6 Steps to Evaluate Solar Power Plant Prices and Electricity Sales Revenue

Table of Contents

• Don't judge the price of a solar power plant solely by revenue from electricity sales

• Step 1: Align the project overview and the assumptions for electricity sales revenue

• Step 2: Check monthly and annual power generation records

• Step 3: Interpret the electricity sales conditions and the remaining term

• Step 4: Factor in maintenance costs and outage risks

• Step 5: Reflect equipment degradation and future repairs in electricity sales revenue

• Step 6: Connect land conditions and on-site risks to the revenue outlook

• Points to note when comparing price and electricity sales revenue

• Summary: Verify the basis for electricity sales revenue on site and assess the price

Do not judge the price of a solar power plant solely by electricity sales revenue

When considering the purchase or acquisition of a solar power plant, many practitioners first check the quoted price and the expected revenue from electricity sales. Projects whose electricity sales revenue appears stable look attractive, and projects that seem to offer high revenue relative to their price are easier to move forward in internal approval processes and investment decisions. However, the price of a solar power plant and its electricity sales revenue cannot be simply compared by listing them side by side.

A solar power plant is a business asset that integrates power-generation equipment, land, electricity sales conditions, generation performance, management status, equipment degradation, the local environment, and contractual relationships. Even if electricity sales revenue appears high, if generation performance is unstable the outlook for future revenue becomes uncertain. Even if past electricity sales revenue has been strong, the practical valuation changes if major equipment is nearing its repair period, vegetation management is inadequate, there are drainage problems, or there are records of output curtailment or shutdowns.

Also, revenue from electricity sales is determined by the combination of the amount of power generated and the sales terms. No matter how favorable the terms, income will not increase if the site cannot generate sufficient power. Conversely, even if generation performance is stable, if the remaining operational period is limited or the burdens of maintenance costs and future repairs are large, you should carefully verify whether the price is justified.

In power plants that appear inexpensive, attention should be paid to the assumptions behind electricity sales revenue. If those assumptions are based on optimism rather than past performance, you may not receive the expected revenue after acquisition. Even power plants that appear expensive can be easier to consider in the long term if their generation performance is stable, the electricity sales conditions are clear, and the equipment and land risks are small.

For practitioners searching "solar power plant price," what matters is not merely a sense of the market but a decision-making framework that can explain the relationship between the price and electricity sales revenue. It is necessary to confirm which generation performance the presented electricity sales revenue is based on, whether the same revenue can be expected going forward, and whether it remains reasonable after deducting operation and maintenance costs and repairs.

This article lays out six steps for checking the price and revenue from electricity sales of a solar power plant. Rather than specific prices or income amounts, it focuses on perspectives that practitioners can use before purchase, when comparing options, and when explaining things internally. Use this as a way of thinking to make judgments that reflect the actual condition of the power plant, rather than being swayed by superficial electricity-sales revenue figures.

Step 1: Align the project overview and assumptions for electricity sales revenue

The first step in evaluating the price of a solar power plant and its electricity sales revenue is to align the project summary and the revenue assumptions. When comparing multiple projects, you cannot make a correct judgment by comparing only electricity sales revenue while the installed capacity, location, start of operations, electricity sales conditions, land use type, period of generation performance records, and the scope of operation and maintenance differ.

First, as part of the project overview, we confirm the installed capacity, installation location, operation start date, equipment configuration, land ownership or usage status, whether a management contract exists, inspection history, and repair history. Before reviewing the documents on revenue from power sales, understanding what kind of power plant it is makes it easier to determine whether the revenue figures are realistic.

Next, review the assumptions behind electricity sales revenue. It is important to separate whether the revenue is based on past performance or on future projections. For operating power plants, past electricity sales records should be available for verification. For projects that are nearly new or have only recently begun operation, explanations will often focus on generation simulations and projected generation volumes.

If a projection of revenue from electricity sales is presented, verify the basis for its calculation. Check whether the assumptions about generation are based on past actual performance, an average of monthly results, or only a specific period, and whether they reflect equipment downtime, output control, or declines in generation. A revenue projection that picks out only the good periods is insufficient as a basis for future decision-making.

