Fine-grained energy metering in homes and buildings provides a promising technique for addressing the unmaintainable energy consumption levels of worldwide buildings. Metering electricity, lighting, natural gas, HVAC, occupancy, and water on a per appliance or room basis can provide invaluable insight when trying to reduce a building's energy footprint. A myriad of sensor designs and systems collect data on particular building aspects, but are often hampered by installation difficulty or ongoing maintenance needs (like battery replacement). We address these common pitfalls for water and heat metering by developing a small, energy-harvesting sensor that meters using the same thermoelectric generator with which it powers itself. In short, the rate at which the harvester captures energy is proportional to the heat production of the monitored appliance or pipe and this relationship allows us to estimate energy use simply based on the sensor's ability to harvest. We prototype our sensor in a bracelet shaped form-factor that can attach to a shower head pipe, faucet, or appliance to provide local hot water or heat metering.