ISEE-3 plasma and field data were analyzed to estimate the power dissipated across slow-mode shocks in the distant geomagnetic tail. A set of 26 unambiguous examples of slow-mode shocks encountered by ISEE 3 near X(GSM)≈-200 RE was used for this purpose. The analysis yielded an average cross-tail electric field of 1.6¿0.7 mV/m an upstream Alfv¿n Mach number of 0.19¿0.08 and a decrease in the Poynting flux at the shocks of 9.2¿7.4¿10-3 ergs/cm2/s. Assuming a mean cross-tail potential of 70 keV and a location of the neutral line near X(GSM)≈-100 RE, the average power dissipated tailward of the neutral line from lobe magnetic energy density to plasma sheet convection is 5¿1018 ergs/s, a value comparable to the total power dissipated near the earth during moderate-strength substorms.