6 Items to Check for Solar Power Plant Prices and Inverter Replacement Costs

Table of Contents

• Don't judge the price of a solar power plant by equipment price alone

• Impact of inverter replacement costs on purchase decisions

• Checklist item 1: Align remaining service life and replacement timing

• Checklist item 2: Check inverter degradation symptoms and shutdown risk

• Checklist item 3: Confirm replacement scope and ancillary construction work

• Checklist item 4: Assess the impact of reduced power generation on revenue from electricity sales

• Checklist item 5: Check for warranties, maintenance contracts, and availability of spare parts

• Checklist item 6: Verify site conditions and constructability

• Practical procedures for comparing prices of solar power plants

• Summary

Don't judge the price of a solar power plant by equipment cost alone

When checking the price of a solar power plant, many practitioners first focus on the sale price and the nominal yield. However, when making an actual purchase decision, it is necessary to consider not only the price of the plant itself but also future replacement costs, repair costs, operation and maintenance costs, and the risk of power generation stoppage. This is especially true for used solar power plants, where, even if they are operating normally at the time of purchase, major equipment may already have many years of service. A typical example of such equipment is the inverter.

Power conditioners (inverters) are important devices that convert the direct current power generated by solar panels into alternating current power. They serve a role close to the heart of a power plant, and if a power conditioner stops, the generation connected to that system stops. Solar panels are equipment that can be used for relatively long periods, but power conditioners include electronic components and cooling parts, so they are equipment that is likely to require replacement or major repairs during the operating period of the power plant. Therefore, when looking at the price of a solar power plant, investment decisions can change significantly depending on whether you anticipate power conditioner replacement costs as future expenses.

Even if the yield shown in the sales materials appears high, if an inverter replacement is required immediately after purchase, the effective acquisition cost increases. Conversely, a plant that looks expensive when judged only by the sales price can still be considered a stable long-term project if its inverters are relatively new and its maintenance arrangements and replacement history are clear. In other words, the price of a solar power plant should be viewed not simply as the sale price but as the total cost that includes future equipment replacements.

In practice, we comprehensively check the purchase price, remaining feed-in period, expected power generation, maintenance costs, property tax, land-related costs, insurance premiums, weed-control costs, and electrical equipment inspection costs. Among these, inverter replacement costs directly affect cash flow and earnings projections depending on when they occur. Whether a replacement occurs immediately after purchase, several years later, or is not required until the end of the feed-in period will alter the valuation even at the same selling price.

Also, replacing a power conditioner (inverter) may not be limited to simply swapping the main unit. It is necessary to check compatibility with existing equipment, installation space, wiring, circuit breakers, communication devices, monitoring equipment, grid interconnection conditions, protection settings, and the downtime during construction. The difficulty and risk of the work differ between cases where the existing unit can be simply replaced with an equivalent-specification unit and cases where adjustment of peripheral equipment is required. For that reason, if you treat the cost of inverter replacement lightly at the price-comparison stage, unexpected burdens are likely to arise after purchase.

To avoid failing on the price of a solar power plant, you should not simply accept the documents presented by the seller; it is essential to verify the condition of the equipment, replacement history, shutdown history, maintenance records, and on-site conditions against your own standards. In particular, power conditioners (inverters) are equipment whose real condition is difficult to judge from the model number and installation year shown in the documents alone. Only by performing on-site visual inspections, checking operational data and alert histories, and confirming temperature environment and ventilation conditions can you arrive at a substantive price evaluation that incorporates replacement costs.

Impact of inverter replacement costs on purchasing decisions

Inverter replacement costs are not simply a component of repair expenses when evaluating the purchase of a solar power plant. They are a critical factor that affects a plant’s profitability, availability, financial planning, and resale value. Solar power plants are valued based on the assumption that revenue from power sales will be generated over a long period. Therefore, the source of value is the plant’s ability to continue generating electricity stably for a set period. If an inverter malfunctions, not only does generation fall, but you also lose opportunities to sell electricity during the downtime. In addition to the replacement cost itself, you must also consider the revenue loss caused by the outage.

A common oversight in practice is treating inverter replacement costs as unforeseen post-purchase expenses and not reflecting them in price negotiations at the time of purchase. Seller-provided documentation often focuses on current operating status and past power-sales performance and may not incorporate future equipment renewal costs in detail. If a buyer purchases without confirming the inverter’s age or expected replacement timing, the actual post-purchase yield may be lower than anticipated.

