Well i as i have never tried this myself, but being an electrician for a living gives me a great understanding of how it works. So as long as you are not drawing more watage combined than your thermostat can safely control there is not an issue. Now getting the temps to be what you want them to be could be a seperate issue. Just remember not to exceed what your particular thermostat can safely handle. Another note would be not attempting to push the thermostat all the way to the edge either, since this is an electrical item if you were to run it at say 98% of its rated capacity there is a chance this could lead to a failure faster than say 75% constantly. Now that may be argued by some who run there thermostats all out all the time and dont have any issues, that is just my opinion having a 9 year electrical background. Hope this helps.