In order to reduce the memory footprint used for monitoring specific absorption rate (SAR) in a magnetic resonance imaging (MRI) system, a hybrid sliding window method is provided. The method includes receiving a measured value once every first time interval, processing the measured value, and storing a value resulting from the processing in a first memory element. Measured values stored in second memory elements are summed every second time interval, where the first time interval is less than the second time interval. A representation of SAR is calculated every first time interval based on the value resulting from the processing and the sum of the measured values of the second memory elements. When the second time interval is reached, the value stored in the first memory element is moved to one of the second memory elements, and the value stored in the first memory element is reset to zero.