Defrost Energy Calculator for Construction Projects

Inputs

Enter site conditions and defrost settings. Results appear above this form after you submit.

All calculations use SI internally for consistency.

Project / Area

Ice / Frost Mass

Mass of ice removed per defrost cycle.

Temperature Unit

Initial Frost Temperature

deg

Typical: -25 to -1 (or equivalent).

Final Meltwater Temperature

deg

Final water temperature after defrost.

Defrost Duration

min

Used to estimate average power demand.

Advanced Material Properties (editable)

Specific Heat of Ice

kJ/kg·K

Typical: 2.0–2.2 kJ/kg·K.

Latent Heat of Fusion

kJ/kg

Typical: ~334 kJ/kg for melting ice.

Specific Heat of Water

kJ/kg·K

Typical: ~4.186 kJ/kg·K.

System / Heater Efficiency

%

Accounts for losses to air, coil, and structure.

Electricity Tariff

per kWh

Set to 0 if cost is not needed.

Currency Code

Displayed on the cost line and exports.

Example Data Table

These examples help validate input ranges for typical site scenarios.

Scenario	Mass (kg)	Ti (°C)	Tf (°C)	Eff (%)	Duration (min)	Input (kWh)	Avg kW
Cold room coil, light frost	8	-8	3	90	20	0.99	2.97
Large air-handler bank, moderate frost	25	-10	5	85	35	3.36	5.76
Outdoor intake screen, heavy icing	60	-15	8	80	45	9.44	12.59

Tip: If your measured input is far higher than the table, review efficiency and heat losses.

Formula Used

The calculator estimates the heat required to raise the ice to 0 °C, melt it, then warm the meltwater:

Q_useful = m·c_ice·(0 − T_i) + m·L_f + m·c_water·(T_f − 0)

Q_input = Q_useful / η

Where m is ice mass, c values are specific heats, L_f is latent heat of fusion, and η is overall defrost efficiency. Energy is converted using 1 kWh = 3600 kJ.

T_i below 0 increases the ice-warming term.
T_f above 0 increases the meltwater-warming term.
Efficiency includes heat lost to air, metal, and surrounding structure.

How to Use This Calculator

Measure or estimate the ice mass removed per defrost cycle.
Select units and enter the initial frost temperature and final water temperature.
Set defrost duration to estimate average power demand (kW).
Adjust efficiency to reflect your heater, airflow, and installation losses.
Enter a tariff to estimate cost, then press Calculate.
Use Download PDF or Download CSV for reporting.

For design checks, compare the computed average kW with available panel capacity and circuit limits.

Why defrost energy matters on site

Defrosting iced coils, intake screens, or chilled slabs draws load. Knowing kWh per cycle helps size power, avoid trips, and schedule defrost away from demand.

Key inputs and typical ranges

Mass is the driver; double the ice doubles energy. For quick checks, material properties are commonly c_ice≈2.0–2.2 kJ/kg·K, L_f≈334 kJ/kg, and c_water≈4.18 kJ/kg·K. T_i is often -25 to -1 °C, while T_f is 0 to 10 °C depending on drainage, air temperature, and how quickly meltwater is removed.

Energy per kilogram benchmark

Per kilogram, the useful heat is roughly 0.10 kWh/kg when T_i=-10 °C and T_f=5 °C: (2.1×10 + 334 + 4.186×5)/3600 ≈ 0.104 kWh/kg. The melting term usually dominates, so small changes in T_i move the total less than large changes in mass. With 85% efficiency, input becomes about 0.123 kWh/kg.

Interpreting average kW demand

Average kW is input kWh divided by hours. The example “moderate frost” case (25 kg, -10 to 5 °C, 85%, 35 min) gives about 3.36 kWh and 5.76 kW. If the same energy is delivered in 20 minutes, the average demand rises to about 10.1 kW, which can exceed a single circuit.

Costing and QA checks

Cost is kWh times tariff, so monthly defrost cost equals kWh per cycle × cycles per day × days. If measured consumption is higher, lower the efficiency, increase T_f, or include extra ice mass retained on fins and drains. Efficiency can represent heat lost to metal, air bypass, and surrounding structure during the defrost period. If results look too low, verify total ice mass and confirm the selected temperature unit.

FAQs

1) What does “ice mass” represent?

It is the total ice/frost melted in one defrost cycle. Include ice on fins, trays, screens, and drains if it must be melted to restore airflow or function.

2) Why does efficiency change the answer so much?

The calculator divides useful heat by efficiency to estimate input. Lower efficiency captures losses to air, metal, and surrounding structure, increasing required kWh.

3) Can I use this for hot-gas or steam defrost?

Yes for energy estimation. Enter an equivalent efficiency that reflects how much supplied heat actually melts ice. For fuel-fired sources, treat the tariff as your cost per kWh-equivalent.

4) What if the initial temperature is above 0 °C?

The ice-warming term is capped at 0 °C, because ice cannot exist above freezing in this simple model. The melt and water-warming terms still apply.

5) What if the final temperature is below 0 °C?

The meltwater-warming term becomes zero, reducing useful heat. This can be realistic if you stop defrost at “just melted,” or if drainage is fast and water does not warm further.

6) How can I estimate ice mass quickly?

Collect meltwater in a container and weigh it; 1 L of water is roughly 1 kg. For coils, multiply average ice thickness by iced area and an ice density estimate.

7) How do I use the results for power planning?

Use average kW to check circuit capacity and feeder sizing, then add other concurrent loads. For short defrost, consider start-up and control loads before selecting breakers or generators.