With power outages becoming more common, having a backup generator at home is practically a necessity these days. But how do you pick the right size generator for your house? Getting one that’s too small means some appliances won’t run when the power goes out. On the other hand, an oversized generator is needlessly expensive and wasteful.
Choosing the ideal size generator for your home’s electrical requirements takes a bit of planning. But it ensures your family stays comfortable and your essentials stay powered up, even during prolonged blackouts.
This comprehensive guide will walk you through the key factors to consider when determining what size generator you need for your house in 2023.
Calculate Your Power Requirements
The most important factor in selecting a home backup generator is calculating your power requirements. This involves totaling the starting and running wattages of the appliances and devices you want to power during an outage.
Here are some average power consumption figures for common home appliances and systems:
- Refrigerator – 500-1500 watts
- Freezer – 500-1000 watts
- Sump Pump – 800-3000 watts
- Furnace Fan – 750-1500 watts
- LED Lights – 4-8 watts per bulb
- Laptop – 50-100 watts
- TV – 100-500 watts
- Microwave – 1000-1500 watts
- Coffee Maker – 900-1200 watts
- Air Conditioner – 3000-6000 watts
Add up the wattages of the essential appliances you want to run on a generator. Be sure to use the higher starting wattage for motors in appliances like refrigerators, sump pumps, and furnaces. Also, factor in 20% more capacity as a safety buffer. This total wattage is the minimum size generator you need.
Choose Between Portable and Standby
The two main types of generators for homes are portable and standby. Portable generators range from small inverter models around 1000-3000 watts for basic power needs up to large 15,000+ watt units capable of backing up most household circuits.
Standby generators are permanently installed, connect to your home’s electrical panel, and supply backup power automatically when the grid power goes out.
For occasional short outages, a portable generator may suffice if you don’t mind manually connecting it when needed. For frequent or extended outages, a standby unit is worth the higher cost for automatic, whole-home backup capability.
Consider Fuel Type
Most portable generators run on gasoline while standby models use natural gas or liquid propane which are safer for extended use. Gasoline generators need careful storage and fuel stabilization for long shelf life.
Propane and natural gas give standby generators unlimited runtime. Also, factor in generator noise – standby units are quieter for home use since they’re permanently installed outside.
Determine if a Transfer Switch is Needed
Using a portable generator safely requires a transfer switch installed by an electrician to isolate your home wiring from the utility lines when running the generator. Otherwise, back feed from the generator could harm utility workers trying to restore grid power. All standby generators must utilize transfer switches for grid isolation.
Calculate Whole House Power Needs
To determine the size of a whole house standby generator, calculate the total wattage used by your home’s essential circuits. The average wattage demand per square foot is around 3-5 watts. Multiply this by your home’s square footage and add large appliance loads like AC units. This gives an estimate of your total household power needs. Add at least 20% as a buffer.
For example, a 2500 sq ft home with central air may need:
2500 sq ft x 5 watts per sq ft = 12,500 watts Central AC unit = 6000 watts
Total = 18,500 watts Add 20% buffer = 22,000 watts
So a 22kW standby generator would power this sample home. Always consult an electrician for your specific needs.
New Technology Improves Generator Performance
Recent generator technology advancements like inverters, CO sensors, and remote monitoring apps are making home backup power systems smarter, safer, and more efficient. Here are some key innovations:
- Inverter generators provide clean, stable power for sensitive electronics. More affordable models are available in the 1000-3000 watt range.
- CO sensors automatically shut down the generator if carbon monoxide builds up to dangerous levels. This safety feature is now required in portable models.
- Remote monitoring apps give you status updates and control of your standby generator from your smartphone.
- Soft start technology reduces fuel consumption and appliance wear by gradually ramping up to operating power.
- Quieter and more efficient engines make generators less noisy and reduce fuel costs.
- Smart throttling matches generator output to current household power demand to optimize efficiency.
Consider Generator Placement
Proper generator placement is critical for safety, performance, and compliance with codes. Generators should be located outdoors in an open, well-ventilated area at least 20 feet from buildings, windows, and doors to prevent dangerous carbon monoxide buildup. Exhaust should be directed away from any building openings.
Follow all manufacturer clearance recommendations and local electrical codes which dictate minimum distances from structures, property lines, combustible surfaces etc. Consider ease of access for fueling, maintenance, and testing under load.
Choose a location with good drainage that won’t flood. Allow sufficient room for safe operation and maintenance access. Place on a concrete pad for stability. Locate as close as possible to fuel supply lines and electrical interconnection points to simplify installation and reduce voltage drop.
Consult professionals to ensure proper placement that won’t compromise safety or function. Taking the time to determine the optimal generator location will maximize reliability when you need it most.
Proper placement of your standby or portable generator is critical for safety and performance.
Here are key placement tips:
- Allow at least 20 ft distance from the home for ventilation and to prevent CO buildup.
