5 ways to interpret PVSyst numbers for use in estimates

When preparing an estimate for a solar power plant, simply adding up equipment costs, construction costs, design fees, and application fees often leaves it lacking persuasive power as a power generation project. In particular for commercial solar, the project owner or client does not only want to know how much it will cost to build. They want to confirm, for that amount of investment, how much electricity will be generated, how much revenue can be expected, and where the risks lie.

What becomes important then are the figures from PVSyst. PVSyst is a representative software for simulating the power generation and losses of photovoltaic systems, and it is highly effective as supporting evidence for an estimate. However, simply pasting the numbers that appear in a PVSyst report may be difficult to use as an estimate. It is important to determine which estimate items correspond to PVSyst outputs such as generation, PR, Specific Yield, loss rates, irradiation, temperature loss, wiring loss, PCS loss, and so on.

An estimate is a document that shows price, but in solar power it is also a document that demonstrates the basis for performance. For example, even solar power plants with the same capacity can have different annual energy production depending on the mounting angle, azimuth, shading, panel layout, PCS capacity, wiring distance, snowfall, soiling, and terrain conditions. By correctly reading the figures from PVSyst, it becomes easier to explain why this design yields this amount of generation, why this equipment configuration is reasonable, and why these construction costs are necessary.

This article outlines five ways to interpret PVSyst figures so they can be used in estimates. Rather than merely showing how to read simulation results, it explains from a practical perspective how to link them to estimate amounts, energy production, design conditions, losses, scope of work, and explanations for customers.

Interpreting Annual Power Generation as the Basis for Revenue Assumptions

The first thing to verify when applying PVSyst figures to a quotation is the annual energy production. Estimates tend to draw attention to the total equipment and construction costs, but for a solar power plant it is important to understand how much generation value that amount will produce in the future. Annual energy production is the central figure for that explanation.

In PVSyst reports, annual energy production is shown in kWh or MWh. This number represents how much electricity the plant is expected to generate in one year. When reflecting this figure in a quotation, you should not simply list the energy production; you need to read it in combination with the feed-in tariff, the self-consumption unit price, the electricity reduction unit price, and other related rates.

For example, if the annual generation is 1,000,000 kWh and the selling price of electricity is constant, you can calculate an approximate annual revenue from electricity sales. In the case of self-consumption systems, you can estimate the annual electricity cost savings based on the price of purchased electricity. In other words, PVSyst’s annual generation is the starting point for investment decisions in a quotation.

However, it should be noted that PVSyst's annual energy production is not a guaranteed value but a simulation output based on the specified conditions. Results will vary depending on meteorological data, solar irradiance, temperature, equipment specifications, loss settings, shading conditions, and so on. Therefore, when including it in a quotation, it must be presented together with the underlying assumptions.

In the estimate explanation, it is appropriate to present the annual energy generation as "expected energy generation based on these design conditions." For the client, explaining not only the generation figure but also the conditions under which that figure was calculated increases credibility. Briefly including the source of the solar irradiance data, panel capacity, PCS capacity, azimuth, tilt angle, installation location, and loss assumptions makes the basis of the estimate clear.

Also, annual energy production provides material to justify the reasonableness of the estimated cost. Even if an estimate is inexpensive, if the design leads to a significant decrease in energy production, the project's viability will deteriorate. Conversely, even if the initial cost is somewhat higher, a layout that reduces the impact of shading, appropriate PCS capacity, and proper wiring design that increase energy production can be advantageous in the long term.

Thus, PVSyst's annual energy production is not merely a numerical result but a central metric that supports the overall persuasiveness of the estimate. By presenting annual energy production, projected revenue, and an estimated payback period alongside the quoted price, customers can more easily evaluate the investment return as well as the price.

Interpreting Specific Yield as a Comparative Metric per Unit Volume

The next important metric is Specific Yield. Specific Yield is an indicator that shows the annual energy generation per 1 kWp of installed capacity, and its unit is generally kWh/kWp. In quotations, it is very useful when comparing projects of different capacities or different design proposals.

If you look only at annual generation, higher-capacity power plants tend to show larger figures. Therefore, simply comparing annual generation alone can make it difficult to assess the quality of a design. For example, if you compare a 1 MW plant and a 2 MW plant, the 2 MW plant will likely have a larger annual generation, but that alone does not mean it is more efficient.

