Sizing a generator, transfer switches, fuel types, and battery backup for keeping the lights on.
A dual fuel generator runs on either gasoline or propane, which mainly buys you fuel-storage flexibility: propane keeps indefinitely, gasoline degrades in months. Expect roughly 10% less output on propane — the trade for fuel that is still good next winter.
For a standby generator the dealer and service network matters more than the spec sheet — an unrepairable unit is worse than none. For portables, compare engine sourcing and parts availability, noise rating in dBA, inverter capability, and warranty terms.
A 1/3 to 1/2 HP sump pump draws roughly 600–1,050 W running and 1,800–3,000 W starting, so the surge sets the requirement. The pairing matters because the storm that floods a basement is usually the same weather event that cuts the power.
A 1/2 HP submersible well pump needs about 900–1,200 W running and 2,000–3,000 W starting; a 1 HP unit roughly doubles that. Because the starting surge dominates, a rural home usually needs a 5,000–7,500 W generator — or a soft starter to bring the surge down.
Generator noise is measured in dBA at a stated distance, and a 10 dB difference is roughly twice as loud. Inverter generators typically run 50–60 dBA against 70–80 for a conventional unit of similar output, because they throttle the engine to match load instead of running at fixed RPM.
The two mistakes that undersize a generator are ignoring starting surge and forgetting the well or sump pump; the two that oversize it are adding every appliance surge together and sizing to the panel rating. The correct method is running watts plus the single largest surge, plus about 25%.
Size a generator by adding the running watts of everything you need at once, then adding the single largest starting surge — not the sum of all surges, since motors rarely start together. Add about 25% margin and round up to the next standard size.
A portable generator costs $500–$2,500, must be rolled out, fuelled and connected manually, and runs the circuits you choose. A standby unit costs $4,000–$8,000 plus $3,000–$6,000 installed, runs on natural gas or propane, and starts automatically within seconds of an outage.
The RV air conditioner decides generator size: a 13,500 BTU unit needs roughly 2,800–3,000 starting watts and 1,300–1,800 running, which is why 3,000–3,500 W inverter generators dominate. Everything else in an RV runs on comparatively little.
A conventional generator produces a rougher waveform with higher total harmonic distortion, typically above 5%, while an inverter generator delivers under 3% — close to grid quality. Motors and heaters tolerate the difference; laptops, variable-speed HVAC boards and modern appliance electronics may not.
A "solar generator" generates nothing — it is a battery with an inverter, recharged from solar or an outlet. That reframes the comparison: a gas generator makes power continuously while fuel lasts; a battery delivers stored energy silently and indoors, then needs recharging.
What a generator runs is set by its continuous watts, but what it can start is set by surge capacity — motors draw roughly three times running watts for a second or two. A 5,000 W unit typically covers a fridge, furnace blower, sump pump and lights, but not central AC.
An inverter generator produces AC, converts it to DC, then inverts it back to a clean sine wave — which is why it can safely run laptops and electronics that a conventional generator can damage. It also throttles the engine to match load, making it markedly quieter and more fuel-efficient at partial load.
True whole-house backup requires a generator sized for every load simultaneously, including central AC and the range. Most systems marketed as whole-house use load management to shed circuits instead — which is the smarter design, and far cheaper than sizing for a peak that never occurs.
A gas furnace mostly burns gas. The electricity is for the blower and controls — which makes it one of the cheapest loads to back up.
A fridge that runs on 200 watts can demand 1,200 for a second. Sizing to the running number is how generators end up too small.
Back-feeding a house through a double-male cord into an outlet energises the utility transformer in reverse, putting distribution voltage on lines a crew may be working on — and leaving live exposed prongs on the other end of the cord. NEC 702.5 requires transfer equipment precisely to make this impossible.
A generator connection needs a weatherproof inlet box, transfer equipment (interlock or transfer switch) per NEC 702.5, a feeder sized to the generator output, and correct neutral bonding — bonded or floating must match the transfer method under NEC 250.30 and 250.34.
