Yes, of course but it's reasonably efficient as it's class E. Worst case is 85% efficiency so then 15% loss, so at 10W o/p that's 1W5 of heat and 4 times that on mod peaks. It does NOT need a Massive heatsink, just mount in a metal case and bolt to that with the supplied insulating kit.
The IRF510 (o/p FET) is easy to drive but has a fairly pants on resistance of 0R5. This is what causes the loss, as if it was 0R it would be the perfect switch.
Class E tries to be the perfect switch as it's either on or off, so S/C or O/C (Short/Open Circuit). As long as you switch quick and have a low on resistance and you have a efficient amp.
An amplifier is just a switch, that's all!
Sooper simple once you get your head round a few basic principles!
Wierd I know but this is RF at its most basic and efficient of modes, you simply cannot beat class E, it's the Biz. It truly is!