Estimate tool
Radiator (panel) calculator
This page is a free tool that estimates the panel radiator type, height and length needed for each room of a home in Antalya. The result is an estimate and does not replace an engineering project.
Calculate the heat load room by room and the panel radiator length required at your chosen flow temperature. Condensing boilers and heat pumps run at lower temperatures, so the same room needs a longer radiator.
Result
Fill in the form and press “Calculate”; the result appears in this area.
This is a preliminary estimate; the final appliance and radiator selection is made during a free site survey.
The lower the regime, the longer the radiator
Catalogue outputs for panel radiators are measured at 75/65/20 °C. At the 55/45/20 regime typical of a condensing combi the same panel delivers only about 51.5% of that output, and at the 45/35/20 regime of a heat pump about 30.4%. Existing radiators are therefore usually undersized when you move to a heat pump: either the panels grow or the system moves to underfloor heating. This tool corrects the length directly for the regime you select.
How we calculate
The heat load of each room is room area × base W/m² × climate × floor × external walls × room temperature. Rooms other than bathrooms are calculated for 20 °C indoors, bathrooms for 24 °C.
Required radiator length = room heat load ÷ (W/m output of the selected panel × regime correction factor). The result is rounded up to the next 10 cm.
The regime correction uses the EN 442 based formula Q = Qn × (ΔTm / 50)^1.3. The exponent varies between 1.28 and 1.33 by manufacturer; for a final selection consult the product’s own low-temperature table.
Coefficients used
Panel radiator output table (W/m at 75/65/20 °C)
| Height | Type 21 | Type 22 | Type 33 |
|---|---|---|---|
| 300 mm | 764 | 967 | 1,373 |
| 400 mm | 962 | 1,225 | 1,748 |
| 500 mm | 1,152 | 1,474 | 2,103 |
| 600 mm | 1,337 | 1,718 | 2,440 |
| 700 mm | 1,518 | 1,959 | 2,762 |
| 900 mm | 1,874 | 2,432 | 3,366 |
Temperature regime correction ratios
| Temperature regime | ΔTm | Output ratio |
|---|---|---|
| 75/65/20 °C — conventional boiler | 50 K | 100.0% |
| 55/45/20 °C — condensing combi | 30 K | 51.5% |
| 45/35/20 °C — heat pump / low temperature | 20 K | 30.4% |
Room and building factors
| Coefficient | Value |
|---|---|
| Yes (insulation + glazing) | 80 W/m² |
| Partial (glazing only) | 110 W/m² |
| None (older building) | 135 W/m² |
| Coefficient | Value |
|---|---|
| Middle floor | × 1.00 |
| Top floor (under the roof) | × 1.12 |
| Ground floor | × 1.12 |
| Detached house / villa | × 1.22 |
| Coefficient | Value |
|---|---|
| 1 external wall | × 1.00 |
| 2 external walls (corner) | × 1.08 |
| 3 or more external walls | × 1.15 |
| Coefficient | Value |
|---|---|
| Rooms other than bathrooms (20 °C) | × 1.00 |
| Bathroom (24 °C) | × 1.22 |
| Coefficient | Value |
|---|---|
| Antalya (TS 825, 1. zone) | × 1.00 |
| Korkuteli (TS 825, 3. zone) | × 1.55 |
Worked example
Kaş, 90 m², insulated middle floor, 45/35 regime (18 m² living room)
| Room area | 18 m² |
|---|---|
| Base value (insulated) | 80 W/m² |
| Climate (Antalya, zone 1) | × 1.00 |
| Middle floor | × 1.00 |
| 2 external walls | × 1.13 |
| Room heat load | 1,627 W |
| Type 22 / 600 mm | 1,718 W/m |
| 45/35/20 correction | × 0.304 → 522 W/m |
| Required length | 1,627 ÷ 522 = 3.12 m → 320 cm |
| Conclusion | The same room needs roughly a 100 cm panel at 75/65, but more than 3 metres at heat pump temperatures; split it into two radiators or choose Type 33. |