A generator inlet box is a weatherproof flanged inlet — a recessed male connector — mounted outside and wired to your transfer equipment. It is what lets the cord connect outside with no exposed live prongs anywhere, and it keeps the generator at a safe distance from the house.
An interlock kit is a sliding plate that makes it physically impossible to have the main breaker and the generator breaker on at once — cheap, and it gives you access to every circuit. A transfer switch is a separate box wired to selected circuits, faster to operate and available in automatic form.
The bond must exist exactly once in the system. Whether the generator provides it depends entirely on what the transfer equipment does with the neutral.
A standby generator needs a level pad — poured concrete or a composite pre-cast — sized larger than its footprint, above expected flood and snow-drift level, with manufacturer clearances maintained. Level matters most: lubrication and fuel systems assume it, and running out of level accelerates wear.
Connecting a generator to house wiring requires an electrical permit in essentially every jurisdiction, and gas or zoning permits often follow. The inspection is also the only independent check that the transfer equipment, neutral bonding and conductor sizing were done correctly.
A portable generator belongs at least 20 feet from the house with the exhaust pointed away from doors, windows and vents — never in a garage, even with the door open. Standby units follow manufacturer and NFPA 37 clearances, commonly 5 feet from openings and 18 inches from walls.
There are three legal ways to hook up a generator to a house: a manual or automatic transfer switch, a listed interlock kit on the panel, or a generator inlet box feeding one of those. What is never legal is a double-male "suicide cord" into an outlet — it energizes the utility line and can kill a lineworker.
A manual transfer switch requires someone present to operate it and takes minutes; an automatic transfer switch senses the outage, starts a standby generator and switches in 10–30 seconds unattended. The deciding question is what happens if the power fails while nobody is home.
A home standby generator runs roughly $4,000–$6,000 for an air-cooled unit plus $3,000–$6,000 installed. The line items that blow budgets are gas supply — an existing meter often cannot feed the generator plus the furnace and range — and placement clearances forcing a longer run.
The physical installation is one to two days: pad, generator set, transfer switch, gas line and electrical connections. The project runs three to eight weeks, because permitting, gas utility scheduling and inspection sit around it — and the gas work is often the long pole.
A transfer switch has one job: make it physically impossible for utility power and generator power to reach the house at the same time. Everything else — automatic starting, load shedding, circuit selection — is convenience layered on that single safety function, required by NEC 702.5.
Carbon monoxide has no smell and no colour, and a generator produces vastly more of it than a car. Most deaths happen in garages and basements with the door open.
A portable generator burning 0.5 gal/hr at $3.50 costs $1.75 an hour, and at 2.5 kW output that is about $0.70 per kWh — roughly four times a typical utility rate. Acceptable for an outage, a poor plan for anything routine.
Untreated E10 gasoline degrades in 1–3 months, and stale fuel is the single most common reason a portable generator will not start when needed. Stabiliser extends it to 12–24 months; propane stores indefinitely, which is the main argument for a dual fuel unit.
A standby generator self-exercises weekly for 10–20 minutes to keep the battery charged, circulate oil and reveal faults before they matter. A portable needs the same discipline manually — about 20–30 minutes monthly, and under real load rather than at idle.
Generator cords must be sized for both load and length: 12 AWG carries 15 A to 50 feet, 10 AWG holds it to 100. Undersized cord means voltage drop, and low voltage is exactly why a refrigerator compressor fails to start and overheats trying.
Natural gas is piped and never runs out but depends on the utility; propane stores indefinitely in your own tank; gasoline is available anywhere but degrades in months; diesel is efficient and long-lived but costlier. Standby units run gas or propane, portables typically gasoline or dual fuel.
Outages happen in bad weather. The generator still has to be outside — the answer is a cover designed for running, not a different location.
Portable generators need an oil change every 50–100 run hours, annual air filter and spark plug, and monthly exercise under load. Standby units add an annual battery replacement — a dead starting battery is the number one reason a standby fails when it is finally called on.
