Build a practical plan for an eight-hour outage
Choose a time window, name the essentials, and work backward from what they actually use. Here is an illustrative eight-hour plan.
Set the device schedule
Use a refrigerator drawing an illustrative 150 W for a total of 2.7 active hours, a 20 W router/modem for eight hours, a 12 W set of lights for two hours, and a 10 W phone charger for one hour. Their energy use is 405 + 160 + 24 + 10 = 599 Wh. Your equipment and schedule will differ.
Allow for the battery itself
With the planner’s illustrative 85% efficiency, 8 W inverter idle draw, and 20% margin, the capacity target is (599 ÷ 0.85 + 8 × 8) × 1.20 ≈ 922 Wh. A battery sold in the roughly 1 kWh class is a capacity candidate for this example. Its output, ports, surge duration, and documented behavior still need separate checks.
Decide what to drop first
Try the plan without each optional load. A large battery is not the only way to improve resilience: reducing use or separating small USB loads may help. Never drop equipment needed for health or safety based on this general calculator. Make those arrangements with the appropriate device supplier or clinician.
Write down the handoff
Keep the plan somewhere everyone in the household can find it. Include which plugs belong to the plan, where lighting is stored, and how to check remaining charge. Test the plan in advance. The example does not include electric heating, central air conditioning, hardwired circuits, or a solar recharge contribution.
Sources & further reading
Numerical examples and default device values are illustrative unless explicitly described as a measurement. Consult the manuals for your own equipment.
Make it a plan for your home.
Choose your devices and edit the assumptions.
Open the backup planner