How to Configure Off-Grid Settings in PVSyst | 7 Key Items to Check First

Table of Contents

• Key concepts to understand first for off-grid setups

• Item 1: Create an accurate load profile

• Item 2: Determine solar panel capacity from load and seasonal variations

• Item 3: Set battery capacity and days of autonomy

• Item 4: Check charge/discharge conditions and the battery's operating range

• Item 5: Verify the control strategy and the handling of surplus power

• Item 6: Read unmet energy and loss diagrams

• Item 7: Reflect site conditions and construction assumptions in the simulation

• Common pitfalls in off-grid design

• How to share PVSyst results in practice

• Summary

Key Concepts to Understand First in an Off-Grid Setup

When handling off-grid systems in PVSyst, the first thing to keep in mind is that the focus of evaluation shifts from annual energy generation to the viability of power supply. In grid-connected solar power systems, it is common to check annual generation, PR, losses, monthly generation, etc., on the assumption that generated power will be exported to the grid or consumed on-site. In contrast, in off-grid systems there is no grid to accept power, so surplus power during periods of high generation cannot be fully used, and at night or during bad weather the load must be supported solely by the energy stored in batteries.

Therefore, in off-grid design, it is not a simple judgment that increasing solar panel capacity is always better. Increasing the solar panel capacity raises the available charging margin on sunny days, but generation produced after the battery is fully charged is discarded as unusable power. Increasing battery capacity increases the margin during nights and cloudy periods, but if the solar panel capacity is insufficient, the battery cannot be charged adequately in the first place. Furthermore, whether the load is daytime-biased or nighttime-biased, and whether it is constant day to day or varies seasonally, can greatly change the outcome even with the same system capacity.

In PVSyst's off‑grid settings, you primarily combine the load, PV array, battery, control settings, losses, and meteorological conditions to check whether power shortages occur. The important point here is not to try to enter perfect numbers from the start, but to first create an initial case based on realistic assumptions and adjust the design while observing the results. If power shortages are frequent, determine whether to increase PV capacity, increase battery capacity, or review the load. If surplus power is too large, consider whether the system capacity is oversized or whether the timing of the loads can be changed.

In practice, it is not uncommon to begin simulations with the load side left insufficiently defined compared with the generation-side design. In off-grid systems, even a slight change in load conditions can significantly alter the required battery capacity and the amount of energy deficit. First, organize which devices run at what times, for how many hours, and at how many W, and then take seasonal variations and the simultaneous use rate into account.

Item 1: Create the load profile correctly

The most important element in an off-grid setup is the load profile. A load profile is data that represents how the power-consuming side uses electricity over time. In PVSyst, you can configure not only the daily energy consumption but also time-of-day consumption patterns and seasonal variations. In off-grid systems, this load profile becomes the foundation of the design.

For example, even with the same 5 kWh per day load, the required battery capacity changes depending on whether consumption is higher during the daytime or at night. If the load is concentrated during the day, reliance on the battery is relatively low because the solar panels generate power during that time and it can be consumed directly. Conversely, if the load is concentrated at night, the flow becomes charging the battery during the day and discharging at night, so battery capacity and charge/discharge efficiency strongly affect the outcome.

When setting loads, first check the rated power consumption for each piece of equipment and determine the actual operating hours. Identify all loads included in the target equipment, such as lighting, communications equipment, pumps, control panels, sensors, monitoring devices, air conditioning, and cooling systems. Next, confirm whether each item runs continuously, operates only for a set period, runs only during daytime, or also runs at night. If there are devices that require a large amount of power temporarily at startup, you need to consider peak loads as well as average power consumption.

In PVSyst inputs, you can set it as a simple daily load, but in practice we recommend creating a time-of-day profile whenever possible. This is because the viability of an off-grid system cannot be judged by the annual total energy consumption alone. Whether the power generated during the day is used immediately on site or stored in batteries for later use affects the required equipment. By entering loads by time of day, you can verify battery charge/discharge behavior and energy shortfalls in a way that more closely reflects reality.

