Energy consumption: propane fueled hydronic floor heating vs cold climate mini split
I could use some input on a comparison I am doing being two systems.
-1300 square foot home, slab on grade, with a heat loss of 20,000 BTU
-$0.1385/Kwh is the average winter cost of electricity in my area
-$0.698/litre is the cost per litre of propane that I was quoted today
Essentially, I would like to determine which system would consume more energy to heat the home to 20C in a cold climate?
1. Propane fueled hydronic radiant floor heating, with a condensing tankless water heater with high efficiency; or
2. Cold climate mini split, non-ducted, with an HSPF of 10 BTU/Watt-hour
I would like to do an operational cost comparison of both systems. By these rates, and running the math with available conversion factors, I think that the mini-split would cost nearly half as much to run as the hydronic floor heating.
What I am unsure of is, and intuitively speaking, once the slab has heated to temp, wouldn’t it have such a significant thermal mass that it wouldn’t take much additional heat to maintain the room temperature or heating load? I mean, relatively speaking to the mini-split?
I guess what I’m asking is, if the slab is up to temperature, and the home requires 20,000BTU/h to heat, surely that doesn’t mean that the boiler needs to inject 20,000 BTU/h to meet the load? It’s “top up” needs would have to be less than the mini-splits, no? And if that’s correct, then would this mean that an operational cost comparison of the two systems might be too difficult to theoretically calculate?
Any info is appreciated.
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