Letter Re: Detecting the Presence or Absence of Grid Power

If your retreat is isolated and you can not see any of your neighbors buildings, then how do you know when the power grid is back on (re-energized)? That might not be clear, so this is what happens: We have many power outages per year, which can last from hours to days, last year power was out for (9) nine days. So I disconnect from the grid, and start the generator. I have no way to know when the line is fixed. And with the price of fuel; I am wondering is there some do-dad, thing-a-ma-gig, like a light I could mount in a tree near the main line that would pick up electromagnetic energy when the line is hot. Or some trick one of your readers may know about. Thank you, – D.V.

JWR Replies: Here are a few possible solutions for you:

1.) Most of the common transfer switches for home generator sets (“gensets”) do not disconnect the grid power. Instead, the switch is in a sub-panel box with breakers for several circuits that you want energized all the time. It acts as a “mains” disconnect for that sub-panel only. Unless you have a large genset capable of powering everything in your house, then that is typically just your refrigerator-freezer and a few lights. Therefore, any electrical devices or lights that are on the other circuits will be energized when the grid power is restored. You can simply leave a table lamp and a radio on one of these circuits, both switched in the “on” position. The light and radio will come on when the grid power is restored. This of course won’t be possible if you have one of the very basic “Wylie E. Coyote” or “Disaster Cord” type system without a dedicated sub-panel. (I DO NOT recommend this type of arrangement!)

Important Safety Note: As previously mentioned in SurvivalBlog, it is absolutely essential that you do not inadvertently “back feed” the grid power line, or you might accidentally fry the hapless utility employee that is working on restoring your power!

2.) Many power meters have a status light, showing that the incoming grid power line is “hot.” The easiest solution is to ask your local utility if they have any meter boxes available with status lights. They may be able to install one of these for you free of charge or at nominal cost.

3.) If your utility can’t or won’t install a meter panel with a status light, then any qualified journeyman-level electrician could rig a status light the meter box that should meet the approval of your local power utility. (Of course be sure to ask, first, since utilities have a long tradition of suspicion of any modifications to meter panels. They don’t like giving power away!)

4.) If your utility doesn’t allow an indicator light at the meter panel, then you can have one rigged at your indoor breaker panel to show the presence of “mains”external power. It can be something as simple as a small neon tube. No muss, no fuss. Again, any electrician can do this for you in just a few minutes if you let them know what you need in advance of when they come to your house.

For those if us that live in the boonies that have photovoltaics or other alternate power sources, there is also an inverse corollary to your question: detecting when the grid power goes off. (Many of us wouldn’t notice, otherwise.) I found a web site with a fairly simple power failure alarm circuit diagram and assembly instructions. (This is a little more complicated than just showing the presence of grid power. To announce the loss of grid power requires a relay and a battery, as well as a lamp or some sort of alarm horn/buzzer/annunciator.)

I should mention that there is nothing like the joy of watching a power meter run backwards–knowing that for more than half of of each year that the power company will be paying you for power. Selling power back to power utility is possible throughout the United States. However, most pay you only the “avoided cost” rate–typically 2 or 3 cents per kilowatt hour–rather than at the same rate that you buy it from them. The latter is called “net metering” or “net billing.” The utilities that presently pay at the net metering rate are in the minority, but I predict that it will be legislatively mandated within a few years.

There are essentially three types of photovoltaic (PV) power systems: 1.) Stand-alone, 2.) Grid-tied, and 3.) Grid-connected but stand-alone capable. Of the three, the only type that I do not recommend is grid-tied. These systems–typically without a battery bank–leave you vulnerable whenever the power grid goes down. If you want to sell power back to your utility, yet still be self-sufficient, then I recommend that you install “grid-connected but stand-alone capable” system. (The same would apply to wind power and micro-hydro systems.) For details on alternate energy system hardware, siting/exposure, and system sizing, contact Ready Made Resources. They graciously offer alternate energy system consulting free of charge.