Also, you need to align not only the income but also the period covered. Even if annual income appears the same, its value changes if the remaining operating period is different. For projects that can operate for a long time versus those with a limited remaining period, the approach to equipment repairs and maintenance will also differ. When checking figures for revenue from electricity sales, always confirm the period over which that revenue is expected.

Assumptions about the scope of the land and management contracts are also important. Whether you acquire the land, assume a land lease, continue the operation and maintenance contract, or include tasks such as mowing and inspections will change the effective burden relative to the income. Even if power sales revenue is the same, differences in maintenance costs or land-related obligations will alter the reasonableness of the price.

Aligning the project overview and the assumptions about power sales revenue is the foundation for comparison. Projects with unclear information at this stage should be treated cautiously, even if the price appears attractive. By clarifying the assumptions upfront, you will be able to interpret the figures more accurately when verifying generation performance and power sale conditions in the next step.

Step 2: Review monthly and annual power generation performance

The most important basis for verifying revenue from electricity sales is the actual power generation record. Because revenue from electricity sales is heavily influenced by the amount of power generated, you cannot determine the reasonableness of the price without checking how stably it has generated power in the past. In particular, for operational solar power plants, actual generation data should be given more weight than on-paper projections.

When looking at power generation performance, it is important not to judge based only on the annual total. Even if the annual figures appear stable, monthly data may reveal drops in generation during specific seasons. There are site-specific reasons for such fluctuations—for example, weeds growing in summer casting shadows on the panels, surrounding trees or terrain casting longer shadows in winter, effects from snow or falling leaves, or equipment shutdowns and maintenance stoppages.

By checking monthly generation performance, the stability of revenue from electricity sales becomes clear. For power plants where income drops sharply in specific months, it is necessary to investigate the cause. If it is a temporary effect due to the weather, it may be acceptable, but if generation falls at the same time each year, there may be structural causes such as shading, vegetation, snow accumulation, drainage, or the condition of the equipment.

Also check the year-by-year trend. Even if a single year’s power generation performance is good, that year may simply have had favorable weather. Look to see whether it is stable over multiple years, gradually declining, or suddenly dropping from a certain point. If it is declining year by year, factors such as panel soiling, equipment degradation, growth of surrounding trees, insufficient vegetation management, or malfunctioning power conversion equipment may be involved.

If there has been a decline in power generation performance, check whether that decline is reflected in the projected revenue from electricity sales. If revenue is projected based only on past good periods, future income may appear overstated. Conversely, if there were temporary failures or management shortcomings in the past that have since been remedied, you can evaluate future prospects by confirming the details of those improvements.

Downtime history is also important. If there are months with low power generation, check whether there was equipment downtime, how long the downtime lasted, what the cause was, and whether the recovery response was appropriate. The fact that there was downtime is not necessarily a problem in itself. What matters is whether the cause has been identified and measures to prevent recurrence have been implemented. Unexplained stoppages or repeated occurrences of the same fault are factors that reduce the stability of electricity sales revenue.

To assess revenue from electricity sales, it is essential to consider not only the generation performance figures but also the background behind them. A plant with stable generation can make income projections easier, even if its price appears high. A plant with unstable generation can, even if its price appears low, leave uncertainty regarding future income.

Step 3: Interpreting the electricity sales terms and remaining period

When checking the price of a solar power plant and its revenue from power sales, the selling conditions and the remaining period are central factors. Even if the generation output is the same, how the income appears changes depending on the conditions under which the power can be sold.

Also, for plants already in operation, because a certain amount of time has passed since the start of operations, the remaining period has a large impact on the revenue outlook.

When checking the conditions for selling electricity, organize the contract terms, the start date of operation, certification-related information, procedures with the utility, and the conditions required for name changes or succession. Even if the documents make the conditions look favorable, if there are discrepancies in the location, installed capacity, registered name, or contract terms, additional verification or procedures may be required after acquisition. As a premise for revenue from electricity sales, it is important to confirm that the contract can be continued without issues.

The remaining period affects the outlook for the timeframe during which future electricity sales revenue can be earned. Power plants with a long remaining period have many revenue opportunities left, but it is also necessary to consider the possibility of equipment degradation or repairs occurring during that time. For power plants with a short remaining period, it becomes important whether they can generate power stably over the short term, and the impact of major repairs, if they occur, becomes more severe.

