How Many Watts Do I Need for Home Backup? (2026)

The short version

Most homes need 800–2,000W of continuous power for essential backup (fridge, freezer, lights, internet, phones, and a few extras) and 2–10kWh of energy depending on outage length. The method: list your loads, multiply watts × hours for each, add 20% headroom, and check both numbers against the battery — watts against the inverter, watt-hours against the capacity. Work through the worksheet below once, and you'll know exactly which size class to buy instead of guessing.

This is a research-based guide built on standard electrical math and manufacturers' published specs. No bench testing was involved — just arithmetic you can verify with a $25 plug-in watt meter.

The two numbers everyone confuses: watts vs. watt-hours

• Watts (W) = power right now. Your fridge draws ~120W while the compressor runs. This number must fit inside the station's inverter rating (e.g., 1800W).
• Watt-hours (Wh) = energy over time. That fridge at 120W for 10 hours uses 1200Wh. This number must fit inside the station's battery capacity (e.g., 1024Wh).

A station can fail you two completely different ways: too small an inverter (it shuts off when the microwave starts) or too small a battery (it runs everything fine for three hours, then dies). Size both.

Two more terms that matter: surge watts (the brief spike when motors start — a fridge can surge 5–8× its running watts for a second) and duty cycle (a fridge compressor runs maybe 30–50% of the time, so its average draw is far lower than its nameplate watts).

Step 1: list your loads (the worksheet)

Walk through your house and write down everything you'd want powered in an outage. Typical running watts:

Appliance	Typical running watts	Notes
Refrigerator (full-size)	100–200W	Surges 800–1200W at compressor start; ~35% duty cycle
Chest freezer	80–150W	Similar surge; ~40% duty cycle
Wi-Fi router + modem	10–20W	Runs 24/7 — small but constant
LED lights (per room)	10–40W	Trivial individually
Phone charging	10–20W	Negligible for sizing
Laptop	40–90W	Use the charger's rating as a ceiling
TV (55")	80–150W	—
CPAP (no humidifier)	20–60W	See our CPAP guide
Microwave	900–1200W	Short bursts — big inverter demand, small energy
Coffee maker	800–1200W	~10 min per pot ≈ 150–200Wh
Sump pump (1/3 HP)	800–1300W running	Surges 2000W+; critical in storms
Well pump	1000–2000W	Large surge — check LRA rating
Space heater	750–1500W	Battery killer: 1500W × 1h = 1500Wh
Window AC (8k BTU)	700–1000W	Surge at compressor start
Central AC (3-ton)	3000–5000W	Needs a whole-home system, not a portable

Wattages are typical ranges from DOE/EIA appliance data and manufacturer specs — your models will vary. A plug-in watt meter ($20–30) gives you exact numbers for your own appliances and is the single best $25 a backup planner can spend.

Step 2: do the math (worked example)

Take the Johnsons' essentials during a 12-hour overnight outage:

Load	Watts	Hours	Duty cycle	Wh
Fridge	150W	12	35%	630
Freezer	120W	12	40%	576
Router + modem	15W	12	100%	180
LED lights	30W	5	100%	150
Phones (2)	20W	3	100%	60
CPAP	40W	8	100%	320
Total	—	—	—	1916Wh

Peak simultaneous watts: the fridge and freezer compressors rarely start together, but plan for it: 150 + 120 + 15 + 30 + 40 = 355W running, with a worst-case surge around 1500W if both compressors kick on at once. Verdict: a 2kWh-class station with a 2000W+ inverter (Bluetti AC200L, or a Delta 2 with an extra battery) covers this night with margin. A 1kWh station would need the freezer unplugged or a midday solar top-up.

Now add 20% headroom for inverter inefficiency and estimation error: 1916 × 1.2 ≈ 2300Wh. That's the honest target.

