Explicit checks passed
2 explicit checks passed for the entered values. This does not replace independent verification where the decision is safety-critical, contractual, statutory, financial or medical.
2 pass1 info
🌡️
Temperature Loss
Power derating from cell temperature above STC 25 °C.
PerformanceCore inputs only — quick sizing with engineering defaults.
Inputs (SI units)
Signed — cold climates legitimately go negative.
Mounting condition adds a temperature adder above the open-rack NOCT model.
Signed and typically negative — never enter as positive.
Results
✓ PASS — Cell temperature below the 85 °C durability concern threshold.
✓ PASS — Power loss within a typical operating range (<20%).
Solar PV decision support
PV design decision summary
This section organises the existing calculator output into design checks, governing criteria and comparison cases. Core solar formulas and the calculator's original results are unchanged.
Governing criterion
Cell temperature and Pmax temperature coefficient
13.34 %
Ambient temperature, irradiance and NOCT determine cell temperature, which is then applied to the module Pmax temperature coefficient.
Design checks
Solar engineering check 1
pass✓ PASS — Cell temperature below the 85 °C durability concern threshold.
Structured directly from this solar calculator's own runtime alert.
Solar engineering check 2
pass✓ PASS — Power loss within a typical operating range (<20%).
Structured directly from this solar calculator's own runtime alert.
PV cell-temperature review
info63.1 °C
Temperature is reported for loss and thermal-design context; module datasheet limits and mounting ventilation still govern.
Next design actions
Engine recommendation 1
This uses a single representative operating point (fixed ambient/irradiance); a full annual estimate needs hourly weather + irradiance data (e.g. TMY).
Engine recommendation 2
Open-rack NOCT is the reference; close-roof and BIPV adders are indicative — confirm with manufacturer thermal test data where available.
Engine recommendation 3
Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.
Primary design output
63.1 °C
Use as a preliminary result and verify the project-specific limits listed below.
Scenario comparison
Lower and higher cases are recalculated by the same solar calculator engine. They are comparison cases, not weather forecasts or guaranteed production values.
Lower ambient temperature
ambient temperature = 28
- Operating cell temperature
- 56.1 °C
- ΔT from STC (25 °C)
- 31.1 °C
- Power loss due to temperature
- 10.89 %
- Actual module output
- 490.1 W (of 550 Wp)
Current inputs
ambient temperature = 35
- Operating cell temperature
- 63.1 °C
- ΔT from STC (25 °C)
- 38.1 °C
- Power loss due to temperature
- 13.34 %
- Actual module output
- 476.6 W (of 550 Wp)
Higher ambient temperature
ambient temperature = 42
- Operating cell temperature
- 70.1 °C
- ΔT from STC (25 °C)
- 45.1 °C
- Power loss due to temperature
- 15.79 %
- Actual module output
- 463.1 W (of 550 Wp)
Decision sensitivity
ambient temperature · up
For the same calculator engine, the lower case changes Operating cell temperature by -11.1% and the higher case by +11.1%.
This is a deterministic input sensitivity check, not a statistical uncertainty or weather forecast.
Methodology & limit
Decision support is structured from the existing solar calculator engine and the current user inputs. PASS/FAIL is shown only where the engine or entered project criteria support an explicit check. Final PV design still requires site survey, exact module/inverter datasheets, structural/electrical design and applicable statutory approval.
Engineering Recommendations
- →This uses a single representative operating point (fixed ambient/irradiance); a full annual estimate needs hourly weather + irradiance data (e.g. TMY).
- →Open-rack NOCT is the reference; close-roof and BIPV adders are indicative — confirm with manufacturer thermal test data where available.
- →Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.
Detailed Calculation Log
γ=-0.35%/°C (signed, negative expected), ΔT=38.13°C → power ratio 0.8666.
Save & Load Project
Designs are stored privately in this browser — nothing is uploaded.
Engineering Formula
- T_cell = T_amb + (NOCT−20)/800 × G (+ mounting adder)
- ΔT = T_cell − 25 (STC)
- Power ratio = 1 + γ·ΔT (γ signed, %/°C → fraction)
- P_loss% = −γ·ΔT (positive when ΔT>0 and γ<0)
Cell temperature rises above ambient in proportion to irradiance. Pmax coefficient (typ. −0.30 to −0.40 %/°C) then determines power derate.
Step-by-step Calculation
- 1.Base cell temperature (open-rack NOCT model)
Ta+(NOCT-20)G/80063.13 °C - 2.Operating cell temperature
Tcell63.13 °C - 3.ΔT from STC
Tcell − 2538.13 °C - 4.Power ratio
1+γ·ΔT0.8666 - 5.Power loss (%)
−γ·ΔT13.34 % - 6.STC array power
Pmod × N / 100011 kWp - 7.Actual module output at this operating point
Pmod × ratio476.6 W - 8.Actual array output at this operating point
Parray_STC × ratio9.532 kW - 9.Annual energy at STC efficiency (no thermal derate)
Parray_STC × H_POA19,800 kWh/yr - 10.Annual energy impact at this operating point's ratio
× power ratio17,158 kWh/yr
How to use this calculator: Temperature Loss
Power derating from cell temperature above STC 25 °C. The example below is calculated by this page's real engine from the displayed inputs.
