You can monitor 120v plug loads with a Kill-A-Watt, 240v loads with a TED or similar, or do circuit level monitoring of entire electrical panels with systems from Powerhouse Dynamics, Brultech, and others. A good site to check out is Energy Circle http://www.energycircle.com/
Peter, is your objective personal or an offering for customers? After the first run through what each appliance uses I have found it unnecessary to continue monitoring them. And, the initial use can in most cases be simply estimated. My only use for my meters has been an occasional search for something using too much, but I have in each case found the problem without the meter, a heater left on or a motor running continuously.
With my electrical background I thought it would be a neat addition to my service offerings, but my return on investment has been negligible.
If the customer has a smartmeter installed by the local utility they may be able to get whole house usage data on-line for free.
Last one used was power house Dynamics. Its for a home owner and data just went back 30 day only. with USB port you can use most programs, If use use one of the free on line it can do yr by yr. I put in a Ground Type Heat pump with just one tank and a desuper heater and I have proof that you get 0 from the AC side after the buffer tank is put in you get 30% savings. I have proof If you set the temp on the tank to 150' then to 120' it goes to $140 mo to $55MO. I have proof if you set a solar hot water tank and only use hot water only in early AM you have no saving Use hot water in mid day and it all there - just stand by loss. I learned a lot with data loggers its real for that job. its a must!
Wow, sorry, got busy for a couple of days there. I was looking for something that taps in at the first panel that would monitor power conditions as well as load over time so i could have an idea when there are voltage spikes and how large, if certain appliances were turning on excessively frequently or getting noticeably less efficient, etc. The data logging aspect was for the purpose of being able to map summer versus winter usage patterns, occupied versus vacant patterns, changes in usage with changes in infrastructure and other utilities, but mostly because I have a lot of energy hog clients who always want to know why their electric bills are so high on their multi-million dollar homes and they refuse to believe that it simply costs more to run a larger home, whether or not they actually live there. Data with real numbers from which I could generate charts would be extremely useful and definitive. I have a couple of Kill-A-Watt meters and they are very useful for certain kinds of short term testing but i also have a clamp on multi-meter that i always have to carry anyway and with a special pigtail I fabricated and the calculator in my smart phone I have found the Kill-A-Watt to be redundant.
Thanks for all the tips, I'll be doing a little research now to see what I can use, I'll report back what I find.
Definitely a different customer group as mine have always been looking for savings. And that is one of the reason why most would be unhappy. They would end up paying me and still have the high electric bills. And still believe there is a problem somewhere regardless of how I produced my conclusions. A real time monitor that they could purchase and watch might keep them busy, but running back and forth to install/remove equipment doesn't make many happy.
With the database, they can do an inventory or I can do one. A few minutes discussing run time and plugging in standard guesses where necessary and up pops an estimated monthly bill. If it is way out of line, a second run through (fine tuning) the numbers and you get closer. Surprisingly, you have to be way off to move the monthly numbers much.
I admit measuring helps to improve your confidence in your guesses, but after you have done a few, the guesses are much faster and close enough.
Now commercial customers are another issue. Unfortunately an Energy Auditor in Maine cannot touch commercial work without an engineering degree. But I have helped a few small customers, no charge, and their bills are huge. A small restaurant was running $1,200 a month when the AC was running. They also get hit with peak demand.
You need circuit level monitoring for most of what you're talking about. You can monitor multiple loads over weeks or months and give them a web portal to look at cumulative usage for each load in their house. A lot of people want to know "where did all the electricity go?" and this is how you answer the question. A clamp meter in the panel only gives you a snapshot at a certain moment in time. Who knows what turned on or off after you left?
Power quality issues such as spikes are totally different, but I suppose it would be easy to monitor for that also.
How much detail do you want? Kill-A-Watt can give simple loads, TED gives better details (but they can be flaky), there are multiple vendors with devices like the TEDs (The Energy Detective). If you choose a device that can provide volt, amp, and phase angles at second intervals - it is actually possible to detect and disaggregate the power data and identify individual loads as they start and stop -- with only a few current transformers.
Also google/bing "electric power meter monitor for home" and you'll find lots of possible sensors.
Many of the home automation dealers carry the devices. Now days you can get internet ready devices, zwave, bluetooth and zigbee... just depends if you want off the shelf complete solutions or something you intend to build on.
http://aeotec.com/z-wave-home-energy-measure <-- an example
http://www.home-energy-metering.com/energy-monitor.html I thought you could use this.