When you start exploring solar electricity, one of the first decisions is what kind of system you need. The three broad categories are off-grid (standalone), grid-connected, and hybrid systems that combine solar panels with battery storage. Each type uses a different mix of components and has different rules for installation and safety. Understanding how they differ helps you plan a project that matches your goals, whether that is powering a remote cabin, lowering a utility bill, or keeping the lights on during a blackout.

Quick overview: Off-grid systems operate independently, grid-connected systems send excess power to the utility, and hybrid systems add batteries for backup while staying linked to the grid.

Standalone (Off-Grid) Systems

A standalone photovoltaic system is not connected to the utility grid at all. According to the Hong Kong Electrical and Mechanical Services Department (EMSD), the balance-of-system components for a standalone setup include charge controllers and storage batteries, along with combiner boxes, wiring, switchgear, fuses, surge arrestors and earth-fault protection. The solar panels generate DC electricity, and because sunlight is not constant, batteries store energy for use at night or on cloudy days.

The EMSD explains that a charge controller regulates the current flowing from the solar array to the batteries. When the battery is full, the controller disconnects it from the array to prevent overcharging. Some charge controllers use maximum power point (MPP) tracking, which includes a DC-to-DC converter so the array can operate at the voltage that delivers the most power under the current sunlight conditions. For off-grid systems that need to run standard household appliances, a standalone inverter converts the DC output from the batteries into AC electricity. The EMSD notes that conversion efficiencies of inverters generally range from 85% to 95%, and that factors like harmonic content, voltage and frequency stability, and protection features should be considered when choosing an inverter.

Deep-cycle lead-acid batteries are the most common type for standalone photovoltaic systems, the EMSD states, because they are designed to be charged and discharged frequently and can handle deep discharges. The lifespan of these batteries varies from 3 to 8 years. Battery capacity is usually expressed in ampere-hours (Ah). As an example, a battery rated at 50 Ah could deliver 1 ampere for 50 hours or 2 amperes for 25 hours. To convert to kilowatt-hours, multiply the Ah rating by the voltage and divide by 1,000. When sizing a battery bank, an important factor is “days of autonomy,” the number of days the batteries can support the loads without being recharged during overcast weather. As a simple example, a cabin using about 1 kWh per day with two days of autonomy would need at least 2 kWh of usable storage.

Standalone systems are often used in locations where running a utility line is impractical. For more on the components that make up these systems, see our charge controllers and batteries guides.

Grid-Connected Systems

Most rooftop solar installations are grid-connected. The U.S. Department of Energy’s Homeowner’s Guide to Going Solar describes net metering as an arrangement where system owners are compensated for any solar power generation exported to the electricity grid. The name originally came from the meter running backwards when power was exported, but the guide notes that today it is rarely that simple. Whether a system qualifies for net metering payments depends on state and utility policies.

The Pennsylvania Public Utility Commission’s solar electricity system basics fact sheet explains that a residential solar system generates DC electricity that must be converted to AC before it can be used at home. This conversion is done by an inverter. The fact sheet lists other balance-of-system equipment that may be present, such as ground-fault protection, overcurrent protection, surge protection, and disconnect devices. Batteries are described as optional and can be configured for backup during power outages.

The DOE’s inverter basics page states that a grid-tie inverter converts DC to AC by switching the direction of the DC input back and forth very rapidly, producing a sine wave that can be injected into the power grid. In a typical household solar system, the inverter may also monitor the system and provide a communication portal. The page explains that standard small inverters are designed to remain on during minor voltage or frequency disruptions and will disconnect themselves if a disruption is large or prolonged. Grid-following inverters need an outside signal from the grid to produce the correct sine wave, while more advanced grid-forming inverters can generate that signal themselves, potentially allowing a network of solar panels to form a stable grid without turbine-based generation.

The DOE adds that only systems designed for it, such as solar-plus-battery systems with advanced inverters, can operate without grid support during an outage, so ask an installer what your design will do when the grid goes down. For a deeper look at how these systems are planned, visit our system design page.

Backup Power with Battery Storage

Adding batteries to a solar system can keep essential loads running when the grid fails, but only if the system is designed for backup. The New York State Energy Research and Development Authority (NYSERDA) fact sheet on energy storage states that a battery storage system looks like a box mounted on a wall or outside the home. During everyday operation, the home remains connected to the grid, but if there is a power outage, the backup storage system will continue to function. NYSERDA notes that it will not power the entire home; critical functions like heat, refrigeration, and lighting will still operate without a backup generator.

