| Small Bedroom | 10 m² 2.5 m ceiling height | Good insulation Modern double glazing | 500–700 W | 600–800 W | 600 mm wide × 600 mm high Single-panel radiator | Setting 2–3 Approximately 16–18°C | Choose a compact radiator with a lower output if the room receives strong sunlight or has limited external walls. |
| Large Bedroom | 16 m² 2.5 m ceiling height | Average insulation Double glazing | 800–1,100 W | 900–1,200 W | 800 mm wide × 600 mm high Double-panel radiator | Setting 3 Approximately 18°C | Allow additional capacity where the room has two external walls, a north-facing aspect, or frequent ventilation. |
| Living Room | 20 m² 2.5 m ceiling height | Average insulation Double glazing | 1,200–1,600 W | 1,400–1,800 W | 1,000 mm wide × 600 mm high Double-panel radiator | Setting 3–4 Approximately 18–21°C | Use a higher-output radiator if the room has large windows, high occupancy, or open-plan connections to cooler areas. |
| Dining Room | 14 m² 2.5 m ceiling height | Good insulation Modern double glazing | 700–950 W | 800–1,100 W | 800 mm wide × 600 mm high Single- or double-panel radiator | Setting 3 Approximately 18°C | A moderate output is normally sufficient, but increase the size if the room is used regularly with doors opening to unheated spaces. |
| Home Office | 12 m² 2.5 m ceiling height | Average insulation Double glazing | 700–950 W | 800–1,100 W | 700 mm wide × 600 mm high Double-panel radiator | Setting 3–4 Approximately 18–21°C | Consider a slightly higher output where the room is occupied for long periods or has equipment that requires a stable temperature. |
| Kitchen | 12 m² 2.5 m ceiling height | Average insulation Double glazing | 600–850 W | 700–1,000 W | 600 mm wide × 600 mm high Compact double-panel radiator | Setting 2–3 Approximately 16–18°C | Cooking appliances provide additional heat, so avoid oversizing unless the kitchen has extensive glazing or multiple external walls. |
| Bathroom | 6 m² 2.4 m ceiling height | Average insulation Ventilated space | 500–750 W | 600–800 W | 500 mm wide × 800 mm high Heated towel rail or compact radiator | Setting 3–4 Approximately 18–21°C | Allow for regular extraction and ventilation. A corrosion-resistant finish is preferable in humid conditions. |
| Hallway | 8 m² 2.5 m ceiling height | Average insulation Frequent door opening | 450–650 W | 500–700 W | 500 mm wide × 600 mm high Single-panel radiator | Setting 2–3 Approximately 16–18°C | Select a durable, compact model and avoid placing the TRV behind a coat rack, curtain, or enclosed furniture. |
| Poorly Insulated Room | 15 m² 2.5 m ceiling height | Limited insulation Older windows | 1,300–1,900 W | 1,600–2,100 W | 1,000 mm wide × 600 mm high Double- or triple-panel radiator | Setting 3–4 Approximately 18–21°C | Improve insulation and seal drafts where possible. Heating calculations should account for cold external walls and window losses. |