multiple solar panels on a house

A home that consumes 1,000 kWh per month will normally need between 20 and 30 solar panels. The exact number changes depending on the specifications of the chosen panel model, as well as the sunshine available at the project site. Before purchasing a solar energy system for your home, an important step is finding out how many solar panels you need.

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1. How many kilowatt hours (kWh) do you use per month?
2. What percentage of this power do you want to offset with solar?
3. Which state is your house in?

Minimum PV System Size (in watts)
Recommended PV System Size (in watts)

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Solar panels have been successful as a clean energy source thanks to their modular design. You can purchase just the right number of panels according to your home needs, instead of having to choose between predetermined system sizes. Solar energy can adapt to buildings of any scale, ranging from small homes to large industrial parks.

To size a solar system correctly, the best recommendation is getting in touch with a qualified solar contractor. He/she will also help you in knowing how much solar panels cost to install. A residential system has an average installed price of $3 per watt. Solar installers consider the following factors to calculate the number of panels needed:

  • Local sunshine: How much energy a solar panel produces depends on the sunlight received. If two homes in different locations need the same amount of energy, the home with the sunniest weather will need less panels.
  • Home size and energy usage: A larger home typically needs more panels to cover its consumption. However, usage habits and the efficiency of home appliances are also important. Two homes of the same size can have very different energy needs.
  • Panel specifications: The power rating of panels varies depending on the model and manufacturer, but most range from 250 watts to 330 watts. For any given energy production target, you need fewer panels if their individual wattage is higher. When roof size is limited, efficient panels with a high wattage can make the system more compact.

How Many Solar Panels do I Need – Solar System Size Comparison

System Size

Average Annual KWh Production

Estimated Number of Solar Panels Needed

4kW

5,000

10-12

5kW

6,250

13-15

6kW

7,500

15-18 

8kW

10,000

20-24

10kW

12,500

25-29

12kW

15,000

30-35

20kW 

25,000 

50-59

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How to use a Calculator to Calculate how Many Solar Panels you Need

Our solar calculator can estimate the number of panels needed for your home. The tool works by taking your average monthly energy usage in kilowatt hours (kWh).

  • Calculators that use kilowatt hours are more accurate because they consider your exact energy needs
  • Those that ask for home area must assume the electricity consumption

Each electric company has a different power bill format, but they all display your electricity consumption for the billing period. The exact description will vary, but you should look for a term such as “kWh used” or “kWh consumed”.

Solar calculators also ask for your home location to determine how much sunshine is available. Based on those two values, they can estimate the system size in kilowatts. Some solar calculators assume a wattage for panels, while others ask you directly. Based on the total kilowatts and the rated watts per panel, the calculator can determine how many are needed.

woman calculating how much she saves by using solar panels on her house

It is important to understand the difference between kWh savings and dollar savings. kWh savings refer to the amount of energy that your panels produce. On the other hand, dollar savings are obtained when the solar electricity production is multiplied by the kWh price.

How Many Solar Panels do you Need for 1000 kWh per Month?

A family with several siblings can easily reach a monthly consumption of 1,000 kWh. In places with expensive electricity, this results in monthly electric bills of over $200. However, solar power is an effective solution to reduce energy expenses.

As explained above, the number of panels needed to reach 1,000 kWh per month changes depending on local sunshine and panel wattage. To simplify calculations, solar radiation is specified in peak sun-hours per day. Weather scientists calculate this value by measuring the total sunshine in a location and converting it to equivalent hours of peak sunshine.

  • Peak sun hours should not be confused with daylight hours
  • Since sunlight is moderate in the early morning and late afternoon, these hours do not count as complete peak sun hours
  • You may find a site that gets 12 hours of average daylight, and 6 peak sun hours per day

There are many online databases that provide peak sun hours based on site coordinates, including the Atmospheric Science Data Center from NASA. Once you know the peak sun hours, estimating the number of solar panels needed for 1,000 kWh is simple.

  • The first step is calculating the kilowatts needed. You must simply divide the average daily kWh by the peak sun hours
  • Assuming a 30-day month, an electricity generation of 1,000 kWh is equivalent to 33.33 kWh per day
  • If the site gets 6 peak sun hours per day, you need 5.56 kilowatts

Since no energy conversion system is perfect, you cannot assume the solar array will deliver its theoretical production. To compensate for this, you can increase the calculated wattage by 20%. In the example above, adding 20% yields a capacity of 6.67 kW or 6670 watts. The final step is dividing the total wattage by the individual panel watts.

