Heat loss using furnace runtimes and outdoor temperatures?
I am trying to calculate my homes heat loss as I am looking into adding more mini splits to carry more of my heating/cooling load. I have been impressed with the one I installed in my downstairs so far. I have solar panels and would like to add another mini split or two and use less of my oil furnace. I want to try and get the sizing right as I think my 80k oil btu furnace is way oversized.
I have had a Effergy whole house electricity monitor installed for a couple years that logs all my electrical usage. My furnace running shows up on the charts for exactly how long it ran for. I also have a weather station that has logged all my outside temperatures as well. Trying to decipher the data to see if I can calculate my heat loss using it. Looking on at the data on a 10 degree night, my 80kbtu furnace was running for 15-20 mins, was off for 30 mins then back on. A 20 min cycle would be about 16k btu so with about 2 per hour would a 30k btu loss seem correct?
I attached a run time graph of the furnace on a 10 degree night.
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