This achievement is actually really quick and easy. My friend and I were both able to get it in roughly 20 minutes.
Load up a private match of horde. Set the difficulty to casual and start on Wave 40. I'd suggest playing on Checkout as it's a small map.
You'll want to equip the following cards:
-Health Regeneration Boost
-Shotgun Damage
-Health Boost
-Pickup Distance
-Speed Boost (optional)
Ideally you'll want these cards to be level 3+.
When you pick up all the energy you should get approximately 10,000-11,000 energy, which meets the requirements of the achievement. Just make sure you pick up the money that the boss drops! If you're not able to pick it up you will unfortunately have to restart Wave 40.
This is possible to do by yourself, however a bit harder depending on your card levels. If you choose to do it with a friend, just make sure he/she doesn't pick up any of the energy. This also means he/she can't have pickup distance on otherwise they'll pick up the energy. The wave only supplies enough energy if one person picks it up.
If done correctly, the achievement will pop while the round leader board is on screen.
If you've got any questions, please comment. Good luck and happy gaming!