Traditional utility metering is to be replaced by smart metering. Smart metering enables fine-grained utility consumption measurements. These fine-grained measurements raise privacy concerns due to the lifestyle information which can be inferred from the precise time at which utilities were consumed. This paper outlines and compares two privacy-respecting time of use billing protocols for smart metering and investigates their performance on a variety of hardware. These protocols protect the privacy of customers by never transmitting the fine-grained utility readings outside of the customer's home network. One protocol favors complexity on the trusted smart meter hardware while the other uses homomorphic commitments to offload computation to a third device. Both protocols are designed to operate on top of existing cryptographic secure channel protocols in place on smart meters. Proof of concept software implementations of these protocols have been written and their suitability for real world application to low-performance smart meter hardware is discussed. These protocols may also have application to other privacy conscious aggregation systems, such as electronic voting.