A Comprehensive Guide to Electrical Panel Capacities
Understanding electrical panel capacity helps you make informed decisions about upgrades, additions, and your home's electrical future. This guide explains how panel capacity works and what size you actually need.
What Panel Capacity Means
Amperage Rating
Panel capacity is measured in amps (amperes)—the amount of electrical current the panel can safely handle:
| Panel Size | Typical Use | Common In |
|---|---|---|
| 60 amps | Minimal loads | Pre-1960s homes |
| 100 amps | Basic modern needs | 1960s-1980s homes |
| 150 amps | Average modern home | Some 1980s-2000s homes |
| 200 amps | Standard modern home | Current construction |
| 400 amps | Large/high-demand homes | Larger new construction |
Main Breaker vs. Panel Rating
Two ratings matter:
Main breaker size: The largest load the panel will allow Bus bar rating: What the panel's internal components can handle
These should match. A 200-amp panel should have a 200-amp main breaker.
How Electrical Load Is Calculated
The NEC Method
Electricians use National Electrical Code calculations to determine required service size:
Basic calculation factors: - Square footage of living space - Number and type of appliances - Heating and cooling systems - Special equipment (pools, hot tubs, workshops)
General load allowances: - First 3,000 sq ft: 3 watts per sq ft - Additional space: lower wattage per sq ft - Small appliance circuits: 1,500 watts each - Laundry circuit: 1,500 watts
Large appliance loads: - Electric range: 8,000-12,000 watts - Electric dryer: 5,000 watts - Electric water heater: 4,500 watts - Central AC: 3,000-5,000 watts - Heat pump: 5,000-10,000 watts
Why Professional Calculation Matters
Load calculations involve: - Demand factors (not everything runs simultaneously) - Diversity calculations - Future load considerations - Code requirements and safety margins
Assessing Your Current Panel
Physical Inspection
Look at your panel to gather information:
Main breaker: Usually at the top, marked with amperage Panel label: Shows manufacturer rating Available spaces: Count open slots for new circuits Breaker types: Note any double-stuff or tandem breakers
Signs Your Panel May Be Undersized
Electrical symptoms: - Frequent breaker trips - Dimming lights when appliances start - Unable to run multiple large appliances - Extension cords needed everywhere
Practical limitations: - No room for new circuits - Can't add desired appliances - Electrician recommends upgrade for any new work
Common Capacity Scenarios
60-Amp Service
What it can handle: - Lighting throughout home - A few small appliances - Gas heating and hot water - One window AC unit
What it can't handle: - Central air conditioning - Electric range or dryer - Multiple high-draw appliances - Modern entertainment systems and computers
Verdict: Upgrade recommended for any modern use.
100-Amp Service
What it can handle: - Standard lighting and outlets - Gas or electric water heater - Electric dryer OR range (not both comfortably) - Small central AC - Basic modern appliances
What it struggles with: - Electric range AND electric dryer - Large central AC with electric heat - EV charger - Hot tub or pool equipment
Verdict: May work for modest homes; often needs upgrade for additions or new equipment.
200-Amp Service
What it can handle: - All standard household loads - Electric range and dryer - Central heating and cooling - Pool or hot tub equipment - Level 2 EV charger - Home workshop - Multiple high-draw appliances
What might exceed it: - Multiple EV chargers - Large shop with commercial equipment - In-law suite or major addition
Verdict: Adequate for most homes; the current standard.
400-Amp Service
When needed: - Very large homes (4,000+ sq ft) - All-electric homes with high demands - Multiple EV chargers - Significant workshop or studio - Guest houses or large additions - Homes planning major electrification
Implementation: Usually two 200-amp panels.
Planning for the Future
Electrification Trends
Electrical demand is increasing:
Electric vehicles: Level 2 chargers need 30-50 amps Heat pumps: Replacing gas furnaces adds significant load Induction cooking: Increasing adoption Home batteries: Growing in popularity
Future-Proofing Considerations
When upgrading, consider:
- Current needs plus anticipated additions
- EV charging potential
- HVAC replacement plans
- General buffer for unknowns
Rule of thumb: Size for what you'll need in 10-20 years, not just today.
The Upgrade Process
What's Involved
Upgrading panel capacity typically requires:
- Load calculation to determine new size
- Utility company coordination for service upgrade
- New service entrance cable (meter to panel)
- New panel with appropriate capacity
- Possible grounding system upgrade
- Permit and inspections
What Affects Cost
Major factors: - Current vs. new service size - Need for underground vs. overhead service change - Panel location (basement, garage, exterior) - Age and condition of existing wiring - Local permit and utility requirements
Typical Costs
| Upgrade Type | Typical Cost Range |
|---|---|
| 100 to 200 amp | $1,500-$3,000 |
| 200 to 400 amp | $3,000-$5,000 |
| Complete service upgrade | $2,000-$4,000 |
| Panel replacement (same size) | $1,200-$2,500 |
Making the Right Choice
Questions to Ask
- What's my current calculated load?
- What additions am I planning?
- Will I add EV charging?
- Am I considering heat pump conversion?
- What's my home's long-term plan?
When to Upgrade
Upgrade now if: - Panel is at or near capacity - Adding loads that exceed current capacity - Panel has safety issues - Planning major renovation
Wait if: - Current panel has adequate capacity and spaces - No planned additions exceeding capacity - Panel is in good condition
Our Capacity Services
We help homeowners understand and upgrade their panel capacity:
- Professional load calculations
- Capacity evaluation and recommendations
- Upgrade planning and budgeting
- Complete panel upgrade installation
- Utility coordination and permits
Schedule a capacity evaluation to understand your options.