5 Steps to Calculate the Impact of Solar Power Generation from the Self-Consumption Rate

When calculating solar power generation, looking only at the amount of electricity generated is not enough to properly judge its practical effectiveness. Especially for systems that emphasize self-consumption, it is important how much of the generated electricity can be used within the facility. Even if generation is large, if a big surplus occurs during periods of low demand, there can be a difference between the expected and actual results. Conversely, even if the generation itself is modest, if the timing of demand and generation align, it can lead to a reduction in purchased electricity.

In this article, aimed at practitioners searching for information on "solar power generation calculation", we explain a 5-step procedure to organize the generation effects starting from the self-consumption rate. Rather than merely calculating annual generation, we review daytime demand, surplus power, system capacity, and operating conditions together, and present the approach as an easy-to-use framework for both pre-installation planning and post-installation evaluation.

Table of Contents

• Summarize the relationship between self-consumption rate and solar power generation.

• Step 1 Decide the target period and calculation unit for electricity generation

• Step 2: Check energy consumption by time period

• Step 3 Calculate the portion of generated electricity that can be self-consumed

• Step 4 Evaluate equipment effectiveness from the self-consumption rate

• Step 5 Organize conditions for improvement while reviewing performance gaps

• Practical points to watch when performing calculations using the self-consumption rate

• Summary: Visualize the value of generated power using the self-consumption rate as the axis.

Organize the relationship between self-consumption rate and solar power generation

When calculating solar power generation, attention first goes to "how much can be generated." The basic approach is to estimate the generation over a given period by considering system capacity, solar irradiance, installation tilt, orientation, shading, temperature, power conditioner conversion efficiency, and wiring losses. However, in practice, what you need to know is not just the generation amount itself. You also need to confirm to what extent that generation will help reduce purchased electricity and lead to a review of facility operations.

Here, the important metric is the self-consumption rate. The self-consumption rate refers to the proportion of generated electricity that can be used internally in company facilities, homes, factories, warehouses, stores, and similar places. Generally, the ratio is calculated by dividing the self-consumed electricity by the generated electricity. Even with the same generation output, the nature of the benefits differs between systems with high and low self-consumption rates. When the self-consumption rate is high, because the generated power is used on-site, it tends to lead to a reduction in the amount of electricity purchased from external sources. Conversely, when the self-consumption rate is low, it may indicate that the timing of generation does not match the facility’s demand.

The basic idea of the self-consumption rate is to compare how much of the generated electricity is consumed on-site. For example, if power generated during the daytime is used for air conditioning, lighting, manufacturing equipment, refrigeration, charging equipment, office equipment, etc., that portion counts as self-consumption. Even if generation is occurring, the portion that cannot be used because facility demand is low at that time is treated as surplus. Therefore, when calculating the effect of solar power generation, it is essential to view generation and consumption side by side on the same time axis.

In practice, judging only by annual totals can lead to oversights. Even if comparing annual generation and annual consumption suggests sufficient self-consumption, in reality generation may be concentrated during the daytime while consumption is biased toward the morning, evening, or night. In such cases, despite apparent margins in the annual totals, supply and demand by time of day may not match, which can result in a large amount of surplus. Conversely, facilities such as factories with steady daytime operations or those with refrigeration equipment tend to have generation and demand overlap more easily, making it easier to increase the self-consumption rate.

The advantage of using the self-consumption rate is that it allows you to evaluate not only the "quantity" of generated power but also the "proportion that was usable." When using solar PV generation calculations for planning an installation, increasing the system capacity will raise generation, but it can also increase surplus that cannot be self-consumed. Conversely, reducing system capacity tends to reduce surplus, but may fail to adequately cover daytime demand. In other words, the self-consumption rate is a practical indicator for judging the appropriateness of system capacity and its compatibility with demand.

Also, the self-consumption rate is useful when evaluating effectiveness after installation. Depending on whether actual generation is lower than expected generation, or generation is close to expected but the self-consumption rate is low, the causes to investigate differ. In the former case, check for shading, dirt, equipment stoppage, output control, weather conditions, and installation conditions. In the latter case, check facility operating hours, load fluctuations, holiday demand, seasonal differences, and operational schedules. Being able to distinguish between these makes it easier to devise improvement measures.