When evaluating inverter (power conditioner) replacement costs, it is not sufficient to simply consider whether a replacement is necessary. You need to confirm when it will occur, over what scope, how much downtime it will involve, and how generation performance and maintainability will change after the replacement. For example, if only some inverters are old, a phased replacement may be possible. On the other hand, if all units were installed at the same time and have aged similarly, there is a risk that multiple units will fail around the same time. Such concentration risk is important when assessing the reasonableness of the purchase price.

Also, inverters are related to the overall operational design of the power plant. The load on the equipment varies depending on inverter capacity, solar panel capacity, the degree of oversizing (overloading), whether output control is present, solar irradiance conditions, temperature conditions, and the installation environment. Rather than simply deciding that a recently installed system is safe and an older one is dangerous, it is important to evaluate the actual operating load and environment together. If there are factors such as high-temperature environments, poor ventilation, dust, humidity, salt damage, snowfall, or airflow obstruction due to weeds, the progression of degradation can differ even for installations of the same age.

Inverter replacement costs also affect the future sale of a power plant. A plant whose inverters are old at the time of purchase and whose replacement plans are unclear is more likely to face the same objections when it is sold next. Conversely, a plant with organized replacement history and maintenance records, and with equipment condition that can be clearly explained, provides reassurance to buyers. In other words, properly understanding inverter replacement costs is not only risk management at the time of purchase but also ties into future exit strategies.

What practitioners should pay particular attention to is making sure the inverters are on an equal footing when comparing the prices of multiple power plant projects. Simply lining up the sale price and annual power generation isn't comparable if the timing of equipment renewal differs. If one project requires no major replacements for some time after purchase while another will need an inverter replacement in the near future, the latter must be evaluated after accounting for that future cost. Looking at the effective price including replacement costs rather than the headline price is the first step to avoiding mistakes.

Checklist Item 1: Compare Remaining Service Life and Replacement Timing

The first things I want to confirm are the plant's remaining electricity sales period and the timing for inverter replacements. The price of a solar power plant is assessed based on the future revenue from electricity sales. The longer the remaining period, the longer the period during which the facility can be operated stably. If there is a high likelihood that inverters will need to be replaced during that period, you need to factor that cost in at the time of purchase.

For example, if an inverter has already been operating for a certain number of years at a plant with a long remaining term, you should assume a higher likelihood that a replacement will occur during the power sales period. Conversely, if the remaining term is short and the inverter is in good condition, it may be possible to operate without major replacements until the end of the power sales period. However, this is only a possibility, and in practice you need to verify it by checking the operating conditions and environmental factors.

The reason for aligning the remaining service life with the replacement timing is that it changes how the investment's payback appears. If a replacement is required immediately after purchase, that cost is similar in nature to an additional investment made right after acquisition. On the other hand, if the replacement is expected much later, it can be treated as a future expense that occurs after accumulating revenue from electricity sales. Even if the replacement cost is the same in both cases, the impact on cash flow differs. In practice, dividing replacement timing into multiple scenarios and checking the revenues and expenses makes decision-making easier.

What’s important here is to verify the installation timing and operating status from the equipment ledger and inspection records, not just rely on the seller’s explanation. Check the power conditioner (inverter) manufacturing year, installation year, replacement history, repair history, parts replacement history, and past shutdown records. At plants with multiple units installed, also check whether all units were installed at the same time or only some have been replaced. If only some have been replaced, the non-replaced units may carry future risk.

When assessing replacement timing, consider not only the simple number of years but also operating hours and load. In regions with high solar irradiance, designs with a high overcapacity ratio, or installation locations that tend to become hot in summer, equipment can experience greater stress. Environmental factors such as outdoor enclosures that tend to have high internal temperatures, weak ventilation, abundant surrounding weeds, and susceptibility to rainwater or condensation also affect degradation assessments. Rather than relying solely on the installation year, it is important to confirm the actual environment in which the equipment has been operating.

Aligning the remaining service life with the replacement timing clarifies the basis for price negotiations. Simply asking for a discount because something is old is less persuasive, but explaining that a replacement is likely to be needed during the remaining service life—and that accounting for that cost reduces the effective yield—makes it easier to use as negotiating leverage. It also makes it easier to plan replacements after purchase, helping you determine when to prepare funds and when to schedule the work.

