Solar 101: Grid-Tied and Off-Grid Systems

Will I need batteries for my solar system?  How much does it cost to go completely off the grid? 

These questions often come up as people start thinking about going solar.  So, what does it really mean to go "off-grid" with a PV system?  First, let's take a look at a traditional grid-tied system.

Grid-tied Solar

When most people install a solar electric system, it is connected to the utility grid, hence the name "grid-tied."

When your solar system is connected to the grid, you still have access to energy after dark without batteries.  Your grid-tied system simply pulls the electricity you need from the utility grid.  

A grid-tied system is simple.   When the grid-tied system produces more energy than is being consumed, the excess electricity is sent to the grid, spinning your meter backwards as credit toward your next electricity bill.  When the demand is higher than the energy being produced by the PV system, the home draws energy from the grid.  This is called net metering. 

Just think of the grid as your battery.  

The benefits of grid-tie solar are net metering and a lower upfront cost than off-grid systems.  One of the only down-sides to a grid-tied system is that you'll still experience blackouts when the power goes out in your neighborhood.

Why does my power go out even when I have a grid-tied solar system? 

This is because your are connected to the utility grid.  When there's a power outage, the power company often has to send out a maintenance team to fix the problem.  If there is a live energy feed, this can be especially dangerous for the workers who are repairing power lines. 

For most people, a power outage here and there isn't too much of a concern.  Just keep your refrigerator closed for a couple hours and if you want to make sure that you can charge your iPad, get a JOOS Orange Portable Solar Charger. 

But what about Armageddon? Or the zombie apocalypse?!  I'll need power to fight off the living dead!

If you live in an area that is plagued by frequent blackouts, hurricanes, or some other cause for concern such as the living dead chewing on power-lines, battery backup may be an option for you.

Keep in mind, battery backup is for critical loads, so you really can't blast the AC and leave the television running 24/7 in the aftermath of a natural disaster.  In most cases, it will mean you can keep some lights on and a small refrigerator running.  This combination of a grid-tied system with a backup battery supply for emergency situations is known as a hybrid solar system.

Going Off the Grid

An off-grid solar system, otherwise known as a stand-alone or autonomous solar system, is the kind of solar system you would install in a remote location that would not otherwise have access to usable grid energy.  This includes isolated dwellings, boats, or RVs that use solar electricity.  

If you are setting up an off-grid system for your boat or RV, there's a good chance you won't need an inverter because they are likely designed to run on direct current, or DC power.  If you're using your off-grid system to power your home, you'll need an inverter to convert DC to AC, which is compatible with the appliances in your home (like grid electricity).

outback fx3048t off-grid inverter

For off-grid systems, GoGreenSolar.com usually recommends the 3000-W Outback FX3048T or the 5000-W SMA Sunny Island 5048U Off-Grid Inverters.

The main benefit of an off-grid system is the sense of self-reliance that comes from knowing you don't rely on the power company for electricity.

Though the idea of going off the grid is appealing, for most consumers it is not a practical investment.  The additional equipment that is required for an off-grid system means that your overall system will cost more upfront and incur additional maintenance.

Off-grid solar systems require a battery bank to store the solar energy that is collected by the array.  Without a battery bank to store energy, it'll be lights out by sunset.

Since a battery can only hold a limited amount of energy, you can't depend on the excess energy produced during the summer to be around for those cloudy winter days.

Off-grid batteries will most likely need replacing in about seven years if you're using it correctly.  If you are thinking of installing an off-grid solar system, please educate yourself so you have the know-how to maintain your system properly.  We also ask that you please recycle your used batteries because they can be an environmental hazard.

When is it financially feasible to go off the grid? 

Because of the additional costs associated with off-grid systems, it often makes little sense to go this route unless you live in an area where grid electricity is either too expensive or inaccessible.

Though the idea of going entirely off the grid is sexy, it just doesn't make sense for most people at this point in time.  When superior battery technologies become available at affordable prices, off-grid solar may well become a viable option.  Until then, if you can go with a grid-tied system, it's probably your best choice.

For more articles on solar and renewable energy, click here. 

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Thomas Jackson
www.gogreensolar.com

Lead Image: Solar rooftop via Shutterstock