- Direct exhaust away from windows, doors, and AC intakes.
- Place on a level, stable surface with good drainage if outdoors.
- Ensure easy, safe access for refueling and maintenance.
- Follow local codes for proximity to property lines, combustible surfaces, etc.
- For standby units, install as close as possible to the transfer switch to reduce voltage drop from long cable runs.
Calculate Backup Power Needs for Off-Grid Living
For off-grid homes without utility connections, generator size depends on the home’s total energy usage including lighting, appliances, water pumping, HVAC, and other loads.
Conduct an energy audit to analyze daily and seasonal power needs, factoring in family size, home efficiency, and energy conservation habits. Right-sizing your off-grid solar/generator system reduces wasted capacity and fuel costs.
Consider Generator Runtime Requirements
The fuel tank size and consumption rate determine a portable generator’s runtime before refueling is needed. For occasional outages, a smaller tank providing 4-8 hours may suffice if you have sufficient fuel storage.
For frequent long outages or off-grid use, select inverter or standby generators with large tanks or hardline fuel connections for extended runtimes over 24 hours.
Choose Quality and Reliability
Buying from a reputable brand known for reliability and performance ensures your generator will provide years of dependable service when you need it most. Research and read reviews before purchasing. Also consider warranty, maintenance, and professional installation for standby units.
Frequently Asked Questions
FAQ 1: How often should I exercise my standby generator?
It is recommended to run standby generators at least once per month under load for 30 minutes to ensure proper operation. Exercising the generator helps prevent fuel varnishing, lubricates components, and identifies any issues before an emergency occurs.
FAQ 2: What size breaker is needed for my generator?
Size your generator breaker to match the rated output wattage of the generator. For example, a 16kW standby generator would need a 60 amp double pole breaker (16,000 watts / 240 volts = 66 amps). Always consult an electrician for proper breaker sizing.
FAQ 3: Can I connect a portable generator directly to my home?
No, portable generators should never be plugged directly into a home’s wiring without a transfer switch because of the danger of backfeeding to utility lines. A manual transfer switch safely isolates the circuits powered by the generator.
FAQ 4: How long will my gasoline generator run on a full tank?
Runtime depends on load size, but typical runtime from a full gas tank is between 6-12 hours for a 3000-5000 watt portable generator under 50% load. Larger tanks can extend runtimes.
FAQ 5: What are the advantages of inverter generators?
Inverter generators produce clean, stable AC power suitable for sensitive electronics. They are quieter, more fuel efficient, and more portable than conventional generators. However, they cost more.
FAQ 6: How do I calculate generator size for off-grid solar?
For solar battery charging, size your generator to handle peak charging loads which can range from 2000-5000+ watts depending on system size. Factor in DC-to-AC inverter efficiency.
FAQ 7: Should I hire an electrician to install a standby generator?
Yes, a licensed electrician is highly recommended to ensure proper generator installation and integration with your home’s electrical system according to local codes. Do not attempt a DIY install.
FAQ 8: What are important generator maintenance tasks?
Check oil, air filters, spark plugs, and change oil per manufacturer schedule. Test under load monthly, inspect wiring connections, keep batteries charged, drain fuel for storage, etc.
FAQ 9: How much does a home standby generator cost?
Installed costs for a standby generator system range from $5000-$15,000 depending on size, features, and complexity of installation. Get multiple quotes.
FAQ 10: What are signs my generator is overloaded?
Signs of an overloaded generator include flickering lights, breakers tripping, devices shutting off intermittently, and the generator stalling or shutting down unexpectedly.
Key Facts
Here are the key facts about determining what size generator you need for your house:
- Calculate total wattage needed – Add up the starting and running wattage requirements of essential appliances and devices you want to power during an outage. Remember to factor in motors that need surge power on startup.
- Choose generator capacity – Select a generator rated at least 20% higher than your total calculated wattage as a safety buffer. An undersized generator can overload.
- Consider fuel type – Most home standby generators run on natural gas or liquid propane which provide extended runtimes. Gasoline portable generators need frequent refueling.
- Choose between portable and standby – Portable generators require manual setup but cost less upfront. Standby generators automatically turn on when the power goes out but are a larger investment.
- Whole house vs partial – To power your entire house, size the generator for the home’s total electrical load. For partial backup, calculate load from critical circuits only.
- Get professional advice – Consult an electrician to analyze your home’s specific power requirements and recommend the properly sized standby or portable generator.
- Allow for future expansion – Buy a generator rated for slightly more than your current needs to accommodate potential added loads down the road.
- Follow electrical codes – All generator installations must comply with NEC and local electrical codes for safety. Professional installation is recommended.
Determining the right generator size for your home depends on your specific power requirements, type of use, fuel options, and budget. Carefully calculating your needs and following professional generator sizing recommendations will ensure you select adequate backup power capability.
Investing in quality for your generator purchase provides reliable home power protection for years to come.