I knew Mr Christopher would find something i had forgotten
But still when you compare to a new engine every season and a seasons worth of fuel, glow plugs etc, i still can't imagine it being more expensive than switching to Nitro, not to mention you don't have to find a pit man for every meeting or restrictions due to noise.
As Mark said they run on 2 LiPo packs or alternativley you can pick up a 14.8V LiPo which is designed for 1/8th...
Venom 50C 4S 5000mah 14.8v LiPo Battery