AC Tonnage Calculator London

Sizing an air conditioner in London? Because London has a mild maritime climate, rooms need a different AC size than in a temperate region. The calculator below is pre-set to London’s climate — enter your room’s area for an instant tonnage. London has a mild maritime climate and a short cooling season, though 30–35°C summer heatwaves are becoming more common. Cooling loads are the lowest here of any climate on this list, so rooms need less tonnage — but a properly sized unit still makes heatwaves bearable. Most homes use portable or single-split units.

AC Tonnage Chart for London by Room Size

These are typical AC sizes for London’s climate, for a room with an 8-foot ceiling and average insulation. Larger, top-floor, or west-facing rooms may need the next size up:

Sizing AC for London’s Climate

In London’s mild climate you can size modestly; a small inverter split easily covers a typical room and doubles as efficient winter heating. The calculator applies London’s climate factor automatically; you can still fine-tune ceiling height, insulation, sun exposure, and room type above to match your exact space. Remember that an oversized AC cools quickly but short-cycles and dehumidifies poorly — matching the tonnage to the room gives better comfort and lower running costs.

Frequently Asked Questions — London

What size AC do I need for a bedroom in London? A typical 150 sq ft bedroom in London needs about a 0.5 Ton AC (2,777 BTU/hr). Larger rooms scale up per the chart above.

Why does London need a bigger AC than a mild climate? London’s mild maritime climate raises the cooling load, so the same room needs more capacity than it would in a temperate region — the calculator applies that adjustment automatically.

How many BTU for a 150 sq ft room in London? Around 2,777 BTU/hr under standard conditions. Adjust ceiling height and sun exposure in the calculator for a precise figure.

Background reading: how the refrigeration cycle works.