. When using PVSyst simulation results, this annual energy production is treated as the final outcome, but in the proposal materials it should not be presented on its own; it must always be shown together with the assumptions.

Annual energy generation is affected by module capacity, installation azimuth, tilt angle, solar irradiance, meteorological data, temperature conditions, shading conditions, equipment specifications, loss settings, and other factors. Even with the same installed capacity, results will vary depending on the region of installation, roof shape, nearby buildings, panel orientation, and PCS configuration. Therefore, presenting annual generation simply as “X kWh” does not allow the reader to judge whether that figure is optimistic, typical, or conservative.

In proposal materials, it is helpful to briefly include, near the annual energy production, at least the installed capacity, the meteorological data used, the azimuth, the tilt, and the main loss conditions. You do not need to list every detailed parameter, but if you omit the conditions that underpin the energy production, it becomes difficult later to explain "why this energy production is as stated." In particular, when comparing multiple options, you need to distinguish whether only the capacity differs, or whether the layout and shading conditions also differ.

When assessing annual energy production, be mindful of the deviation from ideal conditions. In solar power generation simulations, the incident solar energy does not directly become electricity. It becomes the final output only after reductions due to module temperature, angle of incidence effects, soiling, mismatch, DC wiring, inverter conversion, AC-side losses, shading, and so on. Therefore, annual generation is a final value, and only by understanding the loss structure along the way does it become persuasive as proposal material.

Also, annual generation is the number you most want to present, but it is also the most easily misunderstood. Customers may take this value as a guaranteed figure, but simulation results are predictions based on input conditions. Actual generation varies with weather, snowfall, soiling, equipment downtime, output curtailment, maintenance conditions, and other factors. Therefore, in proposal documents it is safer to use wording that conveys these are estimates, such as "Assumed annual generation", "Annual generation from simulation", or "Annual generation under PVSyst conditions".

When using the PVSyst manual to check annual energy production, verify not only the final energy value shown on the report but also the assumptions that led to that value. In particular, when calculating economic effects in proposal documents, even a small change in annual energy production can greatly alter impressions of feed‑in revenue, savings from self‑consumption, and the payback period. For that reason, it is important not only to make the annual energy production figure stand out, but also to place a clear note beside it so the reader understands that the value was calculated under those specific conditions.

Specific power generation normalizes differences in plant size for comparison

When comparing multiple design options in a proposal document, judging by annual generation alone can be misleading. Because options with larger installed capacity tend to produce more annually, simply listing generation figures will make larger-capacity options always look better. This is where specific yield, which indicates generation per unit of capacity, is useful.

Specific power generation is generally defined as the annual power generation divided by the installed capacity. For example, given the same annual generation, a design that achieves a high amount of generation with a smaller capacity can be regarded as an efficient layout. On the other hand, if a system has a large installed capacity but low generation per unit capacity, factors such as orientation, tilt, shading, oversizing, equipment selection, and layout density may be reducing generation efficiency.

In proposal documents, using specific yield makes it easier to compare options with different system sizes fairly. For example, when comparing an option that installs panels across the entire roof with an option that avoids shaded areas, the former may appear larger if you only look at annual generation. However, when you look at generation efficiency per unit of capacity, the latter can have higher generation quality. Even if a customer thinks, "I just want to install as much as possible," showing the specific yield can explain how much the portions added just to increase capacity are lowering efficiency.

Specific power generation is suited to explaining the "quality" of a design proposal within submission materials. However, this figure cannot be evaluated in isolation. If a region's solar radiation conditions differ, the specific power generation will change even with the same design quality. It is not appropriate to compare a region with good solar radiation to one with frequent cloud cover and simply judge by whether the number is higher or lower. Specific power generation is particularly useful when comparing proposals for the same site, using the same meteorological data and the same assumptions.

Also, using specific yield keeps the explanations in the proposal from becoming too technical. Even without explaining all the details of the losses, reframing it as "how much is generated per 1 kW" makes it easier for readers to understand intuitively. For internal approvals and customer explanations, having a clear basis for comparison is more important than technical terminology.

When checking specific yield while referring to the PVSyst manual, pay attention to how system capacity is defined. Whether you use the DC-side PV capacity or the AC-side PCS capacity as the basis can change how the results appear. In proposal documents, it is important not to be ambiguous about which basis is being used. Especially for projects with a high DC-to-AC ratio, failing to clarify the capacity basis will reduce the reliability of comparative materials.

