High-efficiency LEDs, government regulations, and the growing demand for cost-effective lighting solutions are making outdoor LED lighting more popular than ever. But the cost of replacing hundreds or thousands of legacy lights with LED luminaires can be substantial. To keep these new lights operating safely and reliably so they can pay back their initial investment, robust protection against damage caused by transient surges in AC power lines and temporary over-voltages is essential. This guide offers a clear, easy-to-read overview of the challenges involved in designing circuit protection for a wide variety of LED luminaires.