Two questions decide whether a home lab is sensible to leave running: what it costs on the power bill, and how long it stays up when the power goes out. Add your gear below and this answers both, using the same wattage numbers.
1. Your gear
Watts fill in with a typical average draw for that kind of device. A plug-in power meter or energy-monitoring smart plug gives you the real figure; type it in if you have it.
- Total draw—
- Energy per month—
- Every 10 W you cut saves—
2. UPS runtime on battery
The battery spec is printed on the battery itself and on the UPS’s replacement-battery listing. Note the rating in watts, not VA.
- Size class—
- Load on the UPS you entered—
How the numbers work
Power cost is watts times hours, divided by 1,000 to get kilowatt-hours, times your rate. A device drawing 10 W around the clock uses about 7.3 kWh a month. The default rate of $0.18 is close to the US residential average, which the EIA put at about 17 cents in 2025 and expects to rise past 18 cents in 2026. Your bill states your real rate, and in many places it is far higher or lower.
UPS runtime is not simply battery watt-hours divided by load. Most home UPS units use sealed lead-acid batteries, which deliver much less of their rated capacity when drained quickly. The calculator applies Peukert’s law (exponent 1.3, against the battery’s 20-hour rating) and an 85% inverter efficiency. The model is deliberately conservative: at light and medium loads it typically reads 20–30% below makers’ runtime charts, so treat the result as a floor. A 12V 7Ah unit carrying 100 W comes out around 16 minutes here, while APC rates its 600VA BE600M1 at about 23. Either figure is well short of the 50-plus minutes that simple division suggests. Batteries also lose capacity with age, which is what the 3-year checkbox accounts for (70% of new). Lithium batteries hold their capacity much better under load, so a power station’s watt-hour rating is used directly, less inverter losses.
UPS sizing follows the common rule of keeping the load at or below about 60% of the UPS’s watt rating. That leaves headroom for startup surges and buys meaningfully more runtime. Most home labs do not need hours of runtime: they need long enough for a graceful shutdown, which tools like NUT or apcupsd can trigger automatically.
Typical device draws used
| Device | Typical average |
|---|---|
| Raspberry Pi or similar single-board computer | 5 W |
| Low-power mini PC (N100 class) | 10 W |
| Mid-range mini PC (Core i5 / Ryzen 5 class) | 20 W |
| 2-bay NAS with hard drives | 20 W |
| 4-bay NAS with hard drives | 35 W |
| Tower server or repurposed desktop | 60 W |
| 1U/2U rack server | 120 W |
| Router or firewall box | 12 W |
| Network switch (unmanaged or light managed) | 10 W |
| PoE switch powering cameras | 40 W |
| Wi-Fi access point | 8 W |
| Cable modem or fiber ONT | 10 W |
These are rough averages at light, everyday load; real draw varies a lot with drives, add-in cards and workload. Measure your own gear for anything you plan around.
Related guides
- How much UPS does a home lab need? Every tier from $60 up
- What running a home lab 24/7 actually costs
- Home server power supplies and idle efficiency
- Energy-monitoring smart plugs, for measuring your real draw
- Keeping Starlink online through a power outage
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Estimates are for planning only. Check your UPS maker’s runtime chart and test a real shutdown before relying on it.