Power sale terms and the remaining contract period must be checked together with the plant’s generation performance. Even if the power sale terms are favorable, you cannot make full use of them if generation output has declined. Conversely, a plant that looks unremarkable based only on its sale terms may still provide steady income if its generation performance is stable and its equipment and land are in good condition.

Output curtailment and interconnection conditions should also be checked. Even if the power generation equipment can operate sufficiently, opportunities to sell electricity may be limited. Examine the extent of past limitations, whether similar impacts are expected in the future, and whether they are reflected in generation performance and electricity sales revenue. Even if projected electricity sales revenue is shown as high, be cautious if restriction or shutdown risks are not reflected.

Also, the reliability of transfer procedures is practically important. If documents related to electricity sales terms or certifications are not organized, post-acquisition procedures can take time. Deficiencies in documentation or discrepancies in registered names may not be reflected in actual power generation, but they pose risks to business succession. When determining the price, confirm not only the figures for electricity sales revenue but also the reliability of the contracts and procedures.

The purpose of interpreting the electricity sales terms and the remaining period is to realistically estimate future income. Rather than focusing only on how favorable the terms are, confirming whether the power plant can consistently benefit from those terms throughout the remaining period makes it easier to assess whether the price is reasonable.

Step 4: Subtract maintenance and management costs and downtime risk

When considering electricity sales revenue from a solar power plant, you need to look not only at the total revenue but also deduct maintenance costs and downtime risk. A plant is not finished once purchased; it requires long-term inspections, generation monitoring, grass cutting, cleaning, repairs, drainage management, and emergency response. Even if electricity sales revenue appears large, if maintenance costs and downtime risk are high, the actual assessment will change.

Maintenance and management costs include regular inspections, checks of electrical equipment, power generation monitoring, mowing, weeding, cleaning, inspection of drainage channels, repairs to fences and gates, management of surrounding trees, and on-site response in the event of abnormalities. These vary greatly depending on the power plant's location and the condition of its equipment. Even for power plants with the same installed capacity, the management burden differs between plants on flat, easily accessible land and those in forested or sloped areas.

When reviewing past maintenance costs, do not take low expenses alone as a positive indicator. It is possible that costs were low because necessary inspections, mowing, drainage management, and repairs were not performed adequately. When examining past costs, review the work performed, frequency, reports, and on-site conditions together to determine whether proper management was carried out.

Downtime risks also have a significant impact on power sales revenue. A power plant can be temporarily halted due to stoppage of power conversion equipment, communication failures, cable damage, faults in connection equipment, natural disasters, poor drainage, and the like. The longer the downtime lasts, the more power sales revenue declines. If there have been stoppages in the past, confirm the causes, duration, restoration actions, and measures to prevent recurrence.

Power generation monitoring and an emergency response framework are also important. Even if an anomaly can be detected, if it is unclear who will verify it and who will arrange on-site response, recovery may be delayed. At remote power plants, it can take time to perform on-site verification. To assess the stability of electricity sales revenue, it is necessary to confirm how quickly a plant can be restored when it stops.

When operation and maintenance costs and outage risk are reflected, the appearance of revenue from electricity sales changes. Even if the headline revenue looks large, projects with heavy burdens for mowing, drainage management, repairs, and emergency response can be less attractive in practice. Conversely, projects whose electricity sales revenue does not stand out may be easier to manage and have lower outage risk, making long-term stable operation more likely.

When checking prices and revenue from electricity sales, it’s important not to take the income figures at face value but to deduct the costs and systems required to sustain that income. Revenue from electricity sales becomes stable only when maintenance and management are properly and continuously carried out.

Step 5: Reflect Equipment Degradation and Future Repairs in Electricity Sales Revenue

To project a solar power plant's power sales revenue into the future, it is necessary to reflect equipment degradation and future repairs. Even if current generation performance is good, equipment degrades over time. If major equipment requires repair or replacement, downtime and repair burdens will occur, affecting the projected revenue outlook.

