Maintenance procedure · Written to ASD-STE100 Issue 9 · Formatted to ANSI Z535

Generator Load List: Running Watts and Starting Watts

Building the written list that decides whether your generator can run what you want it to run — read off your own data plates, totalled the way the generator makers total it, with no appliance wattage printed on this page
ApplicabilityEngine-driven portable generators that a householder supplies equipment from with cords during a power outage. Not permanently installed standby generators, and not any connection to the wiring of a building.
Task time58 min to 1 hr 48 min editorial estimate
PersonnelOne
Revisionv1 · 2026-07-29
BEFORE YOU BEGIN

Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.

Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.

Summary

Almost every "what size generator do I need" answer you will find is a table of appliance wattages. This page does not have one, on purpose. Your refrigerator is not the table's refrigerator, and a number copied off a chart is the single most common reason a load list looks fine on paper and trips the breaker in an outage. Every number you need is already printed on the equipment you own, on the data plate or in the operator's manual, and the whole job here is finding those numbers and adding them up in the right order. What this page gives you is the method and the two arithmetic traps in it.

The first trap is that there are two totals, not one. Running watts is what an item draws once it is going; starting watts is the short extra burst a motor needs to get moving, and Generac puts that burst at two to three seconds. Briggs & Stratton and Generac both say the same thing about how to combine them: total the running watts of everything you want on at once, then add the single highest starting watts of one item. The second trap is what to do when nothing publishes a starting figure, and here the two makers genuinely disagree — Generac says a single-phase induction motor takes three to five times its running watts to start, Briggs & Stratton says approximately two to three times. This page prints both, names who said which, and does not split the difference. Connecting a generator to your house wiring is not covered here at any point; that is a licensed electrician's job and the page says so where it matters.

Safety

DANGER

DO NOT OPERATE THE GENERATOR IN A BUILDING, A GARAGE OR A SHED.
Carbon monoxide in the exhaust can kill the people inside.

Necessary equipment

ItemNote
Paper and a pen, or a spreadsheetKeep the completed list with the documentation for the generator.
FlashlightA data plate is usually at the back or the bottom of an item.
Phone or camera optionalMake a photograph of each data plate before you move the item back.
Calculator optionalThis task uses addition and multiplication only.
The operator manual for each itemThe manufacturer gives the electrical data in this manual.

Make the list of items

Estimated 15 min to 20 min

NOTEDo this task before a power outage. A list that you write in the dark is a list with errors.
Connection of a generator to the wiring of a building
Manufacturer or standard verified
REFUSED ON THIS PAGE. OSHA STATES THAT A QUALIFIED ELECTRICIAN MUST INSTALL A TRANSFER SWITCH FIRST.

Source: Using Portable Generators Safely (OSHA Fact Sheet) · tier 1 · accessed 2026-07-29

NOTICE

READ THE DOCUMENTATION FOR YOUR OWN GENERATOR FIRST.
The manufacturer gives the two ratings that this list must obey.

  1. Read the documentation for your own generator.
    • The rated watts and the starting watts of your machine are in this documentation.
    • These two values are the limits that the completed list must obey.
    5m
  2. Make a list of the items that you must operate during a power outage.
    • Generac states that the first step is a list of the items that the generator supplies.
    5m
  3. Write one item on each line of the list.
    2m
WARNING

DO NOT CONNECT THE GENERATOR TO THE WIRING OF THE BUILDING.
Only a licensed electrician can install a transfer switch. Current from the generator can electrocute a lineworker.

  1. Remove each item that has no plug.
    • A furnace, a well pump and a water heater usually have no plug.
    • Only a licensed electrician can supply these items from a generator.
    2m
  2. Keep on the list only the items that you must operate at the same time.
    • Generac states that the list is the items that the generator supplies at the same time.
    • OSHA states that you must connect each item directly to the generator with a cord.
    1m

Read the running watts from each data plate

Estimated 16 min to 43 min

NOTEThe manufacturer of each item gives the electrical data for that item. This page gives no watts for any item.
Where the running watts and the starting watts of an item are published
Manufacturer or standard verified
THE OPERATOR MANUAL FOR THE ITEM, OR THE DATA PLATE ON THE ITEM

Source: Choosing a Portable Generator · tier 1 · accessed 2026-07-29

Running watts of each item on your own list
Unverified — do not rely on this value
READ THE VALUE FROM THE DATA PLATE ON THE ITEM, OR CONSULT THE MANUFACTURER DOCUMENTATION FOR THAT ITEM

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

  1. Find the data plate on each item on the list.
    • The data plate is a label that the manufacturer attaches to the item.
    • Generac states that the manufacturer prints the electrical data on a plate on each item.
    10m
NOTICE

DO NOT USE A VALUE FROM A CHART ON ANOTHER WEBSITE.
Only the manufacturer of your own item gives a correct value for it.

