When the power goes out in Aiken, it is not just an inconvenience. In the summer, losing air conditioning means your home becomes dangerously hot within hours. In winter, an electric heat pump stops working. Year-round, your refrigerator and freezer start the clock on spoiling food, your sump pump stops protecting your crawl space, and your well pump (if you are on well water) stops delivering water entirely.
A whole-home standby generator eliminates these vulnerabilities. It monitors your utility power continuously and starts automatically within seconds of detecting an outage, restoring power to your home before most people even realize the grid went down. But the most critical decision in a generator project is sizing: choosing a generator that is large enough to handle your home's needs without paying for more capacity than you will ever use.
An undersized generator is worse than no generator at all, because it will overload and shut down exactly when you need it most. An oversized generator wastes thousands of dollars on unnecessary capacity and burns more fuel than needed. Here is how to find the right size for your Aiken home.
Understanding Generator Sizing: Watts and Kilowatts
Generators are rated in watts (W) or kilowatts (kW). One kilowatt equals 1,000 watts. Residential standby generators typically range from 10 kW to 26 kW, with 16 kW to 22 kW being the most common sizes for homes in the Aiken area.
Every electrical device in your home has a wattage rating that tells you how much power it draws during operation. Some devices, particularly those with motors (air conditioners, refrigerators, well pumps, sump pumps), draw significantly more power during the first few seconds of startup than they do during continuous running. This startup surge, called "starting watts" or "locked rotor amps," must be accounted for in generator sizing because the generator needs to handle the surge without overloading.
Generator sizing involves two calculations: the total running watts of all the loads you want the generator to power simultaneously, and the highest starting surge any single motor load will create on top of the running load. The generator must be sized to handle both.
Essential Loads vs. Whole-Home Coverage
The first question in generator sizing is whether you want to power your entire home (every circuit in the panel) or only essential loads (the circuits you need most during an outage).
Essential load coverage uses a smaller, less expensive generator connected through a transfer switch that powers only selected circuits. Typical essential loads include the refrigerator and freezer, a few lighting circuits, the heating and cooling system (or at least the air handler and thermostat), the well pump (for homes on well water), a sump pump, the garage door opener, and one or two outlet circuits for charging devices and powering a television or computer. Essential load generators typically range from 10 kW to 16 kW and cost significantly less than whole-home units.
Whole-home coverage uses a larger generator connected through an automatic transfer switch at the main panel, powering every circuit in the home. With whole-home coverage, your family may not even notice that the utility power has gone out. The air conditioning, kitchen appliances, laundry, entertainment systems, and every outlet in the house continue to function normally. Whole-home generators for typical Aiken residences range from 18 kW to 26 kW.
The choice between essential and whole-home is primarily a budget decision. A 16 kW generator with installation typically costs $6,000 to $9,000 in the Aiken area, while a 22 kW whole-home generator with installation typically costs $10,000 to $15,000. Both provide reliable backup power; the difference is in how much of your home they cover.
Common Appliance Wattage Chart
To calculate your generator size, you need to know the wattage of the appliances and systems you want to power. Here are typical wattage figures for common residential loads.
Central air conditioning (3-ton unit): 3,500 watts running, 7,000 watts starting. This is usually the single largest load in an Aiken home and the primary driver of generator size.
Central air conditioning (5-ton unit): 5,000 watts running, 10,000 watts starting. Larger homes and homes with older, less efficient AC systems require more.
Electric furnace / heat strips: 5,000 to 15,000 watts running (depends on the number of heating elements). Electric heat is an enormous electrical load. If your home uses a heat pump with electric backup strips, the strips can draw 10,000 to 15,000 watts when they activate.
Refrigerator: 150 watts running, 400 watts starting.
Freezer (standalone): 100 watts running, 350 watts starting.
Well pump (1/2 HP submersible): 1,000 watts running, 2,100 watts starting.
Sump pump (1/3 HP): 800 watts running, 1,300 watts starting.
Electric water heater (conventional tank): 4,500 watts running (no significant starting surge).
Electric range/oven: 3,000 to 5,000 watts running.
Microwave: 1,000 to 1,500 watts running.
Clothes dryer (electric): 5,000 watts running.
Washing machine: 500 watts running, 1,200 watts starting.
Lighting (entire home, LED): 500 to 1,500 watts total.
Television and entertainment: 200 to 500 watts.
Garage door opener: 500 watts running, 1,100 watts starting.
How to Calculate Your Generator Size
Here is a simplified method for estimating your generator size. A professional load calculation will be more precise, but this gives you a reliable starting point.