Specific yield serves as a bridge to convey to the customer that "this design is reasonable in terms of generation efficiency." If annual energy production is the star of the proposal, specific yield is the yardstick for calmly assessing that figure. When including PVSyst results in proposal materials, showing both the total production and the production per unit of capacity turns a document that simply displays large numbers into one that is easier to evaluate.

Treat PR as an auxiliary indicator for explaining design quality

PR is an indicator often used to describe the performance of solar power generation systems. In proposal documents, it also serves as supplementary information to demonstrate the reasonableness of the amount of generation and the quality of the design. However, while PR is convenient, it is also a value that can be interpreted differently by readers. Rather than simply judging that a high PR is necessarily good and a low PR necessarily bad, it is necessary to confirm under what conditions the PR was calculated.

PR is an indicator for assessing how effectively a system converts solar irradiance conditions into electrical power. In proposal documents, it serves to supplement annual generation figures, which alone can be insufficient to explain the "degree of minimal waste in the design" or the "magnitude of losses." For example, even if annual generation is high, the system may still exhibit large losses if the solar irradiance conditions are exceptionally favorable. Conversely, annual generation may be modest, but when accounting for irradiance conditions the design quality may not be poor.

When using PR in proposal materials, it is well suited to situations where multiple options under the same conditions are compared. For example, when comparing a layout that avoids shading with a layout that prioritizes installed capacity, reviewing the PR lets you explain which design is less demanding on the system. Also, when equipment configuration or loss settings are changed, checking changes in PR allows you to explain efficiency aspects of the design rather than merely increases or decreases in energy output.

On the other hand, if PR is presented too prominently in a proposal document, it can appear overly technical. If the client is focusing on capital investment and the benefits of self-consumption, what they want to know first is the annual energy production and the economic impact. Therefore, rather than making PR the main headline, it is more natural to position it as a supplement that supports the plausibility of the annual generation. Explaining it as, "In the PVSyst results, we check PR in addition to annual energy production to confirm that losses are not being over- or under-estimated," makes it easier to convey technical credibility.

When assessing PR, you cannot ignore the effects of temperature losses and shading losses. In high-temperature regions, temperature losses tend to be larger, and projects with nearby shading are likely to see PR decrease. Conversely, projects with good solar irradiation conditions, little shading, and appropriate equipment selection can appear to have relatively favorable PR. However, if an excessively high PR is reported, you should review whether loss settings are missing or insufficient and whether shading, soiling, wiring losses, etc., have been appropriately included.

When showing PR in proposal materials, rather than asserting "this value is high so you can be reassured," it is more honest to explain that "it is an indicator used to verify the overall performance of the system after accounting for the major losses." By checking the result items in the PVSyst manual and interpreting PR together with other indicators, the proposal becomes a document that explains the validity of the design rather than merely citing a number.

PR may be unfamiliar to customers. Therefore, it is effective to include a brief explanation of the term in proposal materials. For example, explaining it as "an indicator that shows how effectively the system can generate power under solar radiation conditions" makes it easier for non-specialist readers to understand. The purpose of using PVSyst figures in proposal materials is not to display expertise, but to clearly provide the evidence needed for decision-making.

The loss diagram breaks down and explains the reasons for decreased power generation

When using PVSyst results in proposal materials, the loss diagram is extremely important. Annual energy production is the final result, but the loss diagram shows what kinds of losses occur on the way to that result. The official documentation also describes the loss diagram as a means to identify the main sources of loss in order to assess the quality of a photovoltaic system design.

The greatest benefit of using a loss diagram in a proposal is that it allows you to explain "why this amount of energy is generated." Customers tend to focus on whether the energy figure is high or low when they see the number. However, in photovoltaic system design it is important not only to know the final energy output but also to understand where losses occur. A loss diagram enables you to explain separately the effects of temperature, shading, angle of incidence, equipment losses, wiring losses, and so on.

For example, if the annual power generation for a project appears lower than expected, checking the loss diagram allows you to distinguish whether the cause is solar irradiance conditions, shading, temperature, or equipment configuration. If the impact of nearby shading is large, you can propose layout changes or a reassessment of the installation area. If temperature losses are significant, you will need to provide an explanation that takes into account the installation environment, ventilation conditions, and module characteristics. If inverter losses or clipping are prominent, this can be linked to an explanation of the DC/AC ratio and PCS capacity.

