How to use the calculator
- Choose an application scenario: Select a preset (such as Home Blackout Essentials, Refrigerator, or Camping) to pre-fill typical wattages, or select Custom Load to input your exact equipment specs.
- Enter continuous running watts & surge power: Add up the continuous rated wattage of every light, refrigerator, router, or device you need to power. If running motor-driven appliances (like a fridge compressor), enter its peak starting wattage.
- Specify target runtime & efficiency: Enter how many hours of blackout or camping runtime you require. The tool automatically applies standard pure sine wave inverter efficiency (85%) and battery depth-of-discharge (90% for modern LiFePO4 cells).
- Review sizing recommendations: Read the total watt-hour (Wh) battery capacity, required continuous inverter watts, surge peak capacity, and estimated solar recharge times. Click Copy Specification to save your results.
Formula
Appliance Energy (Wh) = Continuous Running Watts (W) × Runtime (hours)
Inverter Load (Wh) = Appliance Energy ÷ (Inverter Efficiency % ÷ 100)
Nominal Battery Needed (Wh) = Inverter Load ÷ (Depth of Discharge % ÷ 100)
Recommended Capacity (Wh) = Nominal Battery Needed × (1 + Safety Margin % ÷ 100)
Inverter Rating (W) ≥ Running Watts × 1.2 | Inverter Surge (W) ≥ Peak Surge Watts
Equivalent Amp-Hours at battery DC voltage: Capacity (Ah) = Recommended Capacity (Wh) ÷ Nominal Voltage (V).
Units
Electrical power is measured in watts (W); electrical energy storage in watt-hours (Wh) and amp-hours (Ah); electric potential in volts (V); operating runtime in hours (h); and inverter efficiency, depth of discharge, and safety headroom in percent (%).
Typical household appliance power consumption table
| Appliance / Device | Category | Running Power (W) | Startup Surge (W) | Typical Runtime | Energy (Wh) |
|---|---|---|---|---|---|
| LED Room Lighting (4 bulbs) | Lighting | 36 W | 36 W | 6 h | 216 Wh |
| Smartphone / Tablet Recharging | Communication | 15 W | 15 W | 3 h | 45 Wh |
| Wi-Fi Router & Fiber Modem | Communication | 15 W | 15 W | 12 h | 180 Wh |
| Laptop / MacBook Pro | Computing | 60 W | 90 W | 6 h | 360 Wh |
| CPAP Machine (Standard pressure) | Medical | 45 W | 60 W | 8 h | 360 Wh |
| 12V DC Portable Car Cooler / Fridge (45L) | Outdoor | 45 W | 80 W | 12 h | 270 Wh |
| 50-inch LED Smart TV | Entertainment | 80 W | 100 W | 4 h | 320 Wh |
| Full-Size Home Refrigerator (Compressor cycle) | Major Appliance | 150 W | 850 W | 12 h | 720 Wh |
| Compact Microwave Oven (700W cooking) | Kitchen | 1,050 W | 1,250 W | 0.3 h | 263 Wh |
| Electric Drip Coffee Maker | Kitchen | 900 W | 950 W | 0.2 h | 180 Wh |
Featured portable power stations & solar backup systems
Two-way workflow: battery runtime & lumens planning
Source
Calculations use established electrical engineering relations (E = P × t, P = V × I, and standard thermodynamic conversion loss models). No physical device data is hardcoded; all sizing is computed from the ratings you enter. The tool cannot measure a real physical battery or appliance.
Limits and safety
- Inverter conversion losses: DC-to-AC inverters generate heat and experience standby idle drain (typically 10W–30W even with no load connected). Always factor in an 80%–90% efficiency derating when sizing.
- Motor and compressor startup surge: Inductive loads (refrigerators, freezers, air conditioners, sump pumps, and circular saws) require 2x to 5x their steady-state wattage for several seconds to start. Ensure the station's peak surge rating meets or exceeds this startup demand.
- Temperature impact on battery capacity: Lithium-ion and LiFePO4 battery discharge capacity drops significantly in sub-freezing temperatures (0°C / 32°F or below). Crucially, never charge lithium batteries below freezing unless the power station features built-in self-heating thermal pads, as charging below freezing can permanently damage cells.
- Indoor ventilation and electrical connection safety: Never attempt to connect a portable power station to a residential electrical panel or wall outlet using a double-ended male plug ("suicide cord"). Connecting a portable power source to home electrical circuits requires a code-compliant manual transfer switch or interlock kit installed by a qualified electrician to prevent dangerous utility grid backfeeding.
- Calculations only: This calculator provides general planning estimates based on manufacturer label ratings. Real-world runtime will vary depending on operating conditions, battery aging, and duty cycle variations.
Frequently asked questions
How do I calculate what size portable power station I need for my home?
Multiply the running wattage of all devices you intend to power simultaneously by the number of hours you need them to run to get total watt-hours (Wh). Divide this number by inverter efficiency (~85%) and your battery’s usable depth of discharge (90% for LiFePO4), then add a 15% safety margin. For example, running a 150 W refrigerator and a 20 W Wi-Fi router (170 W total) for 8 hours requires (170 × 8) ÷ (0.85 × 0.90) × 1.15 ≈ 2,044 Wh of battery storage.
What is the difference between continuous running watts and peak surge watts?
Running watts is the continuous power an appliance consumes during normal operation. Surge watts (starting watts) is the momentary surge of extra power (lasting from a few milliseconds to several seconds) required by motorized and compressor-driven appliances—such as refrigerators, sump pumps, and power tools—to start up from a standstill. Your power station inverter must meet both continuous and surge thresholds.
Why does pure sine wave inverter efficiency reduce battery runtime?
A portable power station’s built-in inverter converts DC battery energy into 120V or 230V AC household electricity. High-quality pure sine wave inverters operate at 80% to 90% efficiency, with 10% to 20% of the energy dissipated as heat and internal standby power. Factoring in inverter efficiency ensures you size a battery pack that delivers adequate real-world runtime.
Why is LiFePO4 (LFP) preferred over standard Lithium-ion (NMC) for power stations?
LiFePO4 (Lithium Iron Phosphate) batteries offer superior thermal and chemical stability, tolerate a deeper 90% Depth of Discharge without rapid degradation, and deliver over 3,000 to 4,000 charge cycles before dropping to 80% original capacity (compared to 500–800 cycles for traditional NMC lithium cells). This makes LFP the gold standard for reliable home blackout backup.
Can a portable power station power a full-size home refrigerator during a blackout?
Yes, provided the power station has a pure sine wave inverter rated for at least 1,000 W to 1,500 W surge power to handle compressor motor startup, and a continuous rating of at least 300 W. A modern Energy Star refrigerator consumes roughly 150 W while the compressor runs and cycles about 40% to 50% of the time, consuming approximately 1,200 Wh to 1,800 Wh over a 24-hour period.
Can I connect a portable power station directly to my home breaker panel?
Never connect a power station to a household wall outlet using a double-ended male cord (suicide plug), as this can cause fatal backfeeding, fires, and utility worker electrocution. To power home circuits safely, hire a qualified electrician to install an approved manual transfer switch or interlock kit with a dedicated inlet box.
Related guides
- Watts to Lumens: Practical Energy-Saving LED Lighting Guide
- LED Fixture Lumens Guide: Energy-Efficient Home Lighting