Megawatt to Horsepower (Electric)

In the US, roughly 750–1,000 homes (average consumption ~1.2 kW per home). In Europe, where usage is lower, 1 MW can serve 1,500–2,000 homes. But this is average — on a hot summer afternoon when everyone cranks AC, that number can drop to 300–400 homes. Grid planners must size for peak demand, not averages, which is why installed capacity far exceeds average load.

A small data center uses 1–5 MW; a large hyperscale facility (Google, AWS, Microsoft) draws 50–200 MW — some exceeding 300 MW. The entire US data center industry consumed about 17 GW in 2023, roughly 4% of national electricity. AI training clusters are pushing demand higher: a single large GPU cluster can draw 50–100 MW, and planned AI-focused campuses target 1 GW or more.

Onshore turbines typically rate 2–6 MW; the latest offshore monsters reach 14–16 MW per turbine. Vestas' V236-15.0 MW turbine has a rotor diameter of 236 meters — wider than two football fields. A single sweep of its blades can generate enough electricity for a UK household for two days. Capacity factors run 25–45% onshore and 40–55% offshore, so actual average output is roughly half the nameplate rating.

Most operating reactors produce 500–1,400 MW of electrical power. The world's largest, at France's Gravelines plant, has six reactors totalling 5,460 MW. Small Modular Reactors (SMRs) being developed target 50–300 MW each. Nuclear plants run at 85–95% capacity factor — far higher than wind (~35%) or solar (~25%) — meaning a 1,000 MW reactor actually delivers about 900 MW on average.

MW tells you the maximum instantaneous power the battery can deliver (how fast it can discharge), while MWh tells you total stored energy (how long it can sustain that output). A 100 MW / 400 MWh battery can deliver 100 MW for 4 hours, or 50 MW for 8 hours. Grid operators care about both: MW for handling sudden demand spikes, MWh for sustained backup during extended outages or evening solar fade.

It's a deliberate rounding for simplicity. The mechanical horsepower is 745.69987... watts — an ugly number for electrical calculations. The electric motor industry rounded to 746 W for clean nameplate ratings and straightforward calculations. The 0.04% difference is far below any motor's manufacturing tolerance. Some standards even use 750 W as an approximation. In practice, the distinction between 745.7 and 746 matters only to standards lawyers and unit conversion pedants.

Divide the hp rating by the motor efficiency and power factor. A 5 hp motor at 90% efficiency draws: 5 × 746 / 0.90 = 4,144 W of electrical power to deliver 3,730 W of shaft power. For three-phase motors, also divide by (√3 × voltage × power factor) to get amperage. Real-world efficiency ranges from 75% for small motors to 96% for large premium-efficiency ones. The nameplate always shows shaft output, not electrical input — a common source of confusion.

Because American homeowners and pool contractors have decades of experience sizing pumps in hp: "a 20,000-gallon pool needs a 1.5 hp pump" is ingrained knowledge. The Department of Energy actually mandated variable-speed pool pumps in 2021 and encouraged watt-based efficiency ratings, but manufacturers still prominently display hp because it drives purchasing decisions. A customer choosing between a 1 hp and 1.5 hp pump understands the difference intuitively; 746 W vs 1,119 W means nothing to them.

NEMA (National Electrical Manufacturers Association) defines standard motor sizes using electric hp: 1/4, 1/3, 1/2, 3/4, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100 hp and up. These are standardized frame sizes — a 5 hp motor from any manufacturer fits the same mounting bolts. The hp(E) rating is the shaft output; NEMA also specifies efficiency classes (IE1 through IE4) that determine how much electrical power the motor actually consumes.

Not usually. EV manufacturers rate motors in kilowatts because the electrical connection is obvious and kW is internationally understood. A Tesla Model 3 motor is listed as 211 kW, not "283 hp(E)." However, marketing materials often convert to hp for American consumers: "283 horsepower" sounds sportier. Interestingly, EV motors are far more efficient (90–97%) than combustion engines (25–40%), so a 200 hp EV motor consumes far less total energy than a 200 hp gasoline engine.