When the power goes out, a standby generator can keep your home or business running smoothly. But choosing the right size generator is crucial—too small, and it won’t power everything you need; too large, and you’ll overpay for capacity you don’t use.
So, what size standby generator do you need? This guide will break down everything you need to know to make the right choice.
Why Generator Size Matters
The size of your generator determines:
✔️ How many appliances and systems it can power.
✔️ How efficiently it runs (overloading damages the generator).
✔️ The overall cost of purchase, fuel, and maintenance.
Choosing the correct size ensures you get reliable backup power without wasting money or risking failure.
Step 1: Determine Your Power Needs
Generators are measured in kilowatts (kW), which indicates how much electricity they can produce. The higher the kW rating, the more power it can supply.
Common Generator Sizes & What They Can Power
Generator Size (kW) | Typical Uses |
|---|---|
7-10 kW | Essential circuits: refrigerator, lights, sump pump, small AC unit |
11-15 kW | Small home: refrigerator, HVAC, water heater, lights, Wi-Fi |
16-22 kW | Medium home: all essentials + oven, washer/dryer, well pump |
23-30 kW | Large home: central AC, electric stove, hot tub, heavy appliances |
30+ kW | Whole-house backup for large homes or small businesses |
Step 2: List Your Essential Appliances
Make a list of everything you want to power during an outage. Here’s an estimate of how much power common appliances require:
Appliance | Running Watts |
|---|---|
Refrigerator | 600-800 W |
Freezer | 500-700 W |
Sump Pump (1/2 HP) | 1,000 W |
Electric Water Heater | 4,500 W |
Gas Furnace Fan (1/3 HP) | 800 W |
Central AC (3-ton) | 3,500 W |
Electric Oven | 5,000 W |
Microwave | 1,000 W |
TV & Internet | 200-400 W |
Washer & Dryer | 4,000 W |
Whole-House Lights | 1,000-3,000 W |
How to Calculate Your Power Needs
- Add up the running watts of all appliances you want to power.
- Multiply by 1.5 to 2x for surge power, since appliances like AC units and refrigerators require extra power when they start.
- Choose a generator that meets or slightly exceeds this total.
Example Calculation:
- Refrigerator (800 W) + Furnace (800 W) + Central AC (3,500 W) + Lights (2,000 W) = 7,100 W running power
- Surge power required: 7,100 W × 1.5 = 10,650 W (10.65 kW)
- Best generator size: 11-12 kW
Step 3: Choose the Right Type of Generator
There are different types of standby generators depending on fuel type and power output.
1.0 Whole-House Standby Generators
Best for: Homeowners who want full power backup
Size Range: 16-30+ kW
Powers: All appliances, including HVAC
Fuel Source: Natural gas, propane, or diesel
Pros: Automatic start, no manual operation.
2.0 Essential Circuit Standby Generators
Best for: Homeowners who only need power for essentials
Size Range: 7-15 kW
Powers: Fridge, sump pump, furnace, lights
Fuel Source: Natural gas, propane, or diesel
Pros: More affordable, smaller footprint
Step 4: Consider Installation & Fuel Type
Installation Requirements
- Standby generators must be professionally installed and connected to your home’s electrical system.
- Ensure you have adequate space outside (at least 5 feet from windows and doors).
- Installation costs typically range from $2,000 to $5,000, depending on complexity.
Fuel Type Options
- Natural Gas (Best for homes with existing gas lines)
- Propane (Good for rural areas, requires a propane tank)
- Diesel (Common for large commercial standby generators)
Pro Tip: Always check local regulations and permits before installation.
Frequently Asked Questions (FAQ)
Can a standby generator power my whole house?
– Yes, but you need at least 22-30 kW to run everything, including HVAC.
What happens if I choose a generator that’s too small?
– An undersized generator may not start or will overload and shut down.
Do I need a generator if I already have a portable one?
– Standby generators are automatic and provide whole-home coverage, unlike portable generators that require manual setup.
How long do standby generators last?
– Most last 15-30 years with regular maintenance.
Final Thoughts: Get the Right Standby Generator for Your Needs
Choosing the right size standby generator ensures your home stays powered during outages without overspending on unnecessary capacity.
Key Takeaways:
✅ Add up your essential appliances’ power needs
✅ Choose a generator with at least 10-20% extra capacity
✅ Consider whole-house vs. essential circuit generators
✅ Hire a professional installer for a seamless setup
💡 Need Expert Help?
If you’re still unsure what size generator you need, contact Midwest Generator Solutions for a consultation. We’ll help you find the perfect generator for your home or business!
Schedule Your Generator Maintenance with Midwest Generator Solutions
Don’t wait until the first winter storm hits to discover that your generator isn’t working correctly. Schedule your Fall maintenance with Midwest Generator Solutions today and ensure your home stays powered through the cold months. Our team is ready to provide expert service and keep your generator running smoothly all winter long.