When including a loss diagram in a proposal document, you do not need to explain every item in detail. What matters to the reader is, "Which losses are large?", "Which losses can be improved through design?", and "Which losses are difficult to avoid due to site conditions?". For example, temperature-related losses are heavily influenced by the region and installation conditions and cannot be reduced to zero. On the other hand, shielding losses and excessive wiring losses may have room for design review. Being able to explain this distinction makes the proposal more persuasive.

When reviewing the PVSyst manual, it is useful to understand that the loss diagram can be used not only for the whole year but also for monthly evaluations. The official documentation explains that the loss diagram is included in the simulation report as an annual summary, and that the loss impacts for each month can also be evaluated from the predefined graphs in the detailed results. This is helpful when explaining projects where shading increases seasonally or projects that experience large temperature-related losses in summer.

In projects with near-field shading, special care is needed when interpreting the loss diagram. PVSyst’s official help explains that near shading results include shading losses on the direct, diffuse, and global irradiance components, and that the electrical effects of partial shading depend on module interconnection; a method is provided to evaluate the field by dividing it into rectangles corresponding to strings of series-connected modules. For proposal materials, present this without excessive technical detail; it is easier to communicate if summarized as: "Because the effect of shading not only reduces irradiance but also causes electrical impacts depending on the string configuration, we reflect the shading conditions in PVSyst."

A loss diagram is not material meant to make customers uneasy in proposal documents. Rather, it is material to show that the power generation has been estimated realistically. Losses themselves are not a problem; what matters is how well you understand and can explain those losses. By using a loss diagram effectively, you can convey that the proposal is not merely “showing only the good numbers” but is a proposal that incorporates risk.

Use the monthly results to explain seasonal variations and risks

The annual energy production is the centerpiece of the proposal materials, but in actual operation the output varies greatly from month to month. This is because solar irradiance, temperature, solar altitude, weather, snowfall, and the way shadows fall all change with the seasons. PVSyst’s monthly results can be used to explain these seasonal differences.

Showing monthly results in proposal materials communicates characteristics that are not visible from annual totals alone. For example, for projects with high power generation from spring through summer and lower generation in winter, you can explain the effects of solar irradiance conditions and solar altitude. For rooftop projects where surrounding buildings cast shadows, shading impacts may be stronger in winter. In snowy regions, it is necessary to supplement information about winter generation declines and the associated uncertainty. Such explanations cannot be adequately conveyed by annual generation alone.

Monthly results are important even for proposals focused on self-consumption. Even if the annual generation is the same, the economic effect changes depending on whether periods of high electricity demand and high generation coincide. For facilities with large cooling demand in summer, summer generation can more readily contribute to self-consumption. Conversely, for facilities with high winter demand, winter generation and snow risk need to be examined carefully. In proposal materials, explaining monthly generation together with demand patterns lets you move from a mere generation simulation to an explanation of operational value.

When reading monthly results using the PVSyst manual, pay attention not only to monthly energy production but also to monthly loss trends. Temperature losses tend to increase in summer, while in winter a lower solar altitude and shading effects may become more pronounced. Factors that are not apparent in the annual loss rate can be concentrated in specific months. In proposal documents, rather than explaining every month in detail, it is easier to read if you select and describe representative seasons.

When including monthly results in proposal materials, it's also important not to rely too much on graphs and tables. If numbers are just listed, readers won't know what to look for. For example, adding explanations such as "Generation is high from spring through summer and decreases in winter due to solar radiation conditions and shading" and "Because the effect of self-consumption overlaps with summer demand, we check not only annual generation but also the month-by-month degree of alignment" will help convey the meaning of the materials.

Monthly results can also be used to explain risks. During the proposal stage there is a tendency to want to make the annual energy output look large, but in practice it is important not to hide the factors that cause variability. If you explain in advance why generation is low in specific months, you can reduce misunderstandings after installation such as “it’s less than I expected.” The value of using PVSyst results lies not in making the generation numbers look high, but in sharing realistic projections based on the conditions.

Presenting the monthly results in a proposal document is easier to handle if they are positioned as "Breakdown of annual generation." First show the total annual amount, then present the monthly trends so readers can naturally understand the whole and the breakdown. Rather than simply including PVSyst's monthly results as-is, briefly explaining seasonal differences, the relationship with demand, and the effects of shading and temperature will improve the completeness of the proposal.

In proposal documents, place the numerical basis and caveats on the same page

When using PVSyst figures in proposal materials, the most important thing is not to separate the rationale from the caveats. If you prominently present numbers such as energy production, PR, and specific yield, and relegate the basis for those numbers to a separate appendix with detailed materials, readers will tend to let the figures stand on their own and interpret them in isolation. Conversely, if you write at length only about the caveats, the attractiveness of the proposal becomes harder to convey. What is needed is to present the key figures and their underlying assumptions in the same context.

