Vibration energy harvesting is an emerging technology aimed at turning mechanical energy from vibrations into electricity to power the microsystems of the future. Most current vibration energy harvesters (VEH) are based on a mass-spring structure: this introduces a resonance phenomenon that enables an increase of VEH output power (compared to nonresonant systems); however, the working frequency bandwidth is limited. Therefore, these devices are not able to harvest energy when ambient vibrations’ frequencies shift. To solve this problem and to increase the frequency band where power can be harvested, one solution consists in using nonlinear springs. This paper introduces H-shaped nonlinear springs, their model, and their benefits to improve VEH output powers. Simulations on real vibration sources show that the output power can be higher in nonlinear devices (up to +48%) compared to linear systems.