What Determines the Price of a Solar Power Plant? 6 Criteria

Table of Contents

• The price of a solar power plant cannot be judged by equipment costs alone

• Criterion 1: Land conditions and site development difficulty

• Criterion 2: Specifications of generation equipment and design approach

• Criterion 3: Conditions for grid interconnection and substation/transformer equipment

• Criterion 4: Scope of construction and construction risks

• Criterion 5: Power generation forecasts and profitability outlook

• Criterion 6: Operation and maintenance after commissioning and future measures

• Considerations practitioners should review when comparing prices

• Summary: Transparency of conditions is more important than low price

The price of a solar power plant cannot be judged by equipment costs alone

When researching the price of a solar power plant, what many practitioners first care about is how much it will cost per unit of installed capacity. Whether making an internal investment decision, considering acquiring a prospective site, or purchasing an existing plant, it is natural to first want to know whether the price is reasonable.

However, the price of a solar power plant is not determined simply by adding up equipment prices such as solar panels, mounting structures, power conditioners, and cables.

Actual prices are determined by a combination of multiple factors, including land shape, ground conditions, earthworks volume, road access, drainage, grid interconnection, construction conditions, design policy, power generation forecasts, maintenance arrangements, and risks associated with future equipment replacements. Even for a power plant that appears to have the same installed capacity, the required construction work can differ greatly when it is built on flat, easy-to-construct land versus on sloped terrain or soft ground. In addition, if the distance to the grid connection or the scale of substation/transformer equipment differs, the total project cost can vary significantly even when the visible generation equipment is the same.

Furthermore, the way to interpret price differs between new projects and used projects. For new projects, you look at the costs that will be incurred from design, permitting, site development, construction, grid connection, inspections, through to the commencement of operations. On the other hand, for used projects, you need to evaluate the condition of the already operating power plant’s equipment, past generation performance, maintenance history, contractual terms, future refurbishment or replacement costs, and so on. If you only look at the purchase price on the surface, unexpected repairs, output degradation, and increased management burden may arise after operations begin.

When evaluating the price of a solar power plant, it is important not only to consider whether it is expensive or cheap, but also to check what is included and what is not. If you compare projects while the scope listed in estimates or sales documents is unclear, the cheaper-looking projects are more likely to incur additional costs later. Conversely, a project that seems expensive at first glance may be reasonable in the long term if it adequately includes site development, drainage, grid connection, monitoring, maintenance, spare parts, warranty support, and so on.

This article organizes what determines the price of a solar power plant into six criteria that are easy for practitioners to check. By identifying judgment points that are not apparent from installed capacity alone, you can improve the accuracy of quote comparisons, project evaluations, investment decisions, and internal explanations.

Criterion 1: Land Conditions and Site Development Difficulty

The first major factor that determines the price of a solar power plant is the land conditions. Unlike rooftop installations, a solar power plant uses the land itself as its foundation. Therefore, the shape of the land, slope, ground conditions, drainage, surrounding environment, and road access conditions directly affect construction and maintenance costs. Even if equipment prices are the same, differences in land conditions can significantly change the overall price of the plant.

If the land is flat and regularly shaped, the amount of earthworks can be kept low and the placement of mounting structures can be planned efficiently. Access for heavy machinery, material delivery, pile driving, wiring, and securing inspection walkways is also relatively easy. On the other hand, on sloped land, land with level differences, irregularly shaped plots, or plots with many trees and remnants, work such as tree felling, stump removal, grading, slope protection, drainage measures, and access road improvements increases. These are not the power generation equipment itself, but they are costs necessary to establish a power plant.

Be especially cautious with projects where estimates for site-formation work are overly optimistic. Even if the initial rough estimate appears to involve only leveling the land, once surveying and design proceed, cut-and-fill work, embankments, retaining walls, drainage channels, sedimentation facilities, and slope protection may become necessary. Designing without considering rainwater flow can lead, after operations begin, to soil washout, scouring around mounting structures, muddy access routes, and drainage problems affecting neighboring properties. These issues tend to be more burdensome to address later than they would be during construction.

Ground conditions are also important. The foundation method for the support structure varies depending on ground stiffness, bearing capacity, groundwater level, the presence of boulders or buried objects, and corrosive environments. If piles can be driven easily into the site, construction efficiency improves, but where bedrock, buried obstacles, or soft ground are present, it may be necessary to reconsider the foundation type or change construction methods. Rework during pile installation can lead to schedule delays, so it affects not only cost but also the construction period and risk.