  • If you use 250W panels, you need 27 of them
  • On the other hand, if they are 330W panels, only 21 are needed

Solar shingles are smaller than panels, and their wattage is lower as a result. However, you can use the same procedure to estimate how many are needed. For example, if the amount of power needed is 5,000 watts and each shingle is rated at 50W, you need 100.

How Many Solar Panels do you Need for a 2000 Sq. Ft. Home?

Estimating the number of panels based on home area is an indirect approach, since you must assume the kWh consumption. Some homes have more efficient appliances, and habits also influence electricity usage. However, average values can be calculated from official data:

  • The US Energy Information Administration estimated that the average home uses 867 kWh monthly
  • The US Census Bureau determined that single-family homes have an average area of 2467 square feet
  • When dividing these values, you obtain 0.35 kWh per square foot

Assuming 0.35 kWh for a 2,000 sq. ft. home, the estimated electricity consumption is 700 kWh. At this point, you can use the calculation procedure described in the previous section. Considering 6 peak sun hours per day and 300-watt panels, you need 16 to produce 700 kWh each month.

If you have limited roof space, the best recommendation is installing the most efficient solar panels available. This will maximize the watts installed per square foot, compensating the area limitation. Finding out how efficient solar panels are is simple: you must only divide their individual wattage and area. The panels with the most watts per square foot have the highest efficiency.

How Many Solar Panels do you Need for Common Household Items?

If you are considering solar energy for your home, you may also be asking how many panels are needed to power specific appliances. However, it is important to understand how solar generation works:

  • Solar systems deliver most of their energy production in the hours around noon
  • During the early morning and late in the afternoon, solar generation is much lower. This is because there is less sunlight reaching the panels
  • Households have the highest energy consumption in the evening and early morning

Since solar panels depend on sunlight, you cannot control their electricity production. Powering home appliances directly with panels is impractical and potentially dangerous, unless you use a solar battery to store energy. If you connect home appliances directly to the panels and inverter, a dark cloud passing over your home will shut off the power. At night, you would have to switch to the local power supply anyway.

house appliances next to a solar panel

The most practical solution is synchronizing solar systems with the local power supply, which lets them operate as a single power source. When solar generation cannot power your home appliances by itself, the rest of the energy comes from the grid. If your panels have surplus production, you can send it to grid to get a credit on the next electricity bill.

Sunlight is a variable input, and your electrical devices need 24/7 availability. For this reason, you cannot compare the wattage of panels directly with that of home appliances. Instead, you must balance the kWh produced with the kWh consumed. The following table estimates the number of solar panels needed for common appliances, assuming 300-watt panels and 5 peak sunlight hours per day.

Appliance

Usage

Monthly kWh

Panels Needed

20 LED bulbs

10 watts each

6 hours per day

36

1

12,000 BTU/h

Mini-split AC

SEER 16 efficiency

8 hours per day

180

5

Refrigerator

Always on

150

4

Water Heater, 5 kW

2 hours per day

300

8

This table considers the most power-hungry appliances found in homes. Most small appliances and electronic devices have a very low consumption, which does not even match the production of one panel.

How Many Hours of Daily Sunlight Does Your State Receive?

The sunlight available to produce electricity varies greatly throughout the United States. Southwest states like California and Arizona get the most sunshine, while northeast states like New York and Massachusetts get the least.

However, you should not discard solar power just because you live in a state that isn’t sunny. For example, New York only gets moderate sunshine, but it has very high electricity prices. Solar panels are worth it in this case, since they achieve high savings even with reduced production. Saving 750 kWh when you are charged 25 cents/kWh is better than saving 1,000 kWh at 12 cents.

After estimating how many panels are needed in your home, you can make better purchasing decisions. Keep in mind that you don’t have to pay the full system cost upfront. Many banks finance for solar panels, and you can pay off the loan with the electricity savings achieved. Leasing solar panels is also a viable option, where you pay a monthly price instead of purchasing the system. Your local solar installer may offer several purchasing options, adapting to your needs.

We hope you liked this article. Please rate it or leave us a comment.

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2 Comments

    1. Leonardo

      Hello Akib,

      This is entirely depending on your location. Check on your bill what is your average consumption in kWh. Then, go to our article and look for “What Size and Wattage Do You Need?”. Use the equation that you will find there to estimate the power capacity that you will need. If the system will be grid-tied, then change the k factor to 0.77.

      With this power capacity, you need to then find out how much energy your PV system will be generating and saving more accurately. Compare with your consumption and costs, and if it’s what you are looking for, then divide the power capacity by the nominal STC power of the solar panels (somewhere between 350-400Wp for your case).

      If you fill out one of the forms that are on all the pages on our website, a local solar installation company near you can help you with all these details.

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