Have you considered a tankless water heater? Here is a thread that's been going for awhile
https://www.rollitup.org/advanced-marijuana-cultivation/410850-well-n-tankless-water-heater.html. This is where I got the idea for my set up. It works great for me, running a $300 Marley tankless heater, and Atlas 3 controller. My area is about a third of the size of yours, but the heater only kicks on for about twenty seconds. I ran a NG pipe to it, so I never have to fill a tank. The thread I referenced above mentions they hooked theirs up to an underground water tank that acts like a heat sink, with the pump activating the water heater. I however, ran an electronic valve on the water supply line that is turned on by the CO2 controller, the heated water then flows straight to a drain, utilizing the pressure from my water supply. I may go with the heat tank idea in the future to save water, but for now, it's bye bye heat!
I don't know if I have ever posted here, but I found the thread I referenced to be really helpful, so hopefully this knowledge will continue to help others.