I have LED signals both front and back with no resistors installed. The "regular" electronic flasher relay that I had been using did not work when I switched to the LED signals. I eventually purchased one that specifically said it was designed for use with LED signals and it works well. In my experience, not all electronic flasher relays are suitable. . . Using LED signals is not going to save you much electrical juice, as they are used so rarely. If you want or need to keep their dual function as marker lights (you would then need to buy dual level units) then they can reduce energy consumption. Obviously, switching to LED brake and tailights can also reduce consumption. . . . .I have yet to find LED signals that are as bright as the stock signals. Nice LED signals are often pretty expensive too. Basically, don't swap to LEDs for brighter signaling. Do it for looks, reduced energy consumption (only if you are also using them as markers), and perhaps weight savings.