Energy Consumption Calculator
Calculate energy consumption step by step: E = P_rated × load factor × hours/day × days/year.
In short
Calculate energy consumption step by step: E = P_rated × load factor × hours/day × days/year.
Formula: E = P_rated × load factor × hours/day × days/year.
Annual energy consumption formula
Energy (kWh) = rated power (kW) x load factor x hours per day x days per year. The load factor is the average share of rated power the equipment actually draws.
Estimating the load factor
A plug-in energy meter or logged reading over a typical period gives the real average draw. Dividing that by the rated power gives the load factor. Using 100% assumes the equipment always runs flat out.
From kWh to cost
Multiply annual kWh by your own electricity price per kWh. Prices vary by supplier, tariff and time of day, so none is built in.
What this calculator does
Calculate energy consumption step by step: E = P_rated × load factor × hours/day × days/year. Worked example, questions and limitations included.
You enter rated power, average load factor, operating hours per day and operating days per year, and the energy consumption calculator shows the answer along with the working, so you can check it or try other numbers.
The page shows the formula, a numeric worked example, and the assumptions that affect this thermal & hvac calculation.
Inputs and what they mean
- Rated power
- — number value.
- Average load factor
- — Share of rated power actually drawn on average.
- Operating hours per day
- — number value.
- Operating days per year
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Load factor is entered by you — no typical value is assumed.
Hours ≤ 24 and days ≤ 366.
For HVAC, compressors cycle, so use a measured or estimated average.
E = P_rated × load factor × hours/day × days/year.
Inputs used: Rated power, Average load factor, Operating hours per day, Operating days per year.
Worked examples
Worked example: 2 kW equipment
- Daily = 2 x 75% x 10 h = 15 kWh
- Annual = 15 x 300 days = 4,500 kWh
- Monthly average = 4,500 / 12 = 375 kWh
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Single average load factor.
- Standby consumption excluded unless included in load factor.
- No seasonal variation.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this energy consumption calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: OpenStax
Last reviewed:
Common questions
What is load factor?
The average power drawn as a share of rated power. A compressor running half the time at full power has about a 50% load factor.
How is this different from the energy calculator?
This one works per year with a load factor for equipment; the energy calculator uses a direct average power over days.
How do I get cost?
Use the equipment energy cost calculator with your own tariff.
How do I use the Energy Consumption Calculator?
Enter the required values for Rated power, Average load factor, Operating hours per day, Operating days per year. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Energy Consumption Calculator use?
E = P_rated × load factor × hours/day × days/year. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Energy Consumption Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Sources
Method based on OpenStax.
Cite this page
Free Calculator. (2026, November 3). Energy Consumption Calculator. https://freecalculator.tech/tools/energy-consumption-calculator
"Energy Consumption Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/energy-consumption-calculator.
Energy Consumption Calculator — Free Calculator, https://freecalculator.tech/tools/energy-consumption-calculator
Related tools
Calculate heat transfer step by step: Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT.
Calculate cooling load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).
Calculate heating load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT − internal gains (not below zero).
Calculate equipment energy cost step by step: Cost = kWh × price per kWh + fixed or demand charges.