Measuring stuff

Eric Sandeen asked how are all these measurements taken. The embarrassing truth is, with very simple hardware, that requires manual reading.

The 240 volt loads - PV inverter output, range, minisplit heat pump, electric resistance water heater - are metered via re-manufactured old-style glass front electromechanical meters that I get from Hialeah Meter. I read them daily. The refrigerator and freezer and HPWH are 120V loads and they are on Kill-A-Watt EZ meters. The EZ model has battery back-up, useful so all data isn't lost in a power failure, or when you unplug it. The Kill-A-Watt logs kWh and elapsed time, as well as providing instantaneous readings of Watts, Volts, and Amps.

The utility meter from NSTAR has cumulative usage as a net, kWh delivered to the house, kWh exported by the PVs, and peak demand in kW. I read this daily also.

I measure hot water usage with a water meter from watermeters.com on the cold water inlet to the Marathon water heater. Mine is a DLJ75. We recently installed a couple of meters from this company that also have pulse output (DLJ75C), and we set them up with a Hobo UX120 pulse logger from Onset computer. This way we'll get cumulative water use and will be able to see usage over time, in order to be able to see peak demand as well as usage.

For ease of monitoring, the web-enabled products such as the eMonitor are great. You get circuit by circuit energy data, and no one has to read any meters! They have a nice interface. The downside is there is an initial cost, of course, but there is also an ongoing monthly cost for the service.

Finally, I am datalogging temperature and relative humidity in the basement and on both levels of the house, and outdoors, using Hobo dataloggers, both the simplest U10 logger for Temperature and TH, and U12-013 which have internal temperature and RH and two external sensor ports, which I am using for additional temperatures (such as inlet and outlet water temperatures to the water heater.) I have current transformers that also can plug into these external ports, for measuring current draw to various devices.

Comments

[Eric]

Cool, thanks. Do the fancier kill-a-watts record prior days' use, or do you have to remember to check them each and every day?

The Hobo loggers look cool, though slightly pricey - I wonder how hard it'd be to do an open-hardware version with an Arduino microcontroller. I may have to look into that project.

I had been looking at a Minomess 130 pulse-output water meter, they seem a bit less expensive - 1 pulse per gallon is fairly coarse, but might do the trick.

[David White]

Hi Marc,

I heard about an energy monitor called Obvius. Looks cost competitive, maybe cheaper if one is willing to set up one's own data interface.