it's for one year, 0.000000008*60*60*24*365=0.252288
Could you provide your calculations on how the PACMiC V3 can achieve a 25% APR? Does that assume the auto rebuy feature is turned on all year long or some portion of the year?
You're not factoring in the reward drops with the amount of BTC remaining on the contract. which drops the average rate of return on the PACMIC by appx. 2/3ds
Antminer S3 undervolted CAN be profitable, if your cost of electric is low enough. Right now I'd guess around .12c/kwh or less is making money for a very undervolted S3, though probably need a fair bit lower yet to have a chance at RoI if you bought one now.
Quote
If after the suspension period, difficulty has dropped or bitcoin price has risen
Which pretty much means "pray for a bitcoin price jump" because bitcoin difficulty drops are uncommon, small, and so far always followed by an increase bigger than the drop was.
A better estimate of annualised rate of return would be more like 8-9% at recent difficulty increases, with a fairly high probability of getting all of your principal back in 8-9 months (shortly BEFORE the halving). This is assuming an average difficulty increase of 2% (the last year has averaged 1.7%, but the last couple months have been a bit over 2% *PROBABLY due mostly to Bitmain deployment of S7s into Hashnest/their own farm and resale of the used S5s they're replacing*).