How can I calculate the number of solar panels I need?

How To Determine The Number Of Solar Panels You’ll Need

If you are equipped with the necessary knowledge, determining how many solar panels you need is not too difficult.

Starting with the load you need solar to provide is the first step.

How much kWh is used if it’s a house?

To size solar panels, follow these steps:

  1. How much is the load? How much kWh is used at home?
  2. What is the irradiation level where you are? (Peak.sun-hours)
  3. Theoretical solar system size may be determined using the load and irradiance.
  4. Adapt solar size to take system losses into consideration.
  5. Subtract the modified solar system size from the wattage of each panel.

Estimate the previous year’s energy expenditure and use the irradiance value for your area in kWh/m2/year (Peak-sun-hours) to get the potential solar output required to determine the quantity of solar panels your house requires.

Divide theoretical solar kWh by the individual solar panel’s watt rating after adjusting for the loss factor of 1.44.

How to Calculate the Number of Solar Panels You Need?

How Much Solar Power Do I Need? How to Calculate Your Needs – Understanding Solar Power

How Many Solar Panels Would It Take To Power A Typical Home?

The typical US home is 2500 square feet, which logically translates to an annual energy use of 11000 kWh, or 30 kWh each day.

State-to-state differences in solar panel electricity production and home size do exist, however.

This is due to the fact that the sun’s energy, or irradiance, differs depending on a location’s geography, which is crucial for estimating the cost of a solar farm.

Table: Comparison Of The Average Home Size In Square Feet Across 10 US States

U.S. StateArea (Square Feet)
New Mexico1838

On websites like, historical figures for irradiance may be discovered for your area.

I’ll take 5.322 kWh/m2/day as the average irradiance figure for the USA in order to calculate the peak solar hours.

How much solar energy do I need to run a typical American home? How many solar panels do I need?

You may calculate the potential solar power production using typical US values by multiplying the daily kWh by the irradiance in daily peak-sun hours:

Required solar power is equal to 30000 watt-hours divided by 5.3 peak sun hours, or 5660 watts.

The amount of solar panels required for the typical US home, using 300 watt solar panels, would be:

5660 watts / 300 watts = 18.86 (19) solar panels

However, there are losses in all solar PV systems of roughly 23%.

This may be considered by multiplying the necessary solar power by 1.4:

Adjusted solar output = 5660 x 1.4 = 7924 watts

The exact number of solar panels required, based on 300 watt solar panels, would be:

7924 watts / 300 watts = 26 solar panels

The chosen supplier of solar panels, kits, batteries, and solar control accessories is quickly evolving to be RENOGY.

Based in the US, where the items are made, they have a solid reputation for quality and innovation.

How Many Solar Panels Are Required To Power A Home That Is 3000 Square Feet?

The typical US house needs 7924 solar watts, or 3.17 watts per square foot, based on the average US irradiance of 5.3 peak sun hours per day.

This figure is multiplied by 3000 square feet to give us the 9510 watts of solar energy needed.

9510 watts / 300 watts = 32 solar panels of 300 watts rating each

How Many Solar Panels Will I Need For A Home With Three Bedrooms?

A three-bedroom, two-bathroom US house typically measures 1300 square feet.

With an average irradiance of 5.3 peak sun hours each day, I previously calculated that the required amount of solar energy is 3.17 watts per square foot.

The price of solar panels for a three-bedroom home

1300 square foot x 3.17 = 4121 solar watts

The calculation for the necessary number of 300 watt solar panels is as follows:

4121 watts / 300 watts = 14 solar panels

Without any subsidies, a system of 4000 watts of solar panels would cost $12,000 at an average installation cost of slightly under $3/watt.

How Many Solar Panels Are Required To Power A Four-bedroom Home?

A house in the US with 4 bedrooms and 2 bathrooms is 1700 square feet in size on average.

In the last section, I calculated the required solar output at 3.17 watts per square foot with an average irradiance of 5.3 peak sun hours each day.

Solar calculation for a four-bedroom house:

1700 square foot x 3.17 = 5389 solar output in watts

The number of solar panels required if 300 watt solar panels are utilized may be calculated by:

5389 watts / 300 watts = 18 solar panels

How Many Solar Panels Are Required To Power A Whole Home Off The Grid?

Off-grid solar systems typically consist of solar panels, a solar battery charger, batteries, and an inverter.

In general, you need the same number of solar panels as for a system that is connected to the grid, plus an additional number of panels based on how much autonomy you need.

Assume your house consumes 30kWh per day and that there are 5.3 peak solar hours per day in your area, which is the US average.

If you ignore PV system losses, a 5.7kW solar system might theoretically enough for your requirements.

Correct Solar Calculation

Maybe 75% of the energy utilized in your house is spent during the day.

