Hi Carol! You can buy heat mats for seed starting trays. They are rather pricey though and I'm not sure how expensive they are to run all the time. Usually anything with a heating element in it draws quite a bit of power. It will probably help speed up germination but I don't think it's really necessary. Look in seed catalogs and local nurseries for them if you're interested.

Thanks Seil!
If it's not necessary, then I'm not doing it! :)
Much obliged.
Carol