My house is wired like a lab bench. Ten temperature and humidity sensors (attic, garage, basement, outside, the AC, even inside the fridge), two radon and air-quality monitors, an energy monitor on the electrical panel that tracks every circuit, and a meter on the main water line. Together they have logged about 6 million rows of data. The attic, garage, basement and outdoor sensors go back to late 2024; the ones in the fridge, freezer, AC and garage attic only joined in June 2026, so their stories are shorter. I finally sat down with all of it. Here is what my house has been trying to tell me.
All times are local (Central). Days when a sensor was offline are left blank, so gaps in the charts are real gaps, not zeros.
1. My attic is a pizza oven
Some context first. My attic has regular roof vents but no ridge vent, and no insulation in the roof itself; the insulation is in the attic floor, which keeps the heat out of the rooms below. The garage is the opposite: fully insulated with batts and a radiant barrier, except for a closed-off section next to our bedroom (the “garage attic”), whose roof is bare.
The result: on summer days the attic’s daily high runs, on average, 27°F above the outdoor high. It peaked at 142°F on July 2, 2025, and crossed 120°F on 97 different days. The garage attic (sensor in place since July 19, 2026) runs about 19°F above outside, while the insulated garage itself mostly tracks the weather.
The ten hottest days on record tell the same story: when it is 100°F outside, it is 120 to 140°F above the ceiling.
Did the radiant barrier work?
On July 2–3, 2026 I installed a radiant barrier in the attic. Honestly, I didn’t feel much difference in the house. The data says the attic did. Comparing how much hotter the attic runs than outside in the afternoon (2–5 pm), before and after, and using the same weeks of 2025 as a control for the season:
In 2025, without a barrier, the attic’s afternoon lead over outside grew by about 5°F from June to July–August. In 2026 it shrank by about 4°F after the install. Net of the season that’s roughly 9°F less attic heat; on a 95°F day the attic now tops out around 119°F instead of 126°F. Why didn’t the house feel it? The insulated attic floor was already doing most of the work of keeping that heat out of the living space.
2. The AC knows exactly how hot it is
Plot each summer day’s outdoor high against how much energy the air conditioner used, and you get a tidy upward curve (correlation 0.75). A mild 75–80°F day costs about 4.4 kWh of cooling. A 90°F-plus day costs about 21.6 kWh, roughly five times as much. The record was July 17, 2026: 55 kWh, with the AC running in 23 of the day’s 24 hours.
Summer 2026 was the hotter one: 43 days at 90°F or above versus 35 in 2025. The AC noticed. It used 1,882 kWh from June through August 2026, compared with 1,183 kWh the summer before, about 59% more. When it runs, air leaves the coil about 14°F colder than the air coming back from the living room, at the low end of the usual 14–20°F rule of thumb. That’s worth mentioning at the next tune-up.
3. Where the electricity actually goes
Over the last twelve months the house used 9,386 kWh. The air conditioner is the single biggest circuit at about a quarter of it. The circuit that feeds the water heater and office outlets is next at 15%, followed by the garage and front-door circuit at 13%. Something out there is hungrier than I expected, and I’ll be investigating. The circuits cover almost everything: less than 1% is untracked. Best fun fact: the garbage disposal used 0.3 kWh in a whole year.
By month, the house has two seasons: summer, when the AC takes over, and winter, when everything else climbs. One surprise: the “furnace” circuit runs all summer too. It also powers the blower fan that pushes the AC’s cold air around the house. July 2026 was the biggest month on record at 1,390 kWh.
The sneakiest number: even at 3 am, with everyone asleep, the house never draws less than about 0.4 kW. That “always-on” baseload adds up to roughly 3,500 kWh a year, about 38% of everything. Chargers, routers, cameras, standby lights and the fridge all add to it. That’s the cheapest place to start trimming.
4. The fridge has a heartbeat (and runs a little warm)
A sensor inside the fridge shows a perfect sawtooth: the compressor kicks on, the temperature drops a few degrees, it shuts off, and the fridge slowly warms back up. That happens about 11 times a day. The freezer adds about two defrost cycles a day, visible as short warm spikes.