- 1Confirm that the Temperature Loss matches the quantity or design check you need.
- 2Enter Ambient temperature, Plane-of-array irradiance, and Module NOCT/NMOT using the units printed beside each field.
- 3Select the applicable Mounting condition options; these choices change the calculation method or factors.
- 4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
- 5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.
Input guide and example values
Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.
| Input | Example value | Why it matters |
|---|---|---|
| Ambient temperature | 35 °C | Signed — cold climates legitimately go negative. |
| Plane-of-array irradiance | 900 W/m² | Measured or known plane-of-array irradiance used by the calculation engine. |
| Mounting condition | Open rack (NOCT basis) | Mounting condition adds a temperature adder above the open-rack NOCT model. |
| Module NOCT/NMOT | 45 °C | Measured or known module noct/nmot used by the calculation engine. |
| Power temperature coefficient γ | -0.35 %/°C | Signed and typically negative — never enter as positive. |
| Module rated power (STC) | 550 Wp | Measured or known module rated power (stc) used by the calculation engine. |
| Number of modules | 20 - | Measured or known number of modules used by the calculation engine. |
| Annual POA irradiation | 1800 kWh/m²/yr | 0 or blank skips the annual energy impact estimate. |
| Module area | 2.3 m² | Optional input; leave the supplied default only when it matches your case. |
Formula inputs & variables for Temperature Loss
These are the named quantities used by this calculator. When the source formula does not define a mathematical symbol, OneCalcApp keeps the real input label instead of inventing one.
| Variable / input | Unit | Meaning in this calculation |
|---|---|---|
| Ambient temperature | °C | Signed — cold climates legitimately go negative. |
| Plane-of-array irradiance | W/m² | Measured or known plane-of-array irradiance used by the calculation engine. |
| Mounting condition | — | Mounting condition adds a temperature adder above the open-rack NOCT model. |
| Module NOCT/NMOT | °C | Measured or known module noct/nmot used by the calculation engine. |
| Power temperature coefficient γ | %/°C | Signed and typically negative — never enter as positive. |
| Module rated power (STC) | Wp | Measured or known module rated power (stc) used by the calculation engine. |
| Number of modules | - | Measured or known number of modules used by the calculation engine. |
| Annual POA irradiation | kWh/m²/yr | 0 or blank skips the annual energy impact estimate. |
How the Temperature Loss works
The Temperature Loss uses Ambient temperature, Plane-of-array irradiance, Mounting condition, Module NOCT/NMOT, Power temperature coefficient γ, Module rated power (STC), Number of modules, Annual POA irradiation, and Module area to calculate Operating cell temperature, ΔT from STC (25 °C), Power loss due to temperature, Actual module output, Actual array output, and Estimated annual energy impact. Its engine applies T_cell = T_amb + (NOCT−20)/800 × G (+ mounting adder); the worked values below come from that same live calculation rather than a separately typed example.
With Ambient temperature 35 °C, Plane-of-array irradiance 900 W/m², Mounting condition Open rack (NOCT basis), Module NOCT/NMOT 45 °C, Power temperature coefficient γ -0.35 %/°C, Module rated power (STC) 550 Wp, Number of modules 20 -, Annual POA irradiation 1800 kWh/m²/yr, and Module area 2.3 m², the main worked-example result is Operating cell temperature = 63.1 °C.
How each Temperature Loss input is used
Ambient temperature
The Temperature Loss worked example uses Ambient temperature = 35 °C. This value is passed directly into the calculation, with an allowed minimum -30 and maximum 55. Signed — cold climates legitimately go negative.
Plane-of-array irradiance
The Temperature Loss worked example uses Plane-of-array irradiance = 900 W/m². This value is passed directly into the calculation, with an allowed minimum 0 and maximum 1300.
Mounting condition
The Temperature Loss worked example selects “Open rack (NOCT basis)”. Available choices include Open rack (NOCT basis), Close roof mount (+adder), and BIPV / no rear ventilation (+larger adder). This selection may change the method or factor used by the engine, so choose the option that matches the real case.
Module NOCT/NMOT
The Temperature Loss worked example uses Module NOCT/NMOT = 45 °C. This value is passed directly into the calculation, with an allowed minimum 38 and maximum 55.
Power temperature coefficient γ
The Temperature Loss worked example uses Power temperature coefficient γ = -0.35 %/°C. This value is passed directly into the calculation, with an allowed minimum -0.6 and maximum 0. Signed and typically negative — never enter as positive.
Module rated power (STC)
The Temperature Loss worked example uses Module rated power (STC) = 550 Wp. This value is passed directly into the calculation, with an allowed minimum 50.
Number of modules
The Temperature Loss worked example uses Number of modules = 20 -. This value is passed directly into the calculation, with an allowed minimum 1.
Annual POA irradiation
The Temperature Loss worked example uses Annual POA irradiation = 1800 kWh/m²/yr. This value is passed directly into the calculation, with an allowed minimum 0. 0 or blank skips the annual energy impact estimate.