Step 1: List every appliance and system you want the generator to power.
Step 2: For each item, note the running wattage and starting wattage (if it has a motor).
Step 3: Add up the running wattages of all items. This is your total running load.
Step 4: Identify the single largest starting surge in your list (usually the air conditioner). Add that starting surge to your total running load. This gives you the peak demand the generator must handle.
Step 5: Select a generator with a rated capacity that equals or exceeds your peak demand. It is good practice to add a 10 to 20 percent margin for safety and to accommodate loads you may have missed.
Sizing Examples for Aiken Homes
Example 1: Small home, essential loads only. A 1,200-square-foot home wants to cover the 3-ton AC (3,500W running, 7,000W starting), refrigerator (150W), lighting (400W), well pump (1,000W running, 2,100W starting), and a few outlets (300W). Total running load: 5,350W. Largest starting surge: AC at 7,000W. Peak demand: 5,350W + 3,500W (AC starting surge above its running watts) = 8,850W. A 10 kW generator handles this with a comfortable margin.
Example 2: Mid-size home, most circuits. A 2,200-square-foot home wants to cover a 4-ton AC (4,500W running, 9,000W starting), refrigerator (150W), freezer (100W), electric water heater (4,500W), well pump (1,000W), lighting (800W), outlets (500W), and a microwave (1,200W). Total running load: 12,750W. Largest starting surge: AC at 9,000W. Peak demand: 12,750W + 4,500W = 17,250W. An 18 kW or 20 kW generator is appropriate.
Example 3: Large home, whole-home coverage. A 3,500-square-foot home wants everything: 5-ton AC (5,000W running, 10,000W starting), electric range (4,000W), electric dryer (5,000W), electric water heater (4,500W), refrigerator (150W), freezer (100W), well pump (1,000W), sump pump (800W), lighting (1,200W), entertainment (500W), home office (500W), and general outlets (1,000W). Total running load: 23,750W. Largest starting surge: AC at 10,000W. Peak demand: 23,750W + 5,000W = 28,750W. A 30 kW or larger generator is needed, or the homeowner should consider managing loads with a smart transfer switch that staggers motor starting.
Common Sizing Mistakes
Several mistakes consistently lead to improperly sized generators.
Forgetting the air conditioner. In Aiken's climate, air conditioning is not optional during summer outages. Any generator intended for summer use must account for the AC's running and starting loads, which are by far the largest loads in most homes.
Ignoring starting surges. Adding up only the running wattages and buying a generator based on that total guarantees overloading when a motor starts. The generator needs to handle the running load plus the largest starting surge simultaneously.
Undersizing to save money. A generator that is too small will overload and shut down during heavy use, leaving you without power at the worst possible time. It is better to size slightly larger than your calculated need than to cut it too close.
Not accounting for electric heat. If your home uses a heat pump with electric backup heating strips, those strips can add 10,000 to 15,000 watts of demand during winter operation. Many homeowners size their generator for summer AC loads and then discover it cannot handle winter heating loads. A professional load calculation accounts for both seasonal scenarios.
Oversizing excessively. While undersizing is dangerous, excessive oversizing wastes money on the generator purchase and increases fuel consumption. A generator running at 30 to 50 percent of its rated capacity is operating efficiently. A generator running at 10 percent of its capacity is wasting fuel and may develop carbon buildup from chronic underloading.
Smart Load Management Transfer Switches
Modern smart transfer switches can help a smaller generator serve a larger home by managing loads intelligently. Instead of powering everything simultaneously, a smart transfer switch monitors the generator's output and staggers the startup of large motor loads. For example, it might delay the AC compressor from starting until the electric water heater element cycles off, preventing both large loads from running simultaneously.
Smart load management can allow a 20 kW generator to effectively serve loads that would otherwise require a 26 kW or larger unit, saving $2,000 to $5,000 on the generator cost. The trade-off is that some loads may be briefly delayed during peak demand periods, and the transfer switch itself adds $500 to $1,500 to the installation cost.
Next Steps
The most accurate way to size a generator for your Aiken home is a professional load calculation performed by a licensed electrician who can evaluate your specific electrical system, identify your actual loads, and recommend the right generator size for your needs and budget.
Unity Power & Light provides generator sizing consultations, load calculations, and complete generator installation services for homeowners throughout Aiken and the CSRA. We are authorized installers for Generac and other major generator brands and handle every aspect of the project, from sizing through installation, permitting, and utility coordination. Contact us for a generator sizing consultation.