The catch: the fridge averages 42.8°F and sits above the FDA’s recommended 40°F about 90% of the time (the freezer averages a healthy 1°F). Part of that may be where the sensor sits, but the dial is getting turned down a notch. The fridge circuit, which also serves the oven and a nearby outlet, uses about 2.7 kWh on a typical day.
5. The basement gets muggy every September
Mold likes relative humidity above about 60%. In winter the basement is desert-dry (around 33–40%). From June to September it averages 56–58% and regularly pokes above the line. September is the worst month: 23% of all September hours above 60% in both years, with a peak of 75%. Across the whole two years it is about 5% of hours. That’s not alarming, but a dehumidifier on a June-to-September schedule would make the line flat.
6. The air: CO2 at breakfast, radon in winter
Carbon dioxide is a good proxy for “is there enough fresh air?”. A common rule of thumb is to keep it under 1,000 ppm. The living-room monitor climbs all night and peaks around 7 am at about 1,490 ppm, then falls through the afternoon as doors open and people move around. It sits above 1,000 ppm about 65% of the time, which says “open a window more often”. The basement is calmer, with a median of about 940 ppm.
Radon is the invisible one. The EPA’s action level is 4 pCi/L. Good news: no month averaged at or above 4 in either room. The medians are 2.5 pCi/L in the basement and 2.0 in the living room, and the worst month was December 2025 at about 3.2. Radon rises in winter, when the house is closed up and warm air pulls soil gas in, then drops in summer. Short spikes above 4 do happen (about 6% of basement readings). The EPA also suggests considering a fix between 2 and 4, so this one stays on the watch list.
7. Water: the sprinklers run the show
From April 1 to November 12 the house used 85,761 gallons, about 382 gallons a day. The busiest hour by far is 8 am, and the busiest days are Mondays and Thursdays at about 580 gallons each, double most other days. That’s the sprinklers. In summer they run at 8 am, and sometimes again around noon or in the evening. I counted 75 sprinkler-sized runs (5+ gallons a minute for 10+ minutes): 41 starting between 7 and 9 am, 12 around midday, and 21 in the evening. Together they used about 41,700 gallons, nearly half of all the water the house used. The ten biggest single water events are all morning runs. The biggest, on May 28, poured 1,518 gallons in 170 minutes. In July the runs were cut to about an hour (about 690 gallons each).
Two reassuring checks. Leaks: a hidden leak shows up as water flowing all night. No night had nonstop flow, and a typical 1–5 am stretch uses under 2 gallons (a toilet refill or the ice maker). Laundry: matching the energy monitor’s washer/dryer circuit with the water meter shows 89 laundry days, most often on Sundays. Those days use about 435 gallons, against 346 on other days.
8. Even sensors take vacations
Over two years I found 19 outages longer than 12 hours. The two big ones, August 4–13, 2025 and August 18–30, 2026, knocked several temperature sensors offline at once, which points to the hub or Wi-Fi rather than the sensors. Both radon monitors also went quiet for most of January to mid-March 2026. The energy monitor and the water meter never missed a beat.
My to-do list, courtesy of the data
- Turn the fridge down a notch (target 37–40°F).
- The radiant barrier took about 9°F off the attic; a ridge vent might be the next experiment.
- Hunt down the 0.4 kW that never sleeps, starting with the garage circuit.
- Run a dehumidifier in the basement from June to September.
- Crack a window at night, or add fresh-air ventilation, to bring living-room CO2 down.
- Keep an eye on winter radon.
How this was made: raw exports from the temperature sensors, the air-quality monitors, the circuit-level energy monitor and the water meter were cleaned and summarized with a Python (pandas) script into small daily, hourly and monthly tables, loaded into the site’s own database, and charted with wpDataTables. Nothing on this page loads chart code or data from anywhere else. Duplicates from overlapping exports were removed, UTC timestamps were converted to local time, and offline periods are left blank.