Additionally, the shape of the land also affects power generation. On irregularly shaped plots, panels cannot be arranged efficiently, so the installed capacity may be smaller even with the same area. Shadows from adjacent forests, buildings, utility poles, and slopes must also be taken into account. On land where shading has a significant impact, increasing installed capacity may not yield the expected power generation. In other words, land conditions are a factor that affect not only initial costs but also long-term profitability.

When comparing prices of solar power plants, it's important not to look only at land area or installed capacity, but also to check the site's pre-development condition, elevation differences across the planned site, drainage planning, geotechnical surveys, access routes for deliveries, shading from surrounding objects, and the provision of maintenance access paths. Even if land appears cheap, if the costs to prepare it as a power plant are high, the overall price may be higher.

Standard 2: Specifications and Design Policy for Power Generation Equipment

The second criterion is the specifications and design policy of the power generation equipment. The cost of a solar power plant varies depending on the types, performance, quantity, layout of the equipment used, and the approach to electrical design. Major equipment includes solar panels, mounting structures, power conditioners, connection boxes, combiner panels, cables, monitoring systems, weather measurement instruments, weed control measures, fencing, and surveillance cameras. The level at which these specifications are selected affects both the initial cost and long-term stability.

Solar panels are the central equipment that generate a power plant’s revenue. It is not enough to simply choose panels with high output; you must consider the available installation area, racking dimensions, string configuration, DC-side voltage, temperature characteristics, degradation rate, warranty conditions, and so on together. If you try to increase installed capacity by adopting an overly dense layout, aisles can become narrow, maintainability can decline, and the system can become more susceptible to shading. Conversely, a more relaxed layout makes management easier but may reduce land-use efficiency.

Racking specifications also have a major impact on price. For ground-mounted solar power plants, it is important that the racking can withstand wind loads, snow loads, ground conditions, and corrosive environments. Choosing specifications that provide a margin above the design loads may increase initial costs, but it makes it easier to reduce the risks of deformation, loosening, and breakage during long-term operation. Conversely, if you prioritize only minimizing initial costs, the ability to cope with strong winds, heavy snow, or changes in ground conditions may be insufficient, potentially leading to future repair costs and the risk of shutdown.

Selection of the power conditioner is also important. In the overall design of a power generation facility, how you set the relationship between the DC-side panel capacity and the AC-side output capacity affects profitability. Designing the DC side somewhat larger can boost generation during mornings, evenings, and periods of weak sunlight, but it can also cause output limitations during periods of strong sunlight. This approach needs to be considered not just as an equipment cost issue but in terms of annual generation, feed-in conditions, output control, equipment lifetime, and maintainability.

Specifications for cables and electrical equipment should not be overlooked. At power plants with long cable runs, it is necessary to select appropriate conductor sizes and wiring routes to minimize voltage drop and power loss. If the wiring design is oversimplified to reduce initial costs, losses after commissioning will increase and affect long-term power generation revenue. In addition, wiring routes that are easy to inspect, clear panel layouts, and configurations that allow safe work during maintenance also influence the value of the power plant.

When evaluating the price of power generation equipment, it is important not to look solely at the unit price of the equipment but to confirm that its specifications match the design conditions of the power plant. Even a low-cost specification can be reasonable if it meets the conditions, but caution is needed when selections are made without considering site conditions or the operating period. Since a solar power plant is equipment intended to operate for a long time, decisions should be made by judging the balance among initial cost, maintainability, power output, and durability.

Criterion 3: Conditions for Grid Interconnection and Substation and Transformer Equipment

The third criterion is the conditions for grid interconnection and power receiving and transformation equipment. A solar power plant becomes a viable business by sending the electricity it generates to the grid. Therefore, even if the generation equipment itself is in place, if the conditions for connecting to the grid are strict, the overall project cost can change significantly. What is often overlooked when comparing estimates are the costs and risks related to this interconnection.

For grid interconnection, the distance from the power plant to the connection point, required utility poles or underground cabling, protective devices, switchgear, substation/transformer equipment, metering equipment, communications equipment, and so on are checked. If the connection point is nearby and existing infrastructure can be readily utilized, planning is relatively straightforward; however, if the connection point is far or grid-side reinforcement is required, the scope of construction expands. Additionally, depending on the connection conditions, additional protective devices or control functions may be required on the power plant side.

Power receiving and transformation equipment vary in specifications depending on the scale of the power plant and the interconnection voltage. At high-voltage or extra-high-voltage power plants, switchgear cubicles, transformers, circuit breakers, protective relays, metering devices, and monitoring and communication equipment are required. These are critical installations related to safety and system protection, and their specifications cannot be easily reduced. The installation location, foundations, equipment delivery routes, maintenance space, and considerations for noise and visual impact must also be included in the planning.

