Outputting your display to a TV does not inherently decrease gaming performance. If your laptop screen supports a maximum resolution of 1366 x 768 and you try playing anything at 1080p (1920 x 1080) you're naturally going to experience a degradation in refresh rate (regardless of whether it's a TV or a regular monitor) as compared to your usual 1366x768 display.
That said, I'll try to answer your question because it's not very clear. If you are using the TV as the only display your laptop is showing at the native resolution of 1366 x 768, it should be updating at the same rate as if it were on the screen of the laptop. If you're duplicating screens or extending display across your screen and TV, you will of course experience a bit of decrease of performance. Any time your computer has to draw more pixels every refresh, you will of course be using more GPU power to draw it all.