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Grid-Tied and Off-Grid Solar 101

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

Let’s take a look at main differences is between a “grid-tied” solar system and the less common “off-grid” solar system.

Grid-tied Solar

Most photovoltaic (PV) systems are 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.

grid-vs-off-grid

Just think of the utility grid as your battery bank.

 

Here’s how it works:   A group of solar panels, known as the array, generate direct current (DC) electricity.  An inverter changes the DC electricity into alternating current (AC) electricity, which is the grid-quality electricity that comes from the power outlets in your home.

When the grid-tied system produces more energy than your home is consuming, the excess electricity is sent into the utility grid, spinning your meter backwards as credit toward your next electricity bill.  When your load requirements exceed the electricity being produced by your photovoltaic (PV) system, your home will draw electricity from the grid.  This is called net metering.

Grid-tie solar systems are a cost-effective way to reduce your net energy consumption. Grid-tied solar systems are ideal for those whose utility provider bill them according to a tiered rate structure –  where rates you pay are higher when you’re consuming more energy (kWh).

Grid-tied solar gets you out of the higher tiers on your electric bill to save you money.

If you need help designing a grid-tied solar system, request a no obligation quote today.

Will I still have power during a blackout?

Not with a grid-tied PV system.  You’ll still experience blackouts when the power goes out in your neighborhood because your are connected to the utility grid.  Sending electricity into the grid during a power outage would be especially dangerous if the utility company has workers repairing power lines.

For most people, a power outage here and there isn’t too much of a concern.  Just keep your refrigerator closed and charge your iPhone with 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 maybe the living dead chewing on power-lines, battery backup may be an option for you.

Keep in mind, battery backup is for critical loads, or the appliances that are imperative to survival.  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 LED lights on and perhaps a small refrigerator running. This combination of a grid-tied system with a battery bank for emergency situations is known as a battery backup or hybrid solar system.

Off-grid Solar

An off-grid solar system, otherwise known as a stand-alone or autonomous solar system, is for remote locations that would not otherwise have access to usable grid energy. This would include remote cabins, boats, or RVs that use solar electricity.

The idea of going off the grid is appealing but for most, it isn’t practical to pour thousands of extra dollars into an off-grid system.   The price of photovoltaics(PV) has been decreasing and solar panels are now very affordable but storing their electricity is expensive.   If you have access to grid electricity and you’re looking to see a return on your investment, go with a grid-tied photovoltaic system.

Not only do off-grid systems cost more upfront, system owners incur the additional cost of maintenance.  If you’re installing an off-grid system, familiarize yourself with battery technology used in solar systems – click here to learn about solar batteries.

OffGridAC

If you are setting up an off-grid system for your boat or RV that’s designed to run on direct current, or DC power, you can opt to work with DC appliances exclusively (i.e. tools, lighting, etc.). If you’re using your off-grid system to power any normal AC appliances in your home,  you’ll need an inverter to convert DC electricity from your solar panels into usable AC electricity.  If you’re powering any sensitive electronics, a pure sine wave inverter is highly recommended.  Modified sine wave inverters may damage these items and they often produce harmonic distortion – which has an annoying “buzzing” sound.

Battery banks will have a limited capacity, which is why many people who have off-grid systems keep backup generators nearby. Keep in mind that the electricity produced by your solar panels during the summer cannot be accumulated for use during the winter.

When designing an off-grid solar system, however, you will plan for days of autonomy, or “cloudy days” where your solar panels aren’t getting enough sunshine.   These are the days that you’ll be drawing almost exclusively form your battery bank.   For an off-grid system, you might size a battery bank with the expectation of a four-day period that your solar array won’t get any sunshine.

If you’re maintaining your off-grid battery bank correctly, your batteries will still likely need replacing in about seven years.  If you are thinking of installing an off-grid solar system, do some homework to figure out if it’s realistic option for you.

Though the idea of going entirely off the grid is sexy, it just doesn’t pencil out financially at this point in time.  When superior battery technologies become available at cost-effective prices, off-grid solar may well become a viable option for homeowners looking into solar energy.  Until then, grid-tied PV systems remain the more economical choice.

Author: Tom Jackson

I believe in a future that’s powered by clean energy. "Idealist" should not be a dirty word.

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