Home Generator Installation Guide

**Portable generators ($500–$3,000):** Portable generators produce 3,000–12,000 watts and run on gasoline or dual-fuel (gas/propane). They must be manually started, positioned outside, connected via extension cords or a manual transfer switch, and refueled every 6–12 hours.

Carbon monoxide risk is the critical safety issue with portable generators. Every year, homeowners die from CO poisoning from portable generators improperly operated in garages, crawlspaces, or too close to windows. NEVER operate a portable generator indoors or in attached structures.

Portable generators are appropriate for: occasional short outages, budget-constrained situations, and homeowners who will be present during outages and can manage the operation manually.

**Standby generators ($7,000–$18,000 installed):** Standby generators are permanently installed on a concrete pad adjacent to the home, connected to natural gas or propane, wired to an automatic transfer switch (ATS) at the main electrical panel, and equipped with an automatic control system that monitors grid power 24/7. When grid power drops below normal voltage for 3–5 seconds, the ATS signals the generator to start and switches the home from grid to generator power automatically.

Standby generators are appropriate for: homes with medical equipment, sump pumps in flood-prone areas, well water systems, frequent or prolonged regional outages, homeowners who travel and want the home protected in their absence, and anyone who has experienced a multi-day outage and doesn't want to again.

Generator sizing is measured in kilowatts (kW). The right size depends on what loads you want to power during an outage.

**Essential circuits only (7–12 kW):** Covers: refrigerator (1.2 kW), lights throughout the home (2–3 kW), select outlets for phones/computers (1 kW), furnace blower or mini-split (1.5–3 kW), internet router (0.1 kW), sump pump if needed (0.7 kW). A 7–10 kW unit handles these loads for most homes under 2,500 sq ft.

**Essential + central AC (14–20 kW):** Central AC is the largest load in most homes (3–7 kW running; 15–30 kW starting surge). A 14–17 kW generator handles one HVAC zone plus all essential circuits. This is the most common residential standby size.

**Whole-home (20–22 kW+):** Covers everything including central AC in larger homes, electric water heaters, and multiple high-draw circuits. 20–22 kW is the standard whole-home size for most 3,000–4,500 sq ft homes.

**The load calculation:** A licensed electrician calculates your specific critical loads before specifying generator size. This is not optional — an undersized generator will either trip its own breaker or damage equipment by failing to start high-draw motors under load.

**Starting vs. running watts:** Electric motors (AC compressors, well pumps, sump pumps) have high starting current (2–3x running current). Generator sizing must account for starting current, not just steady-state running watts. This is why an "adequate" generator can fail to start an AC system.

**Natural gas (preferred where available):** Natural gas generators connect directly to the home's gas service. Advantages: fuel supply never runs out (utility gas service is rarely affected by power outages that affect the electrical grid), no tank to fill or monitor, lower maintenance than propane systems, and typically lower operating cost per kWh generated.

Natural gas generators are available from Generac, Kohler, Briggs & Stratton, Cummins, and other major manufacturers. If your home has gas service, natural gas is almost always the right choice.

**Propane (LP gas):** Propane generators are the solution when natural gas service is not available. Propane is stored in a dedicated tank on the property (100–1,000 gallon tanks are typical for whole-home generators). A 20 kW generator burns approximately 2.2 gallons per hour at full load. A 500-gallon propane tank provides roughly 225 hours of full-load runtime.

Propane disadvantages: tank must be kept above 20–30% full (especially before storm season), requires delivery scheduling, propane prices fluctuate, and the tank has its own installation cost ($500–$2,000 for underground tank placement).

**Diesel (uncommon for residential):** Diesel generators are common in commercial applications but are rarely used for residential standby due to fuel storage requirements, higher purchase cost, noise levels, and maintenance complexity.

The automatic transfer switch is the most critical safety component of a standby generator system. It serves two functions: (1) it automatically disconnects your home from the utility grid when the generator starts, preventing back-feeding into utility lines; (2) it automatically reconnects your home to utility power when the grid is restored and disconnects the generator.

**Why the disconnect is non-negotiable:** Back-feeding utility lines is lethal. Utility workers repairing downed lines assume the lines they are working on are de-energized. A generator connected without an ATS can energize those lines through your panel, electrocuting the workers. This is why an ATS or properly installed manual transfer switch is required by code for any generator connection to a home's electrical system.

**ATS types:** - **Whole-home ATS:** Transfers the entire home's electrical load from grid to generator - **Critical circuits ATS/transfer panel:** A separate subpanel with selected critical circuits that transfers independently — allows a smaller generator to power priority loads - **Smart load management:** Controllers that automatically shed non-essential loads when generator capacity is approached

**Installation:** The ATS is installed by a licensed electrician at or adjacent to the main panel. Permit is required. Installation typically takes 4–6 hours for the electrical work, done at the same time as the generator mounting and gas connection.

**Site assessment:** The electrician and installer assess the proposed generator location for: clearances from windows, doors, and gas meters (typically 5–18 inches minimum per manufacturer spec and local code), proximity to the main panel, gas line routing distance, and concrete pad requirements.

**Permits:** Two permits are typically required: an electrical permit for the ATS installation and circuit wiring, and a gas/mechanical permit for the gas line connection.

**Concrete pad:** Generators must be mounted on a concrete pad to protect against flooding and provide a stable, level mounting surface. Concrete curing takes 3–5 days before the generator can be placed.

**Testing:** System is tested: generator starts, ATS transfers to generator power, all connected loads run, ATS transfers back to utility. Most manufacturers require a 30-minute load test before the warranty is activated.

**Weekly self-test:** After installation, the generator runs a weekly self-test (typically Sunday morning, 12–20 minutes) to verify starting function and exercise the engine. This is normal — not a sign of a problem.

**Full timeline:** 4–8 weeks from contract to active system, accounting for permit processing, concrete cure time, utility coordination, and equipment lead times. Do not wait until storm season.

A standby generator requires regular maintenance to remain reliable. Most manufacturers specify annual servicing.

**Annual service includes:** - Engine oil and filter change - Spark plug inspection and replacement - Air filter inspection and replacement - Battery inspection and replacement every 3 years - Transfer switch contact inspection - Full exercise test with load

Annual service cost: $150–$350 for most residential standby generators.

**Generator exercise:** The weekly self-test exercise is critical for reliability. Generators that sit idle without running develop varnish buildup in the carburetor, battery discharge, and condensation in the fuel system. Never disable the weekly exercise.