Generating and Storing Power with Portable Generators

More than ever, our civilization relies on electrical power for everything: lighting, entertainment, communications, security, heating/cooling, cooking, food refrigeration, the list goes on and on. Our reliance on the electrical grid has made electricity critical to our lives.

Short power outages (under 12 hours) have resulted in widespread traffic chaos, hospital evacuations, and even civil disorder. Multi-day outages can adversely affect water and sewage systems, supermarkets, gas stations, and cellular phone systems.

This subject is huge and I am only scratching the surface here. As a result, I’m not discussing solar, wind, or small-hydroelectric power. All three have pros and cons that are discussed at length in print and online. Here, I will concentrate on what most people can easily put together in a suburban environment with a reasonable investment in time and money.

Generate and Store for Extended Power Outages

Preparing for extended power outages is a little more complicated than you’d think. These days, having a generator is just scratching the surface…EVERYTHING in our lives consumes electricity. While you could run a generator 24 hours a day, it is a horribly inefficient waste of fuel, as well as a surefire way to piss off your neighbors and attract unwanted attention.

Any serious power outage strategy will also include one or more storage batteries, a 12-volt-to-120-volt inverter, and a quality battery charger. You can run your generator in the daytime to power appliances and charge batteries, then shut it down overnight while you quietly run your devices on the stored power in your batteries.

The Basics

The electricity that comes out of your wall sockets is 120 volts, alternating current (AC). AC current is easy to transmit long distances but cannot be stored. It is very dangerous if mishandled, resulting in burns, electrocution, and/or death. Conversely, direct current (DC), which is used in phones, laptops, and car batteries, can be safely and easily stored for later use. A 12-volt DC current is one of the keys to emergency power.

Electrical Definitions

Let’s define a few electrical terms:

• Current: This parameter is measured in Volts; think about a mountain stream, the higher the current number, the stronger the current, and the more power is transmitted through the current. This is a measure of force, or “push.”
• Amperes (Amps): This is a measure of the quantity of electricity. We’re most familiar with amps because an overload of amps on an electrical circuit usually causes a fuse to blow or a circuit breaker to trip. You know, Mom using her blow dryer while Susie heats up her coffee in the microwave…too much power in use. Batteries are rated in terms of “Amp-hours,” which is an expression of how long the battery can provide a certain quantity of power.
• Watts: This is the measure of the amount of work that can be done. It is the key to determining if appliances can be accommodated in a given electrical circuit. It is a familiar measure for light bulbs and blow dryers. More importantly, it is the measure used to rate the power-generating capacity of portable generators and inverters.

AC current can be converted to DC current; we do this every day when we plug in our phone or laptop charger. DC can be converted to AC through the use of an “inverter.” To store power, we use “deep-cycle” batteries, which look like car batteries but are specifically designed to efficiently take in and give back DC current. When we need an AC current to run a refrigerator or lights, our inverter converts the DC current to AC.

Determining What You Need

Like generators, inverters are rated in watts so you can easily choose the model for your needs. Deep-cycle batteries (also called RV or Marine) are rated in amp-hours; using the formulas below, you can calculate the size and number of batteries to support your system.

If you can understand a couple of basic formulas, you are set: Watts=Volts x Amps, and Amps=Watts/Volts. All electrical devices are marked with their power requirements, allowing you to make an electricity “budget” and intelligently plan for your needs. For example, my refrigerator requires 5.0 to 6.5 amps when operating. Using the equation above we can determine the number of watts it needs: 6.5 x 120 volts= 780 watts. Here are some common wattage requirements for various appliances:

• Table lamp: 40-100 watts
• Toaster: 800 watts
• Microwave oven: 1500-2000 watts
• George Foreman grill: 800 watts
• Electric skillet: 900 watts
• Cellular phone charger: 24 watts
• Laptop AC adapter: 72-144 watts
• 42” Plasma TV: 286 watts
• Digital cable box: 40 watts

If I expected to run all of the above devices at the same time, I would need to provide up to 5,100 watts of electricity. However, if I planned ahead and was careful not to use high-wattage devices at the same time, I could get away with only half of that capacity. As you might expect, the more watts you need, the more it will cost.

Building a System

So let’s build a simple system based on the above information, assuming that we will run the generator 12 hours a day (7:00 AM to 7:00 PM), and use inverter-provided power the other 12 hours. If we do all of our cooking while the generator is on, we can get along with a smaller inverter and less battery capacity for our nighttime needs. We can also freeze some ice blocks during the day, putting them in the refrigerator compartment at night and turning the fridge and freezer controls down to low at night; if the fridge stays closed, it will run minimally at night.

Our system will include a 3,500-watt-rated generator ($400), a 1,600-watt inverter ($110), two Sears Diehard Marine batteries with 180 amp-hours capacity ($220), and a Diehard automatic battery charger ($75). This solid, basic system can be upgraded as needed and will maintain your ability to communicate, cook, store food, and stay alert for emergency notifications. Don’t forget to sock away enough extension cords to reach your appliances.

Your electrical preparedness strategy is crucial to your family’s safety and comfort in a disaster. The good news is that you don’t need to be an engineer or electrician to properly prepare for when the lights go out.

READ MORE: If a power outage happens in cold weather, you’ll want ways to stay warm that will help you conserve your stored power. This article has ideas for that.

Fuel Choices

While most consumer generators are available only with gasoline engines, in the last few years there has been an increase in the availability of generators fueled by propane, or propane and gasoline (usually called “Dual-Fuel”). This is very important for the home generator user for these reasons:

• Gasoline is difficult to store safely in sufficient quantities to keep a generator running;
• You may already have propane as fuel for your BBQ grill or patio heater;
• Propane tanks are very safe to store at home, and tank exchanges don’t require power; and
• Having the ability to use different fuels in a disaster situation is priceless.

Using Propane

Using propane with a generator can be tricky at first, as I learned with my first dual-fuel unit. I hooked everything properly and while the generator worked great with gasoline, I couldn’t get it going on propane. Fortunately, the manufacturer was nearby, and the service guy who helped me showed how to slowly open the propane valve to avoid activating a leak-prevention safety device. Once I had that figured out, I was good to go.

Another advantage of using propane is that it is a cleaner-burning fuel than gasoline, and so the exhaust is less of a health hazard if you’re working around it while running.

“Inverter” Generators

Another relatively recent trend is the introduction of the “Inverter” generator, which can be confusing in the context of this article. As I described separately, a 12 volt to 120-volt Inverter can be used as part of a quiet energy storage and retrieval system for overnight use, for a freezer, for example.

An Inverter Generator creates “cleaner” AC power better suited for electronics like computers, and if you need to run a desktop computer directly plugged in to the generator it may be worth the price premium ($100-$300) you’ll pay for one. However, most appliances and battery chargers work just fine with a conventional generator, and since a laptop’s power supply charges its’ DC battery, there’s no problem running it there as well.

Generator Safety

Portable generators are invaluable during power outages, but they can also be dangerous if not used correctly. Here are some essential safety tips:

Frequently Asked Questions