Emergency Lighting | How Long Will That Bulb Last?



Feature | Emergency Lighting | How Long Will That Bulb Last?

One of the most important things to consider in emergency lighting is how long the light will last. There are two issues here. One is the design of the light bulb itself. The other is how long the batteries energizing the light will last. Of course, for those times when home emergency lights do run out, it’s always a great idea to have a backup on hand.

Emergency Lighting | Good-to-Know Facts

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Emergency Lighting: How Long Will It Last?

Emergency Lighting: How Long Will It Last? | Emergency Lighting | How Long Will That Bulb Last?

Emergency Lighting: How Long Will It Last? Photo by The Grife

Electrical light bulbs, fluorescent light tubesand LEDs can last for thousands of hours. Below is a table comparing the operating lifetimes of various emergency lighting sources, showing how long each should last.

If you have electrical power, these lights should last for the hours shown in Table 1.

Emergency Lighting and Battery Power

Emergency Lighting and Battery Power | Emergency Lighting | How Long Will That Bulb Last?

If you’re using battery-powered flashlights or lanterns, the number of hours you can get out of fresh batteries becomes important. Here are some interesting facts concerning the emergency lights battery.

You can determine the battery's capacity by the hours it can put out electrical current (amps or milliamps)—based on the DC voltage remaining in the battery. As shown in Table 2, batteries are rated in the amp-hours (or milliamp hours) of energy they can produce.

An AAA alkaline battery rated at 1,200 mAH and driving a 120 milliamp load can last 10 hours.

When you turn on your flashlight, it draws electricity (actually milliamps) from the battery. As the battery power is used, a point is reached where the battery does not contain enough DC energy to produce the milliamps of current necessary to drive the light source. This when the light goes out. How long before this happens?

Just because a battery contains a lot of amp-hours of stored energy, this does not mean that the battery as a power source will last a long time. It depends on how much current the battery can draw to energize a bulb in the flashlight. For continuous light during a power outage, it’s important to know how long a particular battery (or series of batteries) will last in a dark room. Researching online provided several data points to help me create Table 3 comparing battery manufacturer battery types and how long their battery products could power a load (e.g. bulb).

Emergency Lighting and Battery Power | Emergency Lighting | How Long Will That Bulb Last?

Approximate Battery Life

Approximate Battery Life | Emergency Lighting | How Long Will That Bulb Last?

How long a battery lasts depends on the load put on the battery—how much energy comes from the battery. A tiny bulb with the metal electrical conduction path in a flashlight is an example of a load.

  • In a quality flashlight, a D-size battery will last 10 to 15 hours. In a cheap flashlight, it may only last 8 hours.
  • Most D-cell batteries last longer than AA-size batteries. Draw half an amp out of a D-cell and it will discharge in 4 hours.
  • If a 9V battery is rated at 600 milliamp hours (mAH) and draws 25 milliamps (mA) in an energized flashlight, the battery will last approximately 24 hours.
  • A Duracell rechargeable 9V NiMH battery rated at 170 mAH driving a 17 mA load will discharge the battery in 10 hours.

These are all approximations but they give you a rough idea how long your flashlight will keep the bulb energized and lighting the area around you.

According to online forums, batteries can remain charged longer if stored in a refrigerator.

Drawing less from a battery can significantly increase its useful life. Take a look at Table 4. It shows the time that various lanterns will remain energized based on their brightness setting.


Here's a short video  by Safe Mission about testing emergency lighting:

As you can see, the longest run times relate to the use of D-cell batteries. Table 4 can be helpful when selecting the right lantern for you. While many lighting options exist, it's key to have a longer running light source for use when the power goes out. No one needs to be in the dark. Whether it’s a campout, a nice evening on the patio, or an emergency power outage, light is available.

Did the article give you a better understanding of emergency lighting and its longevity? Share your thoughts in the comments section below!

Up Next: 8 Ways To Generate Electricity At Home


Editor’s Note: This post was originally published in October 2014, and has been updated for quality and relevancy.

(Based on the book Power Out! How to Prepare for and Survive a Grid Collapse)

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  1. Michael W. Perry

    October 27, 2014 at 8:36 AM

    I’d be interested in knowing where those battery life tables come from. There’s a huge difference between an Everready AA (4 hours) and one from Duracell (24 hours). That’s 600% longer.

