How to choose the right size generator for my home?
Quick answer: Choose a generator by listing the circuits you want to run during an outage, totaling their running watts, then adding enough capacity for the single largest motor “starting surge” (A/C, well pump, fridge). Next decide whether you want “essential loads” only or near whole-home coverage, since that changes the target kW significantly. An electrician can confirm the final size using your panel rating and equipment nameplates.
How to choose the right size generator for my home (a practical sizing method)
Start by deciding what you want your home to feel like during an outage: bare essentials (food safety, water, basic lighting, internet) or whole-home comfort (including major HVAC). In Northeast Georgia summers (Athens/Watkinsville and surrounding areas), the biggest sizing swing is often whether you want to run central A/C —because the outdoor condenser can have a large starting surge.
Use this simple process:
1) Make an outage load list. Write down the appliances/circuits you want powered (fridge, well pump, lights, garage door, medical equipment, internet, etc.). Pull watts/amps from the nameplate or manual.
2) Add running watts, then account for starting surge. Total the running watts of everything you want on at the same time. Then identify the single largest starting surge you may need to handle while other loads are already running (common culprits: well pumps, A/C condensers, refrigerator compressors).
3) Convert to generator size (kW) with headroom. As a planning step, kW ≈ watts ÷ 1,000 . Add practical headroom for voltage drop and future changes. Final sizing should be verified against your actual equipment nameplates and how you’ll connect the generator (transfer switch / interlock / essential-loads panel).
Mini example: essential-loads vs whole-home sizing (typical ranges)
Important: The numbers below are illustrative typical ranges. Your actual wattage and starting surge must come from your equipment nameplates (especially HVAC and pumps).
Example A — “Essential loads” (no central A/C)
- Refrigerator: ~600 W running, ~1,800 W starting surge
- Well pump (1/2 HP): ~1,000 W running, ~3,000 W starting surge
- Internet + TV + device charging: ~200 W running
- Lighting (mix of LED): ~200 W running
- Microwave (intermittent): ~1,000 W running (only when used)
Step 1: Running watts total (typical)
600 + 1,000 + 200 + 200 + 1,000 = 3,000 W
(3.0 kW)
Step 2: Largest starting surge (typical)
Largest surge item is the well pump at ~ 3,000 W
starting. When it starts, other loads may already be running.
Step 3: Quick sizing check
Running total (3,000 W) + extra needed for the pump start (3,000 − 1,000 = 2,000 W) ≈ 5,000 W
.
Recommendation (typical):
plan around a 5–7 kW
generator for this essential-loads scenario, depending on what you truly run at the same time and how conservative you want to be.
Example B — “Whole-home feel” (includes central A/C)
- Same essential loads as above (assume ~3,000 W running)
- Central A/C (3-ton condenser, typical): ~3,500 W running, ~12,000 W starting surge (can vary widely)
- Additional household loads (some receptacles, more lighting, etc.): ~1,000–2,000 W running
Step 1: Running watts total (typical)
Essentials 3,000 + A/C 3,500 + extra 1,500 ≈ 8,000 W
(8.0 kW)
Step 2: Largest starting surge (typical)
A/C starting surge ~12,000 W is usually the biggest event.
Step 3: Quick sizing check
Running total (8,000 W) + extra needed for A/C start (12,000 − 3,500 = 8,500 W) ≈ 16,500 W
.
Recommendation (typical):
plan around 17–22 kW
for a “whole-home with A/C” goal, unless you use load management
and/or an HVAC soft-start
to reduce starting demand.
What to gather before you call (and when to consider load management)
Having the right info up front makes sizing faster and more accurate. Before you talk with an electrician, gather:
- Main panel rating (e.g., 150A/200A) and a photo of the panel label
- Fuel availability : natural gas at the home, propane tank size, or whether you’re considering portable gasoline
- HVAC nameplate details (outdoor condenser): model, MCA/amps, and especially LRA (locked-rotor amps) if listed
- Well pump or sump pump horsepower (HP) and voltage (120V/240V), if applicable
- Your “must-have” circuits list (refrigeration, medical equipment, internet, select lights, garage door, etc.)
- Connection plan : transfer switch vs interlock, and whether you want an essential-loads panel
Consider load management or soft-start when you want A/C coverage but don’t want to jump to a much larger generator. In general terms, load management can prevent multiple big loads from starting at once, and soft-start devices can reduce HVAC starting surge—both can change the required generator size.
Safety and connection notes (general best practice)
Generator sizing and safe connection go together. As general safety guidance:
- Never backfeed a home through a dryer outlet or improvised cord—this can energize utility lines and is extremely dangerous.
- Use a properly installed transfer switch or interlock so the generator and utility cannot be connected at the same time.
- Never run a generator in enclosed spaces (garage, basement) due to carbon monoxide risk; follow the manufacturer’s placement and ventilation instructions.
Get Thunderbolt Electric first on Google. Add us as a preferred source and Google will show more of our content in your Top Stories and AI results. Add Thunderbolt Electric as a preferred source on Google →