Costs associated with grid interconnection are characterized by the fact that they are not confined solely to the power plant site. There are aspects that are subject to external factors, such as negotiations with the utility, connection studies, allocation of construction burdens, schedule coordination, and pre-commissioning inspections. Even if construction of the power plant is progressing, delays in the interconnection works will push back the start of operations. Because a delayed start of operations also affects when revenue from electricity sales begins, these costs need to be regarded not just as construction expenses but as risks to the overall business plan.

Conditions for output control also affect price evaluation. Even if a plant’s equipment cost looks attractive, in regions or under conditions where output control is likely, you may not be able to convert the projected generation directly into revenue. Unless you confirm how much of the generated electricity can actually be transmitted and how much impact output control would have, you cannot determine whether the price is reasonable.

When reviewing the conditions for grid interconnection and power receiving and transformer equipment, it is important to clarify the scope included in the quotation. Confirm whether it covers only on-site electrical work, work up to the connection point, whether grid-side construction costs are separate, and whether the applications and inspections required for interconnection are included. If these points remain ambiguous when comparing prices, there is a risk of significant additional costs later.

Criterion 4: Scope of Work and Construction Risks

The fourth criterion is the scope of work and construction risk. The price of a solar power plant varies greatly depending on how much work is included. Even for estimates for the same power plant construction, you cannot compare an estimate that includes site preparation, foundations, racking, panel installation, electrical work, fencing, monitoring equipment, drainage, roadworks, testing, inspections, and documentation with one that includes only some of those works.

A common practical issue is omissions in the scope of estimates. For example, tree felling may be included while stump removal and disposal are excluded; site development may be included while drainage channels are excluded; fences may be included while gates and maintenance access paths are excluded; monitoring equipment may be included while communication lines and configuration work are excluded. Although the price may seem low at first glance, if items necessary to actually bring the power plant into operation are charged separately, the total cost can change significantly.

Construction risks vary from site to site. In mountainous areas, it may be difficult to bring in heavy machinery and materials. Narrow roads, steep access routes, bridge weight limits, and consideration for neighboring residences can restrict transportation methods and construction procedures. In regions with heavy rainfall or snowfall, the periods when construction is possible may be limited. For projects with tight schedules, delays caused by bad weather or poor ground conditions can lead to additional costs and schedule adjustments.

On-site safety measures also affect cost. On land with elevation differences, fall prevention, slope work, and management of heavy equipment operating areas are necessary. For electrical work, prevention of electric shock, insulation verification, and pre-energization testing are important. To carry out safety measures properly, work planning, training, temporary facilities, personal protective equipment, and the assignment of site supervisors are required. These are less visible costs, but they are indispensable for ensuring the reliable progress of power plant construction.

You should also confirm the scope of quality control. By recording construction quality—pile installation depth, rack inclination, panel fastening condition, cable supports, terminal tightening, insulation resistance, grounding resistance, power generation verification, etc.—as you proceed, you can reduce problems after commissioning. Some low-priced estimates may simplify the preparation of quality records and as-built documentation. If documentation that can verify equipment condition after completion is lacking, it may put you at a disadvantage when explaining matters during future maintenance or sale.

When comparing construction scopes, you need to interpret not just the total price but the work items, quantities, specifications, scope of responsibility, exclusions, and the conditions for additional costs. A power plant is not finished when construction is completed; it is equipment that will be operated over a long period. Decisions made during the construction phase affect future power generation, maintainability, accident risk, and asset value. Therefore, construction costs should not simply be judged by how low they are; it is important to confirm that the necessary work and management are appropriately included.

Criterion 5: Power Generation Forecast and Profitability Outlook

The fifth criterion is projected power generation and the outlook for profitability. The price of a solar power plant is assessed not only by equipment and construction costs but also by how much power the plant is expected to generate in the future and how much stable revenue it will produce. Even at the same price, investment decisions differ between projects with high expected generation and low risk and those with significant uncertainty in generation.

When forecasting power generation, we take into account solar irradiance, temperature, orientation, tilt, shading, snow, soiling, electrical losses, equipment efficiency, output control, and degradation over time. Looking only at the design-rated installed capacity does not tell you the actual annual energy production. For example, even plants with the same capacity will produce different amounts depending on whether they are located in an area with good solar conditions or an area with a lot of shading. If the tilt angle or orientation is not optimal, that will also affect the annual generation efficiency.

Shading assessment is particularly important. Shadows cast by mountains, trees, buildings, utility poles, and between mounting structures can reduce power generation depending on the time of day and season. Even short-duration shading can spread its impact depending on string configuration and equipment operating conditions. Estimating power generation without sufficient on-site verification or a three-dimensional understanding of the terrain can result in actual generation falling below expectations.

