The most common mistake homeowners make when buying a heat pump is choosing the wrong capacity. Too small and you run out of hot water. Too large and you overpay. This guide walks you through the sizing calculation in five minutes.
Step 1: Calculate Your Daily Hot Water Requirement
• Per person per day (bathing + kitchen): 60–80 litres at 45°C
• Family of 4: 240–320 litres/day
• Family of 6: 360–480 litres/day
• Add 20% buffer for guests and seasonal variation
Step 2: Account for Your City's Cold Water Temperature
• Mumbai, Bangalore, Chennai — inlet temp ~22°C, lower heating load
• Delhi, Lucknow, Jaipur — inlet temp drops to 12–15°C in winter, higher load
• Northeast, Himachal, Uttarakhand — inlet temp can drop to 5°C, consider EVI series
Step 1: Calculate Your Daily Hot Water Requirement
• Per person per day (bathing + kitchen): 60–80 litres at 45°C
• Family of 4: 240–320 litres/day
• Family of 6: 360–480 litres/day
• Add 20% buffer for guests and seasonal variation
Step 2: Account for Your City's Cold Water Temperature
• Mumbai, Bangalore, Chennai — inlet temp ~22°C, lower heating load
• Delhi, Lucknow, Jaipur — inlet temp drops to 12–15°C in winter, higher load
• Northeast, Himachal, Uttarakhand — inlet temp can drop to 5°C, consider EVI series
Step 3: Match to Sunniva Models
• Family of 2–3 (200–250 L/day): SE-AH-4M (3.5 KW, 105 L/hr) — Monoblock
• Family of 4–5 (300–350 L/day): SE-AH-7M (7.4 KW, 215 L/hr) — Monoblock
• Family of 6+ or large villa (400+ L/day): SE-AH-10M (9.3 KW, 280 L/hr) — Monoblock
• Cold-climate homes (below 0°C winters): SE-EVI-10U with COP 4.42 at -25°C ambient
Step 4: Choose Your Tank Size
• Tank should hold 60–70% of daily requirement
• Family of 4: 200–250 L tank
• Family of 6: 300–350 L tank
• Sunniva ceramic-lined and glass-lined tanks available in 100L to 5,000L
Step 5: Consider Installation Location
• Monoblock units — all components in one unit, suitable for balcony or utility area
• Split units — indoor tank, outdoor unit, ideal when outdoor space is limited
• Minimum clearance: 300mm on all sides for air circulation
• Avoid enclosed rooms — the heat pump needs ambient air to extract heat from
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