Seasonal variation is also important. For equipment where ventilation and cooling loads increase in summer, where insulation and snow-melting–related loads increase in winter, or where operating conditions change during the rainy or snowy seasons, it is necessary to assume monthly loads rather than annual averages. In particular, if a season with low solar radiation overlaps with a season of high load, the design conditions become more severe. By looking not only at the monthly average power generation but also at changes in load, you can identify periods when power shortages are likely to occur.

When creating a load profile, it is important to avoid overly optimistic settings. If measured values are not available, create multiple cases based on rated values, operating hours, and utilization, and compare a standard case with a more conservative case to make judgment easier. Rather than fixing a single value from the start, test scenarios such as a 10% increase in load, extended night-time operation, or higher consumption in winter to verify the design margin.

Item 2: Determining Solar Panel Capacity from Load and Seasonal Variations

Once you have organized the load conditions, next set the solar panel capacity. For off-grid systems, solar panel capacity is not only about increasing annual energy production but also a factor in sufficiently charging the battery and supporting the load during periods of low solar irradiance. What you need to look at here is not just the annual total generation. Check monthly generation, seasonal variations in insolation, battery charging shortfalls, and the amount of surplus power together.

When determining the capacity of a solar PV system, you first base it on the daily energy demand. For example, the larger the daily load, the greater the required generation. However, in practice you cannot use all of the generated electricity for the load. Because there are wiring losses, conversion losses, battery charge/discharge losses, temperature losses, soiling losses, and shading effects, a certain margin on the generation side is necessary. Also, because solar irradiance varies by season, if you base sizing only on the annual average, you may face shortages in months with lower generation.

In PVSyst you can set the solar module capacity, azimuth, tilt, array configuration, temperature conditions, shading conditions, and so on, and view the simulated monthly and annual energy production. In off‑grid systems, increasing the solar module capacity tends to reduce the amount of unmet energy, but it can also increase unusable excess energy. Therefore, you need to not only move shortages closer to zero, but also check whether the system has become oversized.

In practice, we first create a case with a standard solar panel capacity and check the results. If the energy shortfall is large, we compare measures such as increasing the solar panel capacity, increasing battery storage capacity, reducing the load, or changing the timing of the load. If increasing the solar panel capacity does not significantly reduce the shortfall, it may be due to a large nighttime load, insufficient battery capacity, vulnerability to prolonged periods of poor weather, or inappropriate control settings.

Setting the tilt angle is also important for off-grid systems. The angle that maximizes annual energy production is not necessarily the same as the angle that secures winter generation. For standalone power systems with a constant load year-round, prioritizing the season with lower generation rather than the annual total can bring operation closer to stability. In regions prone to winter power shortages, it is worth considering an angle that more easily captures winter solar radiation. However, increasing the tilt affects summer generation, installation conditions, wind loads, and constructability, so decisions should be made by combining simulation results with local conditions.

The same applies to the azimuth angle. Orientations close to true south are often used as the baseline, but depending on the timing of the load you may compare layouts that prioritize morning or evening generation. For example, for facilities with heavy morning loads, you may check the conditions under which morning generation ramps up. However, in off-grid systems, because a battery is interposed, the effect of azimuth varies with the load profile and battery capacity. In PVSyst, creating multiple cases and comparing them under the same load conditions makes the differences easier to understand.

Item 3: Set battery capacity and days of autonomy

In off-grid design, battery storage capacity is as important as solar panels. A storage battery is equipment used to make electricity generated during the day available at night or during bad weather. If battery storage capacity is insufficient, you may experience power shortages at night even on days when generation is sufficient. Conversely, making the battery storage capacity too large increases the amount of capacity that cannot be fully charged, making the system's use inefficient.

A commonly used concept when considering battery capacity is days of autonomy. Days of autonomy refers to an estimate of how many days’ worth of load the battery alone can support when sufficient power generation from solar is not available. For loads that cannot be stopped, such as communications equipment and monitoring systems, it is necessary to provide a certain degree of days of autonomy. On the other hand, for applications where the load can be temporarily suspended or auxiliary power sources can be used, the days-of-autonomy requirement can be set more flexibly.

