Understanding BRU requirements Electric vs. Gas

[PurdueSD]

Any of the HVAC guys care to chime in on BTU requirements for Electric Unit heaters.

After alot of research it seems i need around a 75K BTU propane fired heater that runs at 80% efficiency to heat around 18000 cubic feet of shop.

So if i used an Electric Unit heater, I would only need 60K BTU(because electric is all 100% efficient)...? Is this right? 75,000 * .80 = 60,000

 

[redsky49]

A btu is a btu, regardless whether from a fuel-fired or electric appliance.

So, if your calculations are correct, 60,000 btuh is what you need, either propane or electric resistance heat.

As always, offered only as opinion

 

[lametec]

Furnaces are rated by input BTU.

So OP is right, since electric heat is 100% efficient, he'll need a smaller unit vs. gas.

Same with buying a 90% furnace vs. 80%. You'll need less input BTU with a 90% furnace.

When sizing a furnace the calculations figure the BTU needed to heat the space. You then have to multiply that by a factor depending on the efficiency of the furnace to get your furnace BTU size.

 

[chevelle67]

I agree with OP and lametec.