Using Specific Yield, you can compare generation efficiency per unit of capacity. For example, if one option is 1,250 kWh/kWp and another is 1,180 kWh/kWp, you can interpret that the former is designed to generate more per 1 kWp. This is particularly useful when presenting multiple options in a quotation.

In estimates, presenting panel capacity, PCS capacity, annual energy production, and Specific Yield together makes it easier for customers to compare design proposals. For example, a low-cost proposal may include more installed capacity, but losses from shading and overloading can be large, resulting in a low Specific Yield. On the other hand, arranging the layout with a bit more margin can reduce installed capacity while increasing the energy produced per unit of capacity.

Specific Yield is useful when explaining this difference. In an estimate, rather than simply describing options as "cheap option" or "expensive option," you can organize them as "an option that minimizes upfront costs," "an option that prioritizes power generation efficiency per unit of capacity," and "an option that emphasizes long-term profitability." Using PVSyst's Specific Yield as supporting evidence brings objectivity to the explanation.

Specific Yield is also useful for understanding the impact of regional differences and installation conditions. In Hokkaido, Tohoku, Kanto, Kyushu, etc., solar irradiance and snowfall conditions differ. Even when using the same equipment, Specific Yield changes depending on the installation location. When preparing an estimate that covers projects in multiple regions, examining Specific Yield allows you to explain differences in power generation efficiency caused by regional conditions.

You should not judge Specific Yield on its own. It tends to be higher in regions with high solar radiation and is also affected by shading, snowfall, temperature conditions, orientation, and tilt angle. Therefore, in estimates you should not emphasize Specific Yield alone, but read it together with the installation conditions.

Especially when a customer is comparing quotes from multiple companies, Specific Yield is a useful metric to check. Even if a quote has a low unit price, if the energy generation per unit of capacity in PVSyst is low, it may be disadvantageous in terms of long-term generation revenue. Conversely, a quote that appears expensive can be shown to have superior investment returns if it has high design quality and a high Specific Yield.

Interpreting PR as Indicators of Design Quality and Loss Management

When applying PVSyst figures to an estimate, the Performance Ratio, or PR, is also important. PR is a metric that indicates how efficiently a solar PV system exposed to solar irradiance is producing power relative to the theoretically possible output. In an estimate, it is a convenient figure for explaining design quality and loss management.

The higher the PR, the fewer the losses across the whole system and the more efficiently it is generally considered to generate power. However, PR is not simply a matter of being higher. It is determined by the combined effects of various factors such as weather conditions, temperature, solar irradiance, shading, soiling, wiring, PCS, oversizing, and output limitations. Therefore, in a quotation you should not list only the PR value but confirm which losses are included.

For example, even if the PR appears high, soiling losses, snow losses, auxiliary equipment losses, or downtime losses may not have been adequately accounted for. Conversely, when conservative assumptions are applied, the PR may look somewhat low but the estimate can be realistic in practical terms. Comparing PR alone without understanding these differences can lead to incorrect estimation judgments.

When using PR in an estimate, it is practical to explain "how much PR can be expected under these design conditions and what the main loss factors are." For example, check whether temperature loss, shading loss, wiring loss, or PCS loss is the largest. Then explain the measures that are reflected in the estimated amount.

Specifically, you can explain that you adjusted the racking layout to reduce shading losses, reviewed cable sizes and PCS placement to minimize wiring losses, and optimized PCS capacity to avoid excessive clipping. By linking PR to the estimate items in this way, it becomes easier to convey why those design and construction costs are necessary.

PR can also be used to compare multiple proposals. In low-cost proposals, wiring distances may be longer to reduce installation costs, which can increase wiring losses. Alternatively, packing panels too tightly can increase shading losses. In such cases, looking at the PR makes it easier to determine whether the cheaper estimate is truly advantageous.

When explaining to a client, using PR as a technical term by itself can be hard to convey. In that case, explaining it as "an indicator that shows how effectively the solar radiation received is converted into electricity" makes it easier to understand. In the supplementary materials for the estimate, presenting the PR value alongside the main loss items clarifies the relationship between price and performance.

Read loss items as the basis for construction costs and design scope

PVSyst reports display various loss items. These loss items are very important for explaining the construction costs and scope of design in estimates. By looking not only at the energy production results but also at where and how much loss occurs, the meaning of the measures included in the estimated amount becomes clear.