The equipment to be inspected is not limited to solar panels. You need to inspect all equipment that makes up the entire power plant, such as power conversion equipment, mounting structures, foundations, cables, connection equipment, monitoring devices, fences, gates, and drainage facilities. Cracks or dirt on panel surfaces, corrosion of mounting structures, scouring around foundations, damage to cable sheathing, deterioration of connection points, malfunctioning monitoring devices, and damaged fences can all potentially affect future electricity sales revenue.

Reviewing inspection reports and repair histories makes it easier to anticipate future liabilities. Confirm what kinds of defects occurred in the past, when they occurred, and how they were addressed. The fact that a failure occurred is not necessarily a problem. Power plants that detect anomalies, identify causes, carry out appropriate repairs, and document measures to prevent recurrence are easier to assess in terms of their management condition. The problem is when identified issues remain unaddressed or when repair details are unclear.

When evaluating future repairs, also consider their relationship to the remaining operating period. For power plants with a long remaining life, it is necessary to plan for equipment replacement and maintenance. For plants with a short remaining life, major repairs can have a significant impact on the financial balance if they occur. Check whether projected electricity sales revenue reflects shutdowns or expenditures due to future repairs.

The decline in power generation due to equipment degradation is also important. Dirt and wear on panels, faults in connection points, malfunctions in power conversion equipment, and communication failures in monitoring devices can lead to reduced power output and delays in detecting anomalies. Even if past performance has been good, if equipment degradation has progressed, future revenue from electricity sales may not be maintained at the same level.

For low-priced power plants, the need for unresolved repairs or equipment upgrades may be behind the low cost. For high-priced power plants, good equipment condition and the clarity of repair histories may be reasons for the higher valuation. In either case, it is important to judge based not only on current revenue from electricity sales but also on the expected future condition of the equipment.

Revenue from electricity sales assumes that the equipment will continue to operate stably. Revenue projections that do not reflect equipment degradation and future repairs are insufficient for practical decision-making. When looking at the price and revenue from electricity sales, check the equipment’s current condition and future burdens together.

Step 6: Linking Land Conditions and Site-Specific Risks to Income Projections

Finally, what you should check are the land conditions and on-site risks. Revenue from electricity sales is not determined by the generation equipment alone. The condition of the land, surrounding environment, drainage, road access, boundaries, vegetation, and disaster risks affect power output, operation and maintenance costs, and downtime. When looking at price and electricity sales revenue, you need to connect land conditions to your income projections.

First, confirm the land use type. Check whether the land is owned or leased, whether the land-use contract period is sufficient, and what the renewal and termination conditions are. In the case of leased land, if the land-use rights are not sufficient for the power sales period or the planned operation period, concerns about the future continuity of the business will remain. If there are unclear points in the land contract, uncertainty will also arise in the expected power sales revenue.

Boundaries and the scope of use are also important. Confirm whether fences, panels, mounting structures, drainage channels, maintenance access paths, and cable routes are contained within the property. Even if the drawings appear to show no problems, on site you may find boundary markers hard to identify, fences located near the boundary, or drainage facilities shared with neighboring land. Uncertainties about the boundaries will affect management and repair work after purchase.

Drainage and topography are directly linked to the operation and maintenance of a power plant. Under conditions such as drainage channels that are prone to clogging, easy inflow of sediment, a tendency for water to accumulate, or unstable slopes, inspections and repairs after heavy rain will be necessary. Poor drainage can lead to scour around foundations, impacts on cables and electrical equipment, and deterioration of access roads. These risks can become factors that reduce future power sales revenue.

Also check surrounding trees and vegetation. If trees grow and cast shade, power generation may decrease. Weeds can also cast shadows beneath the panels. There are on-site risks such as fallen leaves clogging drainage channels, fallen trees affecting equipment, and wildlife damaging cables. Because the site environment changes over time, it is important to consider not only the current condition but also the future maintenance burden.

Road access and entry routes also affect the revenue outlook. In locations where it is difficult to access the power plant, on-site response in the event of anomalies may be delayed, and downtime may be prolonged. If service vehicles cannot easily enter, the burden of repairs and equipment replacement also increases. The ease or difficulty of access is an operationally important condition for stabilizing power sales revenue.