  1. Read the watts from the data plate.
    1m
  2. Write the watts against that item on your list.
    <1m
  3. If you find amps and volts on the data plate, multiply the amps by the volts.
    • The result is the watts for that item.
    • Use the volts from your own data plate.
    1m
  4. If the item has no data plate, read the operator manual for that item.
    • Briggs & Stratton gives the operator manual and the data plate as the two places for this value.
    3m
  5. If you find no value, leave that line empty.
    • Speak to the manufacturer of the item before you put a number on that line.
    <1m

Find the items that have a motor

Estimated 10 min to 20 min

NOTEAn item with a motor needs more watts to start than to run. An item with no motor does not.
Starting watts of each item that has a motor
Unverified — do not rely on this value
CONSULT THE MANUFACTURER DOCUMENTATION FOR THAT ITEM. MANY DATA PLATES DO NOT CARRY THIS VALUE.

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

Watts a single-phase induction motor needs to start, as a multiple of its running watts, as Generac gives it
Manufacturer or standard verified
3 to 5 x running watts

Source: Basic Sizing for Mobile Generators (white paper) · tier 1 · accessed 2026-07-29

Two generator manufacturers publish different multiples for the same quantity, and this page publishes both rather than one. Generac (generac-basic-sizing-for-mobile-generators, accessed 2026-07-29) writes that single-phase induction motors 'require 3-5 times the amps or watts to start them', and separately that universal brush-type motors 'Require 1-2 times the amps or watts to start them'. Briggs & Stratton (briggs-motor-starting-101, accessed 2026-07-29, article dated 19 August 2024) writes that 'Approximately two to three times the rated running wattage of an appliance is needed to make it start', and draws no distinction between motor types. The two ranges overlap only at three, and no midpoint is published here. Note also that Generac's figures come from a document about mobile and jobsite generator sets sized by a dealer, not about a householder's portable machine. Both makers are describing an estimate for use when nothing better exists. If the manufacturer of your own item publishes a starting watts figure, that figure governs and neither multiple applies.
Watts a universal brush-type motor needs to start, as a multiple of its running watts, as Generac gives it
Manufacturer or standard verified
1 to 2 x running watts

Source: Basic Sizing for Mobile Generators (white paper) · tier 1 · accessed 2026-07-29

Watts a motor needs to start, as a multiple of its running watts, as Briggs & Stratton gives it
Manufacturer or standard verified
2 to 3 x running watts

Source: Motor Starting 101: How Generators Power Up Your Home Appliances · tier 1 · accessed 2026-07-29

Time the starting demand of a motor continues
Manufacturer or standard verified
2 to 3 s

Source: What does surge/starting wattage mean? · tier 1 · accessed 2026-07-29

  1. Put a mark against each item on the list that has a motor.
    • A refrigerator, a freezer, a pump, a compressor and a power tool have a motor.
    • A lamp, a heater and a kettle do not have a motor.
    • Generac states that an item with no motor needs the same current to start and to run.
    2m
  2. Read the starting watts for each item that has a mark.
    • Many data plates do not give this value. The operator manual can give it.
    • Generac states that this extra demand continues for two to three seconds.
    5m
  3. Write the starting watts against that item on your list.
    1m
NOTICE

USE A PUBLISHED VALUE BEFORE YOU USE A MULTIPLE.
The two manufacturers do not agree about the multiple.

  1. If the manufacturer gives no starting watts, speak to the manufacturer of the item.
    • Generac and Briggs & Stratton do not agree about the multiple of the running watts.
    • The two ranges are in the specifications below. A multiple is an estimate.
    • A published value from the manufacturer is not an estimate. Use it first.
    2m

Add the watts

Estimated 5 min

NOTEThe list has two totals. The two totals are not the same, and each total has its own use.
Method that gives the watts the generator must supply
Manufacturer or standard verified
ADD THE RUNNING WATTS OF EVERY ITEM. THEN ADD THE SINGLE HIGHEST STARTING WATTS OF ONE ITEM.

