As we saw from solar PV a well sized solar PV system can easily handle your home baseload during the day.
However, it cannot overcome the peak demands of your house, or the baseload overnight. If you put a really big solar PV system in, it still won't work overnight, and it still won't get your energy peaks. All a bigger system does is export more power to the grid which is worth very little to you for your outlay.
But a battery system could store up the excess energy that even a modest solar PV is producing, and return it to cover the peaks and the overnight loads! Yep, it sure can! But there is a catch: batteries are expensive. Remember JAWs rule of reducing your energy bill - it's all about saving money. It doesn't matter what magic black box you put in - solar PV, wind turbine, batteries, Mr Fusion home energy reactor - how much is the capital cost, and what is the payback period.
Sorry, but I'm going to kill battery storage in the next two paragraphs rather easily.
Let's pretend for a moment that we could ideally and perfectly store and return energy from batteries with maximum efficiency. 5kWh worth of battery storage will set you back around (AUD2016)$5,000. Let's pretend you use the full 5kWh every day. 5kWh worth of power is $0.25 x 5 = $1.25. Because you would have exported that energy if the batteries weren't there, that is worth $0.08 x 5 = $0.40 so you are down to $0.85 of power saved per day.
365 x 85c = $310 per year, for a 16 year payback on your investment. A bit long really. But here's the final kill shot. Batteries are only good for around 5-8 years. So they will never actually pay for themselves!
The only time you get batteries is if you have to go off grid. And if you are going to do that, you had really better use less power first and foremost to reduce the storage you need.
"What about super-capcitors JAW?" Yep, another excellent idea. Even a small bank of capacitors would knock off some of those power peaks, just 5 minutes of extended power will make a difference. Sadly, capacitors are also still expensive, and although will last a lot longer than batteries, they don't add up financially.
Yep, this is all a bit dissapointing isn't it? But the early adopters are pushing battery technology which will improve price. When we are getting to around the AUD$1,500 per 5kWh mark we are at the 5 year payback. But we need the batteries to do more than 5-8 years otherwise it is close to zero gain.
Roll on battery technology, we need you!