To choose the appropriate wattage for electric heaters, consider the room size, insulation quality, and desired temperature increase, typically requiring 10 watts per square foot.
Selecting the proper wattage for your electric heater ensures efficient heating, lower energy bills, and safe operation. This guide covers wattage requirements for all heater types based on room size, insulation, and heating needs.
Understanding Wattage Basics
Electric heaters convert 100% of their energy into heat, making wattage the key factor in heating capacity. The general rule is:
- 10 watts per square foot for well-insulated rooms
- 15 watts per square foot for poorly insulated spaces
- 20 watts per square foot for garages or drafty areas
Room Size vs. Wattage Chart
| Room Size (sq ft) | Minimum Wattage | Recommended Wattage |
|---|---|---|
| 100 | 1,000W | 1,500W |
| 150 | 1,500W | 2,250W |
| 200 | 2,000W | 3,000W |
| 300 | 3,000W | 4,500W |
Wattage By Heater Type
1. Convection Heaters
These heaters warm air through heating elements and distribute it via fans. Common types include:
- Ceramic Heaters: 1,500W max (best for 150 sq ft)
- Fan Heaters: 750-1,500W (quick spot heating)
- Mica Panel Heaters: 1,000-1,500W (silent operation)
For whole-room heating, consider a wall mounted convector heater with timer for consistent warmth.
2. Radiant/Infrared Heaters
These provide direct heat to objects rather than air. According to Save on Energy, they’re ideal for personal use:
- 300-1,000W for personal warming
- 1,500-3,000W for larger areas
- More efficient for spot heating than whole rooms
3. Oil-Filled Radiators
These provide sustained heat through thermal oil:
- 500W settings for small spaces
- 1,500W standard for 150 sq ft
- 2,500W models for large rooms
For similar radiant heating in a decorative package, electric heaters that look like wood stoves offer both function and style.
Specialty Heater Wattage
Bathroom Heaters
Require GFCI protection and specific wattages:
- 1,500W max for standard bathrooms
- 750-1,000W for small powder rooms
Garage/Workshop Heaters
Need higher wattage due to poor insulation:
- 5,000W for 2-car garages
- 10,000W+ for large workshops
Advanced Wattage Considerations
Voltage Requirements
Most household heaters use 120V, but larger units require 240V:
- 1,500W max on 120V circuits
- 3,000W+ requires 240V wiring
Energy Cost Calculation
To estimate operating costs:
- Check your electricity rate (e.g., $0.15/kWh)
- Multiply heater wattage by hours used
- Divide by 1,000 to get kWh
- Multiply by your rate
Example: 1,500W heater used 5 hours at $0.15/kWh = (1,500 × 5)/1,000 × 0.15 = $1.13
Safety Factors
The U.S. Consumer Product Safety Commission recommends:
- Never exceed 80% of circuit capacity
- Use dedicated circuits for heaters over 1,500W
- Choose models with tip-over and overheat protection
Smart Wattage Management
Modern heaters offer features to optimize wattage usage:
- Programmable thermostats
- Eco modes that cycle power
- Wi-Fi controls for remote adjustment
For outdoor spaces, consider an infrared patio heater with weather-resistant controls.
