I use my work workstation and mine at home so yes and no
Well, it's technically a binary question
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
If you don't pay for power, then solo mine away and hope you find a block. But take into consideration three things: 1) the difficulty of the coin you're mining, 2) the probability of finding a block over 'X' amount of time, and 3) hardware depreciation.
If you're like most people then yes, you do pay for electricity, and no, it's certainly not worth it to solo mine. If you were to pool mine, a 280X uses somewhere around 350W at 100% sustained load (from what I've read). At 350W, you're looking at 8400W consumed per 24 hours, or ~256 Kilowatt hours per month. If mining generates enough revenue to cover 256 kWh worth of power, then keep mining.