Module area
The Temperature Loss worked example uses Module area = 2.3 m². This value is passed directly into the calculation, with an allowed minimum 0.1.
Temperature Loss formulas and result interpretation
Formula 1: relationship used
In the Temperature Loss, T_cell = T_amb + (NOCT−20)/800 × G (+ mounting adder). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.
Formula 2: relationship used
In the Temperature Loss, ΔT = T_cell − 25 (STC). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.
Formula 3: relationship used
In the Temperature Loss, Power ratio = 1 + γ·ΔT (γ signed, %/°C → fraction). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.
Formula 4: relationship used
In the Temperature Loss, P_loss% = −γ·ΔT (positive when ΔT>0 and γ<0). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.
Operating cell temperature
For the displayed Temperature Loss worked example, Operating cell temperature is 63.1 °C. Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
ΔT from STC (25 °C)
For the displayed Temperature Loss worked example, ΔT from STC (25 °C) is 38.1 °C. Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
Power loss due to temperature
For the displayed Temperature Loss worked example, Power loss due to temperature is 13.34 %. Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
Actual module output
For the displayed Temperature Loss worked example, Actual module output is 476.6 W (of 550 Wp). Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
Actual array output
For the displayed Temperature Loss worked example, Actual array output is 9.532 kW (of 11 kWp). Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
Estimated annual energy impact
For the displayed Temperature Loss worked example, Estimated annual energy impact is −2,642 kWh/yr. Uses this single operating point as representative — not a full 8760h simulation Verify Ambient temperature, Plane-of-array irradiance, and Mounting condition and their units before relying on this output.
Temperature Loss accuracy, checks and limitations
- Temperature Loss units check: confirm Ambient temperature (°C), Plane-of-array irradiance (W/m²), Mounting condition, Module NOCT/NMOT (°C), Power temperature coefficient γ (%/°C), Module rated power (STC) (Wp), Number of modules (-), Annual POA irradiation (kWh/m²/yr), and Module area (m²) before calculating.
- Temperature Loss result check: compare Operating cell temperature, ΔT from STC (25 °C), Power loss due to temperature, Actual module output, Actual array output, and Estimated annual energy impact with the substituted formula steps and the displayed rounding precision.
- Temperature Loss: Use this result for preliminary design and cross-checking. Confirm the applicable code edition, manufacturer data, site conditions and qualified-engineer approval before final design or installation.
Understanding the result
Read the main result together with supporting checks, assumptions, limits and intermediate values.
For a manual check, repeat the first equation, confirm the units and change one input at a time.
Common mistakes when using Temperature Loss
- Do not mix units for Ambient temperature (°C), Plane-of-array irradiance (W/m²), Module NOCT/NMOT (°C). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
- Do not leave Mounting condition on the default choice unless that choice matches the real scenario; the selected option can change the calculation path or factor.
- Do not replace the displayed T_cell = T_amb + (NOCT−20)/800 × G (+ mounting adder) relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
- Do not treat Operating cell temperature = 63.1 °C from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.
When the Temperature Loss is useful
Temperature Loss is designed for cases where Ambient temperature, Plane-of-array irradiance, Mounting condition, Module NOCT/NMOT are known and you need Operating cell temperature, ΔT from STC (25 °C), Power loss due to temperature. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.
Use the calculator for the scope described by its inputs and notes. The displayed method is T_cell = T_amb + (NOCT−20)/800 × G (+ mounting adder). If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.
Ambient temperature and Plane-of-array irradiance: what changes the answer
The worked example uses Ambient temperature = 35 °C, Plane-of-array irradiance = 900 W/m², Mounting condition = Open rack (NOCT basis), Module NOCT/NMOT = 45 °C. With those values, Operating cell temperature is 63.1 °C. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.
For this calculator, the main input roles are: Ambient temperature (°C): Signed — cold climates legitimately go negative. Plane-of-array irradiance (W/m²): Measured or known plane-of-array irradiance used by the calculation engine. Mounting condition: Mounting condition adds a temperature adder above the open-rack NOCT model. Available choices include Open rack (NOCT basis), Close roof mount (+adder), BIPV / no rear ventilation (+larger adder). Module NOCT/NMOT (°C): Measured or known module noct/nmot used by the calculation engine.
How to sanity-check a Temperature Loss result
Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Operating cell temperature, because it is the first worked-example output shown by the live engine.
Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.
Next logical calculator
Continue with AC Cable Sizing Calculator
Useful next check because both tools use Ambient temperature, while AC Cable Sizing Calculator answers a different part of the same workflow.
Open AC Cable Sizing CalculatorStandards, source trail and limitations
References show the method used. Check the current local edition, amendments and project specification before a regulated decision.
Design Assumptions
- • Free-flow rear ventilation (open rack).
- • Standard NOCT test at 800 W/m², 20 °C, 1 m/s wind.
Engineering Tips
- ◆Elevate roof mounts by ≥ 100 mm for airflow.
- ◆White roofs reduce Tcell by 3–5 °C.
Warnings
- ▲Tcell > 85 °C accelerates PID and encapsulant browning.
Standards & References
IEC 61215 §10.5IEC 61853
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