When they were going to bring out the DC and AC versions, I think i read the DC was around 92% round trip
efficient, whereas the AC is around 89% round trip efficient, whilst 3% does not sound much, over the lifetime
of hopefully 10 years plus, it added up to quite a bit.
At present I have not been asked how much I would accept to help power the grid in times of need, I have
only checked the box allowing my (tesla)/energy retailer to do this. I suppose I will be offered the FIT for this
power, if this helps grid stabilization then I dont care if I get paid or not, I have not factored this into my calcs
There is a system out there called 'reposit power' that does exactly what you described, you get paid a premium
rate when the grid is under stress and wholesale prices are high, this works for PW1 and many other batteries,
but so far at least not PW2, from my understanding of it, it is because PW2 is AC, and reposit power works
with DC batteries, or at least that is my understanding, I have read that something like what reposit does
will probably come out for the PW2 but there isnt anything at present.
The PW2 app allows you to set your own limits on how low you with to run the battery, I have mine at 5%, but
I dont think I have been that low as yet, I dont think I have been under 10%, not when looking at the app
anyway
