Editor's Note: Last week CE Pro contributor Wayne Ortner wrote the article, “RoseWater Energy: Biggest, Baddest, Cleanest, Greenest $60K Power Supply Ever” from CEDIA Expo 2015. The story prompted a comment from a CE Pro member named Dirk, who posed the question:
“Didn’t the Tesla Powerwall already make this obsolete? I believe the Powerwall has a capacity of 10 kWh of output per unit that runs $7,000. Three of the Powerwall units would have a similar capacity and take up much less space. I am missing something here?”
CE Pro's first article about Tesla's home batteries and low-voltage power in general drew a whopping 43 comments.
Since others in addition Dirk may be wondering the same thing, Ortner provided his reply here.
My article pointed out a number of things the RoseWater Hub incorporated that the Tesla and others simply do not do. To reiterate, here are some important points:
RoseWater’s AC-to-DC-to-AC conversion to produce a pure 60Hz sine wave, the zero transfer time and the programmability are just a few. It’s also not entirely accurate that the Tesla device is a 10kWh unit. That is it’s storage capacity, but it is limited to a 2kW continuous draw. That just won’t run very much in your house.
In addition, the price you quoted is for Tesla’s batteries only, so a system would need to built around it. Currently, there is no inverter for their system as it is a 400v system (while all the others on the market are 48v systems). It is possible they may change that in the coming months, but if they continue with that format, one would obviously need to be built around that. For the moment, there isn’t one available right now that I’m aware of.
So! Once you start to include that, plus all the things RoseWater does (power conditioning, lightning strike defense, zero-transfer time technology), it wouldn’t be surprising to see the price of a multi-Tesla-based system climb up to the $50k area or more, as you’d need industrial-level components such as RoseWater uses to match Rosewater’s performance.
Interesting footnote: the Tesla is also only meant to cycle once a week. That and the 2kW limit on the Tesla is designed to extend the battery life, which in turn, allows a longer warranty.
There is also an interesting difference in how the Tesla utilizes solar input. Their system is designed to peak shave utilizing solar stored during the day. Ironically, this is counter-intuitive to their partner Solar City’s business model because they sell all their excess solar production back to the utility.
They could peak shave from storing power overnight, but that reduces the overall pay back because you need to pay for the overnight power. As a peak shaving device, what they offer may be adequate for many smaller homes, whereas Rosewater’s system is designed to handle larger loads and has no restrictions on cycling or draw.
So to your question Dirk, the Tesla product doesn’t make the RoseWater obsolete, but rather it is kind of like Tesla’s Ford Fiesta to RoseWater’s Ferrari.