Small engines hold very little oil — often under a quart — and run hard under continuous load, so the first change comes after about 20–25 hours of break-in, then every 50–100 hours. During a multi-day outage that interval arrives within days, not seasons.
Work the list in order: fuel valve open, choke set correctly, oil level adequate, fuel fresh, battery charged. Stale gasoline and a dead battery between them explain most no-start calls, and both are entirely preventable with stabiliser and an annual battery replacement.
A portable generator typically runs 8 to 12 hours on a full tank at half load, and manufacturer runtime figures almost always quote a 25% load — so real runtime under a working load is shorter than the box says.
A portable generator burns roughly 0.5 to 0.75 gallons per hour at half load for a mid-size unit, and consumption scales with load rather than with the generator’s rating — which is why an oversized generator lightly loaded wastes fuel.
Natural gas is piped continuously and never needs refilling, but it depends on utility supply and requires an adequately sized gas line. Propane sits in your own tank and stores indefinitely, at the cost of refills and roughly 10% lower generator output than gasoline.
Tank size sets runtime, but in cold weather the vaporisation rate limits you before the fuel does — a small tank cannot boil off propane fast enough to feed a generator at full load. A 250–500 gallon tank is typical for a home standby unit, sized for both capacity and draw rate.
A gas furnace draws surprisingly little electricity — typically 300–600 W for the blower, plus a brief surge at start. The obstacle is not capacity but connection: a hardwired furnace cannot simply be plugged into a battery, so it needs a transfer switch or an interlock.
A home battery starts instantly, runs silently indoors, needs no fuel, and stops when its 10–15 kWh are gone. A generator runs for days on refuelling but takes 10–30 seconds to start, must sit outdoors 20 ft from the house, and needs maintenance and stored fuel.
A CPAP without heated humidification draws roughly 30–60 W and runs all night on a modest power station. Switch the humidifier and heated hose on and consumption can triple, so size for the configuration you actually use and confirm the device tolerates a modified sine wave.
Compare power stations on usable watt-hours, continuous and surge output in watts, and cell chemistry — LFP for 3,000+ cycles and long standby storage, NMC for lighter weight and 500–800 cycles. Model lineups change yearly; those specifications do not.
EcoFlow wins on charging speed, output tech and whole-home ambition; Jackery wins on simplicity, weight and a longer consumer track record. The right answer depends on whether you want a power tool or an appliance: EcoFlow's DELTA line recharges faster and scales to circuit-level backup, while Jackery's Explorer line does the core job with less to configure.
A portable power station is a battery, an inverter and outlets in one enclosure — silent, safe indoors, no fuel or exhaust. Its limit is a single number: usable watt-hours. Continuous and surge wattage decide what it can run; watt-hours decide for how long.
Size a backup power station from your load list: about 1 kWh of usable capacity runs a refrigerator for six hours, a furnace blower wants 2 kWh plus real surge headroom, and backing up circuits rather than devices takes a 240V-capable unit in the 4 kWh class. Multi-day outages need solar recharging or a generator.
A UPS exists to prevent an interruption — it switches in milliseconds to keep a computer or network alive through a brief cut, with minutes of runtime. A power station exists to outlast one, with hours of capacity but a slower switchover unless it offers true UPS-mode pass-through.
Solar input is what turns a finite power station into something that survives a multi-day outage. Expect roughly 70–80% of the panels’ rated wattage in practice, and match the array to the unit’s MPPT voltage window — too few panels in series and the controller never starts.
A whole-home battery transfers in milliseconds, runs silently and needs no attention, but is limited by its stored energy — commonly 13.5 kWh usable per unit. Unless solar can recharge it during the outage, that is roughly a day of essential loads rather than indefinite backup.
Yes — if the surge rating clears the compressor start. Runtime is better than you'd think, because a fridge only runs about a third of the time.
Buy for the load that must run, the surge that must start it, and the hours it must last. Miss any one and the station disappoints.
NMC is lighter and denser. LFP lasts several times longer and is harder to make misbehave. For something that sits in your basement for a decade, that's the trade.
