Energy saving in home HVAC (heating, ventilation, air conditioning) is an area of major interest to vendors of system, software, and components, as there are so many diverse scenarios and so many opportunities for improvement.

On one side, you have advanced whole-house systems which sense and control almost every point and subsystem in the house, including water temperature, airflows, furnace or boiler situation, room temperatures, electricity usage and rates, available electric power (if there’s home-sourced power in the mix), and more. These are coupled with a controller running a presumably smart software app

These systems are relatively expensive, of course, due to all the needed sensors and transducers.

At the other end of the spectrum is a relatively basic enhanced device such as the smart thermostat, typified by the popular Nest unit from Nest Labs.

Most engineers like to be efficient and conserve. To that end I bought two ac power meters. For handy instantaneous measurements, the Kill A Watt is a nifty device (Figure 1). It gives an instant readout of anything you can plug into the wall.

The one thing the Kill A Watt does not do is log the data and let you download it into a spreadsheet or graphing program. For 20 bucks you can’t expect too much. For data logging I use a Watts Up? Pro (Figure 2), now discontinued.

Be cautious when looking at that data. The fact that the peaks are not equal tells you that the data acquisition is too coarse; too few samples per second to accurately record the in-rush peak power.

I was delighted at being able to see my power usage over time.

It’s hard to see the idle power

These meters taught me a lot. One big deal was that I saw that my Denon receiver had a large quiescent power–over 120 Watts. That was with no signal.

The Kill A Watt was a handy, cheap tool.