Wasserstein UL-Certified 24-Volt transformer and C-wire adapter offers a simple powering solution to your WiFi smart thermostats, from any standard 110-Volt/120-Volt electrical outlet, this provides the constant 24-Volt power required by today’s top WiFi Smart Thermostats. It’s safe to use and will protect your WiFi Smart Thermostats from over-voltage, short-circuit input and over-current output.