Step 1 Decide the target period for power generation and the calculation unit

The first step is to decide over what period and in what units you will calculate the power generation. When calculating solar power generation, there are various aggregation units such as annual, monthly, daily, and by time of day. If you are assessing effectiveness using the self-consumption rate, it is important to include a time-of-day perspective as much as possible. This is because self-consumption is determined by the relationship between generation and demand during the hours the power is produced, so annual totals alone can make it difficult to grasp the actual situation.

In pre-installation studies, you first check an estimate of annual power generation, and then organize the monthly generation figures. The annual value is useful for grasping the rough effect of system size, but it does not allow sufficient verification of seasonal differences. Because solar power generation is affected by sunlight conditions, output varies between summer and winter, during the rainy season, and in regions with snowfall. Viewing generation on a monthly basis lets you confirm whether periods of increased consumption overlap with periods of increased generation.

Next, if possible, proceed to daily and hourly calculations. If you want to examine the self-consumption rate, it is useful to compare generation and consumption by time of day. For example, even if generation is high during the daytime, self-consumption is unlikely to increase if the facility is not operating on holidays. Even with a high self-consumption rate on weekdays, large surpluses can occur on holidays. Such differences are difficult to discern from annual or monthly totals alone.

When deciding the calculation unit, also check the granularity of the data available. For existing facilities, you may be able to use historical electricity consumption data, daily reports, equipment operation records, and monitoring device logs. For new or planned facilities, place assumptions based on past electricity usage records, operating patterns of similar facilities, expected operating hours, and projected HVAC and equipment loads. When making assumptions, it is important to clearly state the premises so they can be reviewed later.

Also, clarify the scope for calculating the generated power. The meaning of the self-consumption rate changes depending on whether you view it on a per-building basis, for the entire site, or per specific point of receipt. In facilities with multiple buildings, some buildings may be designed to generate while others consume. If you do not confirm whether the electricity can be used within the same electrical boundary or whether there are contractual or equipment-configuration constraints, it may appear in calculations that self-consumption is possible, but in reality it may not be usable.

In materials explaining the effects of power generation, it is also important to standardize the calculation units. When units are mixed—generation presented monthly, consumption annually, and effects daily—it becomes difficult to make judgments. As a rule, compare using the same time period and the same electricity units, and, if necessary, supplement with annual conversions or monthly breakdowns. Especially when explaining to stakeholders, organizing the relationship between generated electricity, self-consumed electricity, surplus electricity, and purchased electricity within the same framework makes it easier to understand.

The purpose at this stage is not to calculate detailed effects right away. First, determine which range of generation to consider, over what period, and at what level of granularity. If you proceed with calculations while these are left ambiguous, comparisons of self-consumption rates and evaluations of improvements will tend to be inconsistent. When calculating generation, the reliability of the results depends not only on the formula itself but also on clearly defining the assumed period and the scope.

Step 2: Check energy consumption by time period

The next step is to confirm the facility’s electricity consumption. The self-consumption rate is not determined by generation alone. It is determined by how much power the facility uses during the periods when generation is occurring. Therefore, to calculate the impact of solar power generation, understanding the actual demand side is as important as the generation-side estimates.

The first thing to check is the baseline electricity consumption during the daytime. Because solar power generates primarily during the day, facilities with stable daytime demand are better positioned to use that generation for on-site consumption. In offices, the main demands are lighting, air conditioning, and IT equipment. In factories, production equipment, air conditioning, ventilation, compressors, and conveying equipment are involved. In stores or warehouses, refrigeration and freezer systems, air conditioning, lighting, and material handling equipment influence demand. Understanding which loads operate at what times makes it easier to see how generation and consumption overlap.

Organize energy consumption by time of day if possible. A daily total alone does not reveal how much was used during generation hours. For example, even if a day's consumption is high, if it is concentrated at night it is unlikely to contribute to solar self-consumption. Conversely, facilities with a steady daytime load are more likely to channel a relatively stable portion of generation into self-consumption. If you want to increase the self-consumption rate, it is important to check how much the peak generation and peak consumption overlap.

Don't overlook differences by day of the week. In facilities that operate on weekdays but where equipment stops on holidays, the self-consumption rate on holidays may decline. Because a certain portion of the annual power generation occurs on holidays, facilities with low holiday demand are more likely to see increased surplus. In pre-installation calculations, considering weekdays, holidays, and extended shutdown days separately yields results closer to reality. In post-installation evaluations as well, separating the situations for weekdays, holidays, and shutdown days—rather than relying only on weekday averages—makes it easier to identify the causes.

