How much heat do mag12's put out?

[spider86]

Im setting up a new system with sump. Thinking of running 2 mag12's in the sump - 1 for the skimmer (MR1) and 1 for return. How much would they raise the temp? Ive run them externally but never in-sump.

 

[Entropy]

On a 40g? I would say quite a bit. My old mag 9 used to raise the temp of my 90g (+45g sump) about 1 degree.