Business Insider reported that the announcement will be made at the company’s California headquarters, and that Jeffrey Evanson, who is in charge of investor relations, explained that the products would be batteries.

According to Business Insider:

Musk is also chairman of SolarCity, a provider of home solar panels. SolarCity has previously offered home energy storage using Tesla batteries. According to SolarCity’s website, the company will have installed about 450 of these systems through 2015. The idea is that a customer always has backup power.

The batteries could also cost a pretty significant price for customers, according to The Guardian:

The system is offered, currently, in 10 and 15 kwh configurations to solar customers who do not own electric vehicles or plug-in hybrids; the battery pack costs about $13,000, and Pacific Gas & Electric offers a 50% rebate for using the system (presumably because it can be used to decrease load on the grid during peak use hours); financing is set up for the customer to make an initial $1,500 payment, followed by $15 monthly payments for 10 years (at the end of which the battery is returned to SolarCity)…

Tesla batteries are reportedly already being tested in homes, and in Wal-Mart’s (WMT) stores in the U.S.

For more on Tesla’s announcement, read this article by Fortune’s Kirsten Korosec: Tesla’s grid battery ambitions hinge on three crucial factors.