Source: Choosing a Portable Generator · tier 1 · accessed 2026-07-29

  1. Add the running watts of every item on the list.
    • Briggs & Stratton gives this sum as the running watts that the generator must supply.
    2m
  2. Write this sum at the bottom of the list.
    <1m
  3. Find the one item that has the highest starting watts.
    • Use one item only. Do not add the starting watts of two items.
    1m
  4. Add the starting watts of that one item to the sum of the running watts.
    • Briggs & Stratton and Generac both give this method.
    1m
  5. Write this second sum below the first sum.
    <1m

Compare the two totals with the rating of the generator

Estimated 8 min to 14 min

NOTEThe two manufacturers do not agree about the margin. This page gives both positions.
Margin to add above the total, as Briggs & Stratton gives it
Manufacturer or standard verified
20 to 30 %

Source: Motor Starting 101: How Generators Power Up Your Home Appliances · tier 1 · accessed 2026-07-29

Three tier-1 manufacturer documents give three different answers to how much margin sits above the total, and this page publishes all three. Briggs & Stratton (briggs-motor-starting-101, accessed 2026-07-29) writes 'consider the total wattage of the appliances you want to power and add a safety margin of 20-30%'. Generac's consumer worksheet (generac-generator-wattage-worksheet, accessed 2026-07-29) adds nothing above the total and labels the result 'Minimum wattage rating for your needs'. Generac's own sizing white paper (generac-basic-sizing-for-mobile-generators, accessed 2026-07-29) approaches it from the other side and states that 'The optimum power to pull from a generator is 70-85% of the machine's rated capacity', which is a margin expressed as a share of the rating rather than as an addition to the load. No midpoint is published and the three are not reconciled. Consult the documentation for your own generator, which is the only document that describes your machine.
Share of the rating of a generator that Generac gives as the best load
Manufacturer or standard verified
70 to 85 %

Source: Basic Sizing for Mobile Generators (white paper) · tier 1 · accessed 2026-07-29

What the advertised watts of a portable generator describe, as Generac gives it
Manufacturer or standard verified
THE MAXIMUM TOTAL FROM A COMBINATION OF ITS OUTLETS. ONE OUTLET GIVES LESS, BECAUSE THE BREAKER OF THAT OUTLET LIMITS IT.

Source: Understanding Portable Generator Power Limits vs. Advertised Wattage · tier 1 · accessed 2026-07-29

Rated watts and starting watts of your own generator
Unverified — do not rely on this value
CONSULT THE MANUFACTURER DOCUMENTATION FOR YOUR OWN GENERATOR

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

WARNING

DO NOT TAKE THE RATED WATTS OF THE GENERATOR FROM ONE OUTLET.
Generac states that this rating is the total from a combination of the outlets.

  1. Read the rated watts and the starting watts of your own generator.
    • These two values are on the machine and in its documentation.
    2m
  2. Compare the first sum with the rated watts of the generator.
    1m
  3. Compare the second sum with the starting watts of the generator.
    1m
WARNING

DO NOT PUT MORE LOAD ON THE GENERATOR THAN ITS RATED WATTS.
OSHA states that an overload can cause a fire.

  1. If a sum is more than the value of the generator, remove an item from the list.
    • Remove the item that gives you the least. Do not remove a safety item.
    2m
NOTICE

REMOVE AN ITEM IF A SUM IS MORE THAN THE RATING.
Generac states that an overload can damage the equipment that you connect.

  1. Do the two sums again after you remove an item.
    • The highest starting watts can change when you remove an item.
    2m

Write the order of start

Estimated 4 min to 6 min

NOTEHonda states that you can operate a smaller generator if you start items at different times.
  1. Write a number against each item to give the order of start.
    • Honda states that you can start items with high starting watts at different times.
    3m
  2. Do not start two items that have a motor at the same time.
    <1m
  3. Keep the list with the documentation for the generator.
    • Write the date on the list. Do the task again when you get a new item.
    1m

Terminology

This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.

running watts
Also called: running wattage, rated watts, rated wattage, continuous watts, constant watts, how many watts does it use
starting watts
Also called: surge watts, surge wattage, starting wattage, peak watts, peak wattage, start-up watts, inrush
data plate
Also called: nameplate, name plate, data tag, rating plate, spec plate, the sticker on the back, appliance label
load list
Also called: wattage worksheet, generator sizing worksheet, what size generator do I need, generator wattage calculator
transfer switch
Also called: generator switch, hooking a generator to the house, backfeeding, suicide cord

When to use a professional

Stop at the wiring of the building. Do not connect a generator to the wiring of a building. Only a licensed electrician can install a transfer switch. Speak to a licensed electrician about a furnace, a well pump or a water heater. These items usually have no plug.