Check Item 2: Assess inverter degradation symptoms and risk of shutdown

Next, what we want to check are signs of degradation in the power conditioner (inverter) and the risk of it stopping. A power conditioner can stop suddenly, but there may be small signs beforehand. Variations in power output, drops in output during specific time periods, frequent errors, a history of restarts, abnormal cooling noises, rising internal enclosure temperature, unusual odors, corrosion, traces of rainwater ingress, and dirty filters or ventilation openings are points to watch carefully.

An effective way to detect signs of degradation is to compare power generation data. When multiple inverters (power conditioners) are present, compare each unit’s output under the same solar irradiance conditions. If a particular inverter shows lower output, slower ramp-up in the morning and evening, unnatural dips during the daytime, or instability on sunny days, there may be a problem with the equipment or the connection system. Because it is difficult to judge from a single month’s generation alone, check daily and hourly data whenever possible.

When assessing downtime risk, past alert history and maintenance records are also important. If the same error keeps occurring, the root cause may not have been resolved. A single minor outage may not be a major issue, but you should be cautious if recovery has taken a long time or if the same problem is recurring in the same place. Power plants whose downtime history cannot be checked before purchase should be treated as higher risk.

Visual inspections are also indispensable. Conditions such as corrosion on the cabinet exterior, damaged door gaskets, clogged vents, traces of moisture inside, discoloration on terminals, or cables that are not securely fastened can lead to future malfunctions. Check not only the power conditioner itself but also the condition of surrounding junction boxes, collector panels, circuit breakers, communication equipment, and monitoring devices. This is because power generation stoppages can be caused not only by a failure of the power conditioner alone but also by faults in surrounding equipment.

The purpose of checking signs of degradation is not simply to decide whether replacement is necessary. It is to determine whether the condition requires immediate replacement, whether life can be extended through parts replacement or cleaning, or whether a planned replacement within a few years is sufficient. Getting this wrong can lead to unnecessarily replacing equipment that is still usable, or postponing replacement and causing a shutdown of power generation. In price evaluation, it is necessary to avoid excessive pessimism or optimism and make judgments based on actual conditions.

Also, the risk of shutdowns affects not only revenue but also management workload. If inverters at a remote power plant stop frequently, on-site inspections and arranging repairs take time. Including contacting the maintenance company, investigating the cause, procuring parts, and confirming restart, the burden on the person in charge also increases. When comparing prices of solar power plants, it is practical to evaluate not just the cost but also how easy they are to operate.

Check Item 3: Confirm the replacement scope and surrounding work

When looking at inverter replacement costs, the scope of the replacement is what causes large differences. Whether only the main unit needs to be replaced or whether peripheral equipment, wiring, communications, and protection settings also need to be changed will greatly affect the work involved. Sales materials may lump these together as "inverter replacement costs," but in practice you need to carefully check exactly what is included.

First, you should confirm whether the specifications of the existing inverter and the replacement equipment are compatible. If the input voltage range, number of input circuits, output capacity, installation method, dimensions, weight, wiring connection method, protection features, communication method, etc., do not match the existing equipment, additional construction work may be required. You cannot necessarily simply replace it with a unit of the same capacity. It is also important to check whether the existing mounting structures, foundations, panels, and cable routes can be reused.

Next, check whether peripheral equipment needs to be upgraded. When replacing the power conditioner (inverter), upgrades to circuit breakers, terminal blocks, junction boxes, combiner boxes, monitoring equipment, communication devices, etc., may be required. If existing equipment is old and the connection conditions do not match the replaced equipment, work will be needed on the peripheral equipment as well. Also, if integration with the monitoring system changes, the method of acquiring generation data and the alert notification settings will need to be modified. Because such work is often not included in the estimate and can easily lead to additional costs later, prior confirmation is important.

Confirming the scope of shutdown during construction is also necessary. If the power plant allows replacing power conditioners (inverters) one by one, it may be possible to carry out the work while limiting the shutdown scope. On the other hand, depending on the configuration of the electrical equipment, it may be necessary to shut down multiple units together. The longer the shutdown period, the greater the impact on revenue from electricity sales. You need to evaluate not only the estimate for replacement costs but also how much power generation will be halted during the work.

