I actually have a 3kw solar system on my roof, but I never feed back into the grid because I use it all and cannot fit any more than 18 solar panels on my south facing roof.
You must have smaller panels than me, as I have 15 panels on my roof that gives 3.75kw.
In any case, don't forget to factor in that the panels won't be working at max all the time. In the summer it's obviously better but you'll only be generating 3kw at the peak of the day, the rest of the time it will be somewhere between 0kw and 3kw, so you have to take a daily average when working out your figures. Obviously in winter power generation is much reduced.
For example in July 2013 I generated 563Kwh, but in October it was down to 171Kwh, and only 60Kwh in December.
Other than that, if you can successfully channel wasted heat from your rigs to save you having to power the heater, many kudos to you.