Land conditions and on-site risks are factors that do not easily appear directly in documents on electricity sales revenue. However, in actual operation they affect power generation, operation and maintenance costs, and outage risk. When assessing price and electricity sales revenue, it is essential to reflect risks that can be confirmed on site in the revenue forecast.

Points to consider when comparing price and revenue from electricity sales

When comparing the price of a solar power plant and its revenue from electricity sales, be careful not to judge based only on the electricity sales figures. Even if a project appears to have high electricity sales revenue, unless you verify whether that revenue is based on past performance or on assumptions, and whether it reflects operations and maintenance costs and downtime risks, it is insufficient as a basis for practical decision-making.

A common oversight is using only a good year's revenue from electricity sales as the benchmark. Power generation varies depending on weather and local site conditions. Even if a particular year shows strong generation performance, there may be a downward trend when viewed over multiple years. It is important to review monthly data over several years and identify the causes of any outliers or downward trends.

Be careful not to underestimate operation and maintenance costs. Even if revenue from electricity sales looks large, the actual assessment will change if the burdens of mowing, cleaning, inspections, drainage management, emergency response, and equipment repairs are substantial. Even if past operation and maintenance costs were low, that may simply mean that necessary maintenance was not performed. You need to check the scope of maintenance, not just the size of the costs.

Avoid judging solely by the terms for selling electricity. Even if the terms appear favorable, if the power generation record is unstable, revenue from electricity sales will not be stable. If the remaining term is short, you need to assess the balance between the outlook for future income and the burden of repairs. It is important to check the terms, the remaining term, the power generation record, and the equipment condition together.

Also, be aware of discrepancies between the documentation and the actual site. Even if the project overview, drawings, and inspection reports are in order, equipment layout, drainage, vegetation, shading, and boundary conditions on site may differ from those shown in the documents. If you judge revenue from electricity sales based only on the figures in the documents, you may overlook on-site risks.

For low-priced projects, confirm whether the expected power sales revenue is overly optimistic or whether risks related to equipment or land have been factored in. For high-priced projects, confirm whether the high price can be explained by the stability of power sales revenue, equipment condition, land conditions, and management structure. In either case, it is important to be able to explain the relationship between price and power sales revenue with supporting evidence.

Summary: Confirm the basis for revenue from electricity sales on site and determine the price

When evaluating the price of a solar power plant and revenue from electricity sales, it is important to verify six steps: the project overview and revenue assumptions; monthly and annual generation performance; power sale conditions and remaining contract period; operation and maintenance costs and risk of downtime; equipment degradation and future repairs; and land conditions and on-site risks. You should not judge whether the revenue from electricity sales is high or low based only on the figures; you need to confirm the basis on which that revenue is founded.

Revenue from electricity sales is determined by the amount of electricity generated and the conditions for selling it.

However, the amount of electricity generated is not determined by installed capacity alone. It varies depending on the condition of the panels, the operational status of power conversion equipment, the safety of cables and connection equipment, vegetation and shading, drainage, on-site management, and the history of outages. Even if the conditions for selling electricity are favorable, if stable on-site generation cannot be achieved, the revenue outlook will be weak.

What matters for operational staff is ensuring they can explain the basis for electricity sales revenue internally. By linking and organizing past generation performance, electricity sales terms, the remaining term, inspection reports, repair history, management costs, and the results of on-site verification, it becomes easier to justify the price. This is especially essential for used solar power plants, where reconciling past operational history with the current on-site condition is indispensable.

During on-site surveys, it is important to accurately record risks that could affect revenue from electricity sales. If you can record, together with location information, trees that cause shading, the extent of vegetation growth, drainage channels, cable damage, equipment deterioration, fence damage, and inspection points near boundaries, it will be easier to organize the basis for reduced power generation and future costs.

If you want to verify on-site the basis for a solar power plant’s feed-in revenue, using LRTK (an iPhone-mounted high-precision GNSS positioning device) is also effective. By recording the locations of equipment within the plant, drainage channels, causes of shading, the extent of vegetation, candidate repair sites, and points of caution near boundaries together with high-precision location data, you can reconcile discrepancies between drawings and the site and make it easier to share the same information among stakeholders. When assessing the price and feed-in revenue of a solar power plant, it is important to build up not only desk-based figures but also on-site evidence that can be verified.