Devices
What Household Devices Actually Draw
10 loads, each with a running wattage, the share of the hour it actually draws, and an estimate of how long a 1024 Wh battery carries it. Two are here to show what a battery should not be asked to do, and one carries no estimate at all.
No medical or life-sustaining equipment appears anywhere on this site
- There are no oxygen concentrators, CPAP machines, ventilators, or medication refrigerators in this list, in the Runtime Estimator, or in the Load List Builder. That absence is deliberate.
- A runtime estimate is arithmetic built on assumptions about a load nobody here has measured. That is the wrong basis for a decision with a person on the other end of it.
- Powering that equipment is planned with the equipment supplier, who knows the actual draw and the approved backup options, and with your electric utility, which in most service territories keeps a medical registry and a priority restoration list you can join before an outage.
- Your local emergency management office can tell you where a shelter with power opens during a long event. Ask while the power is still on.
Loads this sequence covers
| Device | Running draw | Duty share | Average draw used | Surge | Est. hours |
|---|---|---|---|---|---|
| LED Lighting | 30 W | Continuous | 30 W | No | 29 h |
| Phone Charging | 12 W | Continuous | 12 W | No | 73 h |
| Router and Modem | 15 W | Continuous | 15 W | No | 58 h |
| Laptop | 45 W | Continuous | 45 W | No | 19 h |
| Refrigerator | 150 W | 35% | 52.5 W | Yes | 17 h |
| Chest Freezer | 100 W | 30% | 30 W | Yes | 29 h |
| Box Fan | 60 W | Continuous | 60 W | Yes | 15 h |
The duty share column is the one that makes the rest of the table check out. A compressor is not running for the whole hour, so the hours divide the average draw and not the running draw: average draw is running draw multiplied by the duty share, and hours are (1024 x 0.85) divided by that average. A load marked Continuous draws its running figure the entire time it is on, so its two wattage columns match.
Loads no stage in this sequence covers
These are on the site because people ask about them, and because showing the arithmetic makes the argument better than a warning would. Both are computed from the same battery, with the same formula, as everything above.
| Device | Running draw | Duty share | Average draw used | Surge | Est. hours |
|---|---|---|---|---|---|
| Microwave | 1200 W | Continuous | 1200 W | No | 0.7 h |
| Space Heater | 1500 W | Continuous | 1500 W | No | 0.6 h |
Loads this site publishes no estimate for
The formula needs a duty share, and for these loads there is no duty share that is honest across the conditions in which the load matters. Rather than print a number with a caveat attached, the site prints no number.
Sump Pump: no hour figure
- An earlier version of this page divided by a 10 percent duty share and produced about eleven hours. That number was worse than useless. It described a dry basement on a calm day, which is the one situation in which nobody needs a sump pump. In the weather that takes the power out, the pit refills as fast as it empties and the pump approaches continuous running, which moves the honest answer to somewhere near an hour — and even that assumes the pump starts at all, which its startup surge does not guarantee. A figure that swings by a factor of ten depending on an assumption the reader cannot check is not an estimate, so this site withholds it.
Every hour figure on this page is an estimate produced by the site formula, not a guarantee. None of them account for startup surge, temperature, battery age, or the efficiency of any specific model.