Great question!
Battery back-up, grid hybrid, grid storage, are all common names for the idea of attaching a battery bank to your grid connected solar (Photovoltaic) system.
So what are the practical and financial considerations you should be aware of while making a decision whether or not this is right for you?

What is it?
Grid Storage is simply a grid connected solar power system with the capability to store and use excess solar generation. It’s an excellent concept and captures the imagination.
In effect it allows a grid connected business or home to exist off grid. No more bills, right?  

Unfortunately, not so fast.

How Does It Work?
There’s a couple of variations to the topography of the systems, but effectively grid storage systems use a grid tie inverter, converting solar power into AC power for use immediately, for export to the grid or directed to an inverter-charger which converts that AC power back into DC power, charging batteries, or back again from the batteries into usable power for times of high demand or out of sun hours power.

When does it work best?
Grid Hybrid systems work well where you have power quality issues, frequent black outs, need for uninterrupted power supplies (UPS) or have extremely expensive power; where you could reduce your costs by using your own power.

So how much does it cost?
In most cases, especially where the above issues are not a consideration, far too much; unscrupulous sales people will tell you this is a great investment, promoted with some beautiful lies.

The first lie:
‘You will never get another power bill’. Not true, unless you disconnect from the grid. You will always have ‘standing charges’ or ‘Network Access’ charges, for the pleasure of having a meter in a meter box at your boundary.

The second lie;
‘The system pays for itself in a timely fashion’… this is a complete lie, promoted by either ignorant or greedy sales companies. The reality is that batteries have a finite life. Best case scenario: a battery bank that is only used down to 80% of its State of Charge, and kept at an even 20 degrees temperature, you will get 16 years of usable life. (Lithium or Lead Acid makes no difference)
Amortised over its life, that battery bank costs you over 30cents/kWh. Add in the additional costs of the inverters and required balance of system componentry and the system as a unit ends up costing around 80c/kWh. Far above what your energy pricing is or ever will be.

Third lie:
We will make all your dreams come true!

I love solar power, and I believe in its power for good. I live completely off-grid. We help hundreds of businesses slash their bills, get great returns on investment and reduce their impact on the environment, but we are just part of your energy mix.
Feel free to have a sensible conversation about your energy needs, and sorry if you have bought a system because of dodgy sales people’s lies, or if you have been selling them without really knowing what you’re selling, there’s simply a lack of knowledge on this subject.
 
If you have more questions, see if we can help.