If you throw a blanket over the grow light, it should provide some heating. I routinely do that, in my cold winter garage. I easily get 80F. Fluorescents will heat better than LEDs, though. I use the former. Might need more blankets for LEDs. Regulate the temperature by adjusting the coverage. Get a good thermometer so you know what's going on.

Now, this is kind of early for pepper starts. I assume you're working toward pretty large plants for plant-out. You'll want to do some ventilation under those covers for large plants. That might be challenging if you're trying to keep them warm.

Dan is right that regular fluorescent tubes provide quite a bit of heat. Covering them with something to insulate would work.

I also agree that it is very early to start peppers, even though they do seem to take a long time to get some growth on. I'm up here in Portland and I don't start mine until Feb.. My set up is in an unheated greenhouse attached to the south side of our house, I'd bet it's colder than your laundry room! What I have found to be a valuable source of bottom heat are incandescent plastic

tube lights-cheaper than heat mats. Those, combined with fluorescents, keep my starts warm. I do put something over the lights at night if/when the night temps are cold. Right now is the time to buy the flexible tube lights, they are with the Christmas lights (otherwise they are hard to find).

That's an interesting idea for bottom heat. Heat mats sure are pricey. But you mean "rope lights", I think. Tube lights are usually what fluorescents are called. But LED rope lights have something like a watt per foot or less, which really doesn't make much heat. Incandescent rope lights might work better, but I'm not sure how easy they are to get these days. They might be cheaper than LED rope lights, though.

Thanks for the feedback. I only started germinating the peppers pretty recently, and with my luck they won't for atleast another couple weeks. I usually start in January and most of the peppers have done well except for the C. Chinense varieties. Last year my scotch bonnet maybe grew 3 inches. I read the species is slow growing and therefore should be started earlier, with some people starting seeds in December.

I think I am going to try a heated terrarium with a dehumidifier. There's some very cheap terrariums on craigslist, which can be used with reptile heat mats, and I have found some dehumidifiers on Amazon about the size of a fragrance plug in.

I am in part starting this early because I want to grow some of these peppers to their maximum size, and most of the ones I am growing can get 4 or 5 ft. tall.

I use a seedling heating mat. My winter greens looked very sad until i added the bottom heat. They live under a grow light in my garage which gets to around 50 degrees at night. Bottom heat (heating the roots) is more effective than other heat.

Light the head and warm the butt!

What a cool use of the rope lights, I’m intrigued. Seems Home Depot has the 12‘ lights (perfect for one heating ”mat”) for around 11 bucks.

Correct me if I'm wrong, but I've understood that heat mats are to speed germination. Maybe by a few days. But they don't really make plants grow faster once germinated. The usual rule is to remove plants from the heat mat once they have germinated. That being said, yes the Home Depot Westek 12' incandescent rope lights are 24W, which is pretty much what good heat mats can put out. But most heat mats have thermostats. Rope lights don't. So be careful. Good idea!

My heat mat does not have an adjustable thermostat, I should use my laser thermometer tomorrow to see what temp it maintains.

I recall reading research years ago that keeping the root ball warm was much more important than covering the top for winter protection. Since my seedlings looked pretty terrible after I removed the heating mat (they barely grew for over 4 weeks in our garage at ambient temp), I decided to reinstate the mat and they were much happier. Now that they are more established, I’ll be weaning them off before I send them outside to live under my horticultural fleece.

I have found seedlings do much better for me when the temps are over 60, but the garage is the only place I can have them and that area requires a little heat boost as it can be in the low 50’s.

Well, if the ambient temperature is cold, no question that a heat mat will improve growth. The heat mat is heating both the roots and the surrounding air. I guess the question is whether, once you raise the temperature of the surrounding air, adding extra warmth to the roots is going to make much difference in growth. Easy to understand why raising the soil temp speeds germination. Because of evaporation, moist soil is always going to be somewhat cooler than the ambient air. Also, optimum soil temperature for germination of, say, squash and melons is 95F. Yikes. That's lots higher than you'd want the ambient air temperature.

I think most of us have warmer daytime home temps than night time...we set our thermostats to be lower at night...in our summer time gardens when the soil temp is 70 and the temp at night drops to 55-60...i suspect the soil temp probably stays pretty close to 70...a much larger area to cool down than small pots...I don't think it could hurt to have a heat mat, and may help the seedlings???