What dies first in a multi-day outage

Q: What actually dies first?

Information, if the router has no battery. Then food, if you keep opening the fridge. Then water, if you are on a well and the pump will not start.

Q: Will a 4 kWh portable get me through three days?

Fridge + internet + CPAP, if you shed everything else and you start full. Not a well plus a window AC. Buy the matching extra pack before a second brand.

Q: Does solar fix day four?

After the weather clears, maybe 1–2 kWh from a 400 W folding panel on a clear day. Landfall is not solar weather.

Q: When do I need whole-home instead?

When you will not shed HVAC, or when a well must start every time. Ultra X + SHP3, a large EP900 stack, or Powerwall 3 (185 LRA). Keep a portable while you wait.

Most houses do not go dark all at once. The grid drops, then things fail in an order you can plan for: information first if the router dies, food next, water if you are on a well, then comfort. A battery does not change that order. It buys time on the items you choose to keep.

This is not a lab test and not a homeowner diary. The hours below are average-load planning (nameplate kWh × 92% × 95%). A well pump’s start surge is a separate question. See battery backup for a well pump.

Essentials loads versus whole-home loads

Hour 0–6

Fridge 100–200 W, keep the door shut. Internet 20–40 W. CPAP 30–90 W. Well or sump 800–1,200 W running. A ~4 kWh portable covers fridge + internet + CPAP through the first night if you shed everything else. It is not a house.

Hour 6–24

The fridge is the load that earns its keep. ~4 kWh usable is about 3.5 kWh after inverter loss — roughly 20 hours of fridge + net if you do not add a well or a window AC. Municipal water often lasts a day; a well without a started pump does not. Do not add the range, dryer, or EV charger.

Day 2–3

Night two is an extra battery, not a second brand. Anker BP3800 $1,799.99 (25 Aug 2026). EcoFlow Ultra extra $2,299 (28 Aug 2026, Ultra X PDP). DELTA Pro 3 extra $1,899. EcoFlow 400 W panel $699 public list. Landfall is not solar weather. ~12 kWh is days on fridge + net, hours on a running well. Not multi-day central air.

Day 4+

~20 kWh stretches fridge + net into several days. HVAC is Ultra X + SHP3 or a Powerwall quote. Charge every pack from the wall before a forecast outage. Use the charge list.

What fails first

Keep or shed. Watts are running averages, not surge.
Load	When it fails	Running watts	Plan
Internet + phones	Minutes if the ONT has no battery	20–40 W	Keep
Refrigerator	Hours if you open the door	100–200 W avg	Keep
CPAP / medical	First night	30–90 W	Keep if anyone uses one
Well / sump	First toilet or basement inch	800–1,200 W running	Keep only if the inverter can start it
Furnace fan / controls	First cold night	200–400 W fan	Keep controls. Shed big heat.
Lights	Dusk	10 W per LED	One circuit
Central AC / heat pump	First hot or cold afternoon	Thousands of W	Shed on a portable
Range, dryer, EV, water heater	Whenever you turn them on	3–11 kW	Shed

What this size actually runs

Average-load planning only (kWh × 92% × 95%). A well pump’s start surge is not in these hours.
Size	Fridge + internet	Well (running)	Partial house	Whole-home HVAC
~4 kWh (F3800 / DELTA Pro 3)	~17 hours	~3.5 hours (start is 6–9 kW)	~2 hours	No. Shed HVAC.
~12 kWh (Ultra X starter)	~2 days	~10 hours running if it can start	~6–7 hours	Short automatic backup only. Not multi-day HVAC.
~20 kWh (4× B500 or Ultra extras)	~3–4 days	~16 hours running	~11 hours	Still not a silent whole-home week. Plan to shed.

Run the same formula with your watts on the runtime calculator.

FAQ

What actually dies first? +

Will a 4 kWh portable get me through three days? +

Does solar fix day four? +

When do I need whole-home instead? +

Start with the load you will not give up. Fridge and CPAP do not need 12 kW. A well might.

View F3800 on Anker View Ultra X on EcoFlow Open the calculator