We propose a robust network coding protocol for enhancing the reliability and speed of data gathering in smart grids. At the heart of our protocol lies the idea of tunable sparse network coding, which adopts the transmission of sparsely coded packets at the beginning of the transmission process but then switches to a denser coding structure towards the end. Our systematic mechanism maintains the sparse structure during the recombination of packets at the intermediate nodes. The performance of our protocol is compared by means of simulations of IEEE reference grids against standard master-slave protocols used in real systems. Our results show that network coding achieves 100% reliability, even for hostile network conditions, while gathering data 10 times faster than standard master-slave schemes.