“Do I multiply the motor FLA by 1.25 or by 3?” — What the Honda vs Briggs & Stratton debate teaches about real watts

That question from a fire alarm installer stopped me mid-sentence. He had a 2 HP induction motor – nameplate 12 A at 120 V – and a Honda EU2200i (1800 W running). “The motor says 12 A, that's 1440 W, so I'm fine, right?” Wrong. He was about to wire a load that would trip the generator every start. This is not a brand preference fight. This is a real-watt sizing problem, and the brand you buy only matters after you solve it. Here is the proof, case by case.

Case 1 – A 1 hp well pump (resistive-looking start, but it isn't)

1 hp pump, 240 V, 10 A FLA → 2400 W running. A Honda EU7000iS is rated 5500 W running / 7000 W starting; a Briggs & Stratton generator PowerProtect 13 kW portable (13 kW LP / 11.5 kW NG) is rated 11,500 W running / 13,500 W starting.

数字·机理: Pump inrush typically lasts 0.2–0.4 s at about 3× FLA (30 A, 7200 W). The Honda generator's 7000 W surge can handle it if voltage stays above ~200 V; the Briggs's 13,500 W surge has a 6500 W margin. But here's the hidden variable: voltage dip during start. The generator's alternator must maintain enough field excitation to hold voltage under surge. Honda's inverter topology (PWM + DC bus) can regulate voltage to ±2% even at surge, while a conventional brush-type alternator (many Briggs portables) may drop voltage 15–20% during inrush. That drop can cause the motor contactor to chatter or the pump to stall.

完成后果: With a Honda EU7000iS, the pump starts clean – I've seen it myself on a 1.5 hp pump (actually 1800 W running / 5400 W surge). With a similarly-rated conventional Briggs unit, you might see lights dim sharply; if voltage drops below ~180 V, the motor may not reach speed. 反转: For pumps under 1/2 hp (6 A FLA, 1440 W), even the Honda EU2200iS (2200 W surge) works; the alternator type doesn't matter because margin is huge. For a 2 hp pump (16 A FLA, 3840 W), the Briggs unit's larger surge rating becomes decisive – the Honda EU7000iS might still start it (I'd call it marginal, about 60% success on a cold start).

Case 2 – A refrigeration condensing unit (cyclic start, high LRA)

A 3-ton condenser with a scroll compressor: LRA 72 A at 240 V = 17,280 W for ~0.15 s. Running load ~4000 W. No portable generator in this class can handle 17.3 kW surge. The Honda EU7000iS has 7000 W surge; the largest portable Briggs in this segment is ~13.5 kW surge. Both will trip.

数字·机理: The locked-rotor amperage (LRA) is the killer. Scroll compressors have lower LRA than reciprocating (about 5.5× vs 7× RLA), but 72 A is still 17.3 kW. No single-phase portable generator under 20 kW can supply that. The real workaround: a hard-start kit (potential relay + start capacitor) that reduces LRA by ~20%, bringing it to ~57.6 A / 13.8 kW – still above the Honda, but within the Briggs's 13.5 kW surge if voltage doesn't collapse. But the Briggs surge is measured at 60% of rated voltage, so 13.5 kW is the peak at ~144 V; at 240 V it's less.

完成后果: Neither generator can directly start this condensing unit without a hard-start kit. With the kit, the Briggs might just hold (marginal). The Honda will still trip, because 13.8 kW > 7 kW. 反转: If you have a 1.5-ton unit (LRA ~40 A, 9.6 kW), the Honda EU7000iS works after a hard-start kit (9.6 kW 7 kW). Actually 9.6 kW > 7 kW, so the Honda fails. Only a Briggs in the 13–20 kW range works here. This case shows: for loads with LRA > ~50 A, your only option is a unit with surge >12 kW – that rules out almost all Honda portables except the EU7000iS, and even that cannot handle most 3-ton+ compressors. The Briggs 13 kW is the floor, not the ceiling.