    Also take note of another factor with small LED flashlights. Some use 3 AAA batteries, and some use a single AA battery. My hunch is that, in an emergency situation, a single AA will be easier to find than three AAAs.

    • cmac

      October 28, 2014 at 11:45 AM

      You should note their are Eveready and Energizer batteries listed. The Eveready is the old carbon zinc battery while the Energizer is the battery comparable to a Duracell.

  2. Jamie

    October 27, 2014 at 2:39 PM

    Jamie Lynn Boatwright-Davis

    Hi, please check out this link. We are going into the production phase of our Off-the-GRID power light and lantern. POWER OUTAGE? NO PROBLEM, YOU’LL STILL HAVE POWER AND LIGHT! AND NO MORE BATTERIES! EVER! Charge your cell, Ipad or tablet. ONE 2 hr charge (with handcrank or optional AC adaptor) lasts 9 days or 240 perpetual hours! Please share this with all of your friends. We appreciate your support!

  3. Trish

    October 28, 2014 at 11:30 AM

    I’m an engineer and I question these tables. I’ve got several LED flashlights and an LED lantern that I’ve had for years and never had to change their batteries. Yes, I use them. Grid power goes out in our area on a regular basis. The lantern is also nice for camping trips. Plus I use the flashlights when traveling to find bathroom in middle of night in hotel room without waking husband or roommates. We got flashlights at local hardware store. Several have built-in magnets so we keep them stuck to front of fridge so they don’t get lost.

    Additionally, an online search revealed several devices that use solar to charge rechargeable batteries. Prices very but I found one that didn’t cost much. Solar powered stuff does not rely on grid.

    When we bought house three years ago, one of our first projects was to replace all incandescent light bulbs with florescent bulbs. The CFE bulbs gave us brighter light at lower energy cost. Some rooms we had to replace fixtures but it was worth it. My dark cave of a kitchen became a lighted, cheerful place with a new $30 florescent fixture.

    I have solar panels but they’re not on roof. In a SHTF situation, solar panels on roof will lure looters. There are solar panel setups you can put in yard and hide behind backyard fence to keep private.

  4. cmac

    October 28, 2014 at 11:58 AM

    I realize the article is about light bulb and battery life in long term use situations but I feel you should have mentioned oil lamps for situations such as being at home when there is no power or being at a pre-planned fixed base such as a hunting camp. We can expect to be without power several times a year where I live. Usually for a relatively short period but occasionally for several hours to several days. We use a combination of oil lamps and flashlights for our lighting needs when the power is out.

  5. JJM

    October 29, 2014 at 1:27 PM

    Good to see the reminder of various Amp-Hour capacities of batteries which many of us neglect to note when purchasing.
    Well aware of lighting efficiency with LED as the best, incandescent the worst. The tables would be more valuable if they compared (as close as possible) same LUMENS, ie 160 lumens plus or minus 10%.
    A table of LUMENS vs (incandescent) wattage would be helpful.
    My preferred emergency lighting is Cree LED with brightness selection with oil lamps as a backup. Wish the lamps that used solid chunks and water (??) as fuel (miner’s lamps) were still available.

    • Mark

      November 2, 2014 at 9:10 AM

      The solid chunks you refer to are calcium carbide. The flammable gas put off by the combination of calcium carbide and water is acetylene. The lanterns are still available, but limited sources of supply for them.

    • JJM

      November 2, 2014 at 9:44 AM

      Carbide Lamps is what I was thinking. Prices typically $25 to $100 and the only new one I saw has bad reviews. I do remember these as not too bright but sufficient for walking and fishing at night, not too difficult to light and a hot flame that could light other fires (purposeful or accidental).