Seasonal variability is also important. In facilities with large air-conditioning loads, daytime demand may rise in summer and winter. When there are loads that operate year-round, such as refrigeration equipment or manufacturing equipment, seasonal differences may be relatively small. Because solar PV generation varies by season, it is necessary to view it together with seasonal variations in electricity consumption. If demand is high during periods of high generation, the self-consumption rate tends to increase; if demand is low during periods of high generation, surpluses tend to grow.

When checking energy consumption, pay attention not only to maximum demand but also to minimum demand. From the perspective of the self-consumption rate, a surplus occurs during periods when generation exceeds demand. Therefore, the level of the daytime minimum load is important when considering system capacity. Facilities with few continuously operating loads tend to have insufficient demand relative to generation peaks on sunny days. Conversely, facilities with a certain minimum daytime load can more easily allocate much of their generation to self-consumption.

In this step, it is important not only to collect power consumption but also to organize it so it can be interpreted in conjunction with generation time periods. Calculations of generation output tend to focus on system capacity and solar irradiance conditions, but when determining the self-consumption rate, demand-side data has a major influence on the results. If you organize consumption by time of day, day of week, season, and operating status, you can calculate more concretely in the next step the portion of generated power that can be self-consumed.

Step 3 Calculate the portion of generated electricity that can be self-consumed

Once the assumptions for generated power and electricity consumption are aligned, calculate the portion of the generated energy that can be self-consumed. The basic approach is to compare generation and consumption in the same time periods and treat the smaller value as the self-consumed energy. In time periods when generation is below consumption, all generated energy is considered self-consumed. In time periods when generation exceeds consumption, self-consumption is limited to the consumption amount and the remainder is categorized as surplus.

Using this approach, you can identify supply-demand mismatches that are not visible from annual totals alone. For example, if generation increases around midday and the facility’s load is also high during the same period, the amount of electricity consumed on-site increases. On the other hand, if the facility’s load is low at the time of peak generation, a surplus occurs. The important point here is that a larger total amount of generation does not necessarily lead to a higher self-consumption effect. Generation that does not coincide with demand does not directly contribute to improving the self-consumption rate.

The self-consumption rate is calculated by dividing the amount of electricity self-consumed by the amount of electricity generated. In practical documents, it is easier to understand if you separate and organize generated energy, the amount self-consumed, and the surplus. If you can show what share of generated electricity was used within the facility and what share remained surplus, it becomes easier to explain the appropriateness of the system size and operating conditions. However, because the calculation results are affected by the assumptions, it is important to record the period, the time granularity, and the source of the consumption data together.

If possible, the finer the calculation granularity, the more closely it reflects reality. Looking at intervals shorter than hourly better captures the mismatches between generation and consumption. However, fine-grained data are not available for every project. In pre-installation assessments, it is practically effective to start with estimates by time of day or by representative days and, if necessary, improve the accuracy. The important thing is to understand that these are coarse calculations and not to make overly definitive conclusions.

The handling of surplus electricity should also be clarified. If the self-consumption rate is prioritized, a large surplus is not necessarily bad, but the assessment depends on the original objective. If the primary goal is to reduce purchased electricity, systems with a large surplus may be oversized relative to demand. If environmental value and potential future demand increases are taken into account, designs that allow some surplus can be considered. Therefore, rather than simply dismissing surplus as waste, it is important to evaluate it in light of the installation’s objectives.

Once you calculate the amount of self-consumed electricity, you can also confirm the effect on reducing purchased electricity. The portion of generated power used on site leads to a reduction in the amount of electricity purchased from external sources. However, the way this is evaluated varies depending on actual contract terms, demand fluctuations, the approach to the basic contract, and the relationship with electricity consumption peaks. Therefore, rather than relying solely on monetary conversion, it is safer to first organize the reduction effect on an energy basis. On an energy basis, it becomes easier to compare even if unit prices or contract conditions change.

The outputs to be produced in this step are the expected reductions in self-consumed electricity, the self-consumption rate, surplus electricity, and purchased electricity. Furthermore, observing differences between weekdays and holidays and between seasons will make the direction for improvements clearer. For example, if the self-consumption rate is high on weekdays but there is a large surplus on holidays, there is room to examine the presence or absence of holiday loads and how they are controlled. If the self-consumption rate is high in summer but low in intermediate seasons, it indicates an effect that depends on air-conditioning load.