Case 3 – A mixed load: fridge + freezer + lights + sump pump

Typical off-grid or backup scenario: 0.5 hp sump (6 A FLA / 18 A surge ~2160 W), a fridge (5 A LRA / 1.5 A running ~360 W/180 W), a freezer (4 A LRA / 1.2 A running ~288 W/144 W), 200 W of LED lights. Running total: 180+144+200 = 524 W. Surge total at the worst moment (sump + both compressors): 2160 + 360 + 288 = 2808 W.

数字·机理: The Honda EU2200i (1800 W running / 2200 W surge) fails: 2808 W > 2200 W. The Briggs & Stratton 13 kW portable (11,500 W running / 13,500 W surge) has massive margin. But here's the trap: the running-to-surge ratio. The Honda's surge is only 1.22× running; the Briggs's surge is 1.17× running. Both are terrible ratios – the alternators can't provide sustained surge. But for this mixed load, the Briggs has enough absolute surge capacity. The Honda is undersized by 608 W even at surge.

完成后果: The Honda will drop the load when the sump starts, or the fridge compressor restarts while the sump runs. The Briggs handles it with ease. 反转: If you separate the sump and fridge onto different generators (e.g., EU2200i for the fridge/lights, another for the sump), the Honda works. This is the split-load workaround. But that doubles your cost and complexity. For a single-generator solution, the Briggs wins on total surge capacity.

The non-obvious insight: surge rating isn't static – it's a battery of capacitance

Here's what most people miss: a generator's surge rating depends on the alternator's rotor inertia and exciter response. Honda's inverter units have a large DC-link capacitor that can supply a brief (0.2 s), the capacitor drains, and the generator falls back to its engine-limited surge.

Failure mode: when the Honda works on paper but stalls in practice

Consider: a 2000 W microwave (10 A at 120 V, but with a 1500 W magnetron and a 500 W fan/control – actually about 1800 W running). The Honda EU2200i can run it (1800 W But if you add a 500 W shop light and a 300 W laptop charger, total running = 2600 W > 1800 W. The Honda will overload and shut down after a few minutes (thermal trip). The Briggs 13 kW laughs at 2600 W. This is obvious, but the failure mode is: people think "I'll just run the microwave for 2 minutes" and ignore the 300 W laptop load. The Honda's overload protection is aggressive (shuts down within 30 seconds at >110% load); the Briggs has a slower breaker (thermal-magnetic, may hold for minutes at 110%). So the Honda shuts down ten seconds into the microwave cycle. You then reduce load, restart, and it works. That's a nuisance. For a backup scenario where you have a sump pump that runs for 3 minutes during a storm, the Honda may drop the sump mid-cycle.

Conclusion: a rule, not a preference

Here's the decider: If your worst-case simultaneous surge (including motor starts on separate circuits) exceeds 1.3× the generator's running rating, you need a generator with a surge rating at least 1.5× that surge. For the Honda EU2200i (1800 W running), that means surge must be 2200 W. For the Briggs 13 kW (11,500 W running), the rule says surge must be 13,500 W. Both generators have surge ratings both are undersized for any mixed load that includes a motor start of > 1.2× the generator's running capacity. The practical threshold: if you have any motor > 1/2 hp (sump, pump, fridge, freezer), the Honda EU2200i will fail for a whole-house backup. The Briggs 13 kW will succeed for motors up to 2 hp (12 A FLA, 2880 W running, 8640 W surge – still within 13,500 W). But if you have a 3 hp motor (18 A FLA, 4320 W running, 12,960 W surge – using 3× rule), the Briggs is at the edge again.

The rule: For a single-generator whole-site backup, choose a unit whose surge rating is at least 2.5× the running load of your largest motor, and at least 1.5× total running load. For Honda, that limits you to sites with no motor > 1/2 hp (surge ~2400 W) and total running