Originally Posted By: Brad_C
Originally Posted By: Nick1994
I'm wondering if it's more energy efficient to turn the A/C up a degree or two during the day saves a measurable amount of energy.
Absolutely. Heat infiltration is directly related to differential temperature. The colder it is inside the more heat (in energy terms) that passes through the house envelope and the more energy your A/C is required to remove. The smaller the differential, the smaller the required energy to maintain it. By the time you've got home from work it has cooled down a couple of degrees outside and you can drop the thermostat a couple of degrees. It will take some time to cool down the house and contents that couple of degrees, but with the much smaller heat input from outside its a net win.
Agree 100%.
This is also why settable temperatures by room (by window units, ductless/split systems or other such things) are also beneficial. With my ductless split AC, I can still use radiators in the winter, which is preferable to forced air, and I can program and cool the locations which have higher heat load to cool down before we show up, while avoiding the excessive draw of cooling the whole building. By the evening it is usually bearable outside, so we can then just cool down locations as we inhabit them to remove humidity. In case of the few days out of the whole year when we have a true heat wave and no relief, then we can run the whole thing and cool the whole home as if we had a central system. Even then, we let it rise a good deal during the day, to minimize electric use as the ambient temperatures increase, but to allow enough operation to allow dehumidification (there is something to be said for a dry heat).
We typically run no AC through the day, and only where we sleep at night, and enjoy a decent savings as a result.
I also have a few friends who have bought 5-6000 BTU window units to augment their central systems to do essentially what we do with our ductless split systems, and they have also seen reductions in energy use. The only issue is that a window AC is like 11.2 SEER while a split is over 20.
