Battery storage, Electric car?

I have pricing for two retrofit battery options;

 

1. Add on battery controller and Sonnen 4kwh AC Battery $13,000 approx inc GST.
2. Change existing inverter to Solax X1 Hybrid, emergency power box, 6.5kwh LG Chem battery etc $14,000 approx Inc GST.

The potential savings from storing around 3-5kw per day depending on energy use, sunshine, and efficiency of the battery amount to a few hundred dollars per year. The LG Chem batteries are guaranteed to provide 80% capacity at 10 years, and could last around 16 years.  But by my calculations would never payback the investment.

The most sensible option for me at this stage is do nothing, save/invest some money.  I think the next option wait a year and review, and look at a second hand electric car, once I better understand battery management/ state of health issues, and battery replacement options.

My current set up is solar PV 4.9 kW 20x245w panels and grid tied 4.6 kW inverter installed 2013, recently upgraded to a larger 270 litre hot water cylinder and changed hot water timer to Paladin hot water diverter. Very happy with this set up. 

I had no idea how much PV to install, and went for as much as I could at the time, probably about 3kW would have been optimal. 

Before I installed I upgraded my house over time, with additional ceiling insultation, heat pump, double glazed windows. Have always been low power user.

My power bills amount to around five hundred dollars a year, with winter use heat pump and some hot water heating, family of five, modest sized house with one bathroom. We do get power trust rebates of around $250 per year which keep the cost down. I really do hate to pay for power, mostly fixed daily and other charges.

One of the reasons for all of the above is the environment. Return on investment for any solar is hard to justify, with PV it is a long term solution. You have your own power generation, but have paid in advance for your power. Export buy back rates have been slashed since my install. Although I consider it paid for now. 

We don't have reticulated gas in my location, and I would not ever consider gas. I investigated solar hot water and heat pump options, but not happy with the cost or the durability/ lifespan of the equipment based on advice for several plumbers/ installers.

I have my own little off grid system in separate garage. With 80 w solar panel, 10 amp controller, old batteries, and a cheap 240 v inverter that I use to charge e-bike, electric lawnmower (Masport 58v kit) and 18 volt tool batteries, and power 12v shed stereo.