Energy-efficient forwarding becomes important if resources and battery lifetime are limited such as in Wireless Sensor Networks. Although widely used, simple hop-based forwarding along a path from one node towards a sink can be very inefficient in terms of delivery rate as well as energy efficiency, especially in lossy environments. We will show that just minimizing the expected number of transmissions within the network is not always the most efficient forwarding strategy. Using a realistic link loss model, we derive two new forwarding schemes named Single-Link and Multi-Link Energy-Efficient Forwarding that trade off delivery rate and energy costs best by maximizing energy efficiency. Multi- Link Forwarding further benefits from addressing multiple receivers during packet forwarding, instead of a single one. By mathematical analyses, extensive simulations, and experimental evaluations we contrast the performance of our approaches against a comprehensive framework of other forwarding strategies.