See attached load calcs for our ~2500 SF home in Lincoln, NE.
Attachment 838783
Attachment 838784
The last two days, our weather has been sunny with average temps of 39F & 32F:
Max Min Avg
Oct. 16 62F 30F 46F
Oct. 17 52F 26F 39F
Oct. 18 45F 18F 32F
Our furnace is inoperable, so we’re using a 1500W (~5200 btuH) resistance heater as our only heat source. This heater has easily maintained our home at 67-68F (measured at our furnace thermostat). The heater doesn’t even run continuously. It has a built-in t-stat set at 67F; I would guess it maybe runs 50% of the time when I am home (evenings).
I had a local contractor who insists on running load calcs and seems very knowledgeable size a new 2.5T Mitsu heat pump to replace our 80k BTU NG furnace and 3T A/C. We did a second load calc at 37F/85F heating/cooling design temps to ensure the heat pump would still be able to modulate during more temperate outdoor temps. At 37F, the calculated heating load was ~16,000 BtuH. Our current resistance heater is putting out < 1/3 of that, yet it is maintaining indoor temps just fine. Our furnace tstat shows the house at 67F even at 6:00 AM these last two mornings, so I know even in the dead of night the 1500W heater is keeping up.
During the day, it is just my wife and our 2 small children at home. In the evenings, we have 5 kids (all under 11) and two adults (~2500 btuH total). Yesterday we did not cook dinner, so only internal heat gain was a dishwasher, LED lighting, and maybe a couple hours of TV. Our water heater is a HPWH, so any internal heat gained from showers I’m viewing as a wash since the water heater is pulling the heat from the indoor air in the basement.
Is it plausible that our actual house loads are in fact way less than our load calcs? My experience the last (2) days would suggest so, but I’m wondering what I’m missing. I have robust knowledge of our house construction (extensive remodeling) and do NOT want oversized equipment, so I worked with our contractor to ensure the inputs were aggressive to maintain accurate load calcs. If our load calcs are truly oversized, it may allow us to step down to a 2T HP (or less).