The U.S. department of energy suggests electric radiant heat can be cost effective if preheated during off peak electricity hours if installed within an appropriately massive covering.
Is there a way I can predict heat retention over the course of a winter day? In particular, I'm interested in installing it under porcelain tile. We do have an existing dual source furnace, but want to install this to avoid waking on stone cold floors in the morning.
Department of energy states:
Because of the relatively high cost of electricity, electric radiant floors are usually only cost-effective if they include a significant thermal mass such as a thick concrete floor and your electric utility company offers time-of-use rates.
Time-of-use rates allow you to "charge" the concrete floor with heat during off-peak hours (approximately 9 p.m. to 6 a.m.). If the floor's thermal mass is large enough, the heat stored in it will keep the house comfortable for eight to ten hours without any further electrical input, particularly when daytime temperatures are significantly warmer than nighttime temperatures. This saves a considerable number of energy dollars compared to heating at peak electric rates during the day.