I don't know why it would require 250-260 degrees f to dry your clothes in a dryer. It's the flow of air that dries the clothes coupled with the heat not the heat itself. It just takes time. As was mentioned before you could use a clothes line and they never get to 250-260. Load size, time and power consumption are the determining factors here. The natural properties of flowing warm air on water will cause the drier to work. Air flow, load size and how wet the load is will determine how long it takes to dry. As for power consumption the primary plus or minus for operation is the amount of power used by the heating elements versus the extended amount of drying time used by the blower/drum motor. Under normal usage the blower motor that turns the drum is running any way. Since the original query was based on economic feasibility we are reduced to an uncertain equation. Element ampere consumption for (? time) versus extended run blower ampere consumption (? time). Because we do not know the specific ampere/wattage of either component nor the extended drying time needed we can only guestimate but for simplification most heating elements are rated at or above 1500 watts 220 VAC. Some I have seen take 2200 watts 220 VAC and there are bigger ones. Simplistically If your motor takes 1/4 of the power of your elements you can fairly assume a break even point of 4 to 1. 1 hr regular vs 4 hrs extended run time. Find the draw rates of your elements and your motor and you can determine the specifics. There is probably a tag on the back or bottom front of your dryer that gives the specifics. To prove the capabilities of lower temperature just turn your drier to "no heat-fluff" setting and stick a wet towel in. Eventually it will dry. I use an electric dryer by Frigidaire and heat my home and dhw by an EKO 40. What I save in propane and fuel oil offsets the cost of using my dryer as intended and, though I'm a dreamer at times, I am also lazy enough to see the value in that. Not having seen the hydronic dryers up close I can't be sure but I think they have probably increase air flow to reduce drying time to satisfy the hurried age we live in....Cave2k