In replacement work, arranging the contractor and coordinating with the chief electrical engineer are also necessary. If there are configuration changes related to grid interconnection, procedures with the power company and other stakeholders may also be required. If existing equipment drawings, single-line diagrams, equipment specifications, and protection setting documents are not available, on-site surveys and drawing restoration efforts increase. Because used power plants may lack documentation, the presence or absence of documents should also be considered a risk factor for replacement costs.

Furthermore, on-site constructability also affects the scope of replacement. Whether vehicles can reach the inverter installation location, whether there are obstacles along the delivery route, whether the foundations or mounting racks have deteriorated, whether work can be carried out in rainy or snowy conditions, and whether heavy machinery and sufficient working space can be secured all influence the difficulty of the installation. In mountainous areas, narrow sites, or sloping terrain, the same replacement work tends to become more labor-intensive.

When confirming the scope of replacement, it is important to clearly specify which tasks are included and which are not in the estimate. Confirm how far the estimate covers items such as the equipment itself, removal, transport, disposal, installation, wiring connections, testing, configuration, monitoring integration, power outage work, coordination with stakeholders, on-site survey, drawing preparation, and spare parts. Even without stating prices, simply clarifying the scope greatly improves the accuracy of comparing proposals.

Checklist Item 4: Assess the Impact of Reduced Power Generation on Electricity Sales Revenue

When considering the cost of replacing an inverter, you need to check not only the installation costs but also the impact of reduced power generation on income from electricity sales. If an inverter is deteriorating, even if it hasn't completely stopped, its output can become unstable or it may be losing some opportunities to generate power. In that case, replacing it may restore generation, but you will be missing out on revenue during the period until the replacement is made.

To assess a decline in power generation, check past generation records together with solar irradiance conditions. Simply seeing that generation is lower than the previous year does not allow you to determine whether the cause is weather or equipment. You also need to consider factors such as solar irradiance, temperature, output curtailment, snow, shading, weeds, and soiling. Additionally, comparing output differences among power conditioners (inverters) within the same plant makes it easier to identify abnormal systems.

If there is a problem with the power conditioner (inverter), the generation curve on sunny days can show unnatural shapes. Typical tendencies include a slow ramp-up, capping at a constant output, sudden drops in a short time, repeated restarts during the daytime, or lower output than other systems. These can be caused not only by faults in the inverter itself but also by issues with the strings, junction boxes, protective devices, communication failures, etc. If you only budget for replacement costs without isolating the cause, the problem may persist after replacement.

When assessing the impact on revenue from selling electricity, the expected downtime is also important. If replacement work is carried out, generation from the affected inverter will stop. If the construction period coincides with seasons of high solar irradiance, the opportunity loss caused by the stoppage will be large. Conversely, if the work can be scheduled during periods of low irradiance or when generation is already reduced, it may be possible to limit the impact on revenue. Anticipating the timing of replacements before purchase improves the accuracy of financial projections.

Replacing the power conditioner (inverter) can also improve power generation performance and operability. If conversion efficiency, monitoring functions, anomaly detection, and maintainability are improved, this can lead to long-term stable operation. However, replacing it does not necessarily result in a significant increase in generated power. If the existing decline in power generation is due to panel degradation, dirt, shading, wiring losses, output control, or similar causes, replacing only the power conditioner will not improve the situation. Therefore, when considering the replacement cost, it is important to clarify what the replacement is intended to improve.

When assessing the price of a used power plant, you should check not only its past power-sales record but also the outlook for future generation. Even if past generation was sufficient, future revenue can become unstable if the inverter is nearing its replacement time. Conversely, a plant that had some faults in the past may be more stable going forward if the causes were identified and the affected components properly replaced. Rather than looking only at the generation figures, it is necessary to examine the condition of the equipment behind them.

Checklist Item 5: Check for the Presence of Warranties, Maintenance Contracts, and Spare Parts

When considering inverter replacement costs, warranties, maintenance contracts, and the availability of spare parts are extremely important. Even power plants that appear to have the same equipment condition can incur different future costs and downtime depending on whether warranties remain, whether maintenance support is available, and whether replacement parts can be obtained. When comparing prices of solar power plants, you need to verify the actual support arrangements, not just the age of the equipment.

When it comes to warranties, check not only the warranty period but also what is covered and the applicable conditions. Whether defects in the power conditioner (inverter) main unit are covered, only parts, whether labor and on-site service fees are included, or whether defects caused by natural disasters or the installation environment are excluded — the effectiveness in practice varies depending on the terms. Don't be reassured just by the presence of a warranty certificate; it's important to confirm whether the warranty can actually be used.

