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A Practical Guide for B2B Solar Projects, Electrical Distributors and EPC Contractors
Solar photovoltaic (PV) systems can be designed in different ways depending on how electricity is generated, stored and supplied to electrical loads. For distributors, importers, EPC contractors, system integrators and project buyers, understanding the differences between On-Grid, Off-Grid and Hybrid solar systems is an important first step when evaluating a PV electrical solution.
Although all three configurations use solar PV generation, their relationship with the utility grid and their use of energy storage are different. This guide explains the basic operating principles of each configuration and highlights the electrical protection and sourcing considerations that matter in B2B solar projects.
Photovoltaic (PV) technology converts sunlight into electrical energy. PV modules generate direct current (DC), while most building electrical loads and utility grids use alternating current (AC). An inverter is therefore a key component of a PV system because it converts DC electricity from PV modules into AC electricity for use by loads or for grid connection. A complete PV installation also includes other balance-of-system components, depending on the project design.
A grid-connected or On-Grid PV system is designed to operate in connection with the utility grid. A simplified power flow is:
Solar Panels → Inverter → AC Loads / Meter → Utility Grid
During daylight hours, PV modules generate DC electricity and the inverter converts it into AC electricity. The generated electricity can supply connected loads, while excess generation can be exported to the grid where the applicable utility rules and interconnection arrangements permit it. Modern distributed PV systems can therefore result in two-way electricity flow between the customer installation and the grid.
An important technical point is that a standard grid-connected PV system should not automatically be considered a backup power system. For safety and grid-operation reasons, conventional grid-connected solar systems generally shut down when the grid is unavailable. A properly configured inverter and energy-storage system are required for a solar-plus-storage installation to continue supplying power during an outage.
An Off-Grid or standalone PV system is designed to operate independently of the utility grid. A simplified configuration can be represented as:
Solar Panels → Power Conversion / Inverter → Battery Storage → Loads
Because solar generation varies with sunlight, energy storage is important in many standalone PV systems. Batteries can store energy generated by the PV system for use when solar generation is unavailable or insufficient, such as at night or during periods of low solar irradiation.
It is more accurate to describe an Off-Grid system as independent of the utility grid rather than saying that every Off-Grid system depends exclusively on solar energy and batteries. Some standalone systems can also incorporate other generation sources, such as backup generators, depending on project requirements.
A Hybrid solar system combines PV generation with battery storage and a utility-grid connection. A simplified architecture is:
Solar Panels → Hybrid Inverter → Loads + Battery + Utility Grid
The exact architecture depends on the inverter and system design. Batteries can be integrated through DC-coupled or AC-coupled configurations. In a DC-coupled arrangement, solar energy can charge the battery directly on the DC side; in an AC-coupled arrangement, energy passes through AC conversion before charging the battery.
A Hybrid system should not automatically be described as providing uninterrupted power. Its backup capability depends on the inverter's operating mode, battery capacity, protected-load configuration and other system requirements.
| Feature | On-Grid | Off-Grid | Hybrid |
| Utility grid connection | Yes | No | Yes |
| PV generation | Yes | Yes | Yes |
| Battery storage | Not necessarily | Typically included | Typically included |
| Grid dependence | Uses the grid when PV is insufficient | Independent of utility grid | Can use grid and stored energy |
| Backup during grid outage | Normally unavailable in standard systems | Available when properly designed | Possible when properly designed |
| Typical application | Grid-connected homes and buildings | Remote/off-grid sites | Projects requiring greater flexibility and/or backup |
The actual system architecture varies according to project requirements, inverter technology, local lectrical regulations and the intended operating mode. IEC 60364-7-712:2025 applies to electrical installations of PV systems and includes requirements related to energy storage systems and PV installations capable of island-mode operation.
A solar PV system is more than a collection of PV modules and an inverter. Depending on the architecture, the electrical installation may also include wiring, disconnects, fuses, combiner boxes, distribution equipment and other balance-of-system components.
The DC side of a PV installation requires equipment selected for the actual electrical conditions of the system. Circuit breakers and other switching or protection devices must be matched to the applicable voltage, current, installation configuration and standards.
IEC 60947-2:2024 covers low-voltage circuit breakers and includes ratings up to 1,000 V AC or 1,500 V DC within its scope.
A PV combiner box can combine multiple PV strings and form part of the DC-side balance-of-system architecture. Its configuration should be selected according to the number of strings, voltage, current and protection requirements of the project.
Surge protection is another consideration in PV electrical installations. The appropriate protection arrangement depends on the system architecture, installation characteristics, applicable standards and project risk assessment.
IEC 60364-7-712:2025 provides requirements for electrical installations of PV power supply systems, including requirements associated with PV installations and energy storage systems.
On the AC side, suitable switching and protection equipment may be required between the inverter, distribution equipment, building loads and utility connection. The exact equipment and ratings should be determined from the project electrical design and applicable local requirements.
There is no single PV configuration that is suitable for every application. For distributors, EPC contractors, system integrators and project buyers, the following questions can help define the appropriate architecture.
If reliable grid access is available, an On-Grid or Hybrid configuration may be considered. If a project is located in a remote area without practical grid access, an Off-Grid configuration may be more appropriate.
If selected loads need to remain powered during a grid outage, the system requires an inverter and energy-storage configuration capable of operating in the required backup mode. PV modules alone do not automatically provide backup power when the grid is unavailable.
Project design should consider the electrical loads, operating hours, peak demand and expected energy consumption. For commercial and industrial projects, the load profile can influence PV capacity, battery sizing, inverter selection and electrical protection requirements.
PV installations should comply with applicable national and local electrical requirements. IEC 60364-7-712:2025 is an international reference for electrical installations of PV systems, while local regulations, grid-connection rules and project-specific requirements may also apply.
For a distributor, EPC contractor or project purchaser, sourcing a solar electrical solution is different from purchasing a single PV component. A project may involve several stages of power generation, conversion, protection, storage and distribution.
PV Generation → DC Protection → DC Switching → Inverter → Battery Storage → AC Protection → Distribution → Loads / Grid
When evaluating a supplier, B2B buyers can consider the following factors:
For solar PV projects, electrical protection and switching are important parts of the overall electrical architecture. EBASEE provides low-voltage electrical products that can be considered for different PV and energy-related applications, including DC circuit breakers, DC MCCBs, DC surge protection devices, PV combiner boxes, DC distribution boxes and DC isolators.
The appropriate product should be selected according to the system voltage, current, configuration, installation requirements and applicable standards.For B2B customers, EBASEE supports sourcing requirements including OEM/ODM and customized product configurations. Distributors, EPC contractors, electrical importers, project suppliers and system integrators can contact EBASEE to discuss the electrical protection and distribution requirements of their PV projects.
The main difference between On-Grid, Off-Grid and Hybrid solar systems is how the PV system interacts with the utility grid and how energy storage is incorporated.
For B2B solar projects, however, choosing the system type is only the beginning. PV protection, switching, distribution, inverter compatibility and applicable electrical requirements all need to be considered as part of the overall system design.