This page gives a method only. It gives no watts for any item and no rating for any generator. If you cannot find a value for an item, speak to the manufacturer of that item. Do not put an estimate on the list in place of a published value. The selection of a cord for the generator is a different task and this page does not give it.

Common questions

What size generator do I need?

Nobody can answer that without your list, which is why this page is a method rather than a number. Total the running watts of everything you want on at the same time, then add the single highest starting watts of one item on the list. Briggs & Stratton and Generac both describe it that way. The answer that comes out is the smallest machine that will do your job, not a recommendation to buy that machine. Whether you leave a margin above it is where the makers stop agreeing, and that disagreement is in the specifications on this page.

What is the difference between running watts and starting watts?

Running watts is what an item draws once it is going. Starting watts is the short extra burst a motor needs to get moving, and Generac puts that burst at two to three seconds before the item settles back. Anything with a motor has both; anything without a motor, like a lamp or a kettle, effectively has one number. Generac's own wording is that an item with no motor needs the same current to start as it needs to run. The distinction matters because the burst is what trips a breaker, and it never shows up in a running-watts total.

How many watts does a refrigerator need?

This page will not tell you, and you should be wary of any page that does. The wattage of a refrigerator varies by model, by age, by size and by whether it has an ice maker, and the number that circulates on chart after chart is one number that travelled rather than twenty numbers that were measured. Your refrigerator has its own figure printed on its own data plate, usually inside the door or on the back, and that is the only figure that describes your refrigerator. If the plate gives amps and volts instead of watts, multiply them together. If the plate has neither, the operator's manual or the manufacturer will have it.

Can I just multiply the running watts by three to get the starting watts?

Only as a last resort, and you should know that the manufacturers do not agree on the multiplier. Generac writes that a single-phase induction motor takes three to five times its running watts to start, and that a universal brush-type motor takes one to two times. Briggs & Stratton writes that approximately two to three times the running wattage is needed, without splitting motors into types. The two ranges overlap only at three, so a reader who picks three is picking the one value both happen to include rather than a settled answer. If your item publishes a starting figure, use that and ignore both ranges.

Can I plug the generator into a wall socket to power the whole house?

No. OSHA's wording is that you must never attach a generator directly to the electrical system of a structure unless a qualified electrician has properly installed it with a transfer switch, because doing so can energise wiring for great distances and creates a risk of electrocution for utility workers. That is the practice sometimes called backfeeding, and it is not on this site at any skill level. Everything on this page assumes items with plugs, connected directly to the generator. If what you actually want is your furnace or your well pump, the answer is a licensed electrician and a transfer switch, not a bigger generator.

My generator says 8000 watts. Can I take 8000 watts from one outlet?

No, and this catches people out. Generac's own explanation is that the advertised figure is the maximum total the machine can provide across a combination of two or more of its outlets, not what any single outlet will give you. Each outlet has its own breaker, and Generac's worked example is a model whose 50-amp outlet is protected by a 40-amp breaker. So the total on your list has to fit the machine, and the way you split that total across the outlets has to fit each outlet as well. Your own generator's documentation is the place that tells you what each outlet is rated for.

Should I leave a margin above the total?

The makers genuinely differ, so this page gives you all three positions instead of one. Generac's consumer worksheet adds nothing and calls the total the minimum rating for your needs. Briggs & Stratton says to add a safety margin of 20 to 30 per cent on top. Generac's own sizing white paper comes at it from the other direction and says the best load to draw from a machine is 70 to 85 per cent of its rating. They are not the same statement and this page does not average them. Your generator's own documentation is the tie-breaker.

Do I need to do this again later?

Yes, whenever the list changes. A new freezer, a new well pump or a medical device added to the household changes both totals, and the item with the highest starting watts can change too, which quietly changes the second total even if the first one barely moves. Put the date on the list and keep it with the generator's documentation rather than in a drawer. An outage is a bad time to discover the list describes the appliances you owned three years ago.