Typical losses include solar irradiance-related losses, shading losses, temperature losses, IAM losses, soiling losses, wiring losses, mismatch losses, PCS losses, transformer losses, and auxiliary equipment losses. These are not merely breakdowns in a simulation; they directly inform design and construction decisions.

For example, if wiring losses are significant, there is room to review the placement of the PCS, the locations of junction boxes, cable sizes, and wiring routes. On the estimate, this relates to cable costs, electrical installation costs, conduit and wiring costs, and panel layout planning. If thicker cables are used to reduce wiring losses, material costs will increase, but this may lead to improved energy generation over the long term.

If shading losses are large, it is necessary to consider the racking layout, spacing distances, panel angles, scope of site development, and the effects of trees and surrounding structures. In the estimate, this relates to site development costs, tree removal costs, surveying costs, design fees, the number of racks, and so on. By checking shading losses in PVSyst, you can explain that simply installing more panels is not necessarily the best option.

Temperature losses vary depending on the region and the installation method. In hot regions and for rooftop installations, panel temperatures tend to rise, which can reduce power generation efficiency. In the estimate, this can be tied to explanations of racking height, ventilation, installation method, and module selection. For example, designing to ensure adequate airflow can suppress temperature rise and help maintain generation efficiency.

Soiling losses and snow losses are also important. In particular, in snowy regions they can have a significant impact on annual power generation. In the estimate, this leads to explanations of snow-adapted racking, tilt angle, maintenance costs, snow removal measures, and inspection plans. Even when setting soiling loss to a fixed value, it is necessary to verify its appropriateness according to the local environment.

PCS losses and transformer losses are related to equipment selection. By choosing high-efficiency PCS and an appropriate capacity design, conversion losses and clipping losses can sometimes be reduced. However, high-efficiency equipment may have higher upfront costs. Therefore, in quotations it is important to explain not only the equipment price but also the impact on power generation.

When reviewing loss items, the important thing is not to eliminate losses entirely. In solar power generation there are unavoidable losses, such as temperature losses and conversion losses. What matters is that you can explain which losses the design and construction included in the estimate are intended to mitigate, and to what extent.

For example, low-cost estimates may simplify surveys and design, so consideration of shading and wiring losses can be insufficient. On the other hand, estimates that include detailed on-site surveys and 3D terrain checks make it easier to identify shading losses and construction risks in advance, even if initial design costs increase. Using PVSyst’s loss items here makes it easier to explain the significance of the design cost.

Read solar irradiance and meteorological conditions as assumptions for estimates

When using PVSyst figures in an estimate, knowing how to interpret solar irradiance and meteorological conditions is essential. Annual energy production and PR are the final outputs, but they are predicated on conditions such as solar irradiance, air temperature, wind speed, snow cover, and albedo. The credibility of the estimate depends largely on whether these underlying assumptions are valid.

In PVSyst, energy production is calculated based on meteorological data. If the type or location of the meteorological data used changes, the annual energy production will also change. For example, even when using data from a nearby site, if the actual site is in a mountainous area, a coastal area, a region with heavy snowfall, or an area prone to fog, the energy production may differ.

In an estimate, clarifying the assumptions about solar irradiance makes it easier to explain the basis for the estimated energy production. Especially in materials for clients or financial institutions, they may check which meteorological data were used, which location was referenced, and what period’s long-term average was used. When reflecting PVSyst results in an estimate, it is reassuring to organize the sources of the meteorological data and the assumptions.

Solar irradiance directly affects revenue estimates. When irradiance is high, power generation tends to increase, and when irradiance is low, power generation tends to decrease. However, even in regions with high irradiance, high ambient temperatures can increase temperature-related losses. Conversely, in cold regions, even if irradiance is somewhat low, panel temperatures are less likely to rise, so efficiency can improve. For this reason, it is important to consider not only irradiance but also its relationship with temperature.

In snow-prone regions, how winter solar radiation and snow-related losses are treated as estimation assumptions carries great significance. How snow and albedo are configured in PVSyst changes the projected winter energy output. In the estimate, it is necessary to make clear whether a drop in generation due to snow is being anticipated, or whether snow removal or natural snow shedding is being assumed.

