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Solar battery backup: Does my solar panel system need one?

solar battery backupA common question we get from customers is whether your new solar panel system needs a battery backup.

The answer to this question will depend on your specific needs, and while many opt not to install one, there are many cases where adding one to your system makes good sense.

Battery backups: Continuous power off the grid

While the vast majority of systems installed today are referred to as “grid-tied” or “grid-interactive” systems, that was not the case twenty years ago. Back then the reasons for installing solar energy systems were different from the most common reasons someone would install a one today.

In those days, people weren’t typically looking at solar
as a “financial investment”. That’s because without the grants, incentives and lower equipment costs like today, there was much less return on their solar investment if you had access to inexpensive electricity from the power company.One of the main reasons for purchasing solar panels was typically out of necessity. Be it a remote communications station, hunting cabin, or maybe a ranger’s station, the primary need was to generate power and be able to store it.

Storage played a critical role in this type of system. If you planned on powering any sort of appliance besides just some kind of inductive heater or ventilation system, it had to have the ability to save this energy for later use.

People in these remote locations not only required power when sunlight was unavailable, but a stable voltage that would allow more complex appliances to run. When you consider that the power from a PV inverter can spike and drop rapidly depending on weather, clouds or trees, there needed to be an interactive source of power that can temper the ebb and flow of solar production.

Net metering: The battery backup alternative

Today, the grid-tied system works on a similar principal, but with one big difference. Instead of the battery bank being used to temper the ebb and flow of the solar production, the modern day system uses it’s connection to power lines to temper these ups and down in solar power.

The key to this is with a “net-meter”, and functions much like a battery bank would. Even in houses that might only be offsetting 30% of their usage, odds are that at high noon on any given day they are producing more power than what they are using at that moment.

In this example, if you had a battery system in place, the extra power would go to charge the battery bank. But with a grid-tied system, instead of charging a battery bank it “charges” the grid. Or to put it another way, the power flows backwards through the meter, literally spinning the meter backwards (less visual but same effect on a digital meter).

At the end of the month, it is an easy equation for the utility billing. Say if you produced 1000 kWh’s of energy, but you consumed 1500 kWh’s of energy, the meter would only have ended up moving forward that additional 500kWh’s that you production did not cover.

So as you meter spins backwards in the daytime, then forwards at night time it is much like it would be with a battery bank.

So net metering actually works much in the same way that a solar battery backup might; you “store” electricity in the grid during the day, and get it back at night.

So with net metering, why would you need batteries?

It depends on your particular needs. One concern might be reliability. Grids are pretty good, but they aren’t 100%. Combining grid tying with the battery can make your electricity supply extremely reliable indeed.

Also, solar battery backup does have a disadvantage, and it is a fairly large one: cost. Battery technology has gotten better over time, but they are still very expensive. This is especially true if you need a full backup that will provide all of your energy needs during the night. Batteries wear out, too. They are not a one-time expense by a long shot.

So what is the bottom line?

If you’re like most people, you’re investing in solar in order to lower your energy bills. Which is great. In that case, a solar battery backup will not directly contribute to your returns. But they can be useful indirectly. How reliable is your electric grid, anyway? What would happen if it went down? Would you just have to bring out the flashlights for the night, or would there be bigger problems? What if the grid is down for several days?

Any of those issues with a dead power grid can cause you financial losses, whether it is spoiled milk, lost productivity, or anything else. In this case you would be very grateful to have invested in a solar battery backup, despite the initial expense involved.

Solar power systems have evolved a lot over the years. They now service many different people with different electricity needs. A solar battery backup may or may not be right for your specific needs. Think carefully before deciding on a final solar plan for you and for your family.