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How Much Energy Do Solar Panels Produce?
- David Kranker
- Dec 30, 2025
- 9 min read
Solar energy is no longer a novelty or fad. Around 7% of U.S. homes use solar, and a growing number of commercial businesses like warehouses are following suit. Those who haven’t yet made the transition (but are considering it) usually ask the same question, which is “how much energy do solar panels produce?”
The amount of energy your system generates dictates how much of your electricity bill you can cover with it. It also affects the long-term value of the system, including how much power you can send back to the grid and how quickly the system covers its cost. Energy output depends on measurable factors: the total kilowatts (kW) installed, the wattage of each panel, the average number of full sunlight hours per day, and the actual performance of your inverter and other hardware.
This article explains how to calculate solar energy production. You’ll see what a system produces on an average day, how weather and roof angle change those numbers, and how homes in states like Delaware, Maryland, and Pennsylvania compare. It also shows how to match solar output to your electricity use, with examples for different home sizes and usage patterns.
What Affects Solar Panel Energy Output
Solar panels produce electricity when sunlight hits the photovoltaic cells. The total output depends on four measurable factors: panel wattage, hours of direct sunlight, total system size, and hardware performance.
Panel Wattage: Each panel is rated based on how much electricity it can produce under ideal conditions. Most modern residential panels produce between 350 and 450 watts per hour. If you install 20 panels rated at 400 watts, the system’s peak capacity is 8,000 watts, or 8 kilowatts (kW).
Sunlight Hours: A location’s average daily sunlight hours determine how many hours each day your system can operate near its rated output. For example, homes in Delaware average 4.5 to 5.0 full sun hours per day, while parts of Pennsylvania average around 4.0 to 4.3 hours. If an 8 kW system in Delaware gets 4.8 hours of sun, it produces about 38.4 kilowatt-hours (kWh) per day.
Roof Angle and Direction: The tilt and orientation of your roof change how much sunlight reaches the panels. South-facing panels at a 30–40° tilt perform closest to their rated capacity. If panels face east or west, or the tilt is too flat or steep, output may drop by 10–25%, depending on the angle and seasonal position of the sun.
System Losses: Energy is lost during conversion and transmission. Inverters typically operate at 95–98% efficiency, and other factors, such as shading, wiring, or heat, reduce output slightly. Industry-standard estimates apply a production ratio of 85–90% to account for these combined losses. An 8 kW system producing 38.4 kWh/day under ideal conditions may produce 32.6–34.5 kWh/day in real-world use.
How to Calculate Solar Panel Output
To estimate how much electricity your solar system will generate, use this formula:
Daily Output (kWh) = System Size (kW) × Average Sun Hours × 0.85
The multiplier 0.85 adjusts for real-world system losses from wiring, inverter performance, and minor shading. This number can vary slightly, but 85% is a reliable baseline.
Example: 6 kW System in Delaware
System Size: 6 kW
Sunlight Hours: 4.7 hours/day (Delaware average)
Real Output: 6 × 4.7 × 0.85 = 23.97 kWh/day
Monthly, that’s about 719 kWh, assuming stable sunlight conditions.
System Size | Daily Output (kWh) | Monthly Output (kWh) |
4 kW | 15.96 | 478.8 |
6 kW | 23.97 | 719.1 |
8 kW | 31.96 | 958.8 |
10 kW | 39.95 | 1,198.5 |
These calculations use real values tied to Mid-Atlantic sunlight data. To apply them to your home, you need two numbers: your system size in kilowatts and your area’s average full sun hours per day.
How Much Energy Do You Actually Need?
Before choosing a solar system size, you need to measure your electricity use in kilowatt-hours (kWh). You’ll find this number on your utility bill, usually listed as “total usage” or “total kWh.” It reflects how much energy your home used over the past month.
In the Mid-Atlantic, the average single-family home uses between 850 and 1,100 kWh per month. That range depends on the home’s size, how it’s heated, and what appliances are running.
Electricity Use by Home Type (Monthly Average)
Home Type | Estimated Use (kWh/month) |
Small home, gas heat | 600–750 |
Medium home, mixed systems | 850–1,000 |
Large home, electric heat or AC | 1,200–1,500 |
Home with an electric vehicle | Add 250–300 per EV |
Home with pool or hot tub | Add 200–400 |
If your home uses 1,100 kWh per month and your solar system produces 34 kWh per day (based on an 8 kW system), then your monthly output is about 1,020 kWh. That would offset roughly 93% of your bill before factoring in net metering or utility credits.
