Most people recognize that generators come in different “sizes” and understand that bigger “things” require bigger generators. After that, though, eyes glaze when the discussion turns into techno-babble about kilowatts, horsepower, amps, and loads. Unlike many inconsequential topics, however, these things do matter when you’re thinking about backup power for even part of camp. Simply put, the size of the generator should be determined by the amount of power you want it to deliver.

If this is starting as a do-it-yourself project, be aware that you will be using both unit systems: International System or metric (kilowatts) and imperial (horsepower). Pay close attention to that because mixing them incorrectly will deliver very wrong results. To figure out what the operating demand is, simply add the current draws (amps) from all of the components you plan to run at once and multiply that by the voltage the loads use. For example, a toaster oven that you’d plug into the wall in your kitchen might draw 9 amps. The voltage there is typically 120 v, so the total requirement would be 9 x 120 or 1080 watts, or 1.08 kilo watts (kW). If you had ten appliances, each drawing 1.08 kW, you’d need a 10.8 kW generator to run them all at the same time.

The other thing you need to consider is that certain electrical devices require more than just their running draw to get started. You may have noticed the lights dimming when woodworking equipment in the shop starts. That’s because it takes more power to get that equipment running than it does to keep it running, with the rule of thumb being that you need three times the running power to get the system started. That extra draw is a very real power requirement, and it must be accounted for when determining the size you need. Otherwise, when the equipment tries to start, it may not get all the power it needs, it will run too slowly, and the motor will burn up very quickly. All the generators in the world can’t make a dead motor run.

Keep in mind that many (if not all) of the major building system components (like furnaces, compressors, and commercial appliances) and appliances (like ranges and clothes dryers) use a higher voltage power supply (240 v). Remember to use that higher voltage when calculating those components’ demands. And things get even more complicated when there are heavier loads yet, which require three-phase power. So, if you’re thinking about backup power for any of those kinds of systems, you really will need to hire a professional engineer to make sure your needs are properly met.

Unless you pick and choose what you want to power when the lights go out at camp, a generator will get very large (and very expensive) quickly. Even a modest kitchen facility and dining hall can require a sizeable generator. Which systems are to be powered will vary with the property, the type of programs offered, and the kinds of hosted guests. For example, perhaps the health center is configured to ensure it can serve a significant number of guests who require insulin. Refrigeration is then a critical need and should be included in the plan. If camp is very remote, foodstuffs are delivered infrequently, and power outages are often long, then dining hall refrigeration becomes a priority. Those are obvious critical needs. But what about ancillary systems like telephone and Internet? If camp runs its own internal telephone system and outages are typically pretty short, then a good-quality battery backup may provide the necessary bridge until power is restored. If outages are common or often go on for days, then ensuring communications with camper families and emergency services is not optional by any means. “Our power was out,” will not satisfy a frantic parent who can’t get an emergency message to their child.

It may be prohibitively expensive to get a generator to power an entire building when all you really need is to run the switchboard. If you’re building camp from the ground up, then the engineers, architects, and planners working for you will have identified all of the critical elements and done their best to concentrate all of those critical needs into a single location so only one generator is required. So, perhaps the health center and the administrative offices share a wing of the building that also contains the dining hall and kitchen (with its walk-ins). The electrical circuitry is laid out such that when the generator is needed, only those items intended to be powered with the backup are powered.

Unfortunately, few camps have the luxury of a wholesale “do over” with auxiliary power in mind. Instead, they must make do with the arrangement of buildings they have, with the specialized functions in the spaces where they’ve always been. In that case, camp may have to purchase several smaller, portable generators to accommodate each location. The sizing process is the same — adding the loads and accounting for startup draw to select a unit. Some other things need to be considered to make this decentralized system work though. First is how to avoid overloading those smaller generators. The key here will be to identify which circuits will be on and which will be off at the breaker panel. A simple color coding in the panel works well, and enamel fingernail polish is weather proof, it won’t fade with heat in the panel, and it is hardcore permanent. So put a dab on the description of the circuits you want to power in that panel. Why near the description and not on the breaker tab? Because sometimes breakers fail and need to be changed, but the panel that covers them remains even with the new breaker. Also, pick your color wisely. For example, most people think of red as meaning “no,” so coding the circuits you want on with red polish may be confusing. Perhaps you put that red dab on each circuit you want off instead, or simply buy green polish for the on circuits. Whatever you do, though, you must be unfailingly consistent in your marking of panels from building to building to avoid needless confusion when there’s already plenty to go around.

