Quick answer
Unit of electrical power equal to one million watts or 1,000 kilowatts, used to measure the capacity of large-scale solar installations and power plants.
Key Takeaways
- 1 MW = 1,000 kW = 1,000,000 W
- Used to describe the capacity of commercial and utility-scale solar installations
- A 1 MW solar farm produces roughly 1,300–2,200 MWh per year depending on location
- MW measures instantaneous power capacity; MWh measures energy produced over time
- Distinguish between MWdc (panel rating) and MWac (inverter output) in project specifications
- Residential systems are measured in kW; commercial and utility-scale systems in MW
What Is a Megawatt?
A megawatt (MW) is a unit of electrical power equal to one million watts or 1,000 kilowatts. In the solar industry, megawatts describe the generating capacity of commercial and utility-scale solar installations. While residential rooftop systems are typically measured in kilowatts (5–15 kW), solar farms and large commercial arrays are measured in megawatts (1–500+ MW).
Power is the rate at which energy is produced or consumed at any given instant. A 1 MW solar array, operating at full capacity, generates 1 million watts of electricity at that moment. Over the course of an hour at full output, it produces 1 megawatt-hour (MWh) of energy.
The distinction between MW (power) and MWh (energy) is one of the most commonly confused concepts in solar. Power is like the speedometer reading; energy is the distance traveled. A 1 MW system doesn’t produce 1 MW all day — it produces 1 MW only at peak output under ideal conditions.
Power Unit Scale
Understanding where the megawatt sits in the hierarchy of electrical units:
| Unit | Symbol | Watts | Typical Solar Application |
|---|---|---|---|
| Watt | W | 1 | Individual solar cell output |
| Kilowatt | kW | 1,000 | Residential rooftop systems (5–15 kW) |
| Megawatt | MW | 1,000,000 | Commercial rooftops, solar farms (1–500 MW) |
| Gigawatt | GW | 1,000,000,000 | National installed capacity, global manufacturing |
| Terawatt | TW | 1,000,000,000,000 | Global energy discussions |
Annual Energy (MWh) = System Capacity (MW) × Capacity Factor × 8,760 hoursMWdc vs. MWac
Solar projects are specified in two different megawatt ratings, and confusing them leads to significant errors in project planning:
MWdc (DC Megawatts)
The total nameplate capacity of the solar panels under Standard Test Conditions (STC). A project with 2,500 × 400W panels has a capacity of 1.0 MWdc. This is the rating commonly used for panel procurement, land area calculations, and ITC eligibility.
MWac (AC Megawatts)
The maximum AC power output of the inverters. A 1.0 MWdc project typically uses 0.75–0.85 MWac of inverter capacity (DC/AC ratio of 1.2–1.33). MWac is the rating used for interconnection agreements and power purchase contracts.
When a developer says “a 5 MW project,” always clarify whether they mean MWdc or MWac. The difference is 15–30% and affects everything from land requirements to revenue projections. Solar design suite should clearly distinguish between DC and AC ratings in all outputs.
How Much Energy Does 1 MW of Solar Produce?
The energy output of a 1 MW solar installation depends heavily on location, technology, and design:
| Location | Capacity Factor | Annual Production (MWh) | Equivalent Homes Powered |
|---|---|---|---|
| Phoenix, AZ | 25–28% | 2,190–2,453 | ~200–220 |
| Sacramento, CA | 22–25% | 1,927–2,190 | ~175–200 |
| New York, NY | 16–18% | 1,402–1,577 | ~125–145 |
| Munich, Germany | 12–14% | 1,051–1,226 | ~100–115 |
| London, UK | 10–12% | 876–1,051 | ~80–95 |
Capacity factor is the ratio of actual energy output to theoretical maximum output (if the system ran at full rated power 24/7). A 20% capacity factor doesn’t mean the system is 80% broken — it means the sun only shines for part of the day, clouds reduce output, and panels don’t hit STC conditions in the real world.
Physical Scale of Megawatt-Scale Systems
| System Size | Approximate Panel Count | Land Area (Ground Mount) | Typical Application |
|---|---|---|---|
| 1 MW | 2,200–2,500 panels | 4–6 acres | Small solar farm, large commercial roof |
| 5 MW | 11,000–12,500 panels | 20–30 acres | Community solar farm |
| 20 MW | 44,000–50,000 panels | 80–120 acres | Mid-scale utility project |
| 100 MW | 220,000–250,000 panels | 400–600 acres | Utility-scale solar farm |
| 500 MW | 1.1–1.25 million panels | 2,000–3,000 acres | Large-scale utility installation |
Practical Guidance
- Always specify MWdc vs. MWac. Ambiguity between DC and AC ratings causes design errors, procurement mistakes, and contractual disputes. Label every capacity figure explicitly.
