Generator Wattage Chart for Household Appliances
Running watts and starting watts for the loads that matter during an outage, grouped the way you will actually plan them.
Alex Rivers
Home Improvement Editor
Last Updated
September 2, 2026
In This Guide
Every appliance has two numbers, and the second one is why generators stall. Running watts is what a device draws once it is going. Starting watts is the surge as a motor spins up — often three times higher, and the figure most people never look up.
1. Essentials: What Most People Back Up First
These are the loads that define a tolerable outage. Food stays cold, the house stays warm, the basement stays dry, and you can see and communicate.
| Appliance | Running Watts | Starting Watts | Notes |
|---|---|---|---|
| Refrigerator or freezer | 150-800 | 1,200-2,200 | Compressor surges; runs intermittently |
| Gas furnace blower | 600-900 | 1,500-2,400 | Hardwired; needs a transfer switch |
| Sump pump, 1/2 HP | 800-1,050 | 2,000-2,600 | Hardwired; usually the critical load |
| Lights, TV, router, laptops | 300-600 | Same | Resistive and electronic; no surge |
| Microwave | 1,000-1,500 | Same | Rated by cooking power, not draw |
A household running everything in this table simultaneously totals roughly 2,850 to 4,850 running watts. Add the largest single surge — the sump pump, at about 1,550 above its running draw — and peak demand lands near 6,400 watts with headroom. That is the arithmetic behind the common recommendation of a 7,500 watt portable.
2. Heating and Cooling: Where the Numbers Explode
| Appliance | Running Watts | Starting Watts | Notes |
|---|---|---|---|
| Gas furnace blower | 600-900 | 1,500-2,400 | Only the blower and controls need power |
| Window AC, 10,000 BTU | 1,000-1,200 | 2,200-3,000 | Cools one room affordably |
| Central AC, 3 ton | 3,000-3,800 | 9,000-12,000 | Usually needs a standby generator |
| Space heater | 1,500 | Same | Resistive; no surge but heavy continuous draw |
| Ceiling or box fans | 50-200 | 100-400 | Trivial; run these instead of AC |
The Single Most Important Row
Central air conditioning is the decision point.
A three-ton central air conditioner surges to between 9,000 and 12,000 watts. On its own that exceeds the entire output of most portable generators. If air conditioning is on your outage list you are shopping for a standby unit; if it is not, a portable will very likely serve.
Worth noting for gas and oil heating: only the blower, igniter and controls draw power, not the heat source itself. That is why a gas furnace is so cheap to back up at 600-900 watts, while an electric furnace or heat pump running on resistance heat can draw ten times that. Check which you have before assuming heating is affordable to back up.
3. Water, Kitchen and Laundry
| Appliance | Running Watts | Starting Watts | Notes |
|---|---|---|---|
| Well pump, 1 HP | 1,000-1,200 | 3,000-4,000 | No pump means no running water |
| Sump pump, 1/2 HP | 800-1,050 | 2,000-2,600 | Critical with a finished basement |
| Electric water heater | 4,000-4,500 | Same | Tank holds hot water a day; consider skipping |
| Electric range, one element | 1,500-2,500 | Same | Per element; a full range is far more |
| Electric dryer | 5,000-5,500 | 6,500 | Rarely worth backing up |
| Dishwasher | 1,200-1,500 | Same | Heating element dominates the draw |
| Coffee maker | 600-1,200 | Same | Brief but heavy resistive draw |
Well pumps deserve particular attention because they are easy to forget and expensive to get wrong. If your water comes from a well, no generator means no water at all — not for drinking, washing or flushing. A 1 HP pump surging to 4,000 watts is frequently the largest single surge in a rural household’s calculation, which makes it the number that sizes the whole generator.
The kitchen and laundry rows are mostly candidates for deliberate omission. An electric dryer at 5,500 watts and an electric water heater at 4,500 together exceed the total capacity of a mid-size portable, and neither is genuinely necessary for a few days.
4. How to Read Your Own Appliance Ratings
These charts are planning figures. Your own appliances carry their real numbers, and for the large loads it is worth finding them.
Find the data plate
A label on the back, base, or inside the door of most appliances. It lists watts directly, or volts and amps.
Convert amps to watts
Multiply volts by amps. A plate reading 120V and 8A means about 960 running watts.
Estimate surge from the motor type
Induction motors in pumps and compressors typically surge to two or three times running draw. Resistive loads do not surge at all.
Look up HVAC by model number
Furnaces and air conditioners vary far more than kitchen appliances. Find the manufacturer specification sheet for the real figure.
Verify with a plug-in energy meter
An inexpensive meter between the outlet and the appliance shows actual running draw, settling any uncertainty on plug-in loads.
A Note on LRA
Some motor data plates list LRA, or locked rotor amps, rather than a starting wattage. That is the current the motor draws at the instant it is energised and the rotor has not yet moved — effectively the worst-case surge. Multiply LRA by the voltage for a conservative starting watts figure. It will usually be higher than the typical ranges in these charts, which is appropriate for sizing.