When configuring a battery in PVSyst, it is important to be aware not only of the battery's nominal capacity but also of its usable capacity. Batteries have conditions such as depth of discharge, minimum state of charge, maximum state of charge, charge/discharge efficiency, temperature effects, and lifespan. Even if the nominal capacity appears large, if the actually usable range is limited, the amount of energy that can be supplied to the load will be reduced. Therefore, when assessing the required capacity, you need to take into account the usable range and losses, rather than simply multiplying the daily load by the number of days.

Increasing the battery storage capacity can reduce the amount of unmet energy in simulations. However, if the solar panel capacity is small, making the battery larger may not allow it to charge sufficiently, and the expected effect may not be achieved. In such cases, the results screen may show the battery state of charge remaining low or charging shortages continuing in certain seasons. In other words, battery capacity needs to be evaluated together with solar panel capacity.

Also, when determining battery capacity, consider not only daily averages but also consecutive periods of poor weather and seasonal variations. Even if the annual average insolation looks sufficient, several consecutive days of low generation can cause the battery to discharge deeply and lead to power shortages. It is important to check PVSyst's time-series and monthly results to understand when the battery will be most stressed.

What practitioners should be careful about is not to be biased toward the judgment that a larger storage battery automatically provides security. A storage battery is, at its core, equipment that absorbs the time difference between generation and load, and it does not completely solve long-term generation shortfalls. Design should be carried out with an overall balance, taking into account solar panel capacity, load reduction, operational control, and the presence or absence of auxiliary power sources.

Item 4: Check charging and discharging conditions and the operating range of the storage battery

After entering the battery capacity, next check the charge/discharge conditions and the operating range. In PVSyst’s off‑grid settings, the range over which the battery is charged and how far it can be discharged affects the results. If these are set inappropriately, it may look fine in the simulation but in reality you may be forcing the battery to operate beyond reasonable limits.

The first thing to look at is the concept of minimum and maximum state of charge. A battery cannot be used until it is completely empty. To avoid over-discharge, it is common to control it so that it does not fall below a certain remaining level. In addition, control near full charge and charging efficiency must also be taken into account. The narrower the usable range, the smaller the actual usable energy will be for the same nominal capacity.

Charge–discharge efficiency is also important. When electricity generated by solar panels is charged into a battery and later discharged to supply a load, losses occur in that process. The amount of usable energy ultimately differs between power supplied directly to loads during the day and power used at night after passing through a battery. Therefore, in systems with large nighttime loads, the battery’s efficiency has a greater impact on the results.

When reviewing PVSyst results, check how the battery state of charge evolves. If it drops to near the minimum state of charge almost every day, the design may have little margin. If it reaches full charge quickly on sunny days and surplus power is produced for long periods, the battery capacity or the load may be too small relative to the PV array capacity. Conversely, if it fails to approach full charge over extended periods, the PV array capacity may be insufficient or the load may be too large.

Temperature conditions are another element that is easy to overlook. Battery storage can experience changes in performance and usable capacity depending on temperature. In cold regions, inside outdoor enclosures, or in locations prone to high temperatures, the catalog conditions may differ from the actual on‑site operating conditions. There are limits to how much PVSyst can reflect these details, but at least as a conservative design approach, it is important to provide a margin that takes the local environment into account.

Charge and discharge conditions also affect battery lifetime. Simulations are meant to check the power balance, but in actual installations, operating in a way that frequently subjects the battery to deep discharges can accelerate degradation. Even if PVSyst shows only a small shortfall, if the battery is consistently used within tight limits, the operation cannot be said to have sufficient margin. In practice, you check not only how many kWh the power shortfall is, but also whether the battery’s condition remains within a healthy range.

Item 5: Confirm the control method and handling of surplus power

In off-grid systems, it is important how generated electricity is allocated between the loads and the battery, and how surplus power is handled when the battery becomes fully charged. In grid-tied systems there is the option of sending excess power to the grid, but in off-grid systems there is essentially nowhere for it to go. Therefore, surplus power is dealt with through generation curtailment or by being left as unused power.

When checking results in PVSyst, you look at the relationship between the power used by the load, the power charged into the battery, the power discharged from the battery, and the unused power. If there is a large amount of surplus power, the PV capacity may be oversized. However, the presence of surplus power is not necessarily a bad thing. To prepare for seasons with low generation or bad weather, the system may be designed to produce some surplus on sunny days.

