I finally had a chance to plot my AC cooling runtimes vs. Cooling Degree Days. As I suspected, outside temperature is only one factor in the equation. The length of sunshine during the day also plays a strong role - months with more sun show bigger slopes (runtime / degree day). I might try plotting against CDDs and my daily solar generation to get a better picture. Thanks for your encouragement.
The same charts plotted with solar production as the color. Solar energy production should be a great proxy for solar heating of the stucco on the sides of my house ! Looks about right with the slope increasing with increasing solar energy (except in a few cases).
I would be interested to see your data presented in the same form that @shanefinn03 and @dcdyer presented ours. ‘Total KWH wattage for all A/Cs: y-axis’ vs. ‘CCD index: x-axis’. (one graph, one slope). Could you also provide the R2 correlation and slope variables. That would allow us to compare our analysis with yours. My thermostats do not provide runtimes. I am still impressed at the amount of data you have collected and the detailed data analysis you provide. Thanks Don
I held back on using Sense identified energy because I saw so much conflation of Sense devices depending on the season - I have 5 different identified Sense AC devices that all correlate to my Ecobee runtimes at different points in the year:
Since Ecobee runtimes during cooling are far more accurate than “batched together” Sense energy numbers, and since I have simple 1-stage AC units, what I’ll do is multiply runtime by what think to be the actual power usage of each unit (based on rated numbers and Sense numbers). I think that will give the most accurate view in energy vs. CCD comparisons. Then I’ll do the regression graphs and linear model fitting.
ps: My Ecobee’s are more accurate for cooling, but I have a furnace issue that renders my downstairs Ecobee far less accurate during the heating season. My cold air returns are too small, leading to the cutout switch turning the furnace off after about 5 minutes of runtime, cutting power to the Ecobee, and leading to a subsequent reboot.
Here’s my assessment based on the methodology I outlined. I estimated my lower unit at 4.7kW and upper unit at 3.5kW. The slope numbers are in the same ballpark. As I expected, the upper number has better correlation since we cool the bedrooms more consistently than the downstairs, which has better airflow and stays cool much longer into the day. Most of our AC usage upstairs is from1pm onward. Maybe 3pm or later for the downstairs unit.
@kevin1 I was hoping that you would post one graph with one line that added both your “downstairs” and “upstairs” total daily kwh vs. CDD index. (A whole house consumption comparsion). I forced my linear calculation thru ‘zero’. From your graphs, it appears that your home is more energy efficient than mine. I see a lot of daily values that are 0 kWh usage so I am guessing that you turn off your A/C units when you are not home.
Thanks for straightening me out. Here’s the whole house plot. Our slope numbers are actually quite close - Both 3.6kW / CDD. And my R2/correlation is surprising better as well. But a few additional thoughts / questions.
I’m going to need to redo if I want to match up against your results. I used CDD65 while you used CDD75, because that was the default for the website I used (partially because that’s the typical US baseline standard). That would change my intercept, but not the slope. Sorry I didn’t read your explanation more carefully earlier - I should have noticed the difference when your were showing a smaller number of cooling degree days in Texas than I saw for the CA Bay Area microclimate I’m in.
My AC units are not that efficient - 20 year old SEER 11.5 units. But the Ecobee thermostats do turn up AC threshold when sensors tell it that we’ve been out of that part of the house for 15 min or longer.
House is about 4000 sq feet, with reasonable insulation, but no attic fan. We keep the heating / cooling numbers at 68 degrees and 74 degrees when we are home, but we have someone home nearly all the the time.
Our biggest cooling challenge is solar heating of roof and stucco, not air temp or humidity. That’s why we need to cool, even when the outside temperature might be below the the air temperature.
I’m up on the Wemo now. It was pretty easy. The granularity is also 1 sec, just like the HS-110.
It uses UPnP, but I didn’t bother as I already know its IP and port. Looks like the port is always 49153.
One really bad feature is that the Wemo always disconnects power and leaves it disconnected after an outage. Not good for sump pumps or anything critical. At least it comes back up on wifi.
Shouldn’t take too much to program a message to turn it on periodically, but we shouldn’t have to do that.
Still can’t create a topic…
I’m betting that TP-Link HS-110 and Wemo Insight use the same power monitoring chip, although I know they use different WiFi / host chips. Will be interesting to see if they both give the same data results at 1 sec polling.
HS-110 vs Sense vs Wemo
I got another HS-110. But it was a V1 instead of the V2. I should be getting the V2 soon. The V2 can do 220V, but the chip set is the same. That’s helpful.
With the firmware upgrade to 1.2.5 the HS-100 matches Sense much better, but it still isn’t 100%.
I put the 2 HS-100s on the sump pump and the dehumidifier and switched the Wemo back and forth, piggy backed on the HS-110s.
In the first plot I notice that:
1a. Wemo almost exactly matches Sense for the dehumidifier.
The HS-110 is now down about 25 watts from the Sense/Wemo numbers.
1b. Sense missed when the dehumidifier stopped once, but picked it up when it stopped the next time. In other instances (not shown) Sense comes back down between dehumidifier activities.
1c. It doesn’t notice the drop step where I guess just the fan is running.
1d. It missed all the sump pump activity.
On the second plot with the Wemo on the sump pump, I notice:
2a. The HS-110 is still spot on timing-wise with the sump pump even though I’m collecting on a .5s interval. I’m going to drop the issue of the late reporting by the HS-110 for now. I no longer have any evidence of it.
2b. This time HS-110 and Wemo agree on the wattage while Sense is about 90 watts higher.
2c. Wemo takes a while to ramp up and down. The HS-110 and Sense both nail it.
Pulling the Wemo off the sump pump now before I forget to check it and flood the basement.
Finally figured out a way to locate most Sense monitor errors without comparing with power company results by using hourly Always On here: