8. BOINC Pentathlon

[Dirk Broer]

A nVidia GeForce GT 610 has a Single Precision performance of 155.5 GFLOP and, on the sunny side, a TDP of only 29 Watt.
The somewhat more modern and equally cheap GeForce GT 710 has more than double the SP GFLOPS (and even has Double precision capability) and a TDP of only 19 Watt.
If you want to spend some money (less than $100) on a nVidia card and get good performance at little AC/DC power use, you have to go for a particular model of the GT 730 (with a GK208-301-A1 GPU): 692.7 GFLOP SP/28.9 GFLOP DP at a TDP of a mere 23 Watt ($69–$79). Take care: there are three sorts of GT 730 cards, one with a GF108 GPU that performs a lot worse than the other two.

BTW: the INTEL HD Graphics 5000 of your i5-4260U can also be used for crunching. I run Einstein on the IGP of my i7-3770.