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StopWatt

Product explainer

How StopWatt works

StopWatt is a passive plug-in device that improves the power factor of the circuits near it. This page explains the mechanism in plain English, shows you how many units a home your size needs, and is honest about what a plug-in unit cannot change.

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Quick answer

StopWatt plugs into a wall outlet and uses internal capacitors to supply part of the reactive current your motors and compressors demand, so less total current travels through your home wiring. Most homes use one unit per 800–1,200 sq ft, and one per floor.

The three steps, in plain English

  1. Step 1

    Plug it into a wall outlet

    No wiring, no tools, no app.

    Insert the unit into a standard grounded outlet on a 90V–250V household supply. The indicator light confirms it is live and working. Nothing to configure, nothing to maintain.

  2. Step 2

    Capacitors supply reactive current locally

    The part that does the actual work.

    Motors, compressors and pumps pull reactive current that swings back and forth to the grid. Capacitors inside StopWatt store and release that energy in step with those appliances, so part of it is supplied at the outlet instead of travelling the whole circuit.

  3. Step 3

    Current in your wiring drops slightly

    Lower current, lower resistive loss.

    Less total current through the same conductors means lower I²R losses and cooler-running wiring. That is the honest, physics-based mechanism behind any real-world benefit in a home — and it is why results differ from house to house.

60DAYS

60-Day Money-Back Guarantee

Return it within 60 days of delivery for a refund of the purchase price.

Issued by the official StopWatt store

Test the mechanism in your own home for 60 days

Bundles from $44.10 with free worldwide shipping. If your kWh does not move over a full billing cycle, return it for a refund of the purchase price.

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What power factor actually means

Motors, compressors, pumps and fans are inductive loads. They draw real current that does work, plus reactive current that swings back and forth between the appliance and the grid without doing work. The ratio between useful power and total apparent power is your power factor.

Capacitors placed close to those loads act as a local reservoir for the reactive component, so it no longer travels the full length of your circuit. That reduces total current in the conductors and the resistive (I²R) losses that come with it. For the full background, read what power-factor correction is.

Inside the unit

StopWatt power-factor correction unit showing the plug, housing and green indicator light
Housing
Flame-retardant ABS, sealed, no moving parts
Core
Capacitor bank sized for residential branch circuits
Indicator
LED confirms the unit is powered and active
Input
90V–250V, 50/60 Hz — US and international supplies
Coverage
800–1,200 sq ft per unit, one unit per floor
Maintenance
None — passive design, no firmware, no fans

Full technical sheet on the StopWatt specifications page.

How many units does your home need?

Coverage calculator

How many StopWatt units does your home need?

Sizing rule: one unit per 800–1,200 sq ft of living area, and at least one unit per floor so every circuit area is covered.

Recommended for your home

2 units — 2 StopWatt Devices

Medium home · 1,200–1,500 sq ft

$88.20$196.00

$44.10 per device · free worldwide shipping · 60-day money-back guarantee

Order the 2 devices bundle

Not sure yet? Start with fewer units and add more later — see all bundles.

Will it help your home?

Will StopWatt actually do anything in your home?

Power-factor correction only has something to correct when you run motor-driven appliances. Tick what applies and we will tell you honestly.

Appliances in your home

Where to plug each unit in

Where to plug in each StopWatt unit by area of the home
Area of the homeTypical motor-driven appliancesUnits
Main floor / living areaHVAC air handler, refrigerator, dishwasher1 unit
Upper floor / bedroomsWindow AC, ceiling fans, dehumidifier1 unit
Basement / utility roomWell or sump pump, freezer, laundry1 unit
Garage / workshopPower tools, compressor, garage door motor1 unit
Apartment / condo under 1,200 sq ftFridge, AC unit, washer1 unit total

Do

  • Plug directly into a wall outlet on each floor.
  • Choose an outlet close to motor-driven appliances.
  • Leave it plugged in — it only works while powered.
  • Keep the indicator light visible so you can confirm it is on.

Don't

  • Do not use a power strip, extension cord or timer.
  • Do not install outdoors or anywhere it can get wet.
  • Do not cover the unit or block airflow around it.
  • Do not expect an effect on resistive loads like ovens or baseboard heaters.

Step-by-step setup is on the StopWatt installation guide.

What StopWatt does not do

  • It does not change how your meter records kWh.
  • It does not generate or store electricity for later use.
  • It does not reduce consumption of resistive loads such as ovens, kettles or baseboard heaters.
  • It cannot promise a fixed percentage off your bill — any seller who does is guessing.

Most US residential meters bill real power only, so the savings a home can see come from those smaller in-home losses rather than from reactive power itself. We say that plainly because the 60-day guarantee, not a claim, is what makes testing it safe. More detail in does StopWatt really work.

60DAYS

60-Day Money-Back Guarantee

Test StopWatt for a full billing cycle. Return it within 60 days of delivery for a refund of the purchase price.

Issued by the official StopWatt store · Refund of the purchase price

Frequently asked questions

How does StopWatt work in simple terms?
It plugs into a wall outlet and uses internal capacitors to supply part of the reactive current your motors and compressors demand, so less total current travels through your home wiring and resistive losses drop slightly.
How many StopWatt units do I need?
Plan on one unit per 800–1,200 sq ft and at least one per floor. A 1,000 sq ft apartment needs one, a typical 1,500 sq ft home two, and a 2,000+ sq ft or multi-storey home three.
Does it need to stay plugged in?
Yes. It only affects the circuit while it is powered and the indicator light is on.
How much electricity does the device itself use?
It is a low-draw passive device; its own consumption is negligible compared with household appliances.
Is it safe to leave in overnight?
Yes. It is a sealed passive unit with a flame-retardant housing, no moving parts and no heating element. Use a standard grounded indoor outlet and keep it dry.
Can I use it in an apartment or condo?
Yes. One unit generally covers an apartment under 1,200 sq ft. The device affects the circuits it sits on, so it works the same whether you own or rent.
Does it work on 220V outside the United States?
Yes. The input range is 90V–250V at 50/60 Hz, so it works on international supplies — you may need a plug adapter for your socket type. We ship worldwide.
Can I use it in a garage or basement?
Yes, provided the outlet is a standard grounded indoor outlet within the stated voltage range and the unit stays dry.
Is StopWatt a surge protector?
No. It is a power-factor correction unit, not a surge suppressor, and it does not replace a surge protector or UPS for sensitive electronics.

Keep reading on the official StopWatt site

Order direct from the official store

Ready to try StopWatt risk-free?

Pick the bundle that matches your home size, then complete your order securely on this page — no redirects, no account required.

Sizing rule of thumb: one device per 800–1,200 sq ft, so most homes over 1,500 sq ft use the 3-device bundle.

Checkout — 3 Devices

$105.84

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  • Real supportsupport@getstopwatt.net

Prices in USD. The bundle price shown is the full discount — there is no code to hunt for. Add-ons available only here: add 1 extra stopwatt and 3-year replacement protection.