How Many Kw Is Good For Solar?

When determining how many kW of solar panels to install on your home, there are several factors to consider. kW refers to kilowatts, which is the unit of measurement for solar panel capacity or power output. The size (in kW) of your solar system is important because it will determine how much energy the system can produce.

In this article, we will outline the key considerations in deciding how many kW of solar is optimal for your home. This includes an overview of average home energy use, how much power solar panels produce, maximum utility bill savings, net metering policies, available roof space, upfront costs and financial incentives. We will also provide recommendations for ideal system sizes based on home size and electricity usage.

Having the right size solar array can maximize your long-term savings and energy independence. Read on to learn how to determine the optimal solar system capacity for your home.

Table of Contents

Average Home Energy Use

The average American household uses around 893 kWh of electricity per month. This energy goes towards powering lights, appliances, heating and cooling systems, and other electronics around the home. The specific breakdown will vary based on factors like house size, number of residents, climate, and energy efficiency.

On average, heating and cooling accounts for around 48% of a household’s energy use. Lighting, refrigeration, water heating and appliances make up roughly 33%. The remaining energy goes towards running home electronics like TVs, computers and small appliances. Homes in very hot or cold climates may use up to 70% of their electricity for heating and cooling alone.

Usage also tends to scale up with house and family size. A smaller 2-3 bedroom home with 2 residents may use 600 kWh per month. A larger 4-5 bedroom home with a family of 4 or more could use over 1,200 kWh. Understanding your home’s unique energy profile is an important first step in identifying the right solar system size.

Solar Panel Output

Solar panels are rated based on their power output in kilowatts (kW). This indicates how much power the solar panel can produce at peak performance under ideal conditions. The key factors determining a solar panel’s power output are:

Panel size – Measured in square feet. Larger panels can accommodate more solar cells.
Panel efficiency – Ranges from 15-22% for most panels on the market today. Higher efficiency means more power produced from the same panel size.

Orientation – Panels facing south receive more direct sunlight in the northern hemisphere.
Shading – Obstructions like trees or buildings will reduce the solar irradiance reaching the panels.

For example, a 300W solar panel with 18% efficiency and a size of around 20 square feet would be considered an efficient and powerful residential solar panel. More efficient panels produce more electricity with less roof space required.

To determine the total system output, you add up the wattage of each solar panel installed. A 6 kW system would consist of about 20 of the 300W panels mentioned above.

Optimal System Size

When determining the ideal solar system size for a home, there are several key factors to consider:

Average electricity usage – Review 12 months of electric bills to calculate the home’s average daily usage. This provides a baseline for energy needs. Systems are often sized to cover 75-100% of annual use.

Roof space and orientation – South-facing roofs with plenty of unshaded space are ideal. Limitations here may restrict system size. Use solar assessment tools to calculate potential production.

Utility rates and net metering policy – Higher electricity rates and favorable net metering make solar more valuable. Check your utility’s rates and net metering rules.

Solar panel ratings – Panel wattages typically range from 300-400 watts now. Higher wattage panels generate more electricity in the same space.

Local solar incentives – Rebates, tax credits and performance-based incentives can offset costs. These can make larger systems more affordable.

Budget – Larger systems require higher upfront costs but provide greater long-term savings. Consider your budget and financing options.

To optimize size, balance these factors to meet your electricity needs, fit your usable roof space, and align with your budget and electricity bill savings goals.

Utility Bill Savings

The size of your solar system will directly impact how much you can reduce your electricity bills. With a properly sized system, most homeowners can eliminate a major portion of their utility bill payments.

For example, a 5 kW system can generate around 6,500 kWh per year in regions with good sun exposure. If your average home uses around 10,000 kWh annually, a 5 kW system could provide 65% of your home’s electricity needs. This could result in cutting your electricity bill by about 65%.

Increasing to an 8 kW system may be able to provide over 100% of your home’s needs, allowing you to greatly reduce or even zero out your utility bills and sell excess power back to the grid. However, the larger system comes with higher equipment and installation costs.

When considering system size, aim to match your expected annual solar production with your home’s energy use. Work with installers to run accurate solar production calculations and estimate bill savings. The optimal system size depends on your location, roof space, energy efficiency, and budget.

