When the Power Goes Out: Generating and Storing Power

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When the Power Goes Out: Generating and Storing PowerWhen the Power Goes Out: Generating and Storing Power

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.

As you can see in this 1965 image, even big cities like New York suffer from power outages.

The Basics

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.

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. AC current is very dangerous if mishandled, resulting in burns, electrocution, and/or death. Conversely, direct current (DC) which is used in phone, laptop and car batteries is able to be safely and easily stored for later use. 12 volt DC current is one of the keys to emergency power.

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 quantity of electricity…we’re most familiar with amps because it is usually an overload of amps on an electrical circuit that 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. In general, this is the key measure in determining if appliances can be accommodated in a given electrical circuit. This 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 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

Power 2If 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 is a solid, basic system that can be upgraded as needed, and will maintain your ability to communicate, cook, store food, and keep 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.

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Jim Acosta

Jim has spent time as a volunteer firefighter, Emergency Medical Technician, and wildland fire hand crew member. He is currently a Certified Emergency Manager. In 2011, Jim authored “I Can Overcome That: The Practical Guide to Surviving the Next Big California Earthquake.”

12 thoughts on “When the Power Goes Out: Generating and Storing Power”

  1. Thanks for this info. I’ve been looking at an alternative to running the generator when we don’t need to worry about running our sump pumps. I’ve been wondering about inverters and this really helps give a direction to look into.

  2. THANK YOU for this stripped down, info filled article!
    I have found many articles on this topic, but all are written for the electricity educated and/or MIT graduate!
    With this information, I can EASILY get what I now know I need to sustain me through an electrical outage….
    GREAT stuff!

  3. A couple of things to consider when building such a system:

    1. If you can afford it, I’d suggest a pure sine wave inverter rated to support a power surge of around 2200 Watts (the start-up surge on a refrigerator’s compressor can be about triple the appliance’s running Watts). Some appliances (like anything motor-driven) run less-efficiently on modified sine wave power.

    2. Don’t forget that the batteries in such a system will need to be maintained. Battery University is an excellent resource for learning about the care and feeding of batteries (it’s recommended on a solar power forum on which I participate).

  4. One significant correction: Although you correctly state the basic equation, “Current” is measured in Amperes, and the other quantity, “Potential,” is the one measured in Volts. You can think of the voltage as the potential speed, or pressure, and the amperage as the amount of electricity available to flow. This is WHY the relationship (volts times amps equals watts) works.

    Consider: if you had a job (work) to do such as using water to clean some gunk off a dinner plate, you could either pour many gallons of water over the dirty plate at a sluggish speed of a couple of miles per hour, OR you could squirt only a few onces of water at the plate at 100 miles per hour… both methods would yield a clean plate, although the first is a lot of water at low speed and the second is a tiny bit of water at high speed. 1 Volt at 100 Amps equals 100 Watts, and so does 100 Volts at 1 Amp… or 200 Volts at half an Amp, for that matter… all three are 100 Watts, the SAME amount of work. You can think of Voltage as the speed, Amperage as the amount of water available, and Wattage as the work done.

    Another point: the description you used for deep-cycle batteries actually applies to ALL batteries (geek note: yes, yes, many batteries are manufactured already charged, but the acid or alkaline paste still had to “take in electrical energy” at some point whether the means were chemical or electrical). The salient point for deep cycle batteries is that they are still manufactured with the thicker lead plates that all car batteries had prior to about 1965, and thus can be drained most of the way down to zero charge and still re-charged again and again… up to a thousand times, according to the labels, whereas a typical modern car battery, with its very thin (read: cheaper) plates can only survive a very few such nearly-complete drains of charge.

    One other minor matter: if you use a Mercury-vapor fluorescent (ugh) or much safer LED bulb in your table lamp instead of incandescent, the figure drops down to the 6 to 14 Watt range… not a minor consideration when designing a backup power system.

    I hope this helps.

  5. AC current is very dangerous if mishandled, resulting in burns, electrocution, and/or death. Conversely, direct current (DC) which is used in phone, laptop and car batteries is able to be safely and easily stored for later use.

    It’s not the whether electricity is AC or DC that makes it dangerous. If anything, DC is more dangerous than AC because of inductive effects (the tendency of flowing current to want to keep flowing). What makes electricity dangerous is its voltage along with its maximum current capability. Twelve systems are safe (AC or DC); 120 volt systems can kill you (AC or DC).

  6. Interesting concept. I would definitely go with a high quality pure sine wave inverter to avoid destroying your sensitive electronics. Also, more importantly, two 12 volt 180 amp-hour batteries will not provide as much power as you think. These batteries are rated to provide 180 amps at 12 volts for one hour or a total output of 2 x 180 x 12 = 4.3 KiloWatt-Hours (KWH). However, I don’t recommend totally draining those batteries each night. They won’t last that long. Perhaps 50% usage is more reasonable. In this case you will only have 2.15 KWH available for 12 hours of night. So, on average during the night, you can only use 2.15 KWH / 12H = 180 watts. I think that a very important aspect of emergency power is to use devices with extremely low power consumption. Don’t use incandescent bulbs. Just three 60 Watt bulbs will use up all your available nighttime power. Think LED for lighting. Only use low power electronics, not a 42″ plasma TV. Also, the George Foreman grill and electric skillet will drain those batteries very quickly and leave you with no power. Other low tech methods will be much better for cooking such as a gas grill or a camp stove with propane bottles. You can store more energy in propane than you can in batteries.

  7. Good article except for one thing…Current is not measured in Volts, Voltage is. Current is the flow of electrons through a conductor and it is measured in Amperes, or Amps. Voltage is the actual ‘pushing’ force that you referenced while, as you stated, Current is what actually ‘makes things happen’. (synopsis version)

  8. The start up amps needed are called locked rotor amps, and can be difficult to find out, fridges & air conditioners can get pretty high.

  9. Good introductory article. It’s nice to see a starter system available for under $1,000. I agree with AuricTech that the start up amps of a compressor (refrigerator) is about triple the running amps. Also, you might be interested to know that electrocution is a fatal exposure to electricity. An “electric shock” is a non-fatal exposure to electricity (so saying electrocution and/or death is redundant).

  10. Current is measured in amps (Amperes), not volts. Voltage is measured in volts.

    Comparing electricity flowing through a wire to water flowing through a hose, voltage is equivalent to the water pressure inside the hose, and current is equivalent to the volume of water (gallons/min) flowing through the hose.

  11. It’s great that you’ve thought all this through!

    One important thing to remember is that there are many ways we can reduce our electricity needs. When you need new appliances, buy energy efficient models; it will save you money in the long run, and lower your energy needs in an emergency situation. Maintain your appliances, too; the user manual should cover that. (And keep the manuals accessible for future reference!) Cleaning the coils on your fridge is easy and makes a big difference, but how many people do it?

    And switching to LED bulbs can be great! Not only do they use a fraction of the electricity, but they last many times longer. The initial cost is more, though – maybe a lot more. Definitely pays to shop around!

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