The complicated answer is "depends on surface area, insulation, and ambient temperature."
The easy answer is "absolutely."
I just finished my build and I was very pleased to find that my 1375 watt element (5500 watt, 240 volt running at 120 volts) only lightly pulses inside my RIMS tube to maintain temp. And, in fact, during wet testing, could raise the temperature of 10 gallons of water relatively quickly. We're talking like a degree ever minute or two. But to be clear, my mash tun is insulated and had the lid on. Ambient temp was around 80*F.