Heat Pump COP, SCOP and Why They Matter for Your Bill

Every heat pump datasheet quotes two numbers: COP and SCOP. Both describe how much heat you get per unit of electricity — but only one tells you what you'll actually pay across an Irish winter.

COP — the lab number

Coefficient of Performance is measured at fixed conditions (typically 7°C outside, 35°C flow temperature). A COP of 4.5 means 4.5 kWh of heat per 1 kWh of electricity. Impressive, but a marketing figure.

SCOP — the honest number

Seasonal COP averages performance across the real heating season, including the cold snaps where efficiency drops. In Ireland's Zone C (average climate), a well-installed modern air-source unit hits SCOP 3.8–4.2. That's the number you should compare between models.

What SCOP 4.0 means in euros

For a well-insulated 150m² Irish home using ~12,000 kWh of heat per year:

• Gas boiler (90% efficient): 12,000 ÷ 0.9 × €0.11 ≈ €1,467/year
• Oil boiler: ~ €2,100/year at current prices
• Heat pump SCOP 4.0: 12,000 ÷ 4 × €0.35 ≈ €1,050/year

Add the SEAI grant (up to €6,500) and the payback lands inside 5–7 years for most upgrades.

What kills SCOP in practice

• Radiators sized for 70°C flow (heat pump wants 45°C)
• Poor insulation forcing higher flow temperatures
• Oversized units short-cycling in shoulder seasons

Get the system designed properly — including radiator upsize where needed — and the datasheet number becomes the real number.