Setting loss conditions also plays a major role in profitability assessments. In solar power plants, various losses occur, such as reductions due to panel temperature, soiling, wiring losses, conversion losses, equipment downtime, output curtailment, snow accumulation, and long-term degradation. If these are set optimistically in generation forecasts, apparent profitability will rise, but discrepancies with actual performance are likely to occur. Conversely, if they are set conservatively based on site conditions, the safety of investment decisions increases.

When evaluating an existing power plant, past generation performance is important. However, simply looking at annual generation figures is not sufficient. You need to check whether the year had favorable solar irradiance conditions, whether there were any equipment stoppages, whether output curtailment occurred, whether there are missing measurement data, and what the cleaning and vegetation management status was. Even if past performance looks good, it may be that only certain years had favorable conditions. Conversely, if performance looks poor, the cause may be temporary equipment failures or management shortcomings, meaning there may be room for improvement.

When assessing profitability, it is important to look not only at the electricity selling price and contract terms but also at the cash flow over the entire operating period. Because power output declines slightly year by year, you need to factor in long-term degradation, not just assumptions for the first year. You must also consider the timing when equipment replacement or major repairs will be required. Even projects with a low price may have low power output and high repair risk, which can result in low actual investment efficiency.

When evaluating the price of a solar power plant, it is essential to verify the basis for the generation forecast. Confirm which meteorological data were used, how shading and terrain were assessed, whether the loss assumptions are reasonable, whether output curtailment has been taken into account, and how equipment degradation is projected. Price is a figure on the expenditure side, while generation is the foundation of revenue. You cannot determine the true value of the plant without examining both.

Criterion 6: Maintenance and Future Measures After Commencement of Operation

The sixth criterion is operation and maintenance after commissioning and future measures. A solar power plant is not finished once it has been built and connected to the grid. To continue generating power reliably over the long term, inspections, weed control, cleaning, emergency response, equipment replacement, monitoring, reporting, insurance, and regulatory compliance are required. It is important to evaluate not only the initial cost but also the management burden that will arise during the operating period.

The most fundamental aspect of maintenance and management is regular inspections. These check for panel damage, looseness of mounting racks, cable damage, heating at terminals, grounding condition, the operation of the power conditioner, and the communication status of monitoring devices. If inspection frequency or scope is insufficient, detection of abnormalities may be delayed, which can lead to power generation losses and equipment damage. Especially at large power plants, relying solely on visual inspections by personnel takes time to ascertain conditions, so it is important to prepare efficient inspection methods.

Weed control and vegetation management also affect price evaluation. If weeds grow tall, they can cast shadows on panels and reduce power generation. They can also make inspection access difficult and increase the risk of pest or wildlife intrusion and fire. Methods such as weed-suppressing fabric, crushed stone, mowing, herbicide spraying, or using sheep change the balance between upfront costs and maintenance costs. Whether the site is designed for ease of management during development greatly alters the burden after operations begin.

Don’t overlook equipment replacement. Solar panels are equipment intended for long-term use, but electrical equipment, monitoring devices, communications equipment, switchgear, power conditioners, and the like may need to be replaced or repaired during the operating period. Even if the purchase or construction price is low, conditions such as difficulty sourcing replacement parts in the future, weak maintenance arrangements, or slow response to failures can become long-term risks.

Monitoring systems also affect the value of a power plant. If declines in power generation or equipment stoppages can be detected early, losses can be limited. When remote monitoring is not in place, it can take time to notice abnormalities, leading to missed opportunities to sell electricity. In addition, organizing generation data, weather data, inspection records, and repair histories is useful not only for operational improvements but also for explaining the situation to financial institutions, investors, buyers, and internal stakeholders.

Compliance with laws and regulations is also important for long-term operation. Power plants involve various management obligations such as safety, signage, fencing, inspections, reporting, disposal, and community relations. Because regulations and operational rules may change, a management framework that retains capacity to respond in the future—not just the conditions at the start of operation—is necessary. When valuing a power plant, it is desirable to confirm the scope of the maintenance and management contract, the conditions for emergency response, the contents of reports, the speed of on-site response, and the handling of spare parts.

Maintenance and management after commissioning are aspects that are hard to see in short-term price comparisons. However, a power plant’s revenues accumulate over the long term, so the quality of maintenance and management determines profitability. Even if initial costs are reduced, designs that are difficult to manage or operations that leave no records can diminish long-term asset value. When evaluating the price of a solar power plant, you must consider not only the construction cost but also how stably it can be managed after commissioning.