Step 3: match the math to a size tier

• ~300Wh tier (phones, lights, CPAP one night): Jackery Explorer 300 Plus, Bluetti EB3A, EcoFlow River 3 Plus. Best for: short outages, apartments, keeping essentials alive for an evening.
• ~1kWh tier (fridge + essentials for 8–16 hours): EcoFlow Delta 2, Anker Solix C1000, Jackery Explorer 1000 v2. Best for: the classic "storm knocked out power until morning" scenario.
• ~2kWh tier (fridge + freezer + comfort for 12–24 hours): Bluetti AC200L, EcoFlow Delta 2 Max, Delta Pro 3. Best for: day-long outages with real appliances.
• 3–6kWh tier (multi-day essentials): expanded Delta 2 / Delta Pro 3, Jackery 2000 Plus. Best for: hurricane/wildfire shutoffs measured in days.
• 10kWh+ whole-home (installed systems): Tesla Powerwall 3, EcoFlow Delta Pro Ultra, Bluetti EP900, Anker Solix X1. Best for: running the house, not just the fridge. See our whole-home guide.

The mistakes that waste money

• Buying watts when you need watt-hours. A 3000W inverter on a 500Wh battery runs your microwave brilliantly — for ten minutes. Match the battery to the outage length first.
• Forgetting duty cycle. A fridge labeled 150W does NOT use 150 × 24 = 3600Wh per day. At 35% duty cycle it's ~1260Wh. Nameplate math oversizes everything by 2–3×.
• Forgetting surge. The flip side: a 150W fridge needs ~1000W of surge headroom at compressor start. A 300W inverter will trip even though the "math" says it fits.
• Sizing for the space heater. Electric resistance heat is the fastest way to drain any battery: 1500W × 8 hours = 12kWh — a whole Powerwall for one room. For outage heat, think blankets, a gas fireplace, or a small propane heater (used safely and ventilated) — not the battery.
• No recharge plan. A battery without solar, a generator, or the grid is a one-shot device. For outages over 24 hours, budget recharge (solar panels, alternator charger, or a small generator) alongside capacity.

Quick answers by outage length

• 2–4 hours (brownouts, brief storms): ~300–500Wh covers fridge + router + lights. Any quality 300Wh station works.
• 8–12 hours (overnight outage): ~1–2kWh. The 1kWh tier handles essentials; 2kWh adds comfort margin.
• 24–48 hours (major storm): ~2–4kWh plus a recharge plan (400W+ solar or a generator top-up). Without recharge, even 4kWh is one day of normal life.
• 3+ days (hurricane, ice storm, PSPS shutoff): whole-home battery (10kWh+) with solar, or a portable station paired with a generator for daily refills.

FAQ

How many watts does the average house need for backup?

Essential backup (fridge, freezer, lights, internet, phones, laptop) typically peaks at 800–2,000W simultaneous draw. Whole-home backup including AC, dryer, and oven can peak at 8–12kW — that's installed-system territory, not portable-station territory.

Is 2000W enough for home backup?

For essentials, yes — 2000W of inverter covers a fridge, freezer, and most household loads except central AC, electric dryers, and well pumps. See our 2000Wh runtime guide for exactly what that size runs.

How do I measure my appliances' actual wattage?

A plug-in watt meter ($20–30) measures real draw over time — far more accurate than nameplate ratings. For hardwired loads (well pump, furnace), check the equipment label or have an electrician measure with a clamp meter.

Should I size for the worst outage I've ever had?

Size for the 90th percentile, not the record. Covering a once-a-decade 5-day ice storm with battery alone means buying 3× the capacity you'll use 99% of the time. A mid-size battery plus a recharge plan (solar or small generator) is the economical answer for extreme outliers.

Does a bigger inverter waste battery?

Slightly — larger inverters have higher idle/standby draw (typically 10–30W). But the difference is small compared to right-sizing the battery. Don't buy a 3600W unit for phone charging, but don't fear a 2400W unit for fridge duty either.

Verdict

Do the worksheet once: list loads, multiply watts × hours × duty cycle, add 20% headroom, and check watts against the inverter and watt-hours against the battery. Most households land on a 1–2kWh portable station for overnight outages or a 10kWh+ installed system for true whole-home backup. The expensive mistake isn't buying too little — it's buying blind. Now you're not.