Frequently asked questions

Questions and Answers about Photovoltaic Systems and Energy Storage Batteries

What factors affect the efficiency and annual energy production of a photovoltaic power plant?

The efficiency and annual energy production of a photovoltaic power plant depend on a combination of technical, climatic, and design-related factors.

The main factors include:

Geographic location and solar irradiation

The amount of solar radiation (kWh/m²/year) is a key indicator. For example, Southern Bulgaria achieves up to 20% higher energy production compared to Northern Bulgaria.

Orientation and tilt of the modules

The ideal orientation for maximum energy production is south-facing (180°).

The optimal tilt angle for fixed mounting systems is between 25° and 35°, depending on geographic latitude. Even a deviation of 10° can reduce energy yield by 2–4%.

Temperature and ventilation

Each photovoltaic module has a temperature coefficient (typically –0.35%/°C). During high summer temperatures, module efficiency decreases; therefore, natural ventilation and sufficient air gaps between the panels and the roof are essential.

Electrical losses and inverter type

Losses occur in both DC and AC circuits (typically 2–4%).

The quality of the inverter and its MPPT (Maximum Power Point Tracking) algorithms determine how efficiently the energy generated by the panels is converted.

Incorrect sizing of the DC/AC ratio (typically 1.1–1.3) can lead to power limitations, known as clipping losses.

Shading and soiling

Even partial shading from trees, chimneys, or antennas can cause energy losses of up to 20%. Regular cleaning of the panels can increase annual energy yield by 3–5%.

Monitoring and maintenance

Systems equipped with online monitoring and energy management allow early detection of issues, improving actual system performance by up to 5–7% annually compared to systems without monitoring.

Conclusion: Actual energy production depends not only on the installed capacity of the panels but also on the quality of system design, installation, and operation. Professional engineering can improve plant performance by up to 10–15% compared to standard installations.

What is the optimal size of a photovoltaic system in relation to actual energy consumption and grid capacity?

The optimal size of a photovoltaic system is determined by balancing the daily energy consumption profile, grid constraints, and investment objectives.

Analysis of actual energy consumption

The first step is analyzing hourly and seasonal consumption data from the electricity meter or SCADA system. The goal is to design a system that covers the maximum possible share of self-consumption, without generating a significant surplus that would be exported to the grid at a low price.

Grid connection limitations

Distribution system operators (DSOs) such as EVN, CEZ, and Energo-Pro impose limits on:

  • Maximum installed capacity relative to the contracted power

  • Phase balancing (for single-phase systems, typically up to 8–10 kW)

  • Permitted reverse power flow (export limits)

For this reason, on-grid systems with software-based export limitation (zero export) are often selected.

Optimization through battery storage

Adding a battery allows for a higher installed PV capacity, as excess energy is stored instead of being fed into the grid. This can increase self-consumption efficiency to 80–90%, especially for facilities with evening or nighttime demand.

Economic balance

In commercial and industrial systems, the optimal installed capacity is usually the one that keeps the return on investment (ROI) below 6–7 years. Oversized systems often lead to excess generation and longer payback periods.

Engineering rule of thumb

For facilities with stable daytime consumption:

PV system capacity ≈ 70–90% of the average daily energy consumption

When a battery is added, the installed PV capacity can exceed 100%, as surplus energy is stored rather than exported.

Conclusion: The optimal system size is not simply “matching kilowatts to your electricity bill,” but the result of a detailed energy analysis, grid parameters, and economic efficiency. Professional system sizing ensures a shorter payback period and higher investment performance.

How can I determine whether my roof is suitable for a photovoltaic system?

One photovoltaic panel has an area of approximately 2.60 m². However, the required roof space depends on whether the roof is pitched or flat, as well as on its orientation.

Below is an example of the roof area required for the following systems:

5 kW system (approximately 9 panels – 550 W each):

  • Pitched roof – depending on the roof slope and layout, the required area may vary; approximately 40 m² of rectangular space is needed

  • Flat roof (panels mounted at a 20° tilt) – approximately 60 m²

30 kW system (54 panels):

  • Pitched roof – approximately 165 m²

  • Flat roof (panels mounted at a 20° tilt) – approximately 220 m²

What is the warranty period for photovoltaic panels?

Jinko Solar

Product Warranty:

  • Standard: 12 years

  • Extended: up to 15 or 25 years (for Tiger Pro and Tiger Neo series, depending on the model and market)

Performance Warranty:

Tiger N-Type / Neo

  • Warranty period: 30 years

  • Degradation: ≤1% in the first year, then ≤0.4% per year

  • Guaranteed remaining power: ≥87.4% in year 30

Tiger P-Type / Cheetah

  • Warranty period: 25 years

  • Degradation: 2.5–3% in the first year, then 0.5–0.7% per year

  • Guaranteed remaining power: approximately 80.2–83.1% in year 25

What are the advantages of adding a battery storage system to an existing photovoltaic power plant?

Integrating an energy storage system into an existing photovoltaic power plant significantly increases its autonomy and overall energy efficiency. The battery module enables the storage of surplus energy generated during daytime hours and its use during peak consumption periods or when access to the grid is limited.

This approach ensures maximum self-consumption and reduces the amount of energy exported to the grid under unfavorable feed-in tariffs. In addition, the system supports better load balancing in line with the actual daily consumption profile, optimizing the use of generated energy and extending the service life of electrical equipment.

An additional advantage is the possibility of intelligent energy management through integrated EMS (Energy Management Systems), which analyze production and consumption in real time and automatically select the most efficient energy flow. As a result, the photovoltaic plant becomes more flexible, resilient, and future-ready, capable of adapting to upcoming market and regulatory changes.

How is the optimal battery capacity determined?

