Day 4: Know your essential watts. Before buying any solar panel, battery or UPS, list what you truly need in an outage: a light, phone charging, a fan, the router. Read the watts on each label and add them up. As a rough guide, an LED bulb is around 10 W, a phone charger 10 to 20 W, and a fan 50 to 80 W.
Today's task: total your essential watts and multiply by the hours you need. That number, in watt-hours, is what your backup has to supply.
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