I think one of the lessons of the day is to trust Elon Musk. When he said approximately a month ago that Tesla would be announcing a "major new product line" on April 30, he wasn't using the term "major" in a light way. [Full Disclosure: I'm long (very long) TSLA.]

As someone who follows the battery industry very closely, I know that there are a lot of startups and large corporations looking to get a huge chunk of the battery storage market for themselves via their own innovations, competitive advantages, and perhaps even breakthroughs. It made me a bit cautious in getting excited about Tesla's announcement. Furthermore, while the market is expected to grow in leaps and bounds, it's still a tough financial sell for the huge majority of homeowners in the developed world.

However, I have also read on a number of occasions that Tesla has the lowest-priced battery packs among all electric car manufacturers, and that the scale of production it would gain from the Gigafactory it is building with Panasonic would enable even deeper price cuts. However, it was hard to figure out how all of that might translate to the stationary storage market, and allow it to compete in this market (where home storage is still dominated by low-cost lead-acid batteries, and grid storage can be provided via flow batteries and other technologies).

Yes, there were pilot rollouts of Tesla's batteries pegging them at about $13,000 for 10-15 kWh systems. I didn't want to base any guesses off of those prices, as I knew they could be far higher than the commercial products (they seemed far too high given the estimated per kWh price of Tesla's car battery packs). Indeed, they were. Here's the key statement on price from Tesla on price: "Tesla's selling price to installers is $3500 for 10kWh and $3000 for 7kWh. (Price excludes inverter and installation.) Deliveries begin in late Summer."

Unfortunately, that leaves out the inverter and installation costs, but still, this is a very low price for lithium-ion battery packs. "Nothing remotely in these price points," Elon reportedly noted at the product release last night (or early this morning, my time).