5. Using These Numbers to Size a Generator
The charts are only useful combined correctly, and there is one rule that governs it.
The Combining Rule
All the running watts, plus one surge.
Total the running watts of everything you want on at once. Then add the single largest difference between starting and running watts on your list. Motors do not all start at the same instant, so adding every surge together produces a wildly oversized generator.
Worked through with the essentials: refrigerator 700, lights and electronics 600, furnace blower 900, sump pump 1,050. That is 3,250 running watts. The largest surge belongs to the sump pump, which jumps from 1,050 to 2,600, a difference of 1,550. Peak demand is 4,800 watts. Add twenty percent headroom and you need about 5,760, so the next standard size up is a 7,500 watt generator.
That headroom matters. Generators are not designed to run continuously at their rated maximum — doing so shortens engine life, consumes fuel disproportionately, and leaves nothing in reserve when something unexpected starts. Sizing to roughly eighty percent of the rated output is standard practice.
To run these numbers against your own appliance list without doing the arithmetic by hand, the wattage calculator on our generator sizing guide applies exactly this method and maps the result onto standard generator sizes.
6. Tools, Workshop and Outdoor Equipment
Generators are bought for outages and then used for job sites, workshops and remote projects. Power tools are almost all motor loads, so the gap between running and starting watts is wide.
| Tool | Running Watts | Starting Watts | Notes |
|---|---|---|---|
| Circular saw, 7-1/4 inch | 1,400-1,800 | 2,300-3,000 | Surges under load, not only at start |
| Table saw, 10 inch | 1,800-2,000 | 3,000-4,500 | One of the heaviest portable tool loads |
| Air compressor, 1 HP | 1,500-2,000 | 4,000-6,000 | Very high surge; size around this one |
| Corded drill | 600-900 | 900-1,500 | Modest by comparison |
| Angle grinder | 900-1,200 | 1,500-2,500 | Brief heavy draw when it bites |
| Shop vacuum | 1,000-1,400 | 1,800-2,600 | Universal motor; surges briefly |
| Electric pressure washer | 1,200-1,800 | 2,500-3,500 | Pump motor cycles under load |
Air compressors are the trap in this table. A modest 1 HP compressor can surge to 6,000 watts, comparable to a central air conditioner and far beyond what its running figure suggests. If a compressor is on the list, size the generator around it and expect it to dominate the entire calculation.
Why Tools Behave Differently From Appliances
Household appliances surge once, at start-up, and then settle. Power tools surge repeatedly. A circular saw draws its running figure spinning free and jumps back toward its starting figure every time the blade bites into material. A generator sized tightly to a tool’s running watts will bog down in normal use rather than only at switch-on, so allow generous headroom for workshop use specifically.
7. Quick Reference: The Whole Chart
Everything above condensed into one table, ordered by running watts, for planning at a glance.
| Appliance | Running | Starting |
|---|---|---|
| Ceiling or box fan | 50-200 | 100-400 |
| Lights, TV, router, laptops | 300-600 | Same |
| Refrigerator or freezer | 150-800 | 1,200-2,200 |
| Gas furnace blower | 600-900 | 1,500-2,400 |
| Sump pump, 1/2 HP | 800-1,050 | 2,000-2,600 |
| Window AC, 10,000 BTU | 1,000-1,200 | 2,200-3,000 |
| Well pump, 1 HP | 1,000-1,200 | 3,000-4,000 |
| Microwave | 1,000-1,500 | Same |
| Dishwasher | 1,200-1,500 | Same |
| Space heater | 1,500 | Same |
| Electric range, one element | 1,500-2,500 | Same |
| Central AC, 3 ton | 3,000-3,800 | 9,000-12,000 |
| Electric water heater | 4,000-4,500 | Same |
| Electric dryer | 5,000-5,500 | 6,500 |
Read down the starting watts column and the sizing logic becomes obvious. Everything above the window air conditioner sits comfortably within a mid-size portable. Everything from central air conditioning down is either a standby-scale load or a candidate for deliberate omission during an outage.
8. Common Mistakes to Avoid
Adding Every Starting Wattage Together
Appliances do not all start simultaneously, so summing every surge in the chart produces a number far larger than any real moment of demand. Total the running watts, then add only the single largest surge on your list. This one error is why people end up quoted for standby units they do not need.
Missing That Motors Surge and Heaters Do Not
A 1,500 watt space heater draws 1,500 watts at the moment you switch it on. A 1,050 watt sump pump draws 2,600. Anything with a compressor or pump has a large gap between the two columns; anything that simply makes heat or light does not. Confusing the two categories leads to sizing errors in both directions.
Using Chart Figures for HVAC Equipment
Furnace blowers and air conditioners vary enormously between models, and they are usually the largest loads on the list. For the one appliance where being wrong is most expensive, find the model number and the manufacturer’s specification sheet rather than relying on a typical range.