Considerations Practitioners Should Review When Comparing Prices

When comparing prices of solar power plants, the first thing practitioners should do is align the comparison conditions. Simply having the same installed capacity, the same land area, and similar power sale terms does not make for a valid comparison. If you do not take into account site development scope, grid connection conditions, equipment specifications, construction quality, power generation forecasts, operation and maintenance, and future replacement risks, you may misinterpret what the price actually means.

For example, if a project looks cheap because of favorable land conditions or a rational design, it can be considered an attractive opportunity. However, if it appears inexpensive because necessary construction has been excluded from the estimate, power generation forecasts are overly optimistic, maintenance arrangements are weak, or future equipment replacements are not being accounted for, caution is required. If you make a judgment without breaking down the reasons for the low price, unexpected costs or generation losses may occur after operations begin.

On the other hand, there are reasons why a project may appear expensive. If ground surveys and drainage plans are conducted thoroughly, the mounting structures are specified with durability in mind, grid-connection equipment and monitoring systems are adequately included, and the preparation of as-built documents and inspection records is taken into account, the initial costs may look high but can lead to stable operation in the long term. What’s important is not to simply judge whether something is expensive or cheap, but to check what that price actually includes.

In internal briefings, simply explaining the price difference as a "difference in equipment costs" is insufficient. Organizing the differences as site preparation costs due to land conditions, electrical work costs due to grid interconnection conditions, durability differences due to specification choices, profitability differences due to power generation forecasts, and long-term risk differences due to maintenance and management arrangements makes it easier for decision-makers to understand. Especially for investment decisions, you need to explain not only the initial cost but also estimated power generation, downtime risk, repair costs, management burden, and the asset value at the time of sale.

When checking estimates, also pay attention to excluded items. On an estimate, the items that are not included can be more important than those that are included. If disposal of excavated soil, additional ground improvement measures, grid-side construction charges, application fees, communication costs, monitoring setup, initial maintenance costs, spare parts, disaster recovery, or neighbor coordination are treated separately, the total project cost may increase later. When comparing prices, it is important to identify the excluded items and, if necessary, add rough estimates before making a decision.

Also, it is important to accurately understand the current condition of the power plant. Drawings and estimates alone may not fully reveal the site's elevation differences, drainage flow, shading, the condition of access routes, the status of mounting structure installation, cable routing, or the surrounding environment. By combining on-site inspections, surveying, photographic records, three-dimensional data, and power generation data, you can more accurately assess the reasonableness of the price.

The price of a solar power plant is information that requires interpreting the underlying conditions, not just reading numbers. Practitioners should not simply compare the amounts shown in estimates or sales documents; they are expected to verify the design, construction, operation, and risks behind those figures. The ability to judge price is not the ability to seek out the cheapest option, but the ability to reduce future uncertainty and to organize conditions into explainable terms.

Summary: Transparency of conditions is more important than low price

The price of a solar power plant varies greatly depending on six criteria: land conditions, power generation equipment specifications, grid interconnection, scope of construction, power generation forecasts, and operation and maintenance. Comparing only by installed capacity cannot correctly determine why some projects appear cheap and others expensive. What is important is to make the price breakdown and assumptions transparent and to evaluate them including long-term profitability and risks.

Poor land conditions will increase costs for site development and drainage. Lowering equipment specifications may reduce initial costs, but could affect durability and maintainability. If grid interconnection requirements are strict, construction burdens beyond the power generation equipment will increase. If the scope of construction is ambiguous, additional costs will arise later. If power generation forecasts are overly optimistic, the assumptions underpinning investment decisions will be undermined. If maintenance is inadequate, it can lead to long-term generation losses and increased repair risk.

What project personnel should aim for is not selecting the cheapest power plant, but judging whether a price is reasonable for the given conditions. To do that, they must separately review drawings, estimates, power generation forecasts, site conditions, and maintenance requirements, and be able to explain the assumptions for each internally. In particular, site-derived conditions such as land elevation differences, the volume of earthworks, shading, drainage, equipment layout, and inspection/maintenance access routes are easily overlooked from documents alone, so it is important to grasp them accurately at an early stage.

In valuing a solar power plant, accurately measuring the site, recording its condition, and creating an environment where stakeholders can make decisions based on the same information is effective. By utilizing smartphone-mounted GNSS high-precision positioning devices such as LRTK, it becomes easier to clearly preserve land conditions, as-built status, inspection points, and construction records based on location information and survey data obtained on site. If you want to judge the reasonableness of a price based on field data rather than intuition, such high-precision on-site data-capture mechanisms are an effective option at each stage of a solar power plant’s planning, construction, and maintenance.