The DOE inverter basics page explains that solar-plus-battery storage systems rely on advanced inverters to operate without any support from the grid in case of outages, if they are designed to do so. This means that not every battery-equipped system automatically provides backup; the inverter and system controls must be configured to island the home from the grid safely. The same page describes how inverters can provide grid services such as frequency response and reactive power, and that having a controllable power source like a battery enables these capabilities.

NYSERDA also highlights that energy storage systems communicate with the electric utility through advanced software to charge and discharge when it is most advantageous, helping to reduce energy costs. The fact sheet encourages homeowners to pair solar and storage to increase resiliency; incentives change, so check current official sources.

Hybrid Systems: Solar Plus Storage

The term “hybrid” generally refers to a system that combines solar panels, battery storage, and a grid connection. The DOE inverter page notes that solar-plus, battery storage systems can operate without grid support during outages if they are designed for it. In normal conditions, these systems can send excess solar energy to the grid or store it for later use. The inverter manages the flow between the panels, the battery, the home loads, and the grid.

Because hybrid systems interact with the grid and contain batteries, they require careful planning and professional installation. The DOE Homeowner’s Guide recommends working with a qualified professional who holds a certification from the North American Board of Certified Energy Practitioners (NABCEP). It also advises consumers to understand financing options and to check for state and local incentives using the DSIRE database.

Safety and Professional Requirements

Connecting any solar system to home wiring or the utility grid is not a DIY task. The Electrical Safety Foundation International (ESFI) warns that portable generators should never be connected directly to household wiring without first installing a transfer switch, because this can cause backfeeding that could electrocute utility workers making repairs. The same principle applies to solar inverters and battery systems: they must be installed with proper isolation and approval from the local utility.

The DOE Homeowner’s Guide states that the best way to install solar is through a qualified professional, and that the industry-standard certification is awarded through NABCEP. The Pennsylvania PUC fact sheet lists disconnect devices and other protective equipment as part of a residential solar system, underscoring that these are not optional add-ons. Permits and utility interconnection agreements are required for grid-tied systems. Even for a standalone off-grid system that is not connected to a building’s main electrical panel, the EMSD notes that earth-fault protection, surge arrestors, and properly rated switchgear and fuses are part of the balance of system. For any project that touches a home’s wiring, a licensed electrician must handle the work. Our electrical safety guide covers these topics in more detail.

Comparing System Types at a Glance

The table below summarizes the key components and professional requirements for each system type.

System Type Key Components When a Licensed Electrician Is Required
Off-grid (standalone) Solar panels, charge controller, battery bank, standalone inverter, balance-of-system protection devices Whenever the system connects to a building’s fixed wiring; small portable setups may be assembled by a knowledgeable DIYer, but all fixed installations need a professional
Grid-connected (grid-tie) Solar panels, grid-tie inverter, disconnect switches, utility meter Always; connection to the grid requires permits, utility approval, and a licensed electrician
Hybrid (solar plus storage) Solar panels, advanced inverter, battery bank, transfer switch or islanding capability, grid connection Always; the system must be designed to isolate from the grid during outages and comply with all electrical and utility codes

For a broader introduction to how all the parts work together, read our DIY Solar System Basics article. The DIY Solar Fundamentals section also covers energy production and planning topics that apply to every system type.

Frequently asked questions

Can I add batteries to an existing grid-tied solar system later?

It may be possible, but it is not a plug-and-play upgrade. The DOE inverter page explains that solar-plus-storage systems rely on advanced inverters to operate without grid support during outages, if they are designed to do so. Any change is a job for a licensed electrician, with utility approval.

Will a grid-tied solar system work during a power outage?

Not unless it is designed to. The DOE explains that standard small inverters disconnect themselves from the grid and shut down when a disruption is large or long, and that operating without grid support during outages requires a solar-plus-storage system designed to do so. Ask your installer how your specific system behaves.

What is the difference between a charge controller and an inverter?

A charge controller manages the flow of electricity from the solar panels to the batteries, preventing overcharging. The EMSD states that it is used in standalone photovoltaic systems. An inverter converts DC electricity from the panels or batteries into AC electricity for household use. Grid-tie inverters also synchronize with the utility grid, as the DOE inverter page explains.

For more on system types, visit our System Types category page.

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