Net Metering

Net metering allows homes with rooftop solar panels to send excess electricity they generate back to the grid. With net metering, solar customers only pay the utility for their “net” energy use, which is the amount of electricity they consume minus the amount their system generates. This makes going solar more financially beneficial.

The size of your solar system will impact the amount of energy you can net meter. With a right-sized system, your solar energy production should align relatively closely with your home’s usage. If your system is oversized, you may end up with excess energy that gets sent back to the grid but provides minimal financial benefit. While utilities in many states are required to offer net metering, there are often limits on the capacity that can be net metered. Understanding these limits can help determine the optimal system size for your home.

Overall, net metering enables solar customers to maximize the value of their solar energy and receive credit for excess power sent to the grid. When determining system size, it’s important to aim for an ideal balance between offsetting your home’s energy use and limiting excess generation beyond what the utility will compensate you for.

Roof Space

When determining the optimal solar system size for your home, it’s important to consider the physical space and layout of your roof. The angle, direction and potential shading of your roof can significantly impact the energy production of your solar panels.

In general, south-facing roofs with little shading receive the most direct sunlight throughout the day and year. West-facing roofs receive sunlight in the afternoon and east-facing roofs in the morning. North-facing roofs receive the least sunlight. Panels can still generate electricity on east, west or north-facing roofs but may produce 10-20% less than an ideal south-facing roof over the course of a year.

The pitch or angle of your roof also affects production. In the northern hemisphere, roofs angled at latitude plus 15 degrees get the most yearly sun. However, roofs angled anywhere from 15-50 degrees can be effective. Flatter roofs will need to be tilted or use adjustable mountings to optimize the angle.

When designing your system, your solar installer will evaluate shading from trees, chimneys, adjacent buildings and other obstructions. Even small amounts of shading can disproportionately reduce energy output. Your installer can use specialized tools and 3D modeling to optimize panel placement and avoid shaded areas.

Considering all these roof factors when determining system size and layout allows you to maximize solar production from the available physical space on your home.

Upfront Cost

The upfront cost of a solar system depends on the system size. Larger systems capable of producing more solar power will have a higher initial price tag. A typical 6 kW solar system may cost $15,000 to $25,000 installed, while a 10 kW system often ranges from $25,000 to $35,000. Though the upfront cost is higher for larger solar systems, they can lead to greater long-term savings on your electricity bills.

When weighing the pros and cons of system size, consider how long you plan to live in your home. If you plan to stay for many years, the higher upfront cost of a larger system may pay off over time. However, if you only plan to stay for 5-10 years, a smaller system may make better financial sense. Focusing on your actual energy needs rather than maximum solar production can help optimize system size and return on investment. Discuss your goals with a solar consultant to determine the ideal system size for your home and budget.

Financial Incentives for Residential Solar

There are several financial incentives available to homeowners who install solar panels, which can help reduce the upfront cost.

The main incentive is the federal solar tax credit, which allows you to deduct 26% of the cost of installing a solar energy system from your federal taxes. This credit will decrease to 22% in 2023 before phasing out completely in 2024 for residential projects.

Many states and utilities also offer additional incentives like rebates and renewable energy credits. These local incentives can reduce the cost by thousands more, but usually decrease as the size of the solar system increases. For example, California’s Self Generation Incentive Program provides higher incentives for smaller systems under 10 kW.

Taking advantage of all available federal, state, and utility incentives is key to maximizing savings. Meet with a solar installer to discuss what incentives you may qualify for based on your specific situation.

Recommendations

When deciding how many kW of solar panels to install, there are a few key factors to consider for optimal system sizing:

For the average home, a solar system between 3-8 kW is usually ideal. A smaller 1-3 kW system can offset 30-40% of your electricity usage, while a larger 6-8 kW system can cover 80-100% of your usage.

To determine your specific home’s optimal system size:

Calculate your average monthly electricity usage
Determine how much roof space you have available

Decide what percentage of your electricity usage you want to offset
Factor in financial incentives and your budget

A 4-5 kW system is a good middle-ground size that can cover 50-80% of a typical home’s electricity use. This allows you to maximize solar savings while minimizing system costs.