To ensure an uninterrupted power supply during the night, you must completely charge your battery bank throughout the day.

What if there are multiple days of overcast weather with little sunlight? In this scenario, the lack of energy output would need to be made up by the energy storage battery bank.

I would increase the anticipated solar system size by another 25%, making the system in this example 7.5 kW and the battery bank large enough to power the house for 48 hours without solar energy.

To power a typical US home (30kWh each day), 25 solar panels, each rated at 300 watts, would be required.

A 4 KW Solar System: Is It Worth It?

A 4kW solar system produces about 21.2kWh per day, or 7738kWh per year, at the average U.S. irradiance of 5.3kWh/m2/day (peak sun hours).

This is far less than the average annual energy use for a residence in the United States, which is 11000 kWh.

Given that calculating solar depends on the location and how much the residence consumes, a 4Kw solar system may or might not be able to provide all of the energy needed.

The cost of power, which varies from state to state, also determines whether or not such a system is worthwhile.

The cost of the solar system must also be understood, and state or federal solar subsidies may lower this asset cost.

For Instance, In Houston, Texas, Is A 4kW Solar System Worthwhile?

Determine The Solar Payback For A 4 KW Solar System In Houston, Texas.

How long does a 4Kw solar system in Houston take to pay for itself?

What is the typical solar payback time in Houston, Texas for a 4kW solar power system?

  • City: Houston, Texas
  • Solar system power output: 4kW
  • Solar installation cost = $10960 – 26% federal tax credit = $8110
  • Irradiance level at Houston, Tx = 1552 Peak Sun Hours
  • Power generated by solar panel system = 1552 x 4kw = 6208kWhrs (kilowatt-hours)
  • Houston home electricity cost = 10.98 cents/kWh
  • Yearly savings = solar output x electricity cost = 6208 x 10.98c = $690
  • Solar payback time in Houston, Tx= solar cost/annual savings = 8110/690 = 11.75 years

The payback time may be as little as nine or ten years, or even fewer.

Professional solar installers will provide you with realistic quotes based on their past experience and the degree of irradiance in your area.

What Should The Price Of A 4kW Solar System Be?

In the US, the average price to build a solar power system is little under $3 per kW.

There are differences per state; for further information, check the table below:

Table 6: Cost Of A 4Kw Solar Power System Per Us State

StateInstallation price Per Watt ($) 2021Cost of 4kW Solar System
New Hampshire2.83$11440
New Jersey2.81$11240
New Mexico3.22$12880
New York2.87$11480
North Carolina2.68$10720
North Dakota2.67$10680
Rhode Island2.92$11680
South Carolina3.13$12520
South Dakota2.39$9560
West Virginia2.64$10560

What Is The Price Of An 8Kw Solar System?

Based on the national average pricing for solar power systems, you should budget roughly $24000 for an 8kW system.

To get a more precise estimate, refer to the table above (multiply the results fo a 4kW system by 2).

For 5kW, how many solar panels am I going to need?

The precise number of solar panels required for a 5kW solar power system may vary depending on the area’s local irradiance.

The math is as follows:

  • 5000/300 = 17 solar panels 300 watt rating
  • 5000/200 = 25 solar panels 200 watt rating
  • 5000/100 = 50 solar panels 100 watt rating

What Should The Price Of A 6.6 Kw Solar System Be?

Depending on your state, you might expect to spend about $19500 for installation using the average cost in the USA.

How Many Solar Panels Are There In A 6.6 KW System?

A 6.6kW solar power system will include:

  • 6600/300 = 22 solar panels rated at 300 watts each
  • 6600/200 = 33 solar panels rated at 200 watts each
  • 6600/100 = 66 solar panels rated at 100 watts each

What Kind Of Electricity Can A 6.6 KW Solar Array Generate?

A 6.6kW solar power system will produce the following with an average irradiation of 5.3 peak sun hours/day:

6600 x 5.3 = 34.98kWh/day or 12767kWh/year

Depending on the irradiance value from state to state, this output may change upwards or downwards.

How Much Electricity Is Generated Daily By A 7 Kw Solar System?

A 7kW solar system will result in the following using the 5.3 peak sun hours per day used as the U.S. average irradiance:

7000 x 5.3 = 37.1kWh/day or 13541kWh/year

Depending on the peak solar hours value from state to state, this production may be more or less.

For A 6Kw Inverter, How Many Solar Panels Am I Going To Need?

Generally speaking, a solar system should provide 6 kW of solar output and match the inverter size.

This is so that inverters may operate at their peak efficiency.

A 6kW solar power installation will require:

  • 6000/300 = 20 solar panels, each rated at 300 watts each
  • 6000/200 = 30 solar panels, each rated at 200 watts each
  • 6000/100 = 60 solar panels, each rated at 100 watts each

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Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.