To match your solar system to your actual needs, look at 12 months of past bills. Seasonal use matters: air conditioning, space heaters, and electric water heaters can change energy use by 30% or more throughout the year.
Solar Panel Output in the Mid-Atlantic
The Mid-Atlantic gets fewer sun hours than the Southwest, but it still provides consistent solar production year-round. On average, homes in this region receive between 4.0 and 5.0 full sunlight hours per day, depending on the state and site conditions.
Average Sunlight Hours by State
State | Avg. Sun Hours/Day | Annual kWh per 1 kW Installed |
Delaware | 4.7 – 5.0 | 1,455 – 1,550 |
Maryland | 4.5 – 4.8 | 1,395 – 1,500 |
Pennsylvania | 4.0 – 4.5 | 1,250 – 1,395 |
New Jersey | 4.3 – 4.6 | 1,330 – 1,440 |
These figures use actual weather data and performance ratios that account for system losses. For every 1 kW installed, you can expect 1,300 to 1,550 kWh per year, depending on location and orientation.
Example: 7.5 kW System in Maryland
Sun hours: 4.6/day
Estimated daily output: 7.5 × 4.6 × 0.85 = 29.33 kWh/day
Estimated annual output: 29.33 × 365 = 10,703 kWh/year
That system could offset 90–100% of the annual energy use in an average home with moderate consumption.
Seasonal variation in this region is steady. Winter months produce less, but long daylight hours in late spring and summer raise annual averages. Well-sited systems with minimal shading and a south-facing tilt deliver the most stable results.
How Panel Quality Affects Output
Not all solar panels produce the same amount of electricity. Two systems with the same number of panels can deliver very different results if one uses lower-efficiency models. The key differences come from three measurable specs: wattage, degradation rate, and temperature coefficient.
Panel Wattage
Most modern residential panels fall between 350 and 450 watts. Higher-wattage panels produce more energy per square foot. If you install 20 panels:
At 350W each = 7.0 kW system
At 450W each = 9.0 kW system
That’s a 29% increase in system size using the same roof space.
Degradation Rate
Panels lose output capacity over time. Most degrade at 0.25–0.5% per year. After 10 years:
A panel with 0.5% annual loss will produce 95% of its original capacity
A panel with 0.25% loss still produces 97.5%
Over 25 years, the difference adds up. A 0.5% rate means a 12.5% drop in lifetime output. Higher-grade panels maintain better performance for longer.
Temperature Coefficient
As panels heat up, they lose efficiency. The temperature coefficient tells you how much production drops per degree above 77°F. For example:
A panel with a −0.3% coefficient loses 3% at 87°F
One with −0.5% loses 5% at the same temperature
On a 95°F roof, that gap gets wider. In warmer months, panels with lower heat loss generate more electricity.
If two homes install systems with the same rated wattage, but one uses higher-quality panels with better performance specs, that system will produce hundreds more kilowatt-hours per year without needing extra space.
Seasonal Solar Output: What to Expect Each Month
Solar production doesn’t stay flat throughout the year. Even though the total annual output may meet your goals, month-to-month performance changes with daylight hours, sun angle, and weather patterns. Systems in the Mid-Atlantic typically generate 60-70% of their annual output between March and September.
Monthly Output Estimate Example for Delaware (7.5 kW system)
Month | Avg Sun Hours | Est. kWh Output |
January | 3.2 | 615 |
February | 4.0 | 768 |
March | 5.0 | 960 |
April | 5.5 | 1,056 |
May | 6.2 | 1,190 |
June | 6.5 | 1,248 |
July | 6.4 | 1,230 |
August | 6.0 | 1,152 |
September | 5.5 | 1,056 |
October | 4.8 | 921 |
November | 3.8 | 729 |
December | 3.0 | 576 |
Total | 11,501 kWh |
This table uses a 7.5 kW system with an 85% performance ratio, installed on a south-facing roof in Delaware. Your exact numbers may vary depending on roof angle, panel type, and local shading.
Production Surplus and Deficit
During summer months, your system will likely produce more than your home uses. That surplus gets credited back to your utility account under net metering rules in Delaware, Maryland, and New Jersey. In the winter, production may fall below usage, especially in homes with electric heating.
This seasonal pattern is normal and factored into system sizing. A well-built system uses summer surplus to cover winter gaps, keeping your annual offset high even if a few months run below average.
