Are there real time in-house digital electricity monitors?

From what I can see, utilitie companies all over are putting in what they’re calling “smart” monitors, presumably so that they can monitor electricity use over the air, rather than sending out guys to read the meters. What I see on line are meters that report the information in 15 minute segments at the smallest. I would like a gizmo for inside the house that I could look at that would tell me at that moment how much electricity I’m using, in, say, kilowatt seconds - or whatever units would be feasible. I want to be able to see, for instance, how much more electricity I’m using when the space heater is on, or when the furnace is on, or when the living room lights are all on, etc. Is there such a gadget? I can’t seem to find such a thing on line. Any help, Dopers? xo, C.


Plugging into the outlet (for a few devices at a time), you can use the Kill-A-Watt meter or the better Belkin version.

For whole-house use, there’s The Energy Detective (TED) and a bunch of others, such as the ones listed on this site.

I’ve used the three (Kill-A-Watt, Belkin, TED) and they all work like they’re supposed to – good enough for home use, I presume, but I have no way to calibrate their accuracy for scientific purposes.

It sounds like what you are looking for is a simple wattmeter. I know you can get whole house wattmeters, some with a PC interface that you can use to trend your usage and generate reports and do all sorts of fancy stuff with it. There are also plug-in versions to monitor individual outlets.

Googling “whole house wattmeter” seems to return a lot of useful links if you want to monitor your home’s entire electric consumption. Kill-a-watt seems to be a popular plug-in type.

I don’t have any actual experience with these products so I can’t say how well they work, but a wattmeter is a pretty simple device, electronically speaking.

If you start comparing specs, a better meter will be able to distinguish between watts and vars or will be able to tell you the power factor of the load. The power company only charges you for watts. Some simple meters aren’t able to distinguish the two and will be fooled if your power factor isn’t close to unity.

Ok, I think to OP has an answer.


You already have one; it’s called a meter.

Check the numbers on it, check them again an hour later. Voilà Your current W.
Not very fancy, not very accurate but good enough for billing purposes.

to measure the consumption of one device using your utility meter can be done.

to be accurate what is running has to not change during the measuring period. so nothing else can be on or other things have to stay on in the same mode (level of consumption) for the full measuring period.

the measuring period has to be long enough to show a meaningful change on your utility meter, this could be hours.

so it can be hard to get anything useful that way to the homeowner.

i’ve used a number of the Kill-A-Watt meters, they are good for 120V 15A plugin loads. the ones i’ve used agree with each other and to similar more expensive meters of other brands.

Right. For billing purposes, I could go outside, down into the basement, and check the meter every hour. What I’m looking for, however, is something that will let me track the energy use of various configurations within the house, e.g., turning on a space heater, turning off certain lights, turning off vs unplugging a computer, etc. But thanks for your input.

As mentioned, The Energy Detective is an excellent choice. I have the old-school one which is a plug-in tabletop deal. But the newer one looks really cool and can even be connected to a computer if I’m not mistaken. Mine has served me well for several years and was some of the best money I ever spent. Paid for itself the first month when it alerted me to the fact that I had left the oven on like an idiot. A few months later it told me that my sump pump was burning itself out. Handy stuff.

The only problem with the T.E.D. is you need a spare breaker slot unless you want to bend the rules a bit. This is only a problem if your load center is already full.

If you don’t want to spend $150+ you actually can use your meter outside without going through the hassle of waiting an hour. Just go out there with a stopwatch and time the disc spinning. That’s what I used to do – only takes a minute really. I wrote a PocketPC app to do the conversion for me automatically but nobody uses those PPC’s anymore; perhaps someone has written a modern phone app. Calculation is easy either way.

If you’ve got one of the newer digital meters you can do the same thing but the indication varies by model. Last time I looked (4+ years ago) it was hard to locate decent information online but I’m sure that has improved since then.

I was interested in one of these devices as well couple of years ago and found that real time monitors are very big in Europe. Unfortunately most of them weren’t adopted for the US market and not available here. I ended up buying an Envi monitor from Current Cost. It was a very simple install although you do have to remove the panels to your main breakers so be careful. I have had it for over 2 years and it is working perfectly. It cost around $100 and was able to pay for it in the first month because my bill had jumped by $200 for the prior 2 months (that’s why I started looking at this in the first place) and found that my pool pump was running 24 hours daily. The pool guy had changed the setting and this was now costing me an extra $200 per month. Without this monitor I would have never figured that out. So If you have high unexplained bills or just want to be more energy efficient, a real time monitor helps a lot.

Agreed. On meters that I am familiar with, the multiplier is printed on the meter (e.g. 243.2 revolutions = 1 kWh, or whatever). So if it takes 40 seconds for the disc to turn once, you can calculate that you’re using 370 W at that moment.