So what is Powerwall exactly? It's a rechargeable lithium-ion battery system designed to store energy at a residential level for load shifting, backup power and self-consumption of solar power generation.

Powerwall is made of Tesla's lithium-ion battery pack, liquid thermal control system and software that receives dispatch commands from a solar inverter. The unit can be mounted on a wall and integrated with the local grid to store power and provide backup in your own home.

Currently, Powerwall is available as a Weekly Cycle option (provide backup when the grid goes down) with 10kWh or as a Daily Cycle option (paired with solar power, it extends environmental and cost benefits at night) with 7kWh. Excluding inverter and installation costs, Tesla's selling price to installers is $3,750 for 10kWh and $3,000 for 7kWh.

The specs of the coming upgraded version are not yet known, however this is what Elon Musk had to say, when he stopped off at Tesla Paris on January 29 and said hello to a room full of Tesla owners and supporters: "We'll be coming out with version two of the Powerwall probably around July, August this year, which will see further step change in capabilities."

Take a look at the video below to hear Musk introduce theTesla Powerwall at a launch event in Los Angeles on April 30th, 2015 (video curtesy of Tesla Motors).