What matters is when and to what extent surplus power occurs. Even if there is a large surplus in summer, if there is a shortfall in winter, looking only at the annual total can make it appear that generation is sufficient. In that case, simply reducing installed capacity will worsen winter shortages. Conversely, if there is a consistently large surplus throughout the year and virtually no shortfall, there may be scope to reassess the solar PV capacity and battery storage capacity.

When considering a control strategy, organizing the priority of loads is also useful in practice. Check whether all loads need to run all the time, whether there are loads that can be shut down in emergencies, and whether some loads are better operated during the daytime. In off-grid systems, trying to solve everything by equipment capacity alone tends to lead to overdesign, so it is also effective to optimize the operating times of loads. For example, shifting pumps and charging equipment that can run during the day toward daytime operation can reduce the burden on the battery.

In PVSyst, create these operational changes as a separate load‑profile case; comparing them with the standard operation makes the differences easier to understand. Even with the same solar PV capacity and the same battery capacity, simply changing the timing of the load can alter the amount of unmet energy and the depth of discharge of the battery. This is a very important consideration in off‑grid design.

Even when surplus power might be used for other purposes, first prioritize confirming that the primary load can be supplied stably. If you set additional loads assuming surplus, you need to clarify the priority-control strategy so that those additional loads do not negatively affect the original critical loads. In simulations, it is easier to make decisions if you separate and compare a case with only the primary load, a case including additional loads, and a case under severe weather conditions.

Item 6: Reading the Energy Shortfall and Loss Diagram

One of the most important indicators in PVSyst's off-grid results is the energy shortfall. The energy shortfall is the amount of energy that the load required but could not be supplied by the PV array and the battery. In off-grid systems, this value directly indicates operational risk. Even if the annual generation appears sufficient, if an energy shortfall occurs, the load is not being met at that time.

When reviewing energy shortfalls, check not only the annual total but also monthly, daily, and time-of-day trends. Countermeasures differ depending on whether shortages are concentrated in particular months, occur at night, or follow consecutive periods of bad weather. If shortages are concentrated in winter, it is necessary to review solar PV capacity, tilt angle, and battery capacity to match winter solar irradiance. If shortages are frequent at night, reviewing battery capacity and nighttime loads is effective. If shortages also occur during the daytime, check solar PV capacity, generation losses, and load peak settings.

Loss diagrams are also important. A loss diagram makes it possible to identify where losses occur in the flow from solar irradiance to PV output, conversion, battery, and supply to loads. In off-grid systems, unused power, battery losses, conversion losses, and energy shortfalls are particularly important. A large amount of unused power indicates that generation is not being fully utilized, while a large energy shortfall indicates that supply is insufficient. Both can occur in the same system; for example, there may be large surpluses in summer but shortages in winter.

When reading PVSyst results, don't be distracted only by PR and annual energy production. For off-grid systems, the important metrics are the proportion of generated electricity that could be used by the load, the amount of energy that passed through the battery, the energy that was unused and dumped, and the energy shortfall relative to the load. In particular, during design reviews you need to be able to explain not only whether shortages are zero but also under what conditions shortages occur.

Even if the energy shortfall is small, it becomes problematic if it occurs during a period that would lead to the shutdown of critical loads. For example, for loads that must run continuously—such as monitoring devices and communications equipment—even a brief shortfall poses operational risks. Conversely, for auxiliary loads whose shutdown causes little problem, it may be possible to respond by changing priorities through control. When interpreting simulation results, assess not only the magnitude of the energy shortfall but also its operational importance.

Also, be cautious if the results look too good. If the energy shortfall is zero and the surplus is small—an ideal outcome—possible causes include load settings that are too low, optimistic loss assumptions, neglecting shading or soiling, or meteorological data that do not reflect the site's harsh conditions. In practice, it is important to create a conservative (safety-side) case in addition to the standard case and to perform sensitivity checks assuming increased loads and reduced solar irradiance.