A professional approach includes:

  • Analysis of the hourly consumption and generation profiles

  • Calculation of autonomy (in hours) and the level of self-consumption

  • Consideration of energy tariffs (day/night rates) and contracted power capacity

  • Assessment of seasonal variations in production and load

  • Evaluation of battery system efficiency (charge/discharge efficiency, losses, and degradation)

  • Modeling of different operating scenarios – normal, peak, and emergency modes

The goal is for the battery to be fully charged by solar energy, without leaving unused excess energy, while achieving an optimal balance between energy independence and economic efficiency.

The optimal battery capacity is also determined through an economic analysis, which calculates the payback period, expected return on investment, and savings from reduced grid consumption. Intelligent EMS (Energy Management Systems) support this process by simulating the operation of the photovoltaic and battery systems in real time, analyzing dynamic electricity prices, and automatically recommending the most efficient charging and discharging strategy.

How is energy managed between the battery, the grid, and on-site consumption?

Energy management is achieved through coordinated interaction between the inverter, the Battery Management System (BMS), and the Energy Management System (EMS).

The inverter converts energy between direct current (DC) and alternating current (AC) and defines the primary operating priorities—on-site consumption, battery charging, or export to the grid.

The BMS (Battery Management System) continuously monitors the internal condition of the battery, including cell voltage, temperature, and state of charge, ensuring safe, reliable, and efficient battery operation throughout its lifecycle.

The EMS (Energy Management System) operates at the highest control level, managing energy flows in real time. By analyzing photovoltaic generation, on-site consumption, and grid price signals, the EMS makes intelligent decisions on when to charge or discharge the battery in order to maximize system efficiency and economic performance.

Thanks to advanced EMS software, the effectiveness of the battery system can be significantly increased by maintaining an optimal balance between self-consumption, grid stability, and battery lifetime, transforming the photovoltaic system into a smart, flexible, and future-ready energy solution.

How do we choose which battery to install?

If you operate an industrial-scale photovoltaic power plant and plan to add battery storage, no changes to the existing electrical schematics or core equipment are required—nor is there any need to replace the plant’s inverters. Professional and reliable energy storage solutions can be integrated into virtually any photovoltaic plant, provided that sufficient space is available and all fire safety requirements are met.

It is recommended to select a battery system with a minimum 10-year performance warranty and to ensure it is properly controlled and scheduled. The battery operation should be coordinated in advance with your electricity trader to avoid unintended effects, such as increased imbalance costs, which could otherwise occur if charging and discharging are not aligned with market schedules.

Frequently asked questions

Energy Efficiency and Energy Management

What is an Energy Management System (EMS)?

An Energy Management System (EMS) enables real-time monitoring, analysis, and control of all energy sources. It uses optimization algorithms to manage the operation of photovoltaic plants, battery storage systems, and energy consumers based on load profiles, electricity market prices, and imbalance energy costs.

EMS solutions support informed decision-making, increase overall efficiency, and allow more precise control over energy generation, storage, and consumption.

How Does an EMS Support Energy Consumption Optimization?

An Energy Management System (EMS) collects real-time data on energy generation, storage, and consumption – from photovoltaic systems, battery storage units, and grid connections.

Using intelligent algorithms, the system analyzes load profiles, energy market price signals, and available energy in order to:

  • Prioritize self-consumption and maximize the use of self-generated energy;

  • Charge the battery during periods of low electricity prices or excess solar production, and discharge it when prices are high or demand peaks;

  • Avoid peak loads through automated load control or by shifting active consumers to more cost-efficient time periods;

  • Provide visibility and control through real-time monitoring, reporting, and alerts that identify where energy losses occur and how performance can be optimized.

As a result, an EMS not only helps reduce electricity costs, but also improves overall system efficiency, enhances sustainability, and enables greater flexibility in responding to market and regulatory conditions.

Can I Monitor Energy Production, Consumption, and Battery Charge in Real Time?

Yes. Modern Energy Management Systems (EMS) provide full real-time visualization of all key energy flows – including photovoltaic generation, current consumption, battery charging and discharging, as well as energy exchange with the grid.

The data is presented through interactive charts and reports, accessible via a web platform or mobile application.

This allows users to track system performance, identify inefficiencies, and make informed decisions to optimize energy consumption and reduce costs.

How Can an EMS Help Reduce Electricity Costs?

An Energy Management System (EMS) analyzes energy generation, consumption, and electricity prices in real time to optimize how energy is used.

Through intelligent algorithms, an EMS can:

  • Use generated energy during periods of highest electricity prices;

  • Charge batteries when electricity prices are lower;

  • Minimize imbalance costs for grid-connected sites.

In this way, the system supports lower energy expenses, more efficient use of resources, and improved return on investment.

Is the Management System Compatible with Existing Photovoltaic Installations?

Yes. Modern EMS platforms are designed to be compatible with various types of inverters, battery systems, and metering devices.

This means the system can be integrated into existing photovoltaic installations without requiring major modifications to the current infrastructure.

Once integrated, the EMS provides monitoring and control of energy flows, improving overall efficiency and enhancing return on investment.

What Types of Analyses and Reports Does the Management Software Provide?

The Energy Management Software delivers detailed analyses and reports, ensuring full transparency over energy generation, consumption, and storage. Users can monitor real-time parameters such as solar irradiation, temperature, active and reactive power, inverter status, and CO₂ emissions.

The system visualizes data through customizable charts and dashboards, allows report exports, and enables the configuration of key performance indicators (KPIs). Thanks to its integration with energy exchanges, it also supports the analysis of revenues, savings, and overall operational efficiency.

You can learn more about the capabilities of our energy management software here: Visible Energy.

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