Depending on the installed power density and the melting practice, the thermal efficiency of the induction furnace can exceed 80 %, but usually it is in the range of 60 % to 78 %.

根据设备设计的功率密度与熔化规程的差异，中频炉的热效率可以超过80%，但通常，这个值只在60%-78%之间。

Induction furnaces are normally kept open during the entire melting process where the workers engage in slag skimming and monitoring of the quality of molten bath. However, this leads to significant heat loss and hence special covers or lids need to be installed for reducing heat losses. In particular, reducing the time the lid is kept open while melting, can lead to substantial energy savings.

操作工为了便于扒渣以及监控炉内钢水的情况，中频炉在熔炼过程中通常保持炉口敞开。然而，这会导致巨大的热量损失，因此有必要为中频炉安装炉盖或者炉罩之内的设备，在熔炼过程中减少炉盖打开的时间，会节省大量的电能。

The theoretical requirement of energy for melting iron is only 340 kWh per ton whereas the actual power required is around 600 kWh. This difference is due to two factors namely (i) inherent in the principle of melting in an induction furnace which include the inefficiency in electrical bus bar losses, eddy current losses, refractory losses,  and cooling water losses etc., and (ii) the operational losses which are largely due to unnecessary and excessive holding of liquid steel in the induction furnace.

理论上，熔化一吨铁水需要的电耗是340度，然而实际上却在600度左右。造成如此巨大的差异是因为：

Induction furnace equipment should be placed with minimum distance between each equipment to reduce wiring losses. To reduce the wiring losses remarkably, it is essential to shorten the distance between furnace body and power factor improving capacitor as very large current flows between them.

中频炉各个设备之间因尽量靠近，从而减少线损。而其中尤其要缩短炉体与功率因子增强电容之间的距离，因为二者之间有巨量的电流通过。

Efficiency of induction furnace is expressed as a total, deducting electrical and heat transfer losses. Typical heat balance diagram of high and medium frequency crucible type induction furnace is shown in Fig. 1. Electrical losses consist in transformer, frequency converter, condenser, wiring, cable, coil, etc. Loss in coil is essential factor, on which the furnace capacity depends. Heat losses in induction furnace consist of conduction loss of heat escaping from furnace wall to coil side, radiation loss of heat released from melt surface, absorption loss in ring hood, slag melting loss, etc. The coils of furnace are water cooled which also results in heat loss. Heat efficiency of high and medium frequency furnaces (60 % – 78 %) is slightly larger than that of low frequency furnace (58 % – 71 %).

下图显示了高中频感应电炉能量平衡的分配。电耗损失的部位包括变压器，变频器，电容器，线，缆以及线圈。其中尤其又以线圈的损耗占比最高，对电炉的产能起决定性的作用。中频炉热量的损失包括炉衬到线圈内壁传导热损失，金属熔池表面辐射热损失，炉罩排烟吸收引起的热损失以及渣损等。由于线圈采用循环水冷却，也会导致大量的热损失。高频及中频感应炉的热效率在60-78%，略高于低频炉，只有58-71%。

Fig 1 Typical heat balance diagram of crucible induction furnace