Item 7: Reflect site conditions and construction assumptions in the simulation

PVSyst's off-grid settings cannot be completed using only the on-screen numbers. In the actual field, the installation site's terrain, shading, orientation, tilt, racking height, wiring distance, maintenance conditions, weather conditions, snowfall, salt damage, dust, surrounding structures, and so on affect power generation and losses. To improve simulation accuracy, site conditions need to be reflected in the design assumptions as much as possible.

First, you should check the solar irradiation conditions at the installation site. If there are mountains, buildings, trees, transmission towers, embankments, or equipment nearby, shadows can occur in the morning, evening, or during winter. In off-grid systems, generation drops due to shading are more likely to lead to insufficient battery charging, so shading must be considered more carefully than for grid-connected systems. Even short periods of shading can affect supply stability if they coincide with seasons of low solar irradiance or times of high load.

Next, verify the actual installation conditions for azimuth and tilt angles. Even if the design uses ideal orientations and angles, the actual layout may differ due to site topography and constraints from structures. On sloped terrain, roofs, narrow sites, or temporary mounting structures, the conditions shown on drawings can diverge from those in the field. In PVSyst, enter the conditions that can actually be installed and compare them with the ideal conditions to make it easier to explain the expected energy yield.

Wiring distance and equipment placement must not be overlooked. In off-grid installations, the positional relationships among the solar panels, control panel, batteries, and loads affect wiring losses and installability. If a load is located far away, wiring losses can increase and consideration of voltage drop becomes necessary. In PVSyst, these factors are reflected as loss conditions, and wiring routes and equipment placement are reviewed as needed.

Soiling and maintenance conditions are also important. Sand dust, bird damage, falling leaves, salt spray along the coast, dust around agricultural land, and snowfall are factors that reduce power generation. At remote sites with low maintenance frequency, overly optimistic estimates of soiling losses can lead to actual power generation shortfalls. The harder it is to reach a site for cleaning and inspection, the more carefully loss settings and equipment margins should be considered.

Furthermore, the accuracy of on-site positional and topographic information also affects the quality of the design. If shadows, panel layout, racking positions, cable routes, and equipment installation locations are not accurately determined in the field, the conditions used in simulations will diverge from the actual construction. In particular, in mountainous areas, reclaimed land, slopes, or sites with many existing structures, it is important not to rely solely on drawings but to concretize installation conditions by utilizing on-site positioning, photographic records, and point cloud data.

Common Pitfalls in Off-Grid Design

A common mistake when configuring off-grid settings in PVSyst is judging feasibility solely by annual energy production. Even if annual generation exceeds the load energy, shortages can occur if the times of generation and consumption do not align. In particular, when nighttime loads are large, relying only on generation figures without checking battery capacity and charge/discharge conditions can lead to power shortages in actual operation.

Another common issue is oversimplifying load settings. If you only input daily energy consumption and do not account for time-of-day or seasonal variations, the battery’s behavior will diverge from reality. Designing without clarifying peak loads, nighttime usage, seasonal increases, startup power, and always-on loads reduces the reliability of the simulation results.

Care must be taken when interpreting battery storage capacity. If you look only at the nominal capacity and judge it to be sufficient, you may overestimate the capacity actually available. You need to consider the minimum charge level, depth of discharge, charge/discharge efficiency, and temperature effects. Also, even if you increase the battery size, it will not charge if the solar panel capacity is insufficient. It is important to evaluate solar panels and batteries as a set rather than optimizing them separately.

There are pitfalls in interpreting surplus electricity. Simply reducing the number of solar panels because there is a large surplus can increase shortages in seasons with less sunlight. Conversely, oversizing the solar panels to avoid shortages can result in generation that cannot be fully used for much of the year. Surpluses and shortages need to be examined not by annual totals but by season, by month, and by time of day.

Neglecting shadows and dirt can also cause failure. Off-grid systems can experience insufficient battery charging from even a small drop in power generation. In particular, when winter’s low solar altitude, surrounding trees, mountain shade, snow accumulation, dust, or environments where regular cleaning is not possible are involved, it is important to estimate losses conservatively. Even if a design works on paper, it is not uncommon for shortages to appear once site conditions are reflected.

