On-Grid vs Off-Grid vs Hybrid Systems

After the sunrise, the photovoltaic cells have access to solar energy with a couple of choices, either you go for On-Grid approach or Off-Grid approach. As the word itself says On-Grid means your PV system is connected to your local electric company’s grid. Whereas Off-Grid means you are independent of generating your own electricity. Both ways of generating solar energy have pros and cons. In both ways the main goal is achieved as due to the clean energy the carbon emission will decrease as the reliance on fossil fuels will be reduced.

This article will enlighten you about the dissimilarity among PV power utilization techniques. Which generally have two major types: On-Grid & Off-Grid. 

The fundamental functioning concept of both PV power utilization techniques are the same. With the help of photovoltaic effect the solar modules first transform sunlight into DC power. The generated DC power is either accumulated in an energy storage system (ESS) or transformed into AC power by the help of an inverter for powering the home appliances or to backfeed the power into the utility grid for the net metering.

On-Grid System

On-Grid is also called a grid-tie solar system. The On-Grid system is the most widely used residentially & commercially PV power utilization technique. This type of PV utilization technique is the simplest form of the PV power utilization technique where no energy storage systems (ESS) are involved, the electricity grid is backfeed by the unutilized solar power with the help of either PV inverters or micro inverters. The backfeed solar power that should have been unutilized if it was not connected to the grid is paid by a feed-in-tariff (FiT) or credits the exported energy which can then be utilized in any month when you consume more electricity.

The surplus solar energy is recorded with the help of a bidirectional meter, which determines the generated power either you are consuming or backfeeding. This lets the utility company know the amount of power coming from solar & grid is consumed or backfeeded, then based on the monthly usage the utility company bills you. This process is called solar net-metering. On-Grid systems can meet the rising demand of power, so it is much easier compared to Off-Grid systems. For instance, an air-conditioning unit takes a lot of power to operate. But in case of Off-Grid systems which will require a large battery bank to run the air-conditioning unit. 

On-Grid solar systems are typically not capable of PV power generation when there is a power outage, this is due to protection purposes. If the PV powered inverter was active & capable of feeding PV power through a damaged grid, it would be very dangerous for the laborers working on the power cables.

Off-Grid System

As the name suggests, Off-Grid means independent of the utility grid. All the PV generated power is utilized by the homeowner, at the day time some amount of energy is consumed to power the home whereas the remaining part of generated energy is consumed to charge your energy storage system (ESS). the Off-Grid systems will only generate power which is demanded within its generating capability, the capability of your PV modules to produce more will be wasted. This issue can be resolved by having larger battery banks but the budget of your system will be increased drastically as energy storage systems (ESS) are expensive with a limited life span. While designing an Off-Grid system you need to design a system which is capable of generating & storing enough power so during less sunlight in winters you should be able to power your home as you do in summers.

Energy storage systems (ESS) are expensive, some may require maintenance, and come with some safety precautions & maintenance. It's important to remember that the size of your battery bank must correspond to your annual usage requirements. 

Being Off-Grid puts you in control of your energy. You will also not be affected by the power outages or failures in the grid. In an Off-Grid system, you are dependent on an energy storage system (ESS) to store power for the times your PV is not producing such as nighttime, cloudy or snowy weather.

Off-Grid systems are substantially more costlier than On-Grid systems due to the high cost of energy storage systems (ESS) and the inverters used for Off-Grid. As a result, they are commonly installed in rural places which are isolated from the electricity grids. However, as the energy storage systems prices drop down, the demand for off-grid solar systems will expand, even in urban & rural areas.

When the weather is very gloomy and the energy storage systems (ESS) are low on charge, a backup source of power is usually required, such as a generator. The backup generator should be sufficient to power your property while also charging the energy storage system (ESS).

As we know now, On-Grid systems do not generate power during power outages and Off-Grid systems do not backfeed the extra power to the utility grid. To overcome these both drawbacks, we can come up with another system commonly known as Hybrid solar system.

Hybrid Solar System

A system which incorporates grid interaction along with an energy storage system (ESS). This type of system will benefit the consumer during power outages. The energy storage system (ESS) will provide power to the critical loads within the backup loads panel. During the off-peak hours in the daytime when sun is not available, the extra generated energy by PV can be stored in the energy storage system (ESS) which can then be utilized during the peak hours when sun is not available. During peak hours the cost of electricity is high, as a result it will benefit the consumer by consuming their own accumulated energy rather than consuming from the grid. 

Hybrid solar systems are capable of islanding in which the energy storage systems (ESS) are able to bypass the grid and supply power to critical loads through energy storage systems during a power outage. Hybrid solar systems are also installed at the large scale commercially.

Cost Comparison

On-Grid systems are cheaper to install compared to Off-Grid and Hybrid systems. ROI (Return on Investment) of an On-Grid is very high compared to Off-Grid and Hybrid Systems. This difference is due to the energy storage system (ESS) inclusion.  

System Complexity: 

On-Grid systems being less complex compared to Off-Grid and Hybrid systems. This is due to the fewer components being used in On-Grid systems.

Lifetime:

Solar modules have 25 years of warranty, inverters have warranty of 5 to 7 years with an option of extendable warranty to 20 to 25 years. Whereas all battery warranties depend on the type. Like Tesla Powerwall 2 battery warranty is 10 years. This means you don’t need to spend for the next 10 years as all the major materials will be covered under the warranty.

Read also: Solar Guide