Forgetting the Well Pump
On a well system, no generator capacity for the pump means no running water at all during an outage — nothing to drink, wash or flush with. A 1 HP pump surging to 4,000 watts is often the largest single surge in a rural household and therefore the figure that sizes the entire generator.
Overlooking Whether the Load Is Hardwired
Wattage is only half the problem. Furnaces, sump pumps and well pumps are typically wired directly into the panel and cannot be reached by extension cord, so they also require a transfer switch or interlock kit. Budget for that alongside the generator or those circuits stay dark.
9. Frequently Asked Questions
What is the difference between running watts and starting watts?
Running watts is the continuous draw once an appliance is operating. Starting watts is the brief surge as a motor overcomes inertia and spins up, often two to three times higher. Motors surge; resistive loads like heaters, kettles and incandescent bulbs draw the same at start-up as in operation.
How many watts does a refrigerator use on a generator?
A refrigerator or freezer typically runs at 150-800 watts but surges to 1,200-2,200 watts when the compressor starts. Because it cycles on and off rather than running continuously, the surge figure is what matters for generator sizing, not the average consumption.
How many starting watts does a sump pump need?
A 1/2 HP sump pump typically runs at 800-1,050 watts and surges to 2,000-2,600 watts on start-up. In many households it is the largest single surge on the backup list, which makes it the appliance that determines the generator size.
How many watts does central air conditioning need?
A three-ton central air conditioner runs at 3,000-3,800 watts and surges to between 9,000 and 12,000 watts at start-up. That surge alone exceeds the output of most portable generators, which is why central air conditioning is usually what pushes a household toward a standby unit.
How do I find the wattage of my own appliance?
Look for the data plate on the back, base or inside the door. It lists watts directly, or volts and amps — multiply those together for watts. For motors listing LRA, or locked rotor amps, multiply by the voltage for a conservative starting figure. A plug-in energy meter confirms running draw on plug-in appliances.
Do I add up all the starting watts to size a generator?
No, and doing so is the most common sizing error. Appliances do not all start at the same instant. Total the running watts of everything you want on, then add only the single largest starting surge among them, and add about twenty percent headroom to that figure.
How many watts does a well pump use?
A 1 HP well pump typically runs at 1,000-1,200 watts and surges to 3,000-4,000 at start-up. On a well system it is frequently the largest single surge in the household, which makes it the appliance that determines the generator size. Without it there is no running water at all during an outage.
How many watts does a microwave use on a generator?
A microwave typically draws 1,000-1,500 watts and does not surge, because the draw is resistive and electronic rather than a motor start. Note that the wattage advertised on a microwave describes its cooking power, not its electrical draw, which is usually somewhat higher.
What appliances should I not run on a portable generator?
Electric dryers at 5,000-5,500 watts, electric water heaters at 4,000-4,500 and central air conditioning surging to 9,000-12,000 are all beyond a typical mid-size portable. Most households leave these off deliberately during an outage, which is what keeps them in portable rather than standby territory.
Do power tools need more watts than household appliances?
Often yes, and they behave differently. A table saw can surge to 4,500 watts and a 1 HP air compressor to 6,000. Tools also surge repeatedly rather than once — a saw jumps toward its starting figure every time the blade bites — so allow generous headroom for workshop use.
Related Generator Guides
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What Size Generator Do I Need?
The full method, with an interactive wattage calculator.
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How Many Watts for a House?
The three tiers of outage power and what each one buys.
Guide
Furnace, Fridge and Sump Pump
Can one generator run all three at once? The arithmetic.
Guide
Electric Water Heater
The biggest resistive load in most houses.
Sizing
Generator for Central AC
Sizing around the largest surge in the house.
The Bottom Line
Every appliance has two numbers. Running watts tells you what it costs to keep something going; starting watts tells you what it costs to get it going, and for anything with a motor that second figure can be three times the first. A refrigerator running at 700 watts surges to 2,200. A sump pump running at 1,050 surges to 2,600.
Combine them with one rule: total the running watts of everything you want on at once, then add only the single largest surge on that list. Appliances do not all start at the same instant, and adding every surge together is the error that sends people shopping for standby generators they do not need.
Then treat these charts as a starting point rather than the answer. Your own data plates carry the real figures, and for furnaces, air conditioners and pumps — the largest and most variable loads — it is worth finding the model number and the manufacturer’s specification. Those are the appliances where a generic range is most likely to be wrong and most expensive to get wrong.
One habit worth adopting before storm season: walk the house with this chart and a notepad, read the data plate on each appliance you would want running, and write your own totals down. Ten minutes of that gives you a figure specific to your house rather than a national average, and it is the number to take shopping.
Where a figure here disagrees with the label on your own appliance, believe the label. These ranges describe typical equipment, and the spread between an efficient modern refrigerator and a twenty-year-old chest freezer is wide enough to matter when you are sizing a generator around it.
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About the Author
Alex Rivers, Home Improvement Editor
Alex has spent over a decade working on residential and light commercial property maintenance, and now tests every tool, coating and machine that appears in these guides personally.