I've always been a strong proponent for properly sizing A/C's together with home performance upgrades but with utility companies moving towards more demand based rate plans we've come across some situations where I find myself having a change of heart. I wrote about it on my blog here http://www.greenintegrateddesign.com/blog/the-ideal-home-for-a-load.... Interested in what other seasoned professionals think.
Well you are in an interesting market as humidity levels there are almost non-existent thus you don't need the long run time to help pull that "heat" from the air. With that set the temp lower just before on-peak & pre-cool the house. The other factor is not how long the fan run but the start-up, as I recall that draws the most power. Your chart is way off, I have seen plenty of houses easily hitting 1000 sf & better per ton so it doesn't help anyone see if their houses unit is just at the cusp. Better to get your ducts in order is the biggest issue there - 10% leakage equals 25% of loss in the attics while most loose close to 50% of the cooling from what I recall.
When it is the high end of a multi-speed/variable speed system just sitting there waiting for climate change to catch up
I feel this ia dangerous train of thought. And i would consider the examples in there of sizing of systems are more on the very oversized scale. What climate are these referring to? But there is no talk of moisture removal in here. The number one issue with oversizing equipment is moisture removal. I would maybe give this article more thought if you had a dedicated dehumidifier.
FYI - APS / SRP basically means Phoenix, AZ with no humidity except for after a monsoon blows through
Thanks for the clarification. I was in PHX last week at a Construction Instruction class (those guys know their stuff, denf worth it!). Without the humidity factor I can see a possibility for this working in this specific application. It would be devastating in my area (Iowa) where we are going for moisture removal in the summer. I would be interested in the added cost of running and repeatedly starting a larger blower motor compared to keeping a smaller one going, as it requires far less energy to keep the fan going compared to starting it. Agreed, look to the ducts first!