Sizing honesty · Week 2

Peak vs continuous watts — why label watts mislead

Portable stations advertise continuous (rated) AC watts and a higher peak / surge number. Fridge compressors, window ACs, and induction cooktops care about both — and the big marketing number is usually the surge. This page is the sizing honesty layer under Wh class and appliance guides.

Two numbers, one box

  • Continuous / rated watts. What the inverter can sustain for long stretches (minutes to hours) without overheating or shutting down. This is the number that decides “can I run this load for a meal / night?”
  • Peak / surge watts. Short burst headroom — often milliseconds to a few seconds — for motor start-up or compressor kick. Marketing loves this number because it is larger.
  • Wh (watt-hours). Energy in the battery — runtime, not startability. A 2,000 W surge on a 500 Wh pack still dies fast under a heavy continuous draw. Pair this page with Wh class guide · 1 kWh compare.
  • Nameplate vs real draw. Appliance labels are often max / design watts, not average running watts. Fridges cycle; ACs modulate. Use a kill-a-watt style meter when you can — QuietWatt runtimes are estimates.

Station surge/continuous figures below are from manufacturer product pages (checked Oct 2026). Appliance bands are order-of-magnitude estimates — check your nameplate. Not electrical advice.

Why motors (fridge / AC) break naive sizing

Fridge / freezer compressor

Surge spike

Running draw often ~100–200 W class for a household fridge (estimate); start surge can be 2–3× (sometimes more) for a brief moment. Station needs continuous ≥ running + headroom and peak ≥ start. Detail: fridge runtime.

Window / portable AC

Often loses

Nameplate 500–1,500 W running with hard compressor starts — many ~1 kWh mid stations fail or trip even when “surge” marketing looks big enough. Honesty: window AC blackout · heatwave fan vs AC.

Induction / resistive heat

Continuous wall

Induction cooktops often want 1,200–1,800 W continuous — surge marketing does not help if rated watts are below the pot setting. See induction cooktop.

Pure sine also matters for many motors and sensitive supplies — pure sine vs modified sine. UPS transfer is a separate axis — UPS vs portable station.

How label watts mislead shoppers

  • “3,600 W surge!” on a 1,800 W continuous box does not mean you can run a 3,000 W heater. Continuous loses; surge only covers the start blip.
  • Adding Wh does not add watts. Extra batteries extend runtime; inverter continuous/peak stay with the main unit unless the OEM says otherwise.
  • Pass-through while charging can reduce available AC headroom or raise heat — brand manuals differ. See pass-through charging.
  • Stacked loads. Fridge + microwave + kettle is not “one surge number.” Sum continuous draws, then check the biggest motor start against peak.

How to size a station (practical checklist)

  1. List continuous watts for everything that may run at once (nameplate or meter). Prefer average running watts for cycling loads when known.
  2. Identify the hungriest motor start (fridge, AC, well pump, garage door). Need station peak ≥ that start (with margin).
  3. Require station continuous ≥ sum of simultaneous running watts with ~20% breathing room if the OEM is vague (rule of thumb estimate — not a lab factor).
  4. Pick Wh for hours, not for startability — overnight fridge math lives on fridge runtime; class bands on Wh class.
  5. Confirm pure sine for motors / medical / induction-class loads — pure sine honesty.

Rough runtime estimate (hours) ≈ (rated Wh × 0.85) ÷ average watts — inverter and temperature eat the other ~15%. Labelled estimate only.

Example stations QuietWatt already cites (surge vs continuous)

Same models as sibling pages — filter by continuous class. Confirm live specs on official URLs.

Model Continuous · peak (mfr) What that usually means Approx. USD
EcoFlow RIVER 2 Max Light ~500 W cont. · ~1,000 W surge (class / mfr) Phones, modem, laptop, lights — fridge start often fails. See Wh class. Check current listing
BLUETTI Elite 100 V2 Value 1 kWh ~1,800 W cont. class · higher surge (confirm SKU) Apartment fridge + Wi‑Fi class when surge matches your compressor — fridge runtime. Check current listing
EcoFlow DELTA 3 Plus Expand 1,800 W cont. · 3,600 W surge (mfr) Strong mid continuous; expand adds Wh not inverter watts. Still thin for many window ACs. Check current listing
EcoFlow DELTA 2 Max 2 kWh class 2,400 W cont. · 4,800 W surge (mfr) More headroom for induction / short high loads; AC overnight still often loses — window AC. Check current listing
Anker SOLIX C1000 Expand ~1,800 W cont. class · surge per mfr sheet 1 kWh LFP + BP1000 expand path — watts stay with the inverter. Check current listing

Quick “will it run?” heuristics

Usually fine on mid ~1 kWh

Router · laptop · fridge*

*Fridge if continuous + surge clear the compressor — verify. CPAP / lights / modem stack is the easy win. UPS angle: UPS vs station.

Often fails mid kits

Window AC · space heater

Continuous wall, not surge marketing. Prefer fans / spot cooling honesty — heatwave · space heater.

Meal-sized only

Induction · microwave

High continuous for minutes — Wh drains fast. Plan one meal, not all-day cooking — induction.

Cross-link: fridge runtime · window AC · induction · Wh class · 1 kWh compare · EcoFlow vs BLUETTI. Estimates only.

Where to buy (affiliate placeholders)

Tracked affiliate links will replace these placeholders once QuietWatt is enrolled in each program. Until then, use the official product URLs in the table above.

Buy via EcoFlow Buy via BLUETTI Buy via Anker Buy via Jackery Buy via Amazon

Placeholder anchors: #aff-ecoflow, #aff-bluetti, #aff-anker, #aff-jackery, #aff-amazon.

Sources