The same applies to maintenance contracts. Check the frequency of periodic inspections, emergency response times, whether remote monitoring is available, the scope of on-site dispatch, the contents of reports, how minor parts replacements are handled, and how estimates are handled in the event of failures. Even if there is a maintenance contract, if power conditioner replacement is treated separately, future costs will need to be borne by the buyer. Also, if past maintenance reports are organized, it becomes easier to grasp degradation trends and the history of malfunctions.

Whether spare parts are available is also important. With older inverters, obtaining parts can take time. If necessary parts cannot be obtained quickly, downtime may be prolonged. Check whether the plant has spare units or spare parts on site, whether the maintenance company can secure the parts, and whether replacement with alternative units is possible. If the outlook for parts supply is unclear, it may be safer to assume a full replacement rather than a repair.

When reviewing maintenance records, verify not only that inspections were performed formally but also whether abnormalities were actually detected and improvement proposals made. If the same issues keep appearing in annual inspection reports without being corrected, it suggests problems not only with equipment condition but also with management practices. Checking whether tasks such as cleaning around the power conditioner, ventilation, wiring inspection, retightening of terminals, and temperature checks are being carried out properly makes it easier to assess the risk of future outages.

Warranty and maintenance agreements are elements that are not immediately apparent in the price of a power plant. However, they have a major impact on post-purchase peace of mind and the speed of response. A plant that appears inexpensive may carry a high risk of future replacement if its warranty has expired, its maintenance structure is weak, and parts supply is unclear. Conversely, even if the price looks somewhat higher, if maintenance records are in order and warranty and support arrangements are clear, the plant can be considered a worthwhile investment in the long term.

Check Item 6: Confirm on-site conditions and constructability

Finally, what I want to confirm is the site conditions and constructability. The cost to replace the power conditioner (inverter) varies not only with equipment specifications and the scope of replacement but also with how easy it is to work on site. Solar power plants are not always flat, easy-to-work locations. There are various conditions such as forested areas, slopes, reclaimed or developed land, converted farmland, heavy-snow areas, coastal areas, and sites with narrow access roads. If you judge replacement costs without inspecting the site conditions, construction-related problems may be discovered later.

The first thing to check is the delivery access route. Confirm whether replacement power conditioners and related materials can be transported to the site, whether vehicles can enter the premises, and whether sufficient workspace can be secured. If the access road is narrow, the slope is steep, it becomes muddy in rainy weather, there is snow or ice, or gates or fences are narrow, work efficiency will decline. In some cases, manual carrying or temporary on-site work may be required.

Next, check the condition of the installation site. If weeds are overgrown around the inverter, drainage is poor, the foundation has subsided, the panel is tilted, or there is no room to work around it, site preparation may be required before the replacement work. In particular, weeds and poor drainage affect the inverter’s ventilation and moisture, so this is not merely an issue of ease of installation but also affects long-term operation after the replacement.

The surrounding environment is also important. Locations that tend to get hot, trap moisture, have a lot of dust, are susceptible to salt damage, or are affected by snow accumulation or falling snow place a greater burden on the power conditioner. If site conditions are severe, attention must be paid to equipment selection and installation methods after replacement. Consider whether it is sufficient to simply replace the unit in the same location as the existing one, or whether ventilation, waterproofing, dustproofing, snow protection, and drainage should be improved.

When inspecting site conditions, also check whether the drawings match the actual situation. At used power plants, as-built drawings and equipment diagrams may not match current conditions. Additions, repairs, wiring changes, or the addition of monitoring devices may have been made but not reflected on the drawings. If discrepancies are discovered on site for the first time during inverter replacement, the construction plan will need to be revised. It is important to conduct an on-site inspection before purchase and ascertain the actual conditions as much as possible.

During the on-site inspection we also check safety. We confirm whether there are passageways that allow workers to move safely, whether there are exposed parts that pose an electric shock risk, whether there are slopes around the panel that are prone to collapse, whether surfaces become slippery in rainy weather, and whether anything would interfere with inspection work. At sites with low safety, the burden of not only replacement work but also routine inspections increases. This affects long-term maintenance costs and management quality.