The task of calculating the portion that can be self-consumed is the process of converting solar power generation into practical value. Rather than stopping at an estimate of generation, overlaying it with the facility’s demand makes it easier to avoid overestimation at the planning stage. It also provides a basis for post-installation performance evaluation to distinguish whether shortfalls are due to insufficient generation, mismatches with demand, or surpluses that exceed expectations.

Step 4 Assess equipment effectiveness from the self-consumption rate

After calculating the self-consumed electricity and the self-consumption rate, use them to evaluate the effectiveness of the installation. The key point here is not to look at the self-consumption rate in isolation. A high self-consumption rate does not necessarily mean the installation is good, and a low self-consumption rate does not necessarily indicate a problem. You need to evaluate generation, system capacity, demand, surplus, and the intended purpose of the installation together.

For example, if the system capacity is small, almost all the power generated can be used, so the self-consumption rate tends to be high. However, if generation is too low compared with daytime demand, the effect on reducing the amount of electricity purchased is limited. Conversely, if the system capacity is large, generation increases, but the periods when generation exceeds demand also increase, and the self-consumption rate tends to fall. Therefore, the self-consumption rate is not a simple metric that is better the higher it is; it needs to be evaluated in balance with the amount of generation.

When evaluating the effectiveness of the installation, first check how much of the generated electricity contributed to reducing purchased electricity. The larger the self-consumed electricity, the clearer the reduction in electricity purchased from external sources. Next, check how much surplus electricity there is. If the surplus is small, the system size may be appropriate for demand. If the surplus is large, verify factors such as oversized capacity, demand being lower than expected, large variations due to holidays or seasonal changes, or a misalignment between generation peaks and load peaks.

In addition, equipment effectiveness should be evaluated not only by the amount of electricity but also in relation to operational objectives. For example, if the goal is to reduce daytime electricity purchases, the amount of self-consumed electricity is important. If the purpose is to use the information as explanatory material for environmental measures, the ability to record generation and usage performance is also important. If emergency response is included as an objective, do not judge based on solar power generation equipment alone; it is necessary to separately confirm conditions such as battery storage, islanded/independent operation, transfer/switching equipment, and the range of loads that can be served. If electricity demand is expected to increase in the future, it is necessary to consider not only the current self-consumption rate but also projections that assume future loads.

In pre-installation assessments, comparing multiple equipment capacity options makes the effects easier to understand. With smaller capacities, the self-consumption rate is high and surpluses are low, but the amount of purchased electricity that can be reduced may be limited. With larger capacities, generation increases, but surpluses grow and the self-consumption rate may decline. Making this comparison makes it easier to choose a capacity that matches the facility’s demand rather than simply maximizing generation.

In post-installation evaluations, it is important to compare projected and actual values under the same conditions. If the projection was calculated on a monthly basis but the actuals are looked at only as an annual total, it becomes difficult to identify the cause of differences. By organizing generation, self-consumed electricity, and surplus electricity by month, day, and time period—just as in the projection—you can more easily see where the discrepancies occurred. Even when actuals fall short of projections, you can distinguish whether it was a reduction in generation due to weather conditions or a decline in the self-consumption rate caused by decreased demand.

When evaluating the self-consumption rate, we also take into account equipment stoppages and the effects of control. Temporary shutdowns of equipment, maintenance work, output curtailment, and missing communication records can affect observed generation and self-consumption rates. Especially in post-installation performance analysis, rather than attributing every day with low generation to weather, we check the condition of the equipment and any missing records. Calculating the self-consumption rate while data are missing can make it appear higher or lower than the actual situation.

When evaluating the effectiveness of equipment, it is also important to consolidate findings into indicators that are easy for stakeholders to understand. Time-of-day supply-and-demand data are useful for technical staff, but for executives and facility managers, explanations organized around reductions in purchased electricity, the proportion that was self-consumed, trends in surplus occurrence, and the potential for future improvement are easier to follow. The self-consumption rate can be used not merely as a calculation result but as a common language to explain how equipment is being used.

Step 5: Organize improvement conditions while reviewing performance differences

The calculation of solar power generation using the self-consumption rate does not end with the pre-installation estimate. By checking actual performance after installation and organizing improvement measures while comparing them with initial assumptions, you can understand the system’s effectiveness more accurately. Because solar power generation is affected by weather conditions, it is risky to judge performance based on a single month’s results. It is important to collect data over a certain period and continuously monitor the relationships among generation, consumption, self-consumption, and surplus.

