"I want to install solar back-up batteries at my house."
"I want to have battery back-up power so I can turn on my TV and charge my laptop during Blackouts."
Well let me just stop you right there. When I first came into the industry back in 2009, there were indeed homes that I helped consult and design (mostly in Marin County or Northern California) that had designed in it dozens of kWh storage. But guess what? These systems (along with 10-20kW worth of solar panels) easily cost well over $100,000 to install. Of course these were multi-million dollar homes with clients that felt a $2,000 diesel-powered generator was just not "sexy" enough.
Another more practical application of solar powered battery back-up systems (or off-grid systems if you prefer the more technical term) works well for applications where the electric grid was either unreliable (i.e. Cuba, Iraq, third world countries, etc.), or non-existent (as was the case in many parts of Kenya). In these instances, the option of having stored electrical power versus having no source of electricity clearly had its advantage.
In fact, my first project for solar came during my senior year at UCSD working with the student chapter of EWB-SD (Engineers Without Borders - San Diego). In this project our goal was to power a Technology Center in Mbita, Kenya, complete with laptops and books, but most importantly lighting at night. (For more information see here.)
Well I have good news, ok news, and some more good news!
First piece of good news: Battery systems no longer need cost $100,000! In fact, case in point, anyone following technology and the very Wall Street friendly Elon Musk-backed Tesla Motors can attest to, Tesla has launched a new line of Home Battery systems. And the larger of the 2 Powerwall systems only cost $3,500 (10 kWh). Darn nearly a steal!
However, a quick back of the napkin calculation tells me that for $3,500, you would need to cycle through about 23,300 kWh's in order to break even (with the assumption that you are offsetting peak loads of about $.30 / kWh (Tier 3 loads) to a more manageable $.15 / kWh (Tier 1 loads). Assuming a typical household uses on average 7,000 kWh / year, with roughly half of these coming in Tier 3 or higher, you could get a break-even in around 6 years. Which is pretty good considering these battery technology is slated to last around 10 years (warranties at 10 years), the average homeowner can take advantage of savings for almost 4 years!
However, as an impartial clean-tech enthusiast, I have to go back to solar technology. Why install these batteries, which in fact does not help you turn on the lights during blackouts, and does not provide the best returns on your investment?
So I will end this entry on going back to the good news. It is great that there is new battery technology out there that hopefully will continue lowering prices while Tesla mass produces them, existing solar technology already offers amazing ROI and energy savings that is guaranteed for decades!
Some food for thought.