Strong flares on the Sun are accompanied by intense ionizing radiation (X-rays, far UV) and are often associated with coronal mass ejections (CMEs), which can be hazardous to astronauts, and infrastructure such as satellites and electrical systems. The rates of the largest flare events are, however, poorly understood. By taking advantage of the exquisite precision of Kepler photometry we derive white-light flare distributions in Kepler open clusters NGC 6811 (1 Gyr) and NGC 6819 (2.5 Gyr) over a range of masses. We use the results to estimate the rate of strong flares for the Sun, and explore the evolution of flare rates with stellar mass and age. Implications for mass loss (via associated CMEs) are also briefly explored.