The Mars II 900 is ~ 400 watts. I'm not suggesting 1800 watts, I'm suggesting about 800 watts of actual power draw. Two of those would be ~800 watts of lighting.....
That means you would save at least 2.4Kw per day. Where I live that comes out to over 85 cent per day. You are likely cheaper than that but you get the point. Saving on the reduced air cooling and extraction and reduces wattage would save you roughly $120 per flowering cycle. Therefore, in 3 grows you have broke even and in the 4th grow and beyond, you are saving money.
