Generator sizing trips people up because there are two numbers, not one. Running watts decides whether the generator can keep a load going. Starting watts decides whether it can get the load moving at all, and an undersized unit will stall on a motor it could otherwise run all day.
A toaster draws about 1,200 W running and surges to roughly 1,200 W on start. The smallest generator that handles both is around 1,600 W running and 2,000 W surge, which is inverter generator, suitcase size.
Check your own toaster
Change any box. The result updates as you type.
Planning estimate. The rate box is prefilled with a regional average; the figure on your own bill is the one that matters. Power is draw while running, not while switched on.
Running watts against starting watts
This is a resistive load, so there is effectively no start-up surge. Running watts and starting watts are close to identical, which makes sizing straightforward: allow a margin above the running figure and you are done.
Pure resistance.
Which generator sizes will run it
| Generator class | What it is | Runs a toaster? |
|---|---|---|
| 1,600 W running / 2,000 W surge | Inverter generator, suitcase size | Yes |
| 3,000 W running / 3,500 W surge | Mid-size portable inverter | Yes |
| 4,500 W running / 5,000 W surge | Large portable | Yes |
| 6,500 W running / 7,500 W surge | Heavy portable, often 240 V capable | Yes |
| 8,500 W running / 9,500 W surge | Large portable or small standby | Yes |
| 11,000 W running / 12,000 W surge | Standby, permanently installed | Yes |
| 20,000 W running / 22,000 W surge | Large standby | Yes |
These are the wattage classes portable and standby generators are actually sold in. A yes here means the unit can both start and sustain this appliance on its own. It does not mean the unit can run this appliance plus everything else you want on at the same time, which is the calculation most people actually need.
Fuel and runtime
At 1,200 W a generator burns roughly 0.18 gallons of gasoline an hour, though consumption depends far more on how heavily the generator is loaded than on the appliance itself. A generator running at a quarter of its capacity is inefficient; one running near 50 to 75 percent is close to its sweet spot.
| Fuel | Runtime | Energy delivered |
|---|---|---|
| 1 gallon | 5.6 hours | 6.7 kWh |
| 2 gallons | 11.1 hours | 13.3 kWh |
| 3 gallons | 16.7 hours | 20.0 kWh |
| 5 gallons | 27.8 hours | 33.3 kWh |
| 8 gallons | 44.4 hours | 53.3 kWh |
Running this appliance for its typical 0.2 hours a day would take about 0.0 gallons. Over a multi-day outage that is the number worth planning around, because fuel availability, not generator capacity, is what usually ends up limiting people.
Sizing for the whole house, not one appliance
Nobody buys a generator for a single load. The realistic method is to list what genuinely must run, add the running watts together, then add only the single largest starting surge on top rather than every surge at once. Motors rarely start simultaneously, and sizing as though they do produces a generator far larger and more expensive than you need.
Two things people forget. A generator running well below capacity wastes fuel and, on conventional units, can suffer wet stacking over time. And connecting to house circuits requires a transfer switch or interlock; running extension cords from a generator into a wall outlet backfeeds the grid and can kill line crews.
Generator or battery for this load
A battery covering one day of this appliance would need roughly 0.25 kWh of usable capacity. Batteries are silent, need no fuel, start automatically and work every day rather than only during failures, but the upfront cost is considerably higher and runtime is fixed by capacity.
Generators win on long outages and on cost per kilowatt-hour delivered. Batteries win on convenience, on short frequent interruptions, and where noise or fuel storage is a problem. For loads with heavy surge like this one, check that whichever you choose can handle 1,200 W momentarily, not just 1,200 W continuously.