High fault tolerance for transient faults and low-power consumption are key objectives in the design of critical embedded systems. Systems like smart cards, PDAs, wearable computers, pacemakers, defibrillators, and other electronic gadgets must not only be designed for fault tolerance but also for ultra-low-power consumption due to limited battery life. In this paper, a highly accurate method of estimating fault tolerance in terms of mean time to failure (MTTF) is presented. The estimation is based on circuit-level simulations (HSPICE) and uses a double exponential current-source fault model. Using counters, it is shown that the transient fault tolerance and power dissipation of low-power circuits are at odds and allow for a power fault-tolerance tradeoff. Architecture and circuit level fault tolerance and low-power techniques are used to demonstrate and quantify this tradeoff. Estimates show that incorporation of these techniques results either in a design with an MTTF of 36 years and power consumption of 102 /spl mu/W or a design with an MTTF of 12 years and power consumption of 20 /spl mu/W. Depending on the criticality of the system and the power budget, certain techniques might be preferred over others, resulting in either a more fault tolerant or a lower power design, at the sacrifice of the alternative objective.