I am looking at the climatemaster tranquility 30 digital series TE026. loop will be a well that is 75 feet distance (level) from the flow center, somewhere between 300-400 foot deep, single loop of 1.25" pipe. (depth is unknown at this point, The well already exists, but if I need to add depth, I will have driller add max depth for the "min cost involved to bring well truck on site".) I like the idea of the internal flow center because the advertisements say "vFlow™ systems reduce water pumping power consumption by 60-80% compared to traditional external pumping modules, which can save over $100 per year in an average 2,000 square foot home" Plus I like the way I can set for temp delta in thermostat and system runs pump at speed required to give me that delta. I am also looking at a single pump QT flow center which has an advantage of me not needing a flush cart. (but I have to be willing to run Propylene Glycol antifreeze). A salesman said the vFlow runs around 70 watts max. The QT runs at 1 amp @ 220V = 220 watts. So I want to figure out how much more the QT will cost to run. (please check my math). 220 watts (QT) - 70 watts (vflow) = 150 watts difference which is .150 Kw running for 1 hour would be .150 kwh. Now GeoDesigner shows the 027 in my house will run 1,828 hours for heat and 547 for cool = 2375 total hours run time. 2375 hours x .150 Kwh = 356.2 Kwh x .13 cents per Kwh = $46.31 more money per year to run the QT. Now I understand this calculation is based on the vFlow running at 100% load, but I think I will only see 100% loads during peak heating and cooling seasons so I guess this calculation is flawed. If the internal flow center cost $463.10, more then the QT, then my payback is 10 years. Is it worth it? (I don't know the price difference yet, but I will tomorrow).