High-voltage electric double layer capacitors (EDLCs) capable of efficient AC line-filtering have been developed. They were fabricated with vertically-oriented graphene nanosheet (VOGN) electrodes using a planar design. Two approaches were examined to series connect EDLC cells and thus achieve high-voltage operation. Electrical performance of VOGN electric double layer capacitors fabricated with an ionic liquid electrolyte was measured at temperatures up to 125 degrees C. Volume comparisons are made between VOGN electric double layer capacitors and aluminum electrolytic capacitors. A practical design is presented that provides the VOGN electric double layer capacitor with more than an order-of-magnitude higher ripple-current filtering performance (120-Hz) than available from present capacitor technology. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.orellicenses/by-nc-ndA.0/), which permits non-commercial reuse, distribution, and reproduction in an); medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.