Selecting the correct electric heater size is the single most important factor in achieving efficient, comfortable heating. An undersized heater will run constantly without reaching your target temperature, while an oversized unit wastes energy and creates temperature swings.
For standard rooms with average insulation (2.4m ceiling height, double-glazed windows), you need approximately 100 watts of heating power per square metre. Here's a quick reference table:
| Room Size | Recommended Power | Best Category |
|---|---|---|
| 10-15 sqm | 1,000-1,500W (1-1.5kW) | Electric Heaters 1-3kW |
| 15-30 sqm | 1,500-3,000W (1.5-3kW) | Electric Heaters 1-3kW |
| 30-50 sqm | 3,000-5,000W (3-5kW) | Electric Heaters 3-5kW |
| 50sqm+ | 5,000W+ (5kW+) | Industrial Electric Heaters 5kW+ |
The 100W/sqm rule assumes average insulation. Adjust your calculation based on these factors:
Ceramic fan heaters use PTC (Positive Temperature Coefficient) elements that self-regulate their temperature. They provide instant heat within seconds, making them ideal for quick warm-up of small to medium rooms.
Best for: Bedrooms, home offices, bathrooms (IP-rated models)
Advantages: Instant heat, safe (no glow), compact, energy-efficient at partial load
Convection heaters warm the air through natural convection currents. They're quieter than fan heaters and provide more even heat distribution.
Best for: Living rooms, bedrooms where quiet operation is preferred
For warehouses, workshops and large commercial spaces, industrial electric heaters rated 5kW and above deliver the power needed. Many models require 400V three-phase supply.
Best for: Warehouses, factories, showrooms, large garages
We've built a heat requirement calculator on our homepage that takes into account room dimensions, ceiling height, outside temperature, and insulation quality. Simply enter your room measurements and it will recommend the correct wattage and suitable products.
A 2kW heater can heat a 30sqm room with good insulation, but it will need to run at full power continuously. A 3kW heater would be more efficient as it can maintain temperature at partial load.
Ceramic (PTC) heaters are more efficient at partial loads because they self-regulate their power output. At full load, all electric heaters are 100% efficient at converting electricity to heat.
Yes, a thermostat is essential for energy efficiency. It prevents the heater from running when the target temperature is reached, typically saving 20-30% on running costs.
Need expert advice? Contact us at kjds_info@dahtec.cn or visit our contact page. All DAHTEC heaters come with a 3-year warranty and free shipping across 22 European countries.
