Guides

Each guide answers one question with numbers from our calculators, the code section behind it and what to watch out for.

Backup power

• What size generator do I need for central AC?Central air is the load that decides between a portable and a standby generator. How to read your condenser nameplate, what soft-start kits change, and the sizes that work.
• Can a 2,000 W inverter generator run a refrigerator?Yes, with room to spare. The real numbers: running and starting watts of a modern fridge, what else fits on a 2,000 W inverter generator, and how long a tank lasts.
• Interlock kit vs. transfer switch: which one do you need?Both let you power your house from a portable generator safely and legally. How each works, what each costs, and which homes suit which.
• How long will a 1,000 Wh power station actually last?Real runtimes for a 1 kWh portable power station on fridges, CPAPs, routers, TVs and heaters, with the inverter losses and duty cycles most charts ignore.
• L14-30 vs 14-50: which generator inlet and cord do you need?A 30 A inlet caps you at 7,200 W, a 50 A inlet at 12,000 W. How to match the inlet, cord, breaker and generator so none of them is the bottleneck.
• Generator carbon monoxide safety: how far from the house?At least 20 feet, exhaust away from the house, never in a garage. The rules from the CPSC and CDC, why open garage doors don't help, and what CO shutoff features do.
• How much propane does a standby generator use?Gallons per hour and per day for 14, 18, 22 and 26 kW standby generators on propane, and how many days each tank size lasts.
• Can a portable power station run a CPAP?How many nights a 256 Wh to 2,048 Wh power station runs a CPAP, with and without the heated humidifier, on AC and on DC. Calculated runtimes and tips.
• How long will a 13.5 kWh home battery last in an outage?A 13.5 kWh battery (the size of a Tesla Powerwall) runs essentials for about a day and an average home for about 10 hours. Runtime by load, and how to stretch it.
• How many watts does it take to run a house?The average US home uses 899 kWh a month, about 1,250 watts on average but 5,000–10,000 W at peak. What that means for a generator, a battery and your service size.

Wiring

• 10 vs 12 gauge wire for a 20 amp circuit12 AWG copper is the code minimum on a 20 A breaker. When 10 AWG is worth it, with voltage-drop numbers by distance.
• What size wire for 50 amps? Why NM-B uses the 60 °C column6 AWG or 8 AWG for a 50 A circuit? It depends on the cable type. The NEC rule behind the confusion, with a table for every common circuit.
• What size wire for a 30 amp breaker?10 AWG copper for a 30 A breaker, 8 AWG aluminum, and when a long run needs 8 or 6 AWG. NEC table, distance chart and the 240.4(D) rule explained.
• What size wire for a 20 amp circuit 100 feet away?12 AWG drops over 5% at 100 feet on a loaded 20 A, 120 V circuit. Voltage drop by wire size and distance, and when 10 AWG or 8 AWG is worth it.
• What size breaker for a water heater?A 4,500 W, 240 V water heater needs a 25 A minimum breaker on 10 AWG; most are wired at 30 A. Breaker and wire for 3,000–6,000 W, and why the 125% rule applies.
• What size wire for a 40 amp breaker?8 AWG copper or 8 AWG aluminum at 75 °C for 40 amps, 8 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size.
• What size wire for a 60 amp breaker?6 AWG copper or 4 AWG aluminum at 75 °C for 60 amps, 4 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size.
• What size wire for a 70 amp breaker?4 AWG copper or 3 AWG aluminum at 75 °C for 70 amps, 4 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size.
• What size wire for a 80 amp breaker?4 AWG copper or 2 AWG aluminum at 75 °C for 80 amps, 3 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size.
• What size wire for a 90 amp breaker?3 AWG copper or 2 AWG aluminum at 75 °C for 90 amps, 2 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size.
• What size wire for a 100 amp breaker?3 AWG copper or 1 AWG aluminum at 75 °C for 100 amps, 1 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size and the 83% service rule.
• What size wire for a 125 amp breaker?1 AWG copper or 2/0 AWG aluminum at 75 °C for 125 amps, 1/0 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size and the 83% service rule.
• What size wire for a 150 amp breaker?1/0 AWG copper or 3/0 AWG aluminum at 75 °C for 150 amps, 3/0 AWG if you use NM-B cable. NEC table by wire type, distance chart, ground size and the 83% service rule.
• What size wire for a 200 amp breaker?3/0 AWG copper or 250 kcmil aluminum at 75 °C for 200 amps, 250 kcmil if you use NM-B cable. NEC table by wire type, distance chart, ground size and the 83% service rule.
• Standard breaker sizesThe standard circuit breaker sizes in NEC 240.6(A), which ones you find in a home panel, the wire each one needs and the circuits they protect, from 15 A to 200 A.

Energy use and cost

• How much does it cost to run a space heater?A 1,500 W space heater costs about 27¢ an hour at the 2026 U.S. average electricity price. Cost per hour, per month and by state, with EIA prices.
• How much does it cost to charge an EV at home?Home EV charging cost per 100 miles and per month in all 50 states and DC, from EIA electricity prices, with charging losses counted and a gasoline comparison.
• How many amps does a refrigerator use?A modern refrigerator draws 1–2 A running and up to about 10 A for a second at start-up. Running and starting amps, what circuit it needs, and what it costs a year.
• How many amps is 1,000 watts?1,000 watts is 8.33 amps at 120 V and 4.17 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 1,000 W.
• How many amps is 1,500 watts?1,500 watts is 12.50 amps at 120 V and 6.25 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 1,500 W.
• How many amps is 1,800 watts?1,800 watts is 15.00 amps at 120 V and 7.50 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 1,800 W.
• How many amps is 2,000 watts?2,000 watts is 16.67 amps at 120 V and 8.33 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 2,000 W.
• How many amps is 3,000 watts?3,000 watts is 25.00 amps at 120 V and 12.50 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 3,000 W.
• How many amps is 5,000 watts?5,000 watts is 41.67 amps at 120 V and 20.83 amps at 240 V. Which breaker it fits, amps at 12 V and 48 V, and how long a power station runs 5,000 W.