Let's say you're in the USA and your nominal household supply is 110VAC. In reality it varies due to fluctuations in the grid and the quality of supply, right? OK, hold that thought.

I'm interested in getting off the grid, it's not likely to happen in this house, but maybe in my next one, however, anything that I can try to take me in that direction I can do here on a trial basis. I think there's two parts to this, namely alternative energy supply, and energy efficiency. With regard to the latter I'd like to undertake some analysis. What I envision is datalogging usage throughout the house, on a circuit by circuit basis. Power equals current times voltage, so if I measure current on each circuit I can calculate power consumption. Knowing actual usage I can ascertain if savings can be made which will a) be a good thing in of itself, and b ) reduce the amount of alternative energy needed to be produced. I can also determine seasonal usage, and match that to seasonal technologies for production.

So back to my opening line, can I take the voltage coming into the distribution box and apply that to all the circuits? I'm thinking yes, only the current drawn will be different on those circuits, assuming only an insignificant voltage drop through the circuit. This would then mean only one measure of voltage, and several current measurements.

Dave, you can do this. Most power is conditioned off the street unless you are in a far rural area and that sometimes suffers. There is a device called a Kill-O-Watt which can help you weed out the really bad users of electricity in your house. This will most likely be your water heater and your refridgerator, followed by your TV and then your furnace if you have one. Other devices can play a huge part too. My TV uses 500 watts. Some use even more. Compressors on freezers and fridges use a large chunk when they start as do washing machines and dryers. They sell "easy start" kits for them to offset the pull. I have yet to see one for freezers.

The most common cause I have found for excess electric usage is poorly insulated houses. Simply running around with a calking gun can save 20-30 dollars a month in current. Your roof is also a huge source of heat if you have a good exposure to the sun. Good amounts of heat are available for a very small investment even in the worst climates.

In my area, sometimes we talk about how we weatherproof our houses instead of small block chevy's and such. Im hoping one day we will be able to compete with each other about the energy efficiency of our houses like we do with lawns and such.

Getting off the grid is an admirable goal and I encourage you to try. Even if you dont get off the grid, you will save a good chunk of money. If you can produce enough power, your local utility will buy it back from you. Then you have done more than just get independant.

Its like printing your own money.

SJ

I agree with Samuraijack. Your first order of the day is to eliminate energy losses. And remember, when you get your house nice and toasty, your refrigerator and freezer will likely cycle more often. Dumb things, they thought summer had come around!

Now, since the general Lumenlab theme involves electronics and the like, I want to toss an idea into the ring, one that I have had for a long time but never pursued.

The electric rating for our homes is usually calculated on the total electric consumption of the dwelling. This could be 5 to 10 KW or whatever, so folks go out and buy 5 or 10KW of generating equipment. This can cost a bundle iF PV panels are to be used.

My question is, when will the appliances and electric devices all run at the same time? Probably never. Are they all needed at the same time? Probably not. So, why not electronically prioritize each device specifying different levels of urgency. Thus, if the refrigerator or freezer were to delay starting for a few minutes, so what? But when you switch on a light you need that to happen instantly. And I'm sure that many other devices between these two extremes can be "managed" in a similar manner.

The sole intent of this idea is to reduce the maximum power surge that could occur if, for example, the refrigerator, the freezer, the dish washer, the clothes washer, and the electric oven were all to start within miliseconds of each other. If you prioritize these guys the maximum surge would be limited to the power drawn mostly by any single appliance or device in the house, and this can be critically important if you arer completely off-grid, or are using the grid as a backup.

Technically it should be fairly easy since there appear to be a number wireless-controlled switches on the market that could be used to control devices and appliances. A suitable microprocessor would have to be programmed to orchestrate everything. Samuraijack should know what I am talking about since Interrupt Requests (IRQs) are commonplace in computers and most of us have had to deal with IRQ conflicts.

And, of course, the remotely controlled switches must be capable of detecting when the appliance's own switch internal has closed and reporting this fact back to the controlcomputer.

