Smart parking systems present one of the essential infrastructure concepts that enable Internet of Things (IoT) in Smart cities. Finding a free parking lot plays a role in reducing traffic congestion, gas emissions, and increasing the quality of life of people living and working in it. Therein, the fundamental part of every smart parking system is the detection of vehicle presence, which is usually employed by devices comprised of power-hungry sensors. This paper gives an extension to state-of-the-art by a systematic in-depth overview of technologies used for the smart parking detection realization consuming mW of power. Deeper insights on the real-scenario performances and power consumption of most popular sensor devices and Low Power Wide Area (LPWA) radio technologies available today (LoRa, Sigfox and NB-IoT) are provided. The results show that based on the architectures of IoT system, lowest consumption is for LoRa devices. Further, analysis of power consumption of commercial LPWA-based Smart parking sensor device is provided along with battery estimation lifetime, which is especially important for the deployment of future smart parking solutions. Battery lifetime heavily depends on the number of parking lots exchanges and based on the less frequent changes, the estimated battery lifetime is approximately 7 years. Inspired by the limitations of power-hungry and relatively expensive smart parking sensor devices, two strategies for the optimization are proposed. First one is based on the premise where a drop in received signal strength of the LPWA device can serve as the presence of the vehicle in the parking lot, while the second one proposes a big picture on a novel architecture for harvesting the surrounding energy and using the same for circuitry wake-up therefore saving the energy.