When the power goes out — a summer storm, a winter nor'easter, a grid fault — a generator is the difference between riding it out comfortably and scrambling in the dark. But the most common generator mistake NYC homeowners make happens before the unit is ever installed: getting the size wrong.
Undersize it and it trips or fails when you ask too much of it. Oversize it and you've spent thousands more than necessary and you're burning fuel inefficiently every time it runs. Right-sizing is the whole game, and it starts with one question: what do you actually need to keep running?
Why sizing matters more than you'd think
Generators are rated in watts (or kilowatts — 1 kW = 1,000 watts). The rating tells you how much load the unit can carry at once. Size below your real demand and the generator overloads — it'll trip its breaker or stall when the AC and fridge kick on together. Size far above it and you've paid for capacity you never use, while the engine runs less efficiently under light loads.
The right answer isn't a number off a shelf — it's a calculation based on the specific appliances and systems you want backed up. That's the difference between a generator that performs for a decade and one that frustrates you every outage.
Essential backup vs whole-home backup
The first decision shapes everything: do you want to power essentials or the whole home?
- Essential backup keeps the critical loads running — refrigerator, some lights, internet/Wi-Fi, heating-system controls, a sump pump, phone charging, maybe a window AC. This is what most homeowners actually need, and it sizes to roughly 7,500–10,000 watts.
- Whole-home backup runs everything as if the grid never went down — central AC, electric range, electric heat or heat pump, the works. This requires substantially more capacity, often 18,000–26,000+ watts (18–26 kW), and a larger standby unit.
Most NYC homes don't need whole-home backup. A well-chosen essential-circuit setup covers what actually matters during an outage at a fraction of the cost. We'll help you decide honestly which you need — see our portable vs standby comparison.
Wattage by appliance (rough guide)
Two numbers matter for each appliance: running watts (steady draw) and starting watts (the surge when motors start, which can be 2–3× running watts). Here's a rough NYC-home reference:
| Appliance / system | Running watts | Starting surge |
|---|---|---|
| Refrigerator / freezer | 600–800 | 1,200–2,200 |
| Sump pump | 800–1,050 | 1,300–3,000 |
| Lights (whole floor, LED) | 200–600 | — |
| Internet / Wi-Fi / electronics | 200–400 | — |
| Window AC (medium) | 900–1,400 | 2,000–3,000 |
| Central AC (3-ton) | 3,500–5,000 | 6,000–8,000 |
| Gas furnace blower | 600–900 | 1,500–2,400 |
| Electric range (one element) | 1,500–2,500 | — |
| Microwave | 1,000–1,500 | — |
These are typical ranges; your appliances' nameplates have exact figures.
How to calculate your generator size
The method is straightforward:
- List what you want to back up — be honest about essentials vs nice-to-haves.
- Add the running watts of everything that could run at once.
- Add the single largest starting surge (the biggest motor starting while everything else runs).
- Add ~20% headroom so the generator isn't maxed out.
That total, in watts, is your minimum generator size. For example, essential backup totaling ~6,000 running watts with a 2,500-watt surge and headroom points to roughly a 10,000-watt (10 kW) unit. Whole-home with central AC quickly climbs past 18 kW. Rather than guess, we do this calculation precisely against your home — it's part of every generator installation quote.
NYC & coastal considerations
Two NYC realities affect sizing. First, coastal flood-zone homes (Howard Beach, the Rockaways, City Island, Throggs Neck, Country Club) often prioritize the sump pump — its starting surge can be the largest single load, and it must never fail during a flood, so size with margin for it. Second, fuel type matters: standby units typically run on natural gas (continuous supply) or propane, and the gas connection requires a DEP fuel permit plus a DOB electrical permit — all of which we handle.
Standby vs portable — how size differs
A standby generator is permanently installed, starts automatically, and is sized for essential-circuit or whole-home backup with an automatic transfer switch. A portable generator is manual and smaller, typically covering a handful of essentials through a transfer switch — never run cords through a window, and never run any generator indoors. Your sizing target is the same calculation; the unit type determines how that capacity is delivered. Full breakdown in our portable vs standby guide, with pricing on our generator cost guide.
Not sure what size generator you need?
We calculate your exact backup load, recommend the right-sized unit — no overselling — and handle the DOB and DEP permits, gas connection, and transfer switch. Coastal-area specialists.
📞 (877) 976-7353 Get a free quote →Frequently Asked Questions
What size generator do I need for my NYC home?
It depends on what you want to power. For a few essentials (fridge, some lights, internet, a sump pump), a 7,500–10,000-watt unit often suffices. For whole-home backup including central AC and electric heat, you may need 18,000–26,000 watts (18–26 kW) or more. The right size comes from adding up your actual backup loads, which we calculate for you.
How many watts does it take to run a house in NYC?
A typical NYC home's essential loads (refrigerator, lights, outlets, internet, a heating system's controls) run roughly 5,000–7,500 watts. Adding central air conditioning, an electric range, or electric heat pushes whole-home backup needs to 18,000+ watts. Coastal homes often size up for sump pumps and extended outages.
Is a bigger generator always better?
No — an oversized generator costs more upfront, burns more fuel, and can run inefficiently under light loads. The goal is right-sizing: enough capacity for what you actually need to back up, with modest headroom, not the biggest unit on the shelf. We size to your real load profile.
Should I get a standby or portable generator for my NYC home?
For automatic, hands-off whole-home backup — especially in outage-prone coastal areas — a standby generator is the answer. For occasional outages and a tighter budget, a portable with a proper transfer switch can cover essentials. See our portable vs standby comparison for the full breakdown.
