During the day, yeah. But at nite you want a red as they can't see it and it keeps them on their day/nite cycle.

But if your house/flat/apartment is heated sufficiently you won't need more than your under-tank heater during the day in winter. I do recommend this. Again, like Shannon said. Garters aren't baskers in the way boas are. Garters, in the wild, will bask in the AM on like asphalt/rocks in the fall/spring when the temps are goofy and all over the place. But they just don't bask for the sake of basking like tropicals do. They seek their temps, using sunlight and burrowing to give them what they need.

While snakes[garters] just need overall warmth to digest, I just feel better with belly heat for them to choose.

During the summer I never used my red heat light at nite. Didn't need to. Now needing it as the nites get cooler for the kids than they do for me. Doubt I'll use it this winter... Unless it gets too hot in here for me (and it did last year; I live in a flat and the thermostat control is in the lower flat; not to mention I live on the upper level and heat rises...) and I have to open windows that will affect the temp the kids are xposed to.

Actually, this past summer I used no additional heat whatsoever due to the temp up here.

It all depends on - for me - the temp the kids are xposed to where their tanks are located.

What's a CHE?