Finally, attention must also be paid to insufficient explanation of the results. Even if a designer runs simulations in PVSyst, if they cannot explain to internal stakeholders and clients under which conditions there is no shortfall and under which conditions there are risks, it becomes difficult to use the results for design decision-making. In practice, it is important to clearly present the rationale for the design by comparing not only the standard case but also scenarios such as increased load, reduced solar irradiance, and changes in battery capacity.

How to Share PVSyst Results in Professional Practice

After performing an off-grid simulation in PVSyst, it is important not to submit the results as-is but to organize them in a way that is easy for practitioners and decision-makers to understand. In particular, for off-grid systems, the annual energy production figure alone does not convey whether the design is good. You need to explain how much of the load can be supplied, when shortages occur, how the battery behaves, and how much surplus power there is.

When sharing, first clarify the design assumptions. Summarize the target load, daily load, time-of-day loads, solar panel capacity, battery capacity, azimuth, tilt angle, loss conditions, weather conditions, and the treatment of shading. If this remains ambiguous, the resulting numbers can take on a life of their own. In particular, because load conditions tend to be changed later, it is important to clearly state which loads were included in the simulation.

Next, we will check the resulting energy shortfall, unused power, the battery’s state of charge, and the monthly supply status. Even if the shortfall is close to zero, explain how much margin remains. If shortages remain, indicate in which months and under what conditions they occur, and compare countermeasure options such as increasing solar PV capacity, increasing battery capacity, reducing load, and changing operating hours.

Comparing cases is also effective. Lining up the standard case, the case with additional solar panels, the case with additional battery storage, the load-reduction case, and the case with stricter weather conditions makes it easier for stakeholders to make decisions. Rather than simply choosing the largest equipment, you can assess the balance by taking into account the required reliability, operational risks, construction conditions, and maintenance conditions.

Also, including information from the on-site survey with the results increases their persuasiveness. By organizing the planned installation site’s orientation, surrounding shading, topography, equipment layout, wiring routes, and maintenance access flow, and correlating these with PVSyst input conditions, you can demonstrate that the simulation is based on actual site conditions. Because off-grid systems are particularly susceptible to site conditions, it is important to explain not only desk-based generation estimates but also to combine them with on-site information.

Summary

In PVSyst’s off‑grid settings, rather than looking only at annual energy production or PR as in grid‑connected systems, you need to focus on whether the system can reliably supply power to the load. The items to check first are the load profile, PV array capacity, battery capacity, charge/discharge conditions, control strategy, surplus energy, energy shortfall, and site conditions. By checking these one by one, you can determine whether the system will function as a practical standalone power source, not merely as a calculation of generation.

What is particularly important is to correctly set the timing of the loads and seasonal variations. Even with the same daily load, the required battery capacity changes depending on whether the load is used during the day or at night. Also, if loads increase during periods of reduced generation, such as winter or the rainy season, you cannot judge based on the annual average alone. In PVSyst, it is important to create multiple cases and, by comparing standard conditions with more severe conditions, explore the balance between system capacity and operating conditions.

Solar panel capacity and battery capacity cannot be optimized by increasing only one of them. If the solar panels are too small, the battery cannot be charged, and if the battery is too small, it cannot support power at night or during bad weather. Furthermore, whether there is a large surplus of power or a remaining shortfall, it is necessary to identify when and why these occur. On the results screen, check not only the annual power generation but also the battery’s state of charge, the amount of unmet demand, unused power, and loss diagrams to understand weaknesses in the design.

And to improve simulation accuracy, understanding the site conditions is essential. Information such as where the panels can be placed, whether there are nearby objects that cast shadows, whether orientation and tilt can be secured as shown on the drawings, how long the wiring distances are, and whether the location is easy to maintain directly affects the reliability of off‑grid designs. If the site's location, topography, and equipment layout can be accurately understood, the input conditions for PVSyst will be closer to reality.

During the site survey phase, utilizing the LRTK, a GNSS high-precision positioning device that can be attached to an iPhone, makes it easier to record candidate installation locations, surrounding structures, shading factors, equipment layouts, and wiring routes with high-precision positional data. When considering an off-grid system in PVSyst, combining accurate positional information and records obtained on site with desktop simulations, rather than relying on desk-based simulation alone, reduces discrepancies in design conditions and enables more concrete pre-construction decisions.