Last month, Tesla CEO Elon Musk announced a new product line via his Ernst Stavro Blofeld Twitter feed.

And earlier this week we learned the identity of the mystery business unit.

I would suggest that Tesla has already unveiled these battery products over the last three years. Tesla already has 97 energy storage projects in motion in California in 2015 alone. Judging from the California SGIP spreadsheet, Tesla offers a 5-kilowatt residential battery that is almost always paired with a PV system. The company has been installing hundreds of these systems in some form for years.

However, Tesla has been booking an increasing number of commercial and government energy storage jobs ranging from 100 kilowatts to 1.5 megawatts. The large systems are just as often standalone batteries as they are paired with PV. In many cases, SolarCity, the nation's largest residential solar installer and financier, is coupling Tesla's battery-based energy storage hardware with its rooftop solar systems.

The big commercial projects appear to be a relatively new development and square with reports in Bloomberg that Wal-Mart has Tesla energy storage systems deployed at 11 California sites, along with a 1-megawatt battery at Cargill in Fresno, Calif.

In an interview late last year, Tesla's Director of Powertrain Business Development, Mateo Jaramillo, said, "Tesla has new industrial and residential units coming out next year at compelling price points." He also said he was disappointed to hear recent reports out of Germany that dismissed batteries as too expensive. He suggested that doubters "shouldn't make that statement until they talk to us about the price of Tesla batteries. People are surprised when we have that conversation about Tesla battery prices."

He concluded, "We see demand going non-linear as soon as we cross the commodity price line -- and sooner than most people might expect."

Erik Fogelberg, SolarCity's VP of commercial sales and storage solutions, told us last week, "We bid energy storage at every job that has demand charges."

Late last year, Peter Rive, the co-founder and CTO of SolarCity, said that the standard offering from SolarCity could eventually include storage. Rive added that the combination of solar and storage "won't look that much different for the customer," but that "the benefit to the customer will be that you will have a little backup power." Rive said, "One of the cool things about storage is that if you're already installing a solar system, the incremental cost of also getting a storage system installed is low." Rive sees this as being particularly true once storage systems are integrated into the same box as inverters.

He added, "Our approach is to basically look at all the things that would make solar more valuable and invest in those things. For example, increasing the capacity value of solar through a combination of load shifting, demand response and integrated storage could dramatically increase the value of solar."

Note that these batteries are not meant to get customers off the grid. Instead, they are intended to offer some relief from demand charges and to provide a little backup power.

Given these signals, we expect that next week's product announcement will look a bit like this.

We'll be reporting from Tesla's offices in Hawthorne next week -- stay tuned.