  6. left coast chuck

    November 3, 2014 at 9:59 PM

    In any extended period of blackout eventually all electrical devices will fail. Even solar powered devices depend upon batteries to supply the electricity to drive the device. Eventually those batteries will go bad and without replacements one is left in the dark. Time to fall back to the 18th century and oil lamps. The most enduring oil lamp is one that burns natural oil, olive oil, corn oil, lard, natural substances that our great grandparents burned. Petroleum products (lamp oil and kerosene lanterns) will disappear as they are used up. The only oils available will be oils derived from natural products. Our ancestors used whale oil, but unless you live close to the ocean and feel like harpooning a whale, that source won’t be available to us until we have once again built ocean capable sailing vessels. Unless we are lucky and some parts of the world that are friendly to the U.S. survive and are able to assist us, we are going to be back to the early 18th century without the life skills that our ancestors possessed. How many reading this list know how to saddle a horse? How to treat a horse with colic? How many have butchered a cow, sheep, goat? How many know how to shear a sheep and spin the wool into thread and weave the thread into cloth? How many have spinning wheels in their home? How many know how to extract oil from plants around them? How many know how to make soap? Having solar panels in your backyard is swell until the battery goes kaput and then it’s back to 18th century time.

    • Mic Roland

      August 29, 2018 at 1:53 PM

      LC Chuck,

      You make valid points.. If the crisis lasted long enough for electrical devices to break/wear-out/fail, then non-electric means will be needed. Lighting, being the common thing that uses batteries, would have to revert to 18th-century means: oil lamps and candles. That, and going to bed when it gets dark instead of trying to light up the night.

      Those 18th-century skills will become valuable again. That’s why I’ve been dabbling in them. Even so, given the huge quantity of already-manufactured stuff laying around, How many people out there already own many changes of clothes? (heck, I’ve got some 20=year-old sweaters that are in fine shape) I wonder how soon people would need to spin their own thread and weave their own fabric. Clothing doesn’t run out as fast as food and post-crisis, AND there’s bound to be a lot of salvage available to last a few years.

      But, to answer your question, yes, I have ventured to hand-spin wool into yarn and weave some (coarse) fabric on a hand-made loom. I have butchered (not an elegant job, but serviceable) and begun to make soap from animal oils (a byproduct of the butchering) and wood-ash. Post-crisis, I might be able to salvage all the soap I’ll ever need, but if not, I’m learning how to make it from scratch.

      — Mic

  7. Sunshine49

    November 4, 2014 at 7:41 AM

    With solar I realize that your battery banks will go bad after a while, but how many years will that be?

    I’m not sure how feasible it would be, but couldn’t someone erect a windmill or water turned combine to constantly produce electricity directly or does it have to go through a battery bank to be converted?

    • Meathead

      November 4, 2014 at 9:11 PM

      Use LED bulbs/flashlights with rechargeable batteries and a 12 volt charger which can be attached to a deep-cycle marine battery that is charged by solar panels.

      Keep in mind that when a rechargeable battery gets below a certain threshold, it generally does not cause the light to go dim, it goes out.

      There are 12 volt LED bulbs available that draw little current and fit a standard lamp socket.

      • Michael

        November 7, 2014 at 8:30 AM

        Any chance you can provide details regarding this approach? I assume one could use the solar panel charger and attached 12 volt car battery. What converter is necessary to to convert the power captured in the 12 volt battery to the battery recharger for your flashlights?

    • Meathead

      November 4, 2014 at 9:19 PM

      If you have a constant source of mechanical motion to turn a generator, you will not need a battery.

      You can connect a 12-volt generator/alternator directly to an inverter to produce 110-volt a/c without utilizing a battery. The battery is used to store energy for periods when generation cannot take place; especially in use with solar panels.

  8. sellC1964 .

    May 26, 2017 at 10:38 AM

    I have always told people to choose flashlight/lantern/radio options that all utilize the same sized battery – a “D” cell alkaline. Then stock and rotate enough to allow for several battery changes of those items. In a pinch, you can always pull batteries from one item for the other.

  9. Robert Brenner

    March 6, 2018 at 3:17 PM

    Good comments. I use ALL resources available to create light. Even wrote articles for Survival Life describing how long batteries last and how long it took to recharge. Today I rely on solar, grid power, portable generator power, and several types of batteries–golf cart and solar rechargeable. No longer worry about power outage. Can even run my gas furnace if grid power goes out. Happy camper, I am.

  10. Pingback: SHTF Life Hacks | Secret Prepper Tip List - Cooking in Quarantine

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