In self-consumption estimates, monthly power generation is also important. Even if the annual generation is the same, the economic effects vary depending on whether the months with high electricity demand coincide with the months with high generation. For example, at facilities with high air-conditioning demand in summer, summer generation can significantly contribute to reducing electricity bills. On the other hand, at facilities with high winter demand, it is necessary to carefully assess winter solar radiation and snowfall conditions.

When showing monthly generation in a quotation, using PVSyst's monthly results makes it easier to explain seasonal variations. Because it can show generation trends that are not visible from the annual total alone, the client can more easily envision how the system will operate after installation. This is especially important for projects involving self-consumption, battery storage, peak shaving, and the customer's electricity contract, where monthly and hourly analyses are important.

Solar irradiance and weather conditions are the foundation of the assumptions in a quotation. Even if an estimate shows high power generation, if the weather assumptions are too optimistic, the gap between the estimate and actual operation can become large. Conversely, when an estimate is based on conservative assumptions, the projected generation may appear somewhat low, but the business plan will be more robust. To incorporate PVSyst figures into a quotation, you must always verify the validity of these assumptions.

Workflow for Reflecting PVSyst Values in an Estimate

To make use of PVSyst figures in an estimate, it is important not only to read the results but also to establish a workflow that incorporates them into the structure of the estimate. In practice, you first clarify the design conditions, run PVSyst under those conditions, check the expected energy production and losses, revise the design as necessary, and finally reflect the results in the final estimate.

First, what needs to be clarified are the installation site, panel capacity, PCS capacity, orientation, tilt angle, racking specifications, layout plan, electrical design, meteorological data, and shading conditions. If you run PVSyst while these remain ambiguous, the basis for the estimate will be weak. Especially at the estimation stage, since the design is often not yet finalized, it is necessary to make the assumed conditions explicit.

Next, check the annual energy production, Specific Yield, PR, loss items, and monthly energy production in PVSyst. When doing so, don’t just look at the results; read them in relation to the estimate items. If wiring losses are large, they relate to electrical design and cable costs; if shading losses are large, they relate to layout, site development, tree clearing, and surveying. Temperature losses and PCS losses lead to explanations about equipment selection and installation methods.

After that, compare the design proposals as needed. Comparing proposals in PVSyst—such as a plan that increases panel capacity, a plan that changes PCS capacity, a plan that alters the tilt angle, or a plan that adjusts the layout—makes it easier to present multiple options in the quotation. For the customer, it becomes easier to understand why a particular option is recommended.

When reflecting this in a quotation, it is not necessary to include all PVSyst figures. The important thing is to select the figures that are relevant to decision-making. Organizing mainly around annual energy production, energy production per unit capacity, PR, major losses, assumptions, and figures related to estimated revenue will make the quotation easier to read.

Also, PVSyst's detailed reports often contain many technical terms, so handing them directly to the client may make them difficult to understand. In the main estimate document, succinctly present the key points, and attach the PVSyst report or a summary table as supplementary material when necessary. For the client, it is important to convert technical terminology into expressions that clarify the relationships between energy production, revenue, losses, risks, and improvement measures.

How to Use PVSyst Values to Make Explanations Easier in Estimates

The numbers in PVSyst each have specific roles. Annual generation provides the basis for revenue estimates and electricity bill reductions; Specific Yield is used for comparisons per capacity; PR indicates design quality and loss management; loss items serve as the basis for construction details and design countermeasures; and irradiance and meteorological conditions are used to explain the simulation assumptions.

In a quotation, it is important not to confuse these. Judging design quality based only on annual generation, or judging project viability based only on PR, results in an insufficient explanation. For example, even if PR is high, annual generation may not increase much in regions with low solar irradiation. Conversely, even if annual generation is large, it may simply be due to a large installed capacity rather than high efficiency per unit of capacity.

When explaining to a customer, it is easiest to first present the overall picture using annual energy generation, then show the capacity-normalized efficiency with Specific Yield, explain the system’s losses with PR, and finally supplement with the main loss items to highlight design considerations and the reasons for the estimated costs.

By following this approach, the estimate becomes not merely a price sheet but a proposal supported by technical rationale. Instead of being compared solely on price, it becomes easier to compare them across energy output, reliability, long-term profitability, and construction risk.