It is not the purpose of this concept to save power, nor is it to save operating costs. And if any of you manage to burn the house down trying to do this, then I don't want to know about it!!! In other words, pass at your own risk!!! When in doubt, get your friendly electrician to do it for you.

I have seen other similar schemes suggested but not quite what I have described above. If I have trodden on anyone's toes, "sorry, mea culpa" If this has been put forward before and I simply haven't heard about it, then I'll go and stand in the corner for the prescribed one hour.

Above all, have fun!

Thanks guys! I won't bother to quote your replies as they were generously lengthy ones. But to answer a couple of quick points.

SJ: Kill-a-watt. Seen those, and they obviously measure what I want, but on a per appliance basis. I'm more than likely going to get one, but eventually I'm looking to monitor my whole house in one go, over a complete year. Why? Because I'm a geek. But also for the reasons highlighted by Spirals. I've been looking at the capabilities of PIC microcontrollers and this stuff fascinates me so I thought it would be a fun and interesting project. (Like I don't have enough of those already!)

Spirals: Living in Alaska we've got a well insulated and energy efficient house. Part of the reason my wife got a low interest mortgage for it. But you've hit the nail on the head as far as usage is concerned, and why I want to monitor the whole house. Reducing the peak load, so that the high load appliances don't all come on at once is a great idea. I hadn't necessarily thought as far as ahead as controlling the switching, but that's a great idea that goes in line with what I'm already thinking, which is determining the peak load so that I can size the 'off grid' equipment to meet my needs. Selling power back to the grid here is a costly and not particularly economic solution.

Oh, and neither of you answered my actual question. Measuring actual voltage at the distribution box can be assumed to be the actual voltage at any outlet in the house? I know SJ mentioned conditioned power from the street, but we are rural and I'm not confident of its condition. I would like to continuously monitor this as well as load on the individual circuits.

Basically yes, your voltage at main switch should be the same throughout the house. A voltage sage detected anywhere would indicate presence of impedance. Current, on the other hand, would be the main variable. The problem is that you would need a ring (inductive?) ammeter to measure AC current, and these can be expensive. I think it does have a proper name but I can't remeber it right now. Unless, of course, somebody has come up with some cute little meter that will give you all the values (AC volts and amps, VARs, power factor, etc) after my time.

I've been looking at semiconductors designed for measuring current, so that I can design and build my own sensors to install. I had found a suitable product before, but can't locate it right now.

Here's a kit that may interest you. It can be purchased from here if you don't want to collect the parts and program it yourself.

And a pre-built unit.

That's the kind of thing I'm interested in, but on a circuit by circuit basis, rather than appliance by appliance. My intention is to log all the data to a PC and then analyze it. Once I have enough information I should be able to tell in real time when someone switches on the TV, or bathroom lights, etc. Or how often the fridge is kicking in.

As an aside a couple of years ago our well pump developed a fault and we didn't realize for a long time that it was constantly on, wasting a huge amount of electricity. A system like I envision could also raise an alarm for exceptional usage.

I guess to expand on my thoughts a little I'm working toward a semi-intelligent solution. But first I need data of actual usage. And then I'll continue to need this as I match various supply technologies to load. I don't really have a game plan, it's something that's going to be continually evolving.

Working on the per circuit approach I may, for example, just have a small solar installation that would cover a single circuit. This would allow me to analyse just how effective solar power is without going to a huge expense, but at the same time getting some measurable benefit.

Here's an idea. Every device has to be connected to power by some hardwired link. Often that is simply a modular plug, like any portable appliance. A very simple crystal (or other) oscillator can be placed parallel with the power lead for any appliance, so that only when the (power consuming) object is energized, a specific frequency is generated by this clock which is concomitantly energized. If the clock is so built, the freq-clock transition will be easily detected on the mains, perhaps "logged" by a simple device like the Pluto-P. The result would be an absolute chronicle of "run time".