Sources

Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.

  1. Tier 1Choosing a Portable GeneratorBriggs & Stratton · accessed 2026-07-29 · re-verification due 2027-01-25
  2. Tier 1Motor Starting 101: How Generators Power Up Your Home AppliancesBriggs & Stratton · accessed 2026-07-29 · re-verification due 2027-01-25
  3. Tier 1Basic Sizing for Mobile Generators (white paper)Generac Mobile Products, LLC · accessed 2026-07-29 · re-verification due 2027-01-25
  4. Tier 1Generator Wattage WorksheetGenerac Power Systems · accessed 2026-07-29 · re-verification due 2027-01-25
  5. Tier 1What does surge/starting wattage mean?Generac Power Systems (Generac Help Center) · accessed 2026-07-29 · re-verification due 2027-01-25
  6. Tier 1Understanding Portable Generator Power Limits vs. Advertised WattageGenerac Power Systems (Generac Help Center) · accessed 2026-07-29 · re-verification due 2027-01-25
  7. Tier 1Using Portable Generators Safely (OSHA Fact Sheet)Occupational Safety and Health Administration, United States Department of Labor · accessed 2026-07-29 · re-verification due 2027-01-25
  8. Tier 1Honda Generator Power ManagementHonda Power Equipment (American Honda Motor Co., Inc.) · accessed 2026-07-29 · re-verification due 2027-01-25 · automated link check returned 403 — verified by hand

Revision history

Current version 1 · updated 2026-07-29 · next review due 2027-07-29

  1. v1 · 2026-07-29First draft. Built from seven tier-1 manufacturer and government documents read in full on 2026-07-29, plus one manufacturer page read by hand after the automated link check returned 403. NO APPLIANCE WATTAGE IS PUBLISHED ANYWHERE ON THIS PAGE, by design and against the pull of every competing page on the topic: the method comes from the makers, and every number the reader uses comes off a data plate the reader finds themselves. Both Honda pages that carry appliance wattage tables were read and are recorded under rejected for that reason, as is Generac's own worksheet table, which was extracted and deliberately not reproduced. TWO GENUINE MANUFACTURER DISAGREEMENTS ARE PUBLISHED RATHER THAN RECONCILED. First, the multiple of running watts a motor needs to start: Generac's sizing white paper gives 3 to 5 times for a single-phase induction motor and 1 to 2 times for a universal brush-type motor, and Briggs & Stratton's Motor Starting 101 (19 August 2024) gives approximately 2 to 3 times with no distinction by motor type. The ranges overlap only at three and no midpoint is published. Second, the margin above the total: Briggs & Stratton says add 20 to 30 per cent, Generac's consumer worksheet adds nothing and calls the sum the minimum rating, and Generac's white paper says draw 70 to 85 per cent of the rating. Three positions from two makers, all three named, none averaged. The method itself is NOT a conflict — Briggs & Stratton and Generac state it identically (total the running watts, then add the single highest starting watts of one item) — and neither is Honda's sequencing advice, which reduces how many items are on at once rather than contradicting the arithmetic; the record says so rather than manufacturing a disagreement. SCOPE REFUSALS: connection to the wiring of a building is refused at three separate points (a WARNING before the step that removes plugless items, a specification whose value is the refusal, and the professional boundary), on OSHA 3286's wording that a qualified electrician must install a transfer switch first; cord selection is named as a different task and not given; and the page stops before the generator runs, routing siting to the sibling record. SOURCING NOTES: three of the eight documents (the Generac white paper, the Generac worksheet and the OSHA fact sheet) returned HTTP 200 but could not be decoded by the fetching tool, and were read by extracting the cached bytes locally with scripts/lib/extract.py; each source entry says so. The Generac worksheet and the Honda page carry no publication date and therefore count as archaic under thresholds.archaic_source_years, so no value rests on either alone — the method specification rests on the dated Briggs & Stratton page instead. Verified specifications carry no spec_key: this record was drafted concurrently with others and the drafting session was not permitted to write data/specs.json, so the ten registry entries must be added when the record is merged. Sources are staged in data/sources-additions-size-a-generator-load-list.json, which also records six rejected URLs including a dead .html variant of the Briggs article and the Generac GP Series owner's manual, which exceeded the fetch size limit and was never seen.

Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.

Comments and corrections

Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.

Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.

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