Netizen asks: What are MW and MWh in new energy? What's the difference?

In discussions and learning about new energy wind, solar, and storage projects, we often see terms like 0.61 yuan/W for components, 1MW for photovoltaic power plants, 100MW for wind power, and 200MW/400MWh for energy storage power plants. Energy storage quotes often show 0.43 yuan/wh, Kw, Kwh, "MW", "MWh", Gw, etc. For many non-professionals, what do these units mean? What are their differences and relationships? What do they mean to investors and developers? Today, I will give you a unified popular science explanation (If you think it's good, please follow and like! Share it with friends in need. Please correct me in the comments section if there are any mistakes).

I. W, Kw, MW, GW are power units, determining "speed"

MW (megawatt) is a unit of power. 1MW equals 1000 kilowatts (kW). It describes the maximum energy rate that an energy storage system or power generation equipment can output or absorb at any given moment. Simply put, it's like a car's "horsepower." The higher the horsepower, the faster the acceleration.

In a photovoltaic system, a 1MW photovoltaic power plant, with a component power of 710W and a price of 0.69 yuan/W, the price of this photovoltaic panel is 710 * 0.69 = 490 yuan.

1GW = 1000MW = 1000000KW = 1000000000W.

For example, an energy storage system labeled "50MW" means that it can release or absorb a maximum of 50 megawatts of electricity at any given moment. For instantaneous demand scenarios such as grid frequency regulation and peak load response, a high power value means that the energy storage system can quickly release a large amount of energy to ensure the stable operation of the power system.

The greater the power, the faster the "work" is done, but it does not represent "how long it can be done," which depends on the capacity.

II. Wh, Kwh, MWh are energy units, determining "range"

Wh (watt-hour), Kwh (kilowatt-hour), MWh (megawatt-hour) are energy units. 1MWh represents the ability to output 1 megawatt of electricity within 1 hour, which is the total amount of time it can continuously output power.

If power is the "horsepower of a car," then capacity (MWh) is the "size of the fuel tank:"

A system labeled "100MWh" means that its total stored energy can supply 1MW of power for 100 hours, or 100MW for 1 hour.

A 50MW/100MWh energy storage system means it can discharge at 50 megawatts for 2 hours.

MWh determines the system's "range," which is particularly crucial in energy storage systems, virtual power plants, and peak shaving and valley filling scenarios.

Usually, if a photovoltaic power plant adds storage, it will have the following wording: 20%, 2h. This means: For example, for a 10MW photovoltaic power plant, the required storage is 2MW/4MWh. Energy storage power plants are usually priced in Wh, such as 0.75 yuan/Wh. The price of a 2MW/4MWh energy storage power plant is 4MWh * 0.75 yuan/Wh = 3 million.

III. Mathematical relationship between the two: Power × Time = Energy

MW and MWh are linked by a basic physical relationship:

Energy (MWh) = Power (MW) × Time (hours)

For example: A 50MW energy storage system operating continuously for 2 hours outputs energy of: 50MW × 2h = 100MWh;

If an area needs to provide 200MWh of electricity within 2 hours during peak hours, the minimum power required is: 200MWh ÷ 2h = 100MW.

This is why we often see combinations like "60MW/120MWh." The latter value is usually 1 to 4 times the former, indicating the configured discharge duration.

IV. Differences in wind and photovoltaic power generation projects

In wind or photovoltaic power plants:

MW describes the installed capacity, that is, the design power generation capacity of the equipment. For example, a photovoltaic power plant with an installed capacity of 100MW means that under ideal conditions, the maximum power generation per hour is 100MWh; however, the actual power generation depends on weather, sunlight, wind speed, etc., so the actual operation may not reach the theoretical maximum.

MWh is often used to describe the annual total power generation of a power plant or the energy output of energy storage. For example:

A 100MW photovoltaic power plant, with an annual average effective operating hours of 1400 hours, has an annual power generation of approximately: 100MW × 1400h = 140,000MWh (i.e., 140 million kWh);

1 kWh = 1000 Wh

Energy storage systems are used to balance photovoltaic fluctuations and need to match the corresponding MWh capacity to absorb the power generation of photovoltaics.

V. Typical application scenarios in energy storage systems

1. Peak-valley arbitrage (making money from price differences)
The peak-valley price difference is one of the main profit models for energy storage. For example, if the daily peak-valley price difference in a certain area is 0.3 yuan/kWh, and a system is configured as "1MW/2MWh," with one discharge per day, the theoretical income is: 2MWh × 0.3 yuan = 600 yuan/day.

2. Grid frequency regulation
This type of demand requires the system to have a high-power response, that is, a "high MW," even if the MWh is a little smaller. Frequency regulation contracts are about speed, not total electricity.

3. User-side backup power
Enterprises installing energy storage systems mainly consider "how long it can be used during a power outage." Therefore, the focus is on how large the MWh is and whether it can support several hours of office work or production.

In conclusion:

Whether it's users installing home energy storage systems, new energy investors, project developers, or new energy technology professionals, understanding MW and MWh is crucial: It determines whether the system can meet your usage needs (power); it also determines how long it can last and its profitability (capacity); both are indispensable when designing energy storage projects, participating in market transactions, and formulating business models.