The basis of proposal materials is to present key figures, assumptions, interpretations, and precautions as a set. For example, on a page showing annual power generation, briefly include installed capacity, installation conditions, meteorological data, and the main loss components reflected. When presenting PR, explain that it is an auxiliary indicator for confirming design quality. When showing a loss chart, briefly describe the major loss factors and the design response policies. When showing monthly results, summarize in a single sentence the seasonal variations and their relationship to demand.

An important point to note is that the PVSyst results are simulations based on input conditions. You don’t need to write this out at length in every proposal document, but wording to avoid misunderstanding is necessary. For example, it is good to include explanations such as “These are simulation values based on meteorological conditions, installation conditions, and loss settings” and “Actual power generation will vary due to weather, maintenance status, equipment outages, output curtailment, etc.” at the end of the document or in a footnote.

However, if there are too many caveats, the proposal materials can appear weak. Therefore, write the cautions not to raise anxiety but to ensure the figures are correctly understood. In particular, in materials explaining payback or profitability, explicitly stating that annual electricity generation may vary depending on the underlying assumptions will help prevent misunderstandings in later stages.

When reviewing the PVSyst manual, separate which figures from the report will be placed directly into the proposal and which will be retained for internal review. The figures that should be included in the proposal are those that directly inform decision-making. Annual energy production, energy production per unit capacity, PR, major losses, and monthly generation trends are items that are useful in many projects. On the other hand, detailed intermediate variables and specialized correction factors are easier to read if moved to technical documentation or appendices as needed.

Also, consistency in how numerical values are presented is necessary. If one page shows many decimal places while another page shows rounded numbers, readers will become confused. In proposal documents, it is important to align the number of displayed digits, units, reference capacity, and period. In particular, units such as kWh, MWh, kWp, kW, and kWh/kWp are easily confused, so write the units accurately. When transcribing from PVSyst screens or reports, always check the units.

The purpose of using numbers in proposal documents is not to create materials that only experts can understand. It is to make documents that customers, management, designers, contractors, and maintenance personnel can judge from the same premises. Therefore, instead of pasting PVSyst results as-is, you need to translate them into an order that makes it easy for readers to judge. Show the effect with annual energy production, compare by specific yield, confirm validity with PR, explain the reasons with the loss diagram, supplement seasonal differences with monthly results, and support reliability with the assumptions. If you create this flow, PVSyst's numbers will have strong persuasive power in the proposal document.

Summary

When reviewing the numbers from the PVSyst manual for use in proposal materials, it is important not simply to extract the figures from the report, but to organize them in a way that aids the reader's decision-making. Annual energy production is the central figure indicating the benefit of installation, but it must be presented together with the underlying assumptions. Specific yield (energy per unit capacity) can be used to normalize differences in system capacity for comparison. Performance ratio (PR) is useful as a supplementary indicator of design quality and the plausibility of losses. Loss diagrams provide the basis for decomposing and explaining the reasons for reduced energy production. Monthly results serve as material to explain seasonal variations, compatibility with self-consumption, and the effects of shading and temperature. And all figures should be accompanied by the assumptions and caveats that underpin them.

What matters in proposal materials is not listing a large number of figures. The reader should be able to judge which option is reasonable, which conditions require attention, and what level of power generation can be expected. PVSyst results contain a lot of specialized information, but in proposal materials it becomes easier to understand if you organize them into six items: annual energy yield, specific yield, PR, loss diagram, monthly results, and assumptions.

Also, PVSyst figures lose credibility when used without a sufficient understanding of local site conditions. Orientation, tilt, shading, surrounding topography, equipment layout, maintenance conditions, and other on-site information affect the reliability of the numbers. The closer you bring desk-based simulations to actual site conditions, the more realistic the power-generation explanations in the proposal documents will be.

During site surveys and when organizing pre-design conditions, leveraging systems that efficiently record on-site location information and surrounding conditions—such as LRTK, a smartphone-mounted high-precision GNSS positioning device—makes it easier to verify the assumptions to be entered into PVSyst and to organize the supporting information to include in proposal documents. By combining the ability to correctly read PVSyst's numerical outputs with the ability to accurately capture field conditions, you can create materials that convey not only the expected power generation but also why the proposal is reasonable.