Ok, so outside of the circulation pumps being oversized for my system I was curious how the math added up for energy cost annually for ONLY the circulation pumps. I made only a few assumptions and based my math off of DTE's current residential rates. I can use DTEs rates because all of the geothermal equipment is on a separate meter. This does not include distribution or delivery rates. Circulation Pump draw = 800w draw for the two pumps(385w * 2 pumps = 770, rounded up to 800w). Avg. yearly runtime = 3000 hrs. Annual use in kWh (3000h * 800w) = 2400 kWh Rate breakdown for seasonal use for on and off peak hours: June-Sept (1/3rd or .333) On-peak = 11.050 per Kwh Off = 3.826 per kWh Oct-May (2/3rd or .666) On - 5.199 per kWh Off - 3.882 per kWh On/Off peak hrs by day On peak = 9hrs Off peak = 15 hrs 9/24 = .375 or 3/8ths 15/24 = .625 or 5/8ths June-Sept (.333 * 3000 = 999) On-peak = .375 x 999 = 374.625 kWh * .11050 (11.050 cents) = $41.39 Off-peak = .625 x 999 = 624.375 kWh * .03826 (3.826 cents) = $23.88 Oct-May (.666 * 3000 = 1998) On-peak = .375 x 1998 = 749.25 kWh * .05199 (5.119 cents) = $38.95 Off-peak = .625 x 1998 = 1248.75 kWh * .03882 (3.882 cents) = $48.47 Total Annual Pump operating cost: $157.69 or about $13/month. To me that estimate seems extremely conservative. Am I missing something here? Mainly I wanted to see if the kWh argument held water if I needed to take it to the installer. If that estimate is even remotely close I can tell you it is a fraction of what propane would cost me out here. Of course if I can reduce that cost by half or better then that's ideal - especially if there is increased risk for reduced life of my heat pump by having oversized circ. pumps. That alone is a compelling argument for right-sizing the circ. pumps. Curious for others feedback. Does my math check out?