How Many Watts to Run a House

A whole house draws far more than a portable power station can supply, so the useful question is how many watts your essential loads need. A router, lights, a refrigerator and a CPAP can total a few hundred watts. Add each load, then compare the total with a unit's watt rating.

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Whole-home loads versus essential loads

Two different questions hide inside "how many watts does it take to run a house." The first is the size of everything a house could draw at once: ovens, dryers, water heaters, central air and heat pumps. The second is the size of what you would actually run during an outage. Those are very different numbers, and only the second one belongs in a plug-in purchase. This guide is built around the second, which is why it sits under our larger question of the best portable power station for home backup.

For a sense of scale on the first question, a main breaker is a ceiling, not a reading. A panel with a 200-amp main breaker at 240 volts is rated for 200 x 240 = 48,000 watts of capacity. That figure is our illustration of how ratings work, not a measurement of what any home uses, and no plug-in unit comes close to it. Neither Grid Doctor model is a whole-home system. My Patriot Supply's own page for the Grid Doctor 3300 says it is not ideal where you need 240V output for large HVAC systems or full-home load panels, and it lists no 240V output.

Do not plug a power station into a wall outlet to power the house. Run each essential device from the station's own outlets, using cords rated for the load.

Load table: running watts and starting watts

Every number in this table is an assumption for arithmetic. None comes from a government table or a manufacturer. Appliances vary widely, and the right figure is on your own appliance label or in its manual. Motors, such as a refrigerator compressor, furnace blower or sump pump, need a burst of extra power for a moment when they start. We assume that burst is about three times the running watts. Your appliance may be lower or higher.

A refrigerator cycles on and off, so "average running draw" is lower than what it pulls while the compressor is on. Our refrigerator runtime guide works through that gap in detail.

How to total your loads: a worked example

The method has four steps, and it works for any home.

1. List what must stay on. Keep the list short.
2. Write each device's running watts from its label or manual.
3. Add the running watts. That total must stay under the unit's continuous watt rating.
4. Find the largest starting watts on the list. Add it to the running watts of everything else. That peak must stay under the unit's surge rating.

Here is the example using the assumed figures above. The essential list is a router (10W), four LED bulbs (40W), a CPAP (40W), a TV (80W) and a full-size refrigerator (150W).

• Running total: 10 + 40 + 40 + 80 + 150 = 320 watts.
• Peak: the refrigerator's assumed start of 450W plus the other four loads at 170W gives 620 watts.

Now compare with the two units. My Patriot Supply lists the Grid Doctor 300 at 300W continuous and 600W surge. The 320W running total is above 300W, and the 620W peak is above 600W, so this list does not fit the 300. The seller's page also says the 300 is not designed for full-size refrigerators. The Grid Doctor 3300 is listed at 3,300W continuous and 6,600W surge, so the same list fits with a wide margin.

Add the furnace blower (400W running, 1,200W starting) and the running total becomes 720W. Add the sump pump (800W running, 2,400W starting) and it becomes 1,520W. If everything started at the same moment, the stack could reach several thousand watts, which is why staggering startups matters. These are still well inside 3,300W running, though you would be using the unit's capacity quickly.

Watts versus watt-hours

Watts describe how fast a device uses power. Watt-hours (Wh) describe how much a battery holds. The Department of Energy's appliance pages give the relationship: watts x hours / 1,000 = kilowatt-hours. A battery's watt rating tells you what it can run at once. Its watt-hour rating tells you how long.

Our planning formula is:

hours = Wh x 0.85 / watts

The 0.85 is our planning assumption for conversion losses. It is not a seller figure. Dropping it gives the ideal ceiling, Wh / watts. For the 320W example, the Grid Doctor 3300 holds 2,048Wh, so 2,048 x 0.85 / 320 = about 5.4 hours. With the seller's maximum expansion of 16,384Wh (see below), 16,384 x 0.85 / 320 = about 43.5 hours.

Single-load estimates from the same formula, at the assumed running watts:

These are our estimates from assumed watts, not seller figures, and they assume one load at a time. Prices and specifications were read on 2026-11-04.

What a plug-in station can't carry

• 240V loads. The 3300's page lists no 240V output. Electric dryers, ranges, well pumps on 240V and central air are outside what either unit offers.
• Anything over the watt rating. Continuous is 3,300W for the 3300 and 300W for the 300, per the seller.
• Loads that run for days. A 2,048Wh battery empties quickly under heavy loads. The seller says the 3300 accepts expansion batteries of 2,048Wh each, up to 7 in its specs (16,384Wh) and "up to four" in its FAQ. The seller's page says one thing in one place and another in another, so we print both and pick neither.
• Hardwired circuits. A furnace or sump pump wired into the house is not something you plug in. Check what can be moved to a cord, and have an electrician handle anything wired into the house.

If you want batteries explained first, our guide to LiFePO4 power stations covers the chemistry both units use, per the seller.

Which unit matches your total

If your essential list is a router, lights, a phone charger and a CPAP, the numbers point to the Grid Doctor 300 review. If it includes a full-size refrigerator, a furnace blower or a sump pump, read the Grid Doctor 3300 review. For the question of power stations against fuel-burning equipment, see portable power station vs generator. For medical equipment, start with our CPAP guide.

FAQ

How many watts does a house use?

It varies too much for one number. A whole house can draw many thousands of watts at its peak with large appliances running, while an outage plan for essentials may total a few hundred. Check your utility bill for monthly kilowatt-hours and each appliance label for its rating.

Do I add running watts or starting watts?

Add running watts of everything you plan to run together. Then check the peak: the largest starting figure plus the running watts of the rest. The first total must stay under continuous watts, the second under surge watts.

Can a portable power station power a whole house?

Neither Grid Doctor unit is a whole-home system. The 3300's seller page says it is not ideal for 240V output for large HVAC systems or full-home load panels. Use it for essential devices on cords.

Where do I find my appliance's watts?

Look on the label, usually on the back or inside the door, or in the manual. If it lists only amps and volts, multiply them: 2 amps at 120 volts is 240 watts. Refrigerators and some appliances also carry an EnergyGuide label with annual kilowatt-hours.

Is the 0.85 loss factor a seller number?

No. It is our planning assumption. Real conversion losses depend on the load and the unit. The ideal ceiling, with no losses, is Wh divided by watts.

Sources

• Energy Saver: appliances and electronics, U.S. Department of Energy, read 2026-11-04
• Grid Doctor 3300 product page, My Patriot Supply: https://www.mypatriotsupply.com/products/grid-doctor-3300-emp-solar-generator, read 2026-11-04
• Grid Doctor 300 product page, My Patriot Supply: https://www.mypatriotsupply.com/products/solar-generator-300w-by-grid-doctor, read 2026-11-04
• Appliance watts in the tables are our labelled assumptions, not sourced figures.

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