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 %.

根據設備設計的功率密度與熔化規程的差異，中頻爐的熱效率可以超過80%，但通常，這個值只在60%-78%之間。

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.

操作工為了便于扒渣以及監控爐內鋼水的情況，中頻爐在熔煉過程中通常保持爐口敞開。然而，這會導致巨大的熱量損失，因此有必要為中頻爐安裝爐蓋或者爐罩之內的設備，在熔煉過程中減少爐蓋打開的時間，會節省大量的電能。

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.

理論上，熔化一噸鐵水需要的電耗是340度，然而實際上卻在600度左右。造成如此巨大的差異是因為：

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.

中頻爐各個設備之間因盡量靠近，從而減少線損。而其中尤其要縮短爐體與功率因子增強電容之間的距離，因為二者之間有巨量的電流通過。

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 %).

下圖顯示了高中頻感應電爐能量平衡的分配。電耗損失的部位包括變壓器，變頻器，電容器，線，纜以及線圈。其中尤其又以線圈的損耗占比最高，對電爐的產能起決定性的作用。中頻爐熱量的損失包括爐襯到線圈內壁傳導熱損失，金屬熔池表面輻射熱損失，爐罩排煙吸收引起的熱損失以及渣損等。由于線圈采用循環水冷卻，也會導致大量的熱損失。高頻及中頻感應爐的熱效率在60-78%，略高于低頻爐，只有58-71%。

Fig 1 Typical heat balance diagram of crucible induction furnace