Solar power is top of mind for New Yorkers right now. With incentives changing, and electricity rates increasing at a dramatic rate, one of the first questions we hear in many of our conversations with New Yorkers researching solar power is, “How many solar panels do I actually need?”
Choosing the right system size is one of (if not the most) important steps in the solar process. It directly impacts your system cost, electricity production and long-term savings. Installing a system that’s too big, your return on investment could be greatly diminished over time. On the other hand, if too small, when you have the space and energy needs, it may lead to unnecessary dependence on your electric company.
Below, we’ll break down how solar system size is calculated, what factors matter the most, and why bigger doesn’t always mean better.
How System Size Is Measured (kW vs kWh Explained)
When talking about solar system size, we are referring to its capacity which is measured in kilowatts (kW). The higher the kW, the more electricity your panels can produce under ideal conditions. Most residential systems in New York range from 7kW to 13kW.
Additionally, the amount of power your panels produce is measured in kilowatt-hours (kWh). One kWh equals the energy required to run a 1,000-watt appliance for one hour. You’ve probably seen this term used throughout your electric bill because kWh is the unit your electric company uses to measure your electric usage, which determines how much they charge you.
Here’s a common example, a 10 kW system in New York typically produces between 11,000 and 13,000 kWh annually. But actual output depends on roof orientation, shading, and local weather patterns. Two homes with the same system size can have very different production numbers if one has significant shading or faces north-east rather than south.
What Determines the Right System Size
Annual Energy Usage
The most accurate method of designing a solar system is to first analyze the past 12 months of electric bills. This helps us consider seasonal differences that lead to fluctuations in your electricity consumption. Higher usage in the summer months is common due to air conditioning / central air being used more frequently or even in the winter months if using electricity for heating.
If your home is using 10,000 kWh annually, that doesn’t necessarily mean you need a 10kW system. In many situations, a well-placed 8.5-9kW system would be more than enough. Now, 1kW may not sound like much, but over time, it adds up. But we’ll get to that later…
Roof Size and Orientation
The amount of usable roof space on your home will be the biggest key factor regarding how many panels you can install. South-facing roofs will always provide a little more production compared to east and west facing roofs. But if a southern-facing roof can only fit a handful of panels compared to an east-facing roof that can comfortably fit 20 panels, the eastern roof has far more solar potential than the south facing roof.
Shading and Location
Shade is one element that can make or break your chances of installing solar panels on your home. If tree removal is not possible, many homeowners in New York find themselves unable to install solar panels because of the lack of sun hours they get on their roof.
But shade doesn’t always come from trees. Neighboring buildings, chimneys and even other areas of your home could cast shade on your panels throughout the day, significantly impacting the system’s overall efficiency and production.
Energy Goals & Expectations
Not every homeowner wants or even needs to offset 100% of their electricity usage. In fact, many homes you see with solar panels, are getting between 40-70% of their house. That’s because most homes were not built with solar in mind. But the economics still make sense, even if solar only provides a percentage of your total energy use.
Some homeowners prefer a smaller system to cover a portion of their bill, while others aim for full offset to eliminate as much utility dependency as possible. A great example of this would be someone commuting large distances using an electric vehicle (EV). The amount of energy needed to power an EV can be as high as 5,000 kWh per year alone. Some homeowners may want to just cover this portion of their bill to increase the savings compared to driving a gas-powered vehicle.
Why Bigger Isn’t Always Better
It’s easy to assume that the bigger the system, the bigger the savings. But oversizing can lead to a reduced savings if you don’t intend on increasing your electricity consumption to match your system’s production.
Some people are under the impression that you can “sell” your excess energy at the end of every year and make money doing so. But if you offer to sell your excess power to your power company, they will likely offer you a rate lower than market value, basically treating your home as a mini power plant on the grid, paying wholesale rates rather than market price.
So while it’s common to oversize your system, it’s not done to make money. It’s done in anticipation of adding large appliances such as electric hot water heaters, hot tubs, pool pumps, heat pumps, electric vehicles, etc.
There’s also the opposite problem – undersizing. Inexperienced or even dishonest salespeople design smaller systems to make their quotes look cheaper and the savings more impressive.
An example of this would be proposing that a 10 kW would be enough for a home using 15,000 kWh. This could be done by either understating your annual usage in their proposal, or even worse, overembellishing the estimated annual production of the system. This might help them win your business but it sets you up for disappointment and unexpected utility bills year after year.
This is why it’s crucial to have an understanding of how much energy you use annually and at least have a basic understanding of how much a system can produce under perfect conditions. Below is a table which will shed some light (pun intended) on exactly how much energy a system could produce annually with optimal conditions.
Approximate Production Ranges (Optimal Conditions)
*Exact production and savings will vary based on location, equipment, and site conditions.
How We Help You Get the Perfect Fit
At Empire Solar, we don’t guess and we don’t exaggerate. Our process includes:
- Reviewing your last 12 months of energy usage
- Performing a site survey and shade analysis
- Designing a custom system tailored to your roof and energy needs
- Factoring in your future energy usage (e.g., EVs, large home appliances)
- Applying all available incentives
This ensures you get a system that meets your goals, avoids hidden shortfalls, and delivers the savings you expect.
Final Thoughts
Choosing the best system for your home isn’t about going as big as possible. While you may see many homes using all their available roof space for solar panels, it doesn’t mean you need to. It’s more important to know exactly how much power you need every year and what your home’s maximum solar output would be.
The safest way forward is to get a personalized solar production analysis from a reputable and transparent installer who has a track record in your area. This way you can make an educated decision based on facts and not sales tactics.
Want to see exactly how many panels your home really needs? Get your Custom Solar Report →