Confirming site conditions and constructability not only increases the accuracy of inverter replacement cost estimates. It also provides a basis for judging how manageable the entire plant will be. When evaluating the price of a solar power plant, it is important not only to consider on-paper financials but also whether it can actually be maintained and managed on site.

Practical procedures for comparing the prices of solar power plants

When looking at the price of a solar power plant and the cost of replacing power conditioners, it is easier to make a judgment if you check things step by step rather than focusing only on the detailed costs from the outset. First, organize the basic information from the sales materials. Confirm the plant capacity, power sale conditions, remaining term, annual power generation, equipment configuration, number of power conditioners, installation year, maintenance contract, land conditions, and past power sale performance. At this stage, the goal is to grasp the overall outline of the project.

Next, extract information about the inverters. Rather than comparing model names in detail, check the installation year, number of units, capacity configuration, replacement history, repair history, error history, and whether monitoring data exists. If there are multiple units, determine whether only some are newer or whether all units are from the same period. If any inverters have been replaced, confirm why they were replaced and whether the same risk applies to the other, unreplaced units.

After that, review the power generation performance. Check not only the annual generation but also monthly and daily trends for any sudden drops or fluctuations. If possible, check the output data for each power conditioner (inverter). If any anomalies are found, you should assume not only inverter replacement costs but also costs for investigating the cause and repairing surrounding equipment. It is important not to attribute all reductions in generation to the inverter; isolate causes including shading, soiling, weeds, wiring, and output control.

Next, carry out an on-site inspection. Check the inverter unit’s exterior, installation location, ventilation, drainage, corrosion, cable condition, condition inside the panel, surrounding equipment, delivery route, and workspace. Organizing photos and location information during the on-site inspection will make it easier to review later within the company. Especially when comparing multiple projects, keeping on-site photos and inspection notes to the same standard reduces variability in decision-making.

Finally, incorporate future costs into the purchase price. For cases where inverter replacement is imminent, treat that cost as part of the effective purchase price. For cases where the timing of replacement is uncertain, evaluate cash flows under both optimistic and conservative scenarios. For cases with many uncertain factors—such as inadequate maintenance records, poor on-site conditions, or an opaque parts supply—assume a higher level of risk. By organizing the assessment this way, you can judge not merely whether the price is low or high, but whether the asset can be operated stably after purchase.

For practitioners, what matters is not investigating every project perfectly but making sure significant risks are not overlooked. The price of a solar power plant cannot be judged solely by the figures in the sales materials. By comparing future costs—including inverter replacement costs—generation-stoppage risks, on-site constructability, and maintenance arrangements, you can reduce unexpected issues after purchase.

Summary

When looking at the price of a solar power plant, it is important not to judge solely by the sale price or gross yield, but to check the actual burden including power conditioner (inverter) replacement costs. The power conditioner is equipment directly linked to the plant’s operation, and if it stops it will affect electricity sales revenue. By considering not only the replacement cost itself but also the timing of replacement, downtime, ancillary site work, maintenance arrangements, and site conditions, you can improve the accuracy of your purchase decision.

Particularly important to check are remaining service life and replacement timing, signs of degradation and risk of shutdown, scope of replacement and associated peripheral construction, impact on reduced power generation, warranties and maintenance contracts, and site conditions and constructability. By organizing these factors, it becomes easier to judge the risks hidden in projects that appear cheap and the stability of projects that may seem expensive at first glance. The price of a solar power plant should be viewed not merely as the acquisition price but as a comprehensive assessment that includes post‑purchase costs and operational risks.

Also, to accurately assess the cost of replacing inverters, it is essential to precisely understand the on-site conditions. Equipment locations, delivery routes, installation environment, surrounding weeds and drainage, the condition of the control panels, and the ease of inspection cannot be determined from desk-based materials alone. If on-site inspections of the power plant can be streamlined and equipment condition recorded with location information, it will aid internal review, sharing with contractors, and future maintenance planning.

LRTK can be used, as a smartphone-mounted GNSS high-precision positioning device, for on-site inspections of solar power plants, recording equipment locations, and organizing inspection notes. By recording high-precision location information for items such as power conditioners (inverters), junction boxes, fences, access roads, drainage points, and places requiring repair, it becomes easier to improve the accuracy of pre-purchase surveys and maintenance management. To make more practical judgments about a solar power plant’s price and the cost of replacing power conditioners, it is important not only to rely on financial documents but also to establish a system that accurately records the site and allows for later verification.