Level 1 · Module 01
Energy Basics
How should we reason about electricity, power and energy?
- 4
- connected lessons
- 8
- guided learning steps
- 150
- estimated minutes
The central idea
How should we reason about electricity, power and energy?
Electricity is an energy carrier, power measures the rate at which energy is transferred, and energy measures the accumulated quantity over time. Reliable reasoning requires the correct unit, time basis, system boundary and operating condition.
Build the vocabulary needed to read electricity and energy claims correctly. Distinguish MW from MWh, connect voltage and current to grid losses, and interpret frequency, power factor, capacity factor and storage duration.
Professional relevance
Why this matters beyond the classroom.
Every technical, commercial and financial energy decision depends on interpreting quantities correctly. Confusing MW with MWh or efficiency with capacity factor can distort asset sizing, production forecasts, revenues and risk.
What you will learn
Four lessons that build one working mental model.
- 01
Power, Time and Energy
power, energy, MW, MWh and time
Power is a rate, while energy is the accumulated result of that rate over time. A 25 MW asset operating at constant output for four hours delivers 100 MWh. Real output varies, so energy is the area under a power-versus-time profile rather than rated MW multiplied blindly by a calendar year. This distinction controls generation forecasts, storage sizing, demand analysis and revenue calculations.
- 02
Voltage, Current, AC and DC
voltage, current, losses, AC, DC and inverters
Voltage is electrical potential difference and current is the flow of electric charge. For a given power transfer, increasing voltage generally reduces current and therefore resistive losses. Most power systems use AC for networks, while solar panels and batteries operate internally in DC and connect through power electronics. An inverter is therefore an electrical interface and controller, not an energy source.
- 03
Frequency and the Power Triangle
frequency, active power, reactive power, apparent power and power factor
System frequency reflects the balance between active-power injections and withdrawals in a synchronous area. Active power performs net work, reactive power supports electric and magnetic fields, and apparent power represents the combined equipment loading. Power factor connects these quantities. A facility can consume modest active power yet still use significant network capacity if reactive demand is high.
- 04
Performance and System Boundaries
efficiency, capacity factor, load factor, battery duration and export limits
Energy metrics answer different questions. Efficiency compares useful output with input. Availability asks whether equipment could operate. Capacity factor compares actual energy with the theoretical rated-power maximum over time. Battery duration divides usable MWh by discharge MW. Export limits describe what can pass through the connection. These values are related, but none can substitute automatically for another.
Key takeaways
What should remain after the details.
- MW measures power; MWh measures energy.
- Energy equals the integral of power over time.
- Higher voltage can reduce current and resistive losses for a given transfer.
- Frequency and voltage describe different system conditions.
- Efficiency, availability and capacity factor answer different questions.
- Battery MW and MWh determine power and duration, not interchangeable size labels.
Correct the shortcut
Common misconceptions
- A 100 MW plant produces 100 MWh every hour of the year.
- Rated MW is capability. Actual MWh depends on time, resource, availability, dispatch, curtailment and losses.
- A 30% capacity factor means a plant is 30% efficient.
- Capacity factor measures realised production against a time-based maximum; efficiency compares output with energy input.
- A 100 MW / 100 MWh battery can discharge at 100 MW indefinitely.
- At that discharge level its idealized duration is one hour before losses and operating reserves.
Worked reasoning
Power accumulated through time
A constant 25 MW output maintained for four hours produces 100 MWh. If output falls to 10 MW for the final two hours, total energy becomes 25 MW × 2 h + 10 MW × 2 h = 70 MWh. The installed rating did not change; the operating profile changed the delivered energy.
Concept map
The vocabulary this module connects.
- power and energy
- MW and MWh
- voltage and current
- AC and DC
- frequency
- power factor
- capacity factor
- battery duration
Evidence boundary
Selected authoritative sources
Research reviewed 2026-07-29. The complete learning package contains the full reference trail and explains where simplified beginner models stop.
- Bureau International des Poids et Mesures (BIPM): The International System of Units (SI), 9th editionFoundational electricity-system terminology and calculation boundaries
- U.S. Energy Information Administration (EIA): Measuring electricityFoundational electricity-system terminology and calculation boundaries
- U.S. Energy Information Administration (EIA): Electricity generation, capacity, and salesFoundational electricity-system terminology and calculation boundaries
- National Renewable Energy Laboratory (NREL): Electricity Generation Baseline ReportFoundational electricity-system terminology and calculation boundaries
- National Renewable Energy Laboratory (NREL): Timescales of Energy Storage Needed for Reducing Renewable Energy CurtailmentFoundational electricity-system terminology and calculation boundaries
Questions answered
Energy Basics FAQ
What is the difference between MW and MWh?
MW measures an instantaneous rate of power. MWh measures the energy transferred when power is sustained over time.
Is capacity factor the same as efficiency?
No. Capacity factor measures utilization over time, while efficiency compares energy output with energy input.
Why do electricity networks use high voltage?
For a given power transfer, higher voltage generally allows lower current, which reduces resistive losses and conductor requirements.
How is battery duration calculated?
A simplified duration is usable energy in MWh divided by discharge power in MW, with real operation also considering losses and reserve limits.
Learn, apply, test
Reading is only the beginning.
The complete module adds guided decisions, feedback, a mastery assessment and a professional challenge. Your progress remains in your learner dashboard.