The new energy storage system is designed to reduce dependence on the electricity grid when there is a power outage, and to maximize the use of power derived from renewable sources.

But it turns out that the products may not be ready to be used in your home just yet, according to a Bloomberg article. In fact, the batteries aren’t compatible with rooftop solar. Solar City (SCTY), which is the supplier and run by Musk, “isn’t ready to offer Tesla’s battery for daily use,” according to the article. It continues:

The new Tesla Powerwall home batteries come in two sizes—seven and 10 kilowatt hours (kWh)—but the differences extend beyond capacity to the chemistry of the batteries. The 7kWh version is made for daily use, while its larger counterpart is only intended to be used as occasional backup when the electricity goes out. The bigger Tesla battery isn’t designed to go through more than about 50 charging cycles a year, according to SolarCity spokesman Jonathan Bass.

Solar City isn’t installing the 7kWh Powerall yet for everyday use, stating that it “doesn’t make financial sense,” according to Bloomberg:

For customers of SolarCity, the biggest U.S. rooftop installer, the lack of a 7kWh option means that installing a Tesla battery to extend solar power after sunset won’t be possible. Want to use Tesla batteries to move completely off the grid? You’ll just to have to wait. ‘Our residential offering is battery backup,’ Bass said in an e-mail.

But demand is booming for the product. There have already reportedly been 38,000 reservations for the Powerwall battery despite it costing users more than the power derived from the grid. Meanwhile, the battery doesn’t provide that much juice yet. Bloomberg continued:

The model puts out just 2 kilowatts of continuous power, which could be pretty much maxed out by a single vacuum cleaner, hair drier, microwave oven or a clothes iron. The battery isn’t powerful enough to operate a pair of space heaters; an entire home facing a winter power outage would need much more. In sunnier climes, meanwhile, it provides just enough energy to run one or two small window A/C units.

The news comes after Tesla reported earnings on Wednesday, posting first-quarter revenue growth of 50%. It also reported a loss of $154 million during the quarter.
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