First, what we want to check is whether the power generation itself is close to the estimate. If the generation is lower than expected, check generation-side factors such as solar irradiance conditions, dirt on the panel surface, shading, equipment stoppages, wiring or connection faults, and output reduction due to temperature. If the generation is close to the estimate at this point, next look at differences in the self-consumption rate. Even if generation is close to the estimate, a low self-consumption rate may mean that the demand-side operating conditions differ from the plan.

In terms of demand-side performance differences, factors such as changes in operating hours, increases in holidays, fluctuations in production volume, changes in air-conditioning operation, equipment upgrades, and tenant turnover have an impact. If the daytime load assumed before installation turns out to be lower, the power generated during high-output periods cannot be fully consumed and surpluses increase. Conversely, if demand is increasing but the self-consumption rate does not rise, the generation periods and the times of increased demand may be misaligned. Looking at the generation side and the demand side separately makes it easier to identify directions for improvement.

When considering improvement measures, first check the range that can be addressed through operations. If there are loads that can be shifted to daytime, operating equipment during the hours when power is being generated may increase the self-consumption rate. For example, if there are loads whose operating times can be adjusted—such as charging, heating, cooling, ventilation, pump operation, and cleaning equipment—you can increase their overlap with generation periods. However, you cannot change operating hours while ignoring work quality, safety, or equipment constraints. In practice, it is important to make adjustments within a reasonable range in consultation with on-site operations.

When considering equipment improvements, there are several options such as adding or controlling power generation equipment, installing energy storage equipment, and upgrading load equipment. However, rather than immediately assuming equipment changes, you should first confirm why the current self-consumption rate is at its present level. By identifying the time periods when surplus occurs, when generation is insufficient, and when demand suddenly spikes, the necessary measures become clearer. Increasing or decreasing equipment without examining the causes may fail to produce the expected effects.

In performance management, it is useful to look not only at monthly self-consumption rates but also at the behavior of representative sunny days. Monthly values are suitable for grasping overall trends, but because rainy or cloudy days, holidays, and equipment outages are mixed in, they have limits for examining causes in detail. By checking time-of-day data for sunny days, you can see whether demand is met at the generation peak, which time periods experience surpluses, and how much generation contributes to morning and evening demand. This allows you to move from merely confirming results to considering improvements.

Also, when evaluating performance variances, it is important to compare like with like. Even when comparing to the same month of the previous year, a simple comparison is not valid if operating days, weather trends, equipment outages, or facility usage differ. When comparing to pre-implementation assumptions, check whether the assumptions at the time of estimation still match the current situation. If the assumptions have changed, the assumed values themselves need to be revised. In practice, it is important not to treat calculation results as fixed answers, but to update them to reflect actual operational conditions.

Ultimately, it is desirable to put in place a system that continuously records changes in generation, self-consumption rate, surplus electricity, and purchased electricity, and uses those records to drive improvements. Calculations of solar power generation are useful not only for making installation decisions but also for post-installation improvement management. By regularly checking the self-consumption rate, it becomes easier to understand how effectively the system is being used, whether it is keeping up with changes in demand, and where there is room for improvement.

Practical points to note when calculating with the self-consumption rate

When calculating the effects of solar power generation using the self-consumption rate, there are several points to note. First, don’t fixate on the self-consumption rate as the sole performance indicator. The self-consumption rate is a useful metric, but it tends to increase if the installed capacity is reduced. Therefore, focusing only on the self-consumption rate can lead to insufficient total generation and reduced effectiveness relative to the installation’s objectives. It is important to consider the self-consumption rate together with total generation and the amount of self-consumed electricity.

Next, it is necessary to clarify the scope of the energy consumption used in the calculation. Whether you use the electricity for the entire building, target only specific equipment, or include multiple power supply points will change the meaning of the calculation results. If you calculate the self-consumption rate while the scope is ambiguous, stakeholders’ interpretations will diverge. It is important to confirm whether the generation equipment and electrical loads are within the same electrical boundary, where the measurement points are located, and which equipment the data include.

Also pay attention to missing data for generation and consumption. Communication failures of monitoring devices or metering equipment can cause actual data to be missing. If missing data are aggregated as-is, the self-consumption rate may differ from the real value. It is necessary to distinguish whether generation was not recorded, actually did not occur, or consumption records are missing. Especially for post-installation evaluations, verifying data integrity before performing calculations is indispensable.