Examples From Mid-Atlantic Homes
System sizing and energy output depend on your usage patterns. Here are three examples based on homes in Delaware and Maryland with different energy needs. Each scenario uses real data and performance estimates based on local sunlight hours.
1. Small Ranch Home – Dover, Delaware
Home Size: 1,400 sq. ft., gas heat
Monthly Use: 600–650 kWh
System Size: 5.0 kW
Avg. Sun Hours: 4.8/day
Estimated Output: 5 × 4.8 × 0.85 × 30 = 612 kWh/month
Offset: 95–100%
This home covers its full usage with 13 high-efficiency panels. Summer months generate surplus credits, which carry the system through lower-production months.
2. Four-Bedroom Colonial – Baltimore, Maryland
Home Size: 2,600 sq. ft., electric HVAC
Monthly Use: 1,100–1,250 kWh
System Size: 9.6 kW
Avg. Sun Hours: 4.6/day
Estimated Output: 9.6 × 4.6 × 0.85 × 30 = 1,122 kWh/month
Offset: 90–100%
This home includes a south-facing roof and minimal shading. The system pushes close to full offset most months. Electric heating raises winter usage, so summer surplus plays a key role.
3. Suburban Home with EV – Newark, Delaware
Home Size: 2,000 sq. ft., gas appliances
Monthly Use: 800 kWh (house) + 300 kWh (EV)
System Size: 10.0 kW
Avg. Sun Hours: 4.8/day
Estimated Output: 10 × 4.8 × 0.85 × 30 = 1,224 kWh/month
Offset: 100%
The owner added an electric vehicle in 2023 and increased system size to match. With 25 panels at 400W each, the system offsets both household and EV charging.
Can Solar Panels Cover 100% of Your Needs?
Yes, a solar panel system can cover all of your electricity use, but only if your roof can fit enough panels to match your energy consumption. A full offset depends on your monthly usage, your roof’s size and orientation, and the amount of sunlight your property gets.
Example: 100% Offset for a 1,000 kWh/Month Home
If your home uses 1,000 kWh/month, you need about 12,000 kWh/year. A system must produce roughly 33 kWh/day to meet that goal.
In Delaware, using 4.8 sun hours/day:
Required system size = 33 ÷ (4.8 × 0.85) ≈ 8.1 kW
That equals around 20 panels, assuming 400 watts each
If your roof has enough unshaded space to hold 20 panels with good southern exposure, then a full offset is realistic. If the available space is smaller or partially shaded, you may only be able to reach 70–90%.
Net Metering Makes It Possible
In states like Delaware, Maryland, and New Jersey, net metering allows you to send excess electricity to the grid during high production months and use credits during lower-output months. This balances production over the year and makes full offset possible, even if daily production and usage don’t always match.
Some homeowners choose to oversize their system slightly if they expect higher future use, such as adding an electric vehicle or switching from gas to electric heating.
Solair’s Approach to Right-Sizing Your System
Solair Green Energy Advisors builds each system to match your home’s energy use, site conditions, and budget. The team reviews your past utility data, measures your available roof space, and uses region-specific solar data to calculate the system size required to meet your goals.
The assessment includes an on-site inspection, where solar consultants evaluate your roof angle, orientation, shading, and any obstructions that could limit output. If full offset isn’t possible, Solair shows exactly how much of your usage solar can cover with the available space.
We use performance data from installations across Delaware, Maryland, Pennsylvania, and New Jersey to project how many kilowatt-hours your system will generate each year. That lets you compare projected production against your electric bills before signing a contract. If you're considering solar and want numbers based on your property’s energy use, we’re glad to offer a free estimate backed by 15+ years of solar experience in the Mid-Atlantic region.
Ready To Start Saving With Solar?
Solar panel output depends on measurable variables: system size, panel wattage, sun hours, and hardware performance. In the Mid-Atlantic, a well-installed residential system produces between 1,300 and 1,550 kilowatt-hours per year per installed kilowatt. That output can fully offset the electricity use of most single-family homes, as long as the roof can support enough panels.
To calculate what your home needs, start with your past 12 months of utility bills. Then compare that usage to the output range of a system based on your location. With the right system size, orientation, and equipment, solar can replace most or all of your utility bill, and Solair can show you exactly what that looks like. For more information or to schedule a no-obligation estimate, call 302-841-1108 or fill out our simple contact form.