Notes on using PVSyst values

There are a few points to be aware of when applying PVSyst numbers to an estimate. First, PVSyst results depend heavily on the input conditions. If equipment specifications, meteorological data, loss rates, azimuth, tilt angle, shading settings, or wiring conditions change, both energy production and PR will change. Therefore, when including figures in an estimate, you must always document the underlying assumptions.

Next, it is important not to overstate generation under optimistic conditions. High generation estimates may appear attractive, but if actual operation falls far short, you will lose credibility. In particular, underestimating soiling, snow, shading, curtailment, outages, and auxiliary consumption can lead to large discrepancies between estimates and actual performance.

Also, when comparing estimates from other companies, you must compare under the same assumptions. If solar irradiance data, loss settings, PCS capacity, panel capacity, or calculation range differ, simply lining up the PVSyst figures will not yield an accurate comparison. When comparing estimates, it is essential to check differences in the input conditions as well as the resulting numbers.

Furthermore, in estimates you also need to be careful not to overuse technical terms. Among engineers familiar with PVSyst, terms like PR, Specific Yield, IAM, Array Loss, and System Loss will be understood. However, when explaining to the client, financial institutions, or non-technical departments within the company, you need to replace them with more easily understandable language.

For example, Specific Yield can be expressed as "annual power generation per 1 kW", PR as "how effectively solar irradiance is converted into electricity", and loss items as "factors that reduce power generation". Rephrasing them in this way makes the estimate easier for the reader to understand.

Confirmation of on-site conditions using LRTK

To incorporate PVSyst figures into a quotation, it is important not only to run simulations but also to verify on-site conditions. In particular, terrain, installation area, causes of shading, existing structures, boundaries, site development status, and the feasibility of racking layout can often be difficult to judge from drawings alone.

In such situations, using LRTK that combines a smartphone and a high-precision GNSS allows you to efficiently verify on-site location and terrain information. For example, while surveying on site you can record the installation area and the positions of obstacles, and by overlaying them with drawings and point clouds for verification, it becomes easier to organize the shading and layout conditions that should be reflected in PVSyst.

During the estimating phase, you often can't devote as much time as you can to detailed design, but if site conditions are not adequately understood, layout changes, wiring changes, additional land development, or additional tree clearing may arise later. Using LRTK to acquire on-site location information at an early stage can lead to improved estimate accuracy.

In particular, on sloping sites, unused land, former golf-course sites, forested areas, snowy regions, and sites with many existing facilities, differences in site conditions can have a large impact on power generation and construction costs. To make PVSyst figures more realistic, it is important to reflect information obtained on site in the design conditions.

Also, keeping records of on-site verifications using LRTK can be used as explanatory materials for the client. Rather than simply stating "we simulated under these conditions," being able to show the areas checked on site, obstacles, terrain, and the positioning results will increase the credibility of the estimate.

Summary

PVSyst figures give strong credibility to estimates for solar power plants. Annual energy production serves as the basis for revenue and electricity cost savings, and Specific Yield is an indicator for comparing generation efficiency per unit of capacity. PR provides material for explaining design quality and loss management, and loss items form the basis for construction costs and design countermeasures. Solar irradiance and weather conditions are indispensable for verifying the validity of the simulation assumptions.

The important point is not to paste PVSyst figures directly into the estimate, but to read and present them in connection with the quoted price and the design. If you can explain how much energy will be generated, why that amount will be produced, which losses are being assumed, and which construction works are related to mitigating those losses, the estimate becomes not merely a price list but a technical proposal.

Also, PVSyst results are greatly influenced by the input conditions. When using them for a proposal, it is important to clarify the solar irradiation data, installation conditions, loss settings, equipment specifications, shading conditions, and so on, and to ensure that the estimated energy production is not overly optimistic. When comparing with other companies’ estimates, you should examine not only the figures but also differences in the underlying assumptions.

Furthermore, verifying on-site conditions is also important. By using smartphone-compatible, high-precision GNSS such as LRTK, you can efficiently confirm the installation area, terrain, obstacles, and existing structures on site, which makes it easier to improve PVSyst input settings and estimation accuracy.

The way to read PVSyst numbers so they can be used in an estimate is not just to look at the energy production. It’s about reading them by linking price, performance, losses, design, construction, and profitability. With this perspective, you can create estimates that are easy for the client to understand, easy to explain within your company, and useful for long-term business decision-making.