- Use location-specific capacity factors. Don’t apply Arizona production numbers to a New York project. Use TMY weather data in your solar software to generate site-specific yield estimates.
- Account for DC/AC ratio in clipping losses. Higher DC/AC ratios increase clipping losses during peak hours but improve low-light performance. Optimize this ratio based on site economics, not rules of thumb.
- Scale land area estimates correctly. Ground-mount projects need 4–6 acres per MWdc including access roads, setbacks, and inter-row spacing. Tracker systems may need slightly more area than fixed-tilt.
- Understand interconnection thresholds. Many utilities have different interconnection requirements at 25 kW, 100 kW, 1 MW, and 5 MW thresholds. Crossing a threshold changes the review process, cost, and timeline.
- Plan logistics for MW-scale projects. A 1 MW project involves 2,500+ panels, 50+ pallets of materials, and weeks of installation labor. Staging, material handling, and crew coordination become critical at this scale.
- Verify transformer capacity. MW-scale systems typically require a dedicated transformer and utility interconnection upgrades. Confirm transformer sizing and lead times early in the project.
- Commission in sections. Large systems are often commissioned in phases (blocks or zones) to allow testing and energization of completed sections while installation continues elsewhere.
- Translate MW into relatable terms. Customers understand “enough to power 200 homes” better than “1 MW.” Use local average consumption data to make the conversion meaningful.
- Present economics in $/MWh. For commercial and utility-scale projects, the levelized cost of energy (LCOE) in $/MWh is the standard metric. Current utility-scale solar LCOE ranges from $25–$50/MWh in most U.S. markets.
- Clarify “peak” vs. “average” output. A 1 MW system only produces 1 MW during peak conditions. Average output is capacity factor × 1 MW. Being upfront about this builds trust and prevents unrealistic expectations.
- Know the local market context. Understanding whether your region measures projects in MWdc or MWac (conventions vary by market) prevents confusion when comparing proposals or discussing with utilities.
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Real-World Examples
Commercial: 1.2 MW Rooftop System
A distribution center in New Jersey installs a 1.2 MWdc rooftop system using 3,000 × 400W panels on a 150,000 sq ft flat roof. With 0.95 MWac of central inverter capacity (DC/AC ratio of 1.26), the system produces approximately 1,450 MWh annually. At an avoided electricity cost of $0.12/kWh, the system saves the building owner roughly $174,000 per year.
Community Solar: 5 MW Solar Farm
A 5 MWdc community solar farm in Minnesota spans 25 acres of agricultural land. Using single-axis trackers, the project achieves a 19% capacity factor and produces 8,322 MWh annually. The energy is distributed to 600 subscribers who receive credits on their utility bills, each offsetting an average of 13.9 MWh per year.
Utility-Scale: 150 MW Solar Farm
A 150 MWdc utility-scale project in Texas uses 375,000 bifacial panels on single-axis trackers across 750 acres. The project connects to the grid via a 120 MWac interconnection agreement (DC/AC ratio of 1.25). Annual production: approximately 290,000 MWh — enough to power roughly 26,000 homes. Electricity is sold under a 15-year PPA at $28/MWh.
Frequently Asked Questions
How many homes can 1 megawatt of solar power?
A 1 MW solar installation typically powers 125–220 average U.S. homes, depending on location and local electricity consumption. In sunny regions like Arizona, 1 MW produces roughly 2,200 MWh/year, enough for about 200 homes at average U.S. consumption of 10,500 kWh/year. In less sunny areas like the Northeast, the same 1 MW may produce 1,400 MWh/year, serving about 130 homes.
What is the difference between MW and MWh?
MW (megawatt) measures instantaneous power — the rate of energy production at a given moment. MWh (megawatt-hour) measures energy — the total amount of electricity produced over time. A 1 MW solar system operating at full capacity for one hour produces 1 MWh of energy. Since solar output varies throughout the day, a 1 MW system typically produces 4–6 MWh per day, not 24 MWh.
How many solar panels make 1 megawatt?
With today’s standard 400W panels, 1 MW requires 2,500 panels (1,000,000W / 400W). Using higher-efficiency 500W panels, you need 2,000 panels. Using older 350W panels, you need about 2,857. The exact count depends on the panel wattage you select. For ground-mount installations, 1 MW of panels requires approximately 4–6 acres of land including spacing and access roads.
Related Glossary Terms
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