Whole-home generator install

A standby generator is a permanently-installed unit on a concrete pad outside your home, connected to your electrical panel through an automatic transfer switch and to a fixed fuel source (natural gas line or propane tank). When the power goes out, it starts itself within 10-30 seconds. When power comes back, it shuts itself off. You don't do anything.

A portable generator is a wheeled unit you store in your garage, run on gasoline, and connect to your home through either an interlock kit on your panel or a manual transfer switch. When the power goes out, you wheel it outside, fill it with gas, start it manually, and switch your panel over. When power comes back, you reverse the process.

The right call depends on your outage profile and tolerance for manual operation. Most homeowners considering "whole-home generator" want standby — the convenience and automatic operation are the entire point. Portable generators are essentially a different product category serving a different need (occasional emergency backup at lower upfront cost, with the user accepting manual operation).

The deciding question: how many hours per year are you out of power, and how disruptive is each outage? If you average 24+ hours of outages per year (cumulative) and are home during them, standby pays back through convenience. If you average 4-8 hours per year, a portable is often the right answer.

Generator sizing failures fall into two predictable patterns: undersized units that drop loads or shut down when major appliances cycle on, and oversized units that run inefficiently on light loads (creates "wet stacking" in fuel-engine generators). Both are install-time failures that are expensive to fix.

The right way to size: a load survey of your actual home. Either an HVAC-certified installer with a clamp meter walks the panel during a typical day and measures real draw, or the installer uses your utility's smart-meter hourly data to identify peak draw periods. The number you size to is "starting watts" (motor inrush current at AC compressor or heat-pump start), not "running watts" (steady-state draw).

Typical sizing for whole-home (running everything, including AC):

- Small home (under 1,500 sq ft, single AC): 14-18 kW standby - Medium home (1,500-2,500 sq ft, single AC): 18-22 kW standby - Larger home (2,500-3,500 sq ft, two AC zones): 22-26 kW standby - Large home (3,500+ sq ft, multiple AC, electric car charger, hot tub): 26-36 kW standby or larger

Load-managed sizing for essentials backup (refrigerator, internet, lighting, well pump, plus selective HVAC): 11-14 kW standby with smart load management. The smart controller automatically shed AC or major loads when the generator approaches capacity, and re-engages them as available capacity returns.

The transfer switch is the device that disconnects your home from the grid and connects it to the generator during outages. The choice between automatic and manual is essentially the choice between standby and portable architecture.

Automatic Transfer Switch (ATS): the default for standby generators. Senses utility power loss within milliseconds, signals the generator to start, waits for stable generator output (typically 10-30 seconds), then transfers the home's load from utility to generator. Reverse process when utility power returns. Requires no homeowner action.

Four main ATS sizes: 100A (essentials only or smaller homes), 200A (most whole-home installs), 400A (large homes with 400A service), and load-managed (smaller ATS with smart load management to support whole-home backup on a smaller generator). The right size matches your panel's main breaker.

Manual Transfer Switch: requires you to physically flip a switch between utility and generator power during an outage. Used with portable generators or as a budget option for very simple backup. Cheaper upfront, but requires you to be home and capable of operating it during outages.

Interlock kit: a code-approved metal slider that prevents your main breaker and generator-input breaker from being on simultaneously. Combined with a generator inlet box, this is the lowest-cost architecture for portable-generator backup. Acceptable in most jurisdictions if installed by a licensed electrician with permit.

Generation interconnect agreement: required by most utilities for any generator that could potentially feed back to the grid. Standby generators with proper transfer switches are isolated and don't require this; portable setups with interlock kits sometimes do, depending on the jurisdiction.

Whole-home generators require ongoing maintenance to be reliable when you actually need them. The maintenance pattern is similar to a car: regular oil changes, periodic filter replacements, annual service.

Weekly self-test: most standby generators run themselves for 5-15 minutes weekly to confirm they'll start. The self-test cycle is configurable; some homeowners turn it off to reduce noise (don't do this — the test is what catches problems before you need the generator for real).

Quarterly visual inspection: walk around the unit, check for visible damage, debris, animal nesting, and verify the battery indicator. 5 minutes; catches problems early.

Annual service: oil change, oil filter, air filter, spark plug check, battery test, fuel system inspection, transfer switch operation. Done by the installer or a generator-certified technician. Typically $200-500 per year. Not optional — generators that miss annual service are the ones that don't start during outages.

2,000-hour service or 5-year service: more comprehensive — coolant, valve adjustment, full system inspection. Major brands publish exact intervals.

The maintenance contract is worth the cost for most homeowners. The brand-certified technician who serviced your unit knows its history and can diagnose problems faster than a generic HVAC tech who's never seen it before.