Underfloor Heating Calculator

Underfloor Heating Guide

Electric vs Water UFH

Electric underfloor heating uses resistive heating mats or cables installed under the floor. It is ideal for smaller areas (bathrooms, en-suites, kitchens), straightforward DIY or professional installation, and retrofitting in existing properties. Water (hydronic) underfloor heating uses pipes circulating hot water — lower running cost per hour but requires significant infrastructure (manifold, pump, mixer valve) and is most cost-effective in new builds or major renovations. For areas under 20m²

Wattage Requirements

Standard electric UFH mats run at 150–200W per m². For bathroom floor warming: 150W/m² is sufficient. For primary heating (bathroom or kitchen): 200W/m². Areas next to exterior walls or ground-floor rooms in cold climates may need higher wattage. Typical bathroom (3.5m² heated area): 3.5 × 150W = 525W total. Running for 4 hours per day at 24.5p/kWh: 0.525kW × 4h × 24.5p = 51.5p per day. Annual cost at this usage: approximately £188.

Floor Covering Compatibility

Best performance (lowest thermal resistance): ceramic and porcelain tiles, natural stone. These heat quickly and retain warmth well. Good performance: LVT/luxury vinyl tile (modern UFH-compatible products). Moderate: engineered wood and laminate — check the manufacturer's maximum surface temperature limit (usually 27°C). Poor: carpet significantly insulates against the heat, reducing efficiency and potentially exceeding floor temperature limits. Traditional underlay adds additional resistance —

Installation Essentials

Always install a thermostat with a floor sensor (not just air sensor) — floor sensors prevent overheating and protect the floor covering. Two-hour concrete screed (for wet UFH) or self-levelling compound (for electric mat systems) must cover the mat before tiling. Electric UFH mats should never be overlapped or cut (except at the turning loops). Plan the mat layout before purchasing — the number of turns and room shape affect which mat size you need. Have an electrician connect the thermostat —