How many solar panels do I need for my home?

by Energy Sage

Determining the size of your solar energy system starts with a simple question: how many solar panels do I need for my home? As most people want to produce enough energy to completely eliminate their electricity bill, the first step is determining what size solar system will produce enough power to meet your household consumption levels. Ultimately, you will be calculating how many kilowatt hours of power you will need and finding the correct system size and number of panels to power your house.

How many solar panels do I need?

If the average household consumes 11,000 kWh per year and we assume 250 watt solar panels, we can use the high and low panel production ratios to calculate an average. Thus, the typical homeowner will need 28 – 34 solar panels to cover 100% of energy usage (dependent on location and roof size).

For those wondering how we estimated those numbers for energy consumption and required number of solar panels, here’s the breakdown. When you want to understand how much power you’ll need, start by looking at how many kilowatt hours (kWh) of electricity you use in a year. Most utilities provide you with your total power consumption for the last twelve months on your monthly bill. To offer some perspective, one kWh is 1,000 watts of power being used in an hour. So, if you have 20 lights in your home and they all use 50-watt bulbs, having every light on in your house for one hour would use up one kWh of electricity. According to the latest data from the U.S Energy Information Administration, in 2013 the average American household used 909 kWh per month. Said differently, the average American household consumes just under 11,000 kWh per year.

In order to find a range for number of solar panels, we compared Arizona and Maine’s solar panel production ratios, 1.31 and 1.61, the highest and lowest in the U.S.. We then took 11,000 kWh and divided it by the respective ratios and then divided that number by 250 (the typical panel wattage). That calculation gave us high and lows for the average number of panels a homeowner will need.

How many kWh can your solar panels produce?

The amount of power (kWh) your solar energy system can produce depends on how much sunlight exposure your roof receives. The amount of sunlight you get in a year depends on both where you are in the country, and what time of year it is. California has more sunny days annually than New England. But in either location, you’ll be able to produce enough power to cover your energy needs! If you live in an area that gets less sun, you’ll just need to have a larger system installed at your home.

Two comparably sized households in California and Massachusetts consume the average amount of electricity for an American household, about 11,000 kWh annually. The California household needs a 7.0 kWh system to cover 100% of their energy needs. By comparison, the comparable household in Massachusetts needs a 8.8 kWh systems to cover their energy needs. Solar panel systems in California are smaller than the solar panel systems in Massachusetts, but are able to produce the same amount of power because they’re exposed to more sunlight each year. Homeowners in less sunny areas, like Massachusetts, can make up for this disparity by simply using more efficient panels or increasing the size of their solar energy system, resulting in slightly more solar panels on their rooftop!

In order to offer comparison data on how many panels and how much power you will need, we’ve compiled a table that compares average annual energy need to estimate the number of panels required to offset typical energy demand. We looked at data for the 6 most common system sizes that we see active in the EnergySage Solar Marketplace. In order to calculate the below data, we averaged annual kWh production in the top 12 solar states and assumed standard 250 watt panels in order to calculate how many panels you would need. The average system size in the U.S. is 5kW (5000 watts) so you can use that as a benchmark if you’re unclear on what your power needs will be.

How many solar panels will I need? System size comparison table

System Size Average Annual KWH production Estimate number of solar panels
3.5kW 4,954 14
5kW 7,161 20
7kW 9,909 28
10kW 14,165 40
12kW 16,987 48
15kW 21,234 60

The table above assumes that you’re using standard-efficiency panel. However, the number of panels you need to power your home, and the amount of space that your system will take up on your roof, will change if you’re using lower-efficiency economy panels or high-efficiency premium panels. Below is a table that will give you a sense of how much space your system will take up on your roof, whether you choose economy, standard, or premium panels.

How many solar panels can I fit on my roof? System size compared to square footage table

System Size Economy Panels (sq ft) Standard Panels (sq ft) Premium Panels (sq ft)
5 kW 306 254 224
10 kW 612 508 448
15 kW 918 763 672
solar panel system size infographic

The average size of 5, 10, and 15 kW solar panel systems using standard panels.

Perhaps one of the most difficult aspects of sizing a solar panel system is estimating annual energy usage for your household. A number of larger consumer products or add-ons can significantly change your annual kilowatt hour requirements and thus can greatly impact how many panels you will need. For example, if you’ll be running central air conditioning or powering a heated swimming pool in your backyard, the size of your solar panel array could be drastically altered. To get a feel for the energy impact of various products you may have or may be considering for your home, check out this table comparison.

How many solar panels will I need for common household products?

From reviewing the various kWh requirements for everyday household appliances and products, one thing is clear: certain add-ons will dynamically change monthly energy use and solar panel system size. For example, pairing your electric vehicle with solar panels is a great way to reduce carbon emissions and improve energy efficiency, however, it should be planned accordingly considering it could potentially double the size of your pv system. Though it is certainly possible to install a solar system and then add more panels later on to accommodate increased energy needs, the most pragmatic option is to size your system as accurately as possible based on your expected purchases such as an electric vehicle, swimming pool or central air system. Asking yourself “how many solar panels will I need for my refrigerator, my hot tub” and etc is a great habit for any new solar homeowner.