When upgrading your electrical panel, one of the most important decisions you'll make is choosing the right amperage. The three most common residential service sizes are 100 amp, 200 amp, and 400 amp. Each serves different needs and comes with different costs and capabilities.
Key Takeaways
- 100-amp service provides about 24,000 watts -- often insufficient for homes with central AC, electric heating, or EV chargers.
- 200-amp service (48,000 watts) is the modern standard and supports most residential needs including EV charging.
- 400-amp service is typically achieved with two 200-amp panels for large homes or properties with exceptional demands.
- When upgrading, choose a panel with extra circuit spaces for future expansion -- a 40-space panel is more flexible than 20-space.
In this comprehensive guide, we'll help you understand what these numbers mean, how to determine which size you need, and what factors should influence your decision.
Understanding Electrical Service Amperage
Amperage (amps) measures the capacity of your electrical service—essentially how much electricity can flow into your home at any given time. Think of it like a water pipe: a larger pipe allows more water to flow through simultaneously. Similarly, higher amperage allows more electrical current to power your home's devices and appliances.
Your service amperage determines the maximum electrical load your home can handle before breakers trip or, in worst-case scenarios, wires overheat. Choosing the right size ensures your home has adequate power for current needs while allowing room for future additions.
Right-Sizing Tip: A Level 2 EV charger alone requires 40-60 amps. If you have a 100-amp panel and plan to add EV charging, the math simply does not work without an upgrade to 200 amps.
100 Amp Service: The Basics
100 amp service was the standard for homes built from the 1950s through the 1970s and is still found in many older Northern Virginia homes. This service level provides approximately 24,000 watts of power, which was adequate for homes before the proliferation of modern appliances and electronics.
Outdated or overloaded electrical panels are a safety risk. Our team specializes in 200-amp upgrades throughout Northern Virginia, with same-day panel assessments available. Call (703) 997-0026 to get started.
100 Amp Service is Suitable For:
- Small homes or apartments under 1,500 square feet
- Homes with gas heating, cooking, and water heating
- Properties with minimal high-draw appliances
- Basic electrical needs without EV charging or major additions
Limitations of 100 Amp Service:
- Cannot support Level 2 EV chargers (which typically require 40-60 amps)
- Limited capacity for electric HVAC systems
- May require load management for multiple high-draw appliances
- Often insufficient for home additions or major renovations
- May not meet current electrical code requirements
200 Amp Service: The Modern Standard
200 amp service has become the standard for new construction and is the most common upgrade we perform at AJ Long Electric. This service level provides approximately 48,000 watts of power—double the capacity of 100 amp service.
200 Amp Service is Ideal For:
- Homes between 1,500 and 3,500 square feet
- Properties with central air conditioning
- Homes with electric ranges, dryers, or water heaters
- Installing one or two Level 2 EV chargers
- Home offices with multiple computers and equipment
- Hot tubs or pool equipment
- Finished basements or home additions
Benefits of 200 Amp Service:
- Meets current code requirements for most new construction
- Provides capacity for future electrical needs
- Supports modern smart home technology
- Eliminates most capacity-related issues
- May be required for home insurance or sale
400 Amp Service: Maximum Capacity
400 amp service is typically achieved through installing two 200 amp panels and is designed for homes with exceptional electrical demands. This service level provides approximately 96,000 watts of power.
400 Amp Service is Necessary For:
- Large homes over 3,500 square feet
- Properties with multiple EV chargers
- Homes with electric heating systems in cold climates
- Properties with workshops or extensive power tools
- Homes with pools, hot tubs, and extensive outdoor living spaces
- Properties with guest houses or accessory dwelling units
- High-end smart home installations with extensive automation
Considerations for 400 Amp Service:
- Requires utility company coordination for larger service drop
- Higher installation costs and permit fees
- May require transformer upgrade by the utility
- Typically uses two separate 200 amp panels
How to Determine Your Electrical Needs
Calculating your electrical needs involves understanding both your current usage and future plans. Here's a simplified approach to determining the right service size:
Step 1: Calculate Your Current Load
Add up the wattage of your major electrical loads:
- Central air conditioning: 3,000-5,000 watts
- Electric range: 8,000-12,000 watts
- Electric dryer: 4,000-5,000 watts
- Electric water heater: 4,500 watts
- Electric vehicle charger: 7,200-11,500 watts
- Heat pump: 4,000-8,000 watts
Step 2: Apply Demand Factors
Not all appliances run simultaneously at full capacity. Electrical engineers use demand factors to calculate realistic loads. A professional load calculation accounts for these factors to determine actual requirements.
Step 3: Plan for the Future
Consider your five to ten-year plans:
- Will you purchase an electric vehicle?
- Are you planning a home addition?
- Will you add a hot tub or pool?
- Might you convert to electric heating?
Cost Comparison in Northern Virginia
Panel upgrade costs vary based on your home's existing electrical system, local permit requirements, and any necessary utility company work. Here are typical ranges for Northern Virginia:
100 Amp to 200 Amp Upgrade:
$2,500 - $4,500 for most installations, including the panel, labor, permits, and inspection. This is the most common upgrade we perform.
100 Amp to 400 Amp Upgrade:
$5,000 - $8,000+ depending on utility requirements and the complexity of the installation. This often requires coordination with the power company for a larger service drop.
New 400 Amp Installation:
$8,000 - $15,000+ for new construction or major service upgrades requiring transformer work by the utility company.
Our Recommendation
For most Northern Virginia homeowners, we recommend 200 amp service. It provides adequate capacity for modern living, accommodates EV charging and home additions, and meets current code requirements. The cost difference between 100 and 200 amp upgrades is relatively small compared to the long-term benefits.
If you have a larger home, multiple EVs, or extensive electrical needs, 400 amp service may be necessary. Our team can perform a comprehensive load calculation to determine the exact service size your home requires.
Future Planning: Consider your 5-10 year plans. Will you purchase an EV? Add a home addition? Install a hot tub? It is far more cost-effective to size your panel for future needs during the initial upgrade.
Schedule Your Electrical Assessment
Unsure which service size is right for your home? AJ Long Electric offers comprehensive electrical assessments that include load calculations, panel inspections, and personalized recommendations. Contact us today at (703) 555-0123 to schedule your evaluation and ensure your home has the electrical capacity it needs.
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Written by
Matt Long
Master Electrician
Our team of licensed electricians brings over 40 years of combined experience serving Northern Virginia. We're committed to providing expert electrical solutions with a focus on safety, quality, and customer satisfaction.
Reviewed by AJ Long Electric Master Electricians · VA License #2705031092 · View Credentials
