I got our February Electric breakdown and was glad to see for that month we had a 58 kwh credit for the month. We now have about 500 kwh excess energy produced for the year. That is the first full year of having our Leaf electric car and our additional 2.5kw solar array plus batteries ( I talked about this earlier –http://bit.ly/2jWj4Oo ). December and January are the least productive months for solar generation and the Leaf uses more energy to drive due to needing the heater, so being positive in February bodes well for another net positive year. Basically we are running a surplus of generation for the year while driving our car powered mostly by the sun. We have had to plug into the grid power for overnight charging several times during December and January and also have taken advantage of the car charging stations in Asheville on trips to town at times. I estimate that for the year we were able to charge, thanks to the sun, for at least 75% of the time. We drove the car over 7000 miles eliminating the need to drive our truck that gets about 18 mpg for most of those miles.
Another thing I learned in our year of living with batteries is that we can power most of our home for 4 days without the grid. The Lead Acid batteries hold about 40kwh though I assume only half of that to make sure they’re lifespan in not shortened too much. In a pinch, if the grid was down we could theoretically use more and a rare discharge below 50% would not do much harm. We had 3 really cloudy/rainy days in early January and with the grid disconnected we were able to operate all the main systems of our house- computer and accessories, refrigerator, Freezer, well pump, kitchen outlets and lights and induction cooktop and a toaster oven. As we went into a fourth day of clouds I connected the grid to recharge the batteries that had gone down to right at 50% of charge.
By controlling the solar plus battery system manually I pay a lot of attention to the state of charge and the use of electricity on a daily bases. I take into account how the weather affects the system and I adjust when I charge the car from the batteries vs the grid tied system.
There are a lot of changes going on in the world of batteries. Of course the Tesla 2 (http://read.bi/2nO5gIa) which is slick and comes with the inverter included making it easy to install. It does look more expensive for the same storage capacity than our lead acid but also is nearly maintenance free. There is also Sonnen batteries which have similar advantages but with higher costs as well (http://bit.ly/2mQmqE7). Those are just two of the new tech options and there are a lot of others in the works. Electric cars are improving and changing at an even faster pace with this year being the year of the Chevy Bolt, a more affordable Tesla, an improved Leaf and many more- (http://bit.ly/2mQohJd)
It seems that the technology is here and if the inverters can forecast the weather and learn my driving patterns it could be as efficient as I am at turning on and off the grid at the right times and eliminate one of my obsessive activities.