Do not oversimplify the impact of weather. Solar power generation is influenced by sunlight conditions, but if you attribute all causes of low output to the weather, you may overlook equipment or operational issues. Conversely, it is premature to immediately conclude that a single month's drop in generation is due to equipment failure. By examining monthly and seasonal trends, power output curves on clear days, surrounding shading conditions, and the presence of dirt or snow together, you can make a more reasonable judgment.

In calculating the self-consumption rate, the treatment of surplus electricity should also be clarified. If a surplus occurs, how that power is evaluated depends on the system design and contractual conditions. However, from the perspective of this article, it is important first to separate and organize the surplus as an amount of energy so it is not confused with the portion consumed on-site. Showing only the total generated amount can lead to the misunderstanding that everything was used within the facility. In practical documentation, explaining the self-consumed portion and the surplus separately helps avoid excessive expectations.

Also, consider future changes in demand. Even if the current self-consumption rate is low, if there are plans to increase daytime loads in the future, the self-consumption rate may rise. Conversely, even if the current self-consumption rate is high, the introduction of energy-saving equipment or shortened operating hours could increase surpluses in the future. Because solar PV systems are used over the long term, considering not only current electricity usage but also equipment plans and operational changes a few years ahead will improve the accuracy of decisions.

When explaining to stakeholders, it's also important not to use too much technical jargon. Terms like self-consumption rate, generation, surplus electricity, and reduction in purchased electricity may be familiar to technical staff but can be difficult for management or on-site personnel to understand. Describing it as the actual flow of power — how much of the generated electricity was used within the facility, how much remained unused as surplus, and how much did not need to be purchased from outside — makes it easier to understand.

Finally, it is important not to make the calculation once and consider it done. The figures can change between pre-installation estimates, results immediately after installation, and results after operations have stabilized. The way a facility is used and the condition of equipment also change. By regularly checking the self-consumption rate and reviewing operations and assumptions as needed, you can continuously grasp the impact of solar power generation.

Summary Visualizing the value of generated electricity with self-consumption rate as the axis

When calculating solar power generation, simply estimating the amount of electricity that can be generated is not enough to fully explain its practical effects. For systems intended for self-consumption in particular, it is important to know how much of the generated electricity was actually used on-site. Checking the self-consumption rate makes it easier to determine to what extent the generated output contributes to reducing purchased electricity, how much surplus is being produced, and whether the system capacity and operating conditions match the demand.

The calculation flow starts by first determining the target period and the calculation unit. Next, check the power consumption by time period and overlay it on the same time axis as the generation output. Then calculate the portion of the generation that can be self-consumed, and整理 the self-consumption rate and surplus electricity. Furthermore, evaluate the equipment effects, and after implementation confirm improvement conditions while monitoring differences between actual and predicted performance. By following these steps, the calculated generation results can be turned into decision-making materials usable on site.

The self-consumption rate is not a metric that can simply determine whether equipment is good or bad. It only becomes a meaningful evaluation when considered together with generation output, self-consumed electricity, surplus electricity, demand patterns, and operational objectives. Even if the self-consumption rate is high, the effect is limited if generation is too low, and conversely, a low self-consumption rate can be reassessed by future demand or operational changes. The important thing is not to isolate a single number, but to visualize the entire flow of electricity.

When practitioners calculate solar power generation, it is useful to consider not only annual estimates but also monthly, weekday, and time-of-day perspectives. Especially when prioritizing the self-consumption rate, it is essential to check the overlap between generation and demand. By verifying whether there is demand during periods of high generation, whether surpluses increase on holidays or in shoulder seasons, and whether equipment outages or data gaps are affecting the results, you can evaluate the effectiveness more safely.

To continuously understand the effects of solar power generation, it is important to record generation and consumption and manage them in a form that makes comparison easy. If you use the calculation results not only for pre-installation explanations but also to improve operations after installation, you can more easily increase the long-term value of the equipment. Organizing generation output, the self-consumption rate, and surplus occurrence, and checking them in connection with on-site operations is fundamental to making solar power generation useful in practice.

If you want to visualize the effect of solar power generation with the self-consumption rate as the focus, it is important to establish a management method that allows you to view generation, consumption, and surplus on the same time axis. By continuously recording on-site generation and consumption conditions and keeping records of assumptions and operational changes, it becomes easier to compare pre-installation estimates with post-installation actuals. As a result, generation calculations are not left as mere rough estimates, and can be more readily used for daily operational improvements and for revising equipment plans.