400w MH to 250w MH - Big temperature difference?

[fkshiu]

I think if you go from a 400W "HQI" down to a 250W electronic you will notice a difference in heat output because actual consumption will be halved from around 500W to 250W. However, if you're using, say, a 400W electronic ballast and go to a 250W HQI (M80) then you will hardly be using any less electricity and there will be no difference in heat.

When I went from magnetic 175W (M57) ballasts to 250W HQI (M80) my tank temps in the summer shot up quite a bit..