Unlike larger, permanently stationed generators (which are largely automatic), smaller, portable units require the user to be focused in setting up, starting, and eventually shutting them down. All the component and supporting parts, including fuel, connecting cords, and plugs, should be kept together where they’ll be needed. Units will be selected for a specific set of loads, so they should be unmistakably marked to serve that particular building. Also, for a portable generator, a manual service disconnect is a code-required safety element at the top of the list of important items. This simple, cartoonish-looking device electrically separates the structure’s service from the wire network that usually powers it. Without that, damaged powerlines and dangerous electrical conditions may energize, starting fires or possibly injuring someone working to restore power to the system. Finally, the only way to get the power from a generator to the power panel is through a properly sized electrical connector cord to a specialized plug and socket (which may look like a dryer plug) used for nothing but powering the panel and the chosen electrical circuits.

When the generator is needed:

  1. Set the transfer switch to “auxiliary” from “line” and then turn off the circuits in the panel that aren’t intended to be powered. (You know which those are because you marked them!)
  2. Fuel the generator away from the structure, wipe away any spilled fuel, and bring the generator to where it will run.
  3. Connect the power cord from the unit’s “out” line to the building connection. Usually there’s a “twist to lock” feature on those plugs to keep them from coming undone by themselves, so be sure to lock them in place.
  4. You’re now ready to start the generator and provide selective power to the building. Once it’s running smoothly, check to see that the panel has all of the right circuits on and off, and check that the systems you want to run are operating correctly with no odd sounds or smells.
  5. Check the units frequently for overheating, fuel replenishment, and oil level according to the manufacturer’s manual.
  6. When power has been restored, return the transfer switch to “line,” turn off and disconnect the generator, and finally, reset the breakers to their normal position.

The process may sound complicated and cumbersome, but it’s really all common sense if you understand how the system is supposed to work. Here are a few other thoughts that should make your backup power plan work even better:

  • Each building with a generator needs to have a detailed instruction manual so someone with basic orientation and only minimal training can properly and safely place and run the unit. That manual should contain all of the manufacturer’s literature including operations manuals and parts lists, where and when it was purchased, important telephone numbers, a listing of the equipment that goes with the unit, and a specific list of the circuits to be powered. Keep all of that in a three-ring binder with each generator or next to the circuit panel.
  • Engine exhaust is deadly! As you plan for the placement of the transfer switch and the stationing of the generator, make sure the exhaust is well away from windows and fresh air returns. Never ever run the generator inside.
  • Consider alternate fuels for larger generators. If you’re planning for a permanent, mounted unit with an automatic transfer switch, consider natural gas or propane as the fuel. While they cost a little bit more than diesel or gasoline, not only do they burn cleaner, but the fuel doesn’t degrade over time like liquid fuels do. The generator must work flawlessly when it’s needed; stale fuel or a fouled carburetor is an ugly surprise in an emergency.
  • Think all the way through the implications of which circuits you want to back up. If it is important for potable water to continue to flow, think also about where that water is going down the drain. To avoid costly spills and environmental hazards, any sewage pumps in your system also need backup power if your water system has power.
  • Don’t shortcut or skimp when the unit is being sized. The proper methods and math to choose a unit are deceptively simple and may deliver what seems to be a very oversized result. The best thing to do is to hire a consultant who has no equipment to sell and no commission to make. Then you can rest assured that the answer simply is what it is. The “paring back to make the budget” should be in removing circuits to be powered, not in the size of the generator.

If your operation and programs need electricity to ensure they run uninterrupted and backup power is necessary, make sure you do all of the homework necessary to guarantee that your contingency plan happens perfectly. You’ll be glad you did!

Rick Stryker is a professional engineer who is passionate about camps and the opportunities that they provide. He’s always delighted to answer email questions at