10 Preparedness Facts Most People Get Wrong (With Sources)

1-3. The power numbers are all optimistic by a third or more

Three battery and solar numbers people quote are wrong in the same direction. First, the power bank. That 20,000mAh on the case is measured at the cell's internal 3.7 volts, which works out to about 74 watt-hours. Then voltage conversion and heat eat 30 to 40 percent of that, so only about 45 to 59 Wh reaches your device, roughly 2.5 to 4 full phone charges, not the five-plus implied. Learn one formula and stop guessing: watt-hours equals mAh times volts divided by 1,000, and runtime equals usable watt-hours divided by device watts. Source: UDPOWER.

Second, the fridge. A refrigerator labeled 500W does not draw 500 watts continuously. The compressor cycles on about a third of the time, so real average draw is closer to 150 to 167 watts, roughly the nameplate divided by three. That is why a modest power station plus a panel can actually keep a fridge cold through a multi-day outage. Source: EnergySage.

Third, solar. A 100W panel does not make 1,200 Wh a day. There are only 3 to 6 hours of usable peak sun, and real output runs 35 to 75 watts, so plan for 300 to 600 Wh per day. For a location-specific estimate, NREL's free PVWatts tool models your exact address and roof angle. Source: NREL PVWatts.

• Power bank: 74 Wh on paper, only about 45 to 59 Wh usable.
• Fridge: nameplate divided by three is the real average draw.
• Solar: plan a 100W panel for 300 to 600 Wh per day, not 1,200.

4. Bleach does not kill everything boiling does

Boiling clear water at a rolling boil for one minute kills bacteria, viruses, Giardia, and Cryptosporidium. That is the complete list, and one minute is enough at normal elevation. Extra time only wastes fuel. Chemical disinfection is not equivalent: household bleach and chlorine do not reliably kill Cryptosporidium, which is chlorine-tolerant.

If you have no way to boil, the CDC and EPA dosing is roughly 8 drops of unscented household bleach per gallon of clear water. Stir it, wait 30 minutes, and confirm a faint chlorine smell. And know the hard limit: nothing on the basic list, neither boiling nor bleach, removes heavy metals, salts, or chemicals. For those, you need a specialized filter.

Source: CDC and EPA.

• Boil: kills bacteria, viruses, Giardia, and Crypto in one minute.
• Bleach: kills bacteria and viruses, but not Cryptosporidium reliably.
• Neither removes heavy metals, salts, or chemicals. Use a specialized filter.
• Dose: about 8 drops of unscented bleach per gallon, then wait 30 minutes.

5. In a blackout, you text. You do not call

Your instinct in an emergency is to call. When cell towers are congested, that is often the worst move. A voice call needs a continuous open channel, and if the network is jammed it simply fails. A text message is low-bandwidth and store-and-forward: the network holds it and keeps retrying until capacity opens, so it lands, possibly delayed, when a call never connects.

The same logic explains why Wireless Emergency Alerts still get through when everything else is jammed. They broadcast one-to-many on a dedicated channel, so congestion on the voice and data channels does not touch them. And when the towers go dark entirely, old technology wins: a NOAA Weather Radio and a plain AM radio keep working, and AM skywave can carry a distant station hundreds of miles at night. Send a text, keep any calls short, and keep a battery radio in the kit.

Source: FCC, FEMA, and NWS.

6. GPS works with zero signal, in airplane mode

No bars does not mean no navigation. GPS is receive-only: your phone listens to satellites and never transmits, so it works in airplane mode, with no SIM, and with no cellular signal at all. The satellites are always overhead whether or not your carrier is.

The only part that needs the internet is the map imagery itself. Download your route and map area before you lose signal, because offline maps expire and often only driving directions work without a connection. Pre-loading the map is the one step people forget.

Source: GPS.gov.

7. A full offline AI plus Wikipedia fits on half a USB stick

People assume a useful AI needs a data center. It does not. A capable 4-bit Llama 3.1 8B model is about 4.9 GB on disk and runs on an ordinary laptop. The full text of English Wikipedia, no images, is about 57 GB and opens offline in the free Kiwix reader.

Add those together and a complete offline reference library, a working AI assistant plus the sum of English Wikipedia, comes to about 62 GB. That is half of a 128 GB USB stick, with room to spare. One honest caveat: a local model is still a language model, so it can produce confident, plausible falsehoods. Treat its factual output as a draft to verify, not an authority.

This is the exact niche PortableMind was built for. It is a plug-and-run offline AI on a USB drive, one-time price, no subscription, 100 percent local, that runs on laptop battery with Wi-Fi off, useful precisely when the grid or internet is down. CORE starts at 49 dollars for Windows chat, v1.5 at 79 dollars adds voice and vision, and a 199 dollar PRO Navigator adds offline GPS.

Source: Hugging Face and Kiwix.

8. The 3-2-1 rule is the backup standard almost nobody follows

The government-backed standard for protecting any important file is simple: 3 copies, on 2 different media types, with 1 stored offsite or air-gapped. Most people keep exactly one copy in exactly one place, which is the precise failure the rule exists to prevent.

The air-gapped copy matters more than it sounds. An encrypted USB stick kept unplugged in a fireproof box cannot be reached by ransomware, which hunts for network-connected and cloud backups. Plug it in only to update, and test it occasionally so it is not silently corrupt on the day you need it.

Source: CISA.

9-10. Heat stroke and lithium batteries: the red flags people miss

Heat exhaustion and heat stroke are not the same emergency, and the line between them is not what movies taught you. Heat exhaustion looks like heavy sweating, cool clammy skin, and dizziness. The fix is shade, water, and cooling down. Heat stroke is a 911 emergency: the decisive signs are altered mental status, meaning confusion, slurred speech, or passing out, plus a very high body temperature of 103 degrees Fahrenheit or higher. The dangerous myth is waiting for the skin to go dry. Exertional heat-stroke victims are often still sweating, so the real red flag is altered mental status plus high temperature, not dry skin. Call 911 and actively cool the person. Source: CDC and NIOSH.

The battery myth is just as costly. The advice to fully drain a battery before recharging is a leftover from old nickel-cadmium cells. Lithium-ion has no memory effect, and full discharges actively shorten its life. Battery University's data shows shallow cycles at around 40 percent depth-of-discharge last 3 to 6 times longer than full 100 percent cycles. Keep your important batteries partial and cool, stored near 40 to 80 percent, not baked at 100 percent in a hot car. That is how a power bank or station stays healthy for the years between emergencies. Source: Battery University BU-808.