Where Does a Solar Panel’s Power Go When It’s Not Connected?

Solar panels use natural energy to charge both large and small appliances and devices. The panels draw energy from the sun and convert it into usable alternating current (AC) with the help of inverter technology. However, when the device is charged, where does the excess power go?

When a solar panel is not connected, the charge potential created from absorbing light simply saturates at some measurable voltage boundary as it is not being directed into a storage device. The amount of energy loss does depend on the panel circuit, though, and surplus energy can be utilized in several ways.

Read on to learn more about where surplus energy from a solar panel goes when it’s not connected and how this surplus energy can be used for other purposes.

How a Solar Panel Produces Power

Solar panels draw energy from the sun and convert it into power. The panels absorb sunlight with photovoltaic cells, which generate direct current (DC) and convert it into usable alternating current (AC) with the help of inverter technology.

The panels, also known as modules, contain silicon photovoltaic — electricity from light — cells that absorb sunlight and transform it into electricity rather than heat. These photovoltaic cells are made up of a film of silicon with a positive and negative charge placed under a thin piece of glass.

When the photons of the sunlight hit the silicon cells, they knock the electrons off the silicon, and the negatively charged free electrons stick to the positive side of the silicon cell. This effectively creates an electric voltage that can be collected and channeled. 

This electric voltage or direct current is then gathered by solar photovoltaic array cables that end in an electrical box, called a fused array combiner. 

Connections in the combiner box then send the direct current (DC) to an inverter that converts the direct current (DC) into alternating current (AC), which is suitable for use in the home (source).

The inverter turns the direct current electricity generated by the solar panels into 120-volt alternating current that can be used in the household to charge devices such as batteries and battery packs.

Where Does a Solar Panel’s Power Go When It’s Not Connected?

Any solar power system first converts solar energy or sunlight into direct current using the photovoltaic (PV) effect. A solar inverter then converts this power into alternating current power that can be used to run or recharge home appliances and devices.

But where does the excess power go once the device has been recharged? When a solar panel is not connected, the charge potential created from absorbing light can be stored in various battery storage systems, or it can be fed directly into the electricity grid for credits. This depends on the type of system in the solar panel.

Smart Solar Panel Systems

There are several different ways a circuit within a solar panel can be designed to use surplus power that isn’t needed.

If the solar panel is used to run appliances in the home, a Smart circuit system will turn additional devices on, including dishwashers, washing machines, or immersion heaters in hot-water storage tanks. If there is still additional power after the appliances are working, it will be sent to the main grid for electricity credits.

Net Metering for On-Grid or Grid-Tie Solar Systems

On-grid or grid-tie solar systems are connected to the public electricity grid using solar inverters or micro-inverters and feed excess power directly into the grid, offsetting power drawn from the grid. This is a common method for utilizing surplus power from a solar panel and can save users a lot of money.

Net metering requires a meter and solar inverters specifically designed to feed surplus power directly to the main grid. These devices need to be able to power down when the grid does to protect men working on the line.

Unlike hybrid systems, however, on-grid solar systems cannot function or generate electricity during a power outage due to safety reasons. The system shuts down automatically when the grid shuts down to prevent causing injury to the people repairing the network’s faults.

Hybrid Solar Systems

Hybrid solar systems and grid-tie systems generate power in the same way — only hybrid systems store energy for later use with special hybrid inverters and batteries. This surplus power can be used when the main grid goes down.

In this case, they’re called “hybrid” systems because they combine solar and energy storage, which is also connected to the electricity grid. Most hybrid solar systems with battery storage can isolate from the grid automatically, a process called islanding, and continue supplying some power during a power outage (source).

Hybrid solar systems are popular with homeowners as they allow solar energy to be stored and used in the evenings when the cost of electricity is typically at the peak rate or on cloudy days.

Standalone System

If the solar panel has a standalone system, a battery is usually attached to the panel where surplus power is sent to be stored. When the battery is full, a resistance heater and heat sink can be used to dump excess generated power.

Will Solar Panels Work During a Power Outage?

Solar panels will not be able to provide electricity during a power outage unless the system is equipped with energy storage in the form of a battery or should it be connected in an off-grid system.

If the solar panel connects directly to the main grid and the grid goes down, the solar panel will only work if connected to batteries.

How to Use Solar Panels During a Power Outage

There are two main ways solar panels can be used during a power outage to ensure electricity is still provided and devices can be charged. An off-grid solar panel system can be installed, or one can use a method of energy storage, such as batteries.

Off-Grid Solar Systems

An off-grid solar panel system features several batteries to store excess power for use during the night and on cloudy days. This system type is often very expensive and may not be a wise investment for general use in the home or business.

Off-grid solar panel systems allow for complete energy independence, meaning power from the solar panel system can be used if the main grid goes down. However, this type of system does not allow the option to draw electricity from the grid when the solar panel system is not generating enough electricity.

If the grid is down and the batteries’ energy has run out, this then leaves the user without electricity, which is not ideal. Therefore, off-grid solar systems must be designed appropriately to generate enough power throughout the year.

Batteries and off-grid inverters are costly, making these systems overall much more expensive than on-grid systems. Thus, they are generally only used in more remote areas that are a long way from the main electricity grid (source).

Battery-Backed Solar Systems

A battery-backed solar panel system features several batteries connected to the solar panel in which excess power is stored for use when the main grid goes down. This is a less expensive option than an off-grid solar panel system as it doesn’t need as many batteries.

This system involves installing one or two batteries for storing unused power generated by the solar panel system. This power can then be drawn without putting utility workers in danger if the electricity grid goes down.

The types of batteries used for storing solar energy are lead-acid and lithium-ion batteries. Lithium-ion based batteries can supply up to 90% of their available capacity per day, while lead-acid batteries only supply 30% to 40% of their total capacity per day to increase battery life. 

However, lead-acid batteries can be discharged fully if needed in emergency backup situations.

A battery-backed solar panel system can be supplemented with a traditional gas-powered generator to keep backup power costs low and ensure there is a constant flow of power to the home or business.

Keep in mind, though, that generators often run on fossil fuels that are not only non-renewable but can be hard to find during emergencies or natural disasters (source).

Final Thoughts

There are several ways to utilize surplus energy that is generated from a solar panel system, including on- and off-grid solar panel systems, battery-back power systems, and hybrid solar panel systems.

The surplus charge created from absorbing light can be stored in a variety of different battery storage systems, or it can be fed directly into the electricity grid for credits. 

Solar panel systems provide environmentally friendly and sustainable energy for use in the business and home and can ensure that electricity is always available even during power outages.   

Tim C

An outdoor enthusiast for decades and a science and physics nerd since 1980, I have recently become very interested in using renewable energy sources for home primary power and as backup for outages, as well as for camping, boating and tailgating.

Recent Posts