# How Many Solar Panels Do I Need For 1000 kWh Per Month?

Updated on November 22, 2022

How much home solar to run 1000 kWh per month?

## How Many Solar Panels Do You Need For 1000 kWh Per Month?

### How Do I Calculate How Many Solar Panels I Need?

Here are the steps you need to follow to calculate the size of your solar panel system:

1. Estimate your home’s energy usage in kWh per day
3. Calculate the theoretical size of the solar system needed in kW
4. Adjust the system size to account for losses
5. Divide the final kW solar system size by the individual solar panel watts

A home consuming 1000 kWh per month would need 27 solar panels, each rated at 300 watts. This assumes an average irradiance of  4 kWh/m2/day (peak-sun-hours) and does not include PV system losses of up to 23%. Good practice is to add 20% to 25% more panels to account for system losses.

### Video – How to calculate how many solar panels you need for 1000 kWh per month

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## How Many Solar Panels Would I Need For 1000 kWh Per Month?

Every solar calculation begins with the load, in this case 1000 kWh. You begin by working out how many kilowatts of solar power would be needed, before calculating the number of solar panels.

It sounds easy, but there are a few things you need to know.

First of all, solar panels don’t put out the same power in every location – it depends heavily on the irradiance, or sun’s energy, in your geographic location.

Secondly, the theoretical power output from a solar panel array is never what you actually get! This is because there are losses in all solar power systems. These losses can be around 23% of the total output, so not insignificant.

### Infographic – Solar Panel Sizing Takes 10 Major PV Losses Into Account

By far the biggest factor affecting solar panel output is irradiance, and this varies by geographic location.

The two worked examples following show the difference in the number of solar panels needed for a home using 1000kWh per month in San Francisco, Ca and Glasgow, UK.

## How Many Solar Panels Do I Need For 1000 kWh Per Month In San Francisco, Ca?

How many solar panels needed for 1000 kWh in San Francisco is hugely affected by the high irradiance

### Solar calculation – panel sizing for San Francisco:

• City: San Francisco
• Home energy use: 1000 kWh per month
• Solar system losses: 23% (same as multiplying energy needs by 1.4)
• Solar energy required per month: 1000 kWh x 1.4 = 1400kWh/month
• Solar energy required per year: 1400 kWh x 12 = 16800kWh
• Irradiance at San Francisco, Ca = 2089.1 Peak Sun Hours/year
• Solar system size required: 16800kWh/2089.1 PSH = 8.042kW
• How many 300 watt solar panels required?: 8042 watts/300 watts = 27 solar panels

### What is the solar system payback period in San Francisco?

Installation costs for a solar power installation in SF is about \$2.5 per kW, so the cost of an 8.042kW system would be about \$20000.

In the calculation below, I’ll work out how many years it will take to recover that capital cost:

• San Francisco residential electricity cost per kWh = 25.7 cents/kWh
• Yearly savings = energy usage x electricity cost = 12000kWh x 25.7 = \$3084/year
• Solar payback time San Francisco = solar cost/yearly savings = \$20000/3084 = 6.5 years

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## How Many Solar Panels Do I Need For 1000 kWh Per Month In Glasgow, UK?

There should be a big difference in the number of solar panels required in Glasgow, because the irradiance is much lower than in California – see the screenshot from GlobalSolarAtlas.info below:

Hoe many solar panels would you need to power 1000 kWh in Glasgow, UK?

The Direct Normal Irradiation 678.8kWh/m2/year (also called Peak-Sun-Hours) in Glasgow is more than 3 times less than in California. Now let’s do the calculation again:

### Solar calculation – panel sizing for Glasgow, UK:

• City: Glasgow, UK
• Home energy use: 1000 kWh per month
• Solar system losses: 23% (same as multiplying energy needs by 1.4)
• Solar energy required per month: 1000 kWh x 1.4 = 1400 kWh/month
• Solar energy required per year: 1400 kWh x 12 = 16800kWh
• Irradiance in Glasgow, UK = 678.8 Peak Sun Hours/year
• Solar system size required: 16800 kWh/678.8 P.S.H = 24.75kW
• How many 300 watt solar panels required?: 24750 watts/300 watts = 82 solar panels!

Clearly, this is a huge difference and it probably isn’t worth it to install solar in Scotland.

### How Much Power Does An Average House Use?

1000 kWh is not far off the US monthly average for a typical home, which is 900 kWh/month. This equates to about 30 kWh per day.

### How Do I Calculate kWh?

It is possible to estimate a home’s energy needs in kWh, but it isn’t very accurate. You would have to add up all the wattages of ‘normal’ appliances (you’ll see what I mean by ‘normal’ later on in the post.)

You also need to guess how many hours per day a particular appliance would be used. As you can see, the approach isn’t too accurate.

What I call ‘normal’ appliances are those with a constant wattage i.e. you switch it on and it takes a constant amount of power in watts.

How many solar panels would you need to run air conditioning?

Some appliances aren’t like that. If an appliance uses a compressor, such as refrigerators, heat pumps, freezers and air conditioners (AC), then it isn’t so obvious what the average power consumption is.

These types of appliances run in cycles. That is, sometimes they are running, sometimes stopped and other times starting up. Compressor motors are subject to surge current.

For the above reason, it’s often difficult to estimate average watts. The best way is to simply take last year’s energy usage from your utility bill, which will be a good estimation of what you use.

## Is 50 kWh A Day A Lot?

Yes, 50 kWh is quite a lot. The average home energy usage in the US is 11000 kWh per year, which is 916kWh per month or just over 30 kWh per day.

So 50 kWh is almost 1.7 times more than the US home average.

## How Many kWh Per Day Is Normal?

‘Normal’ depends heavily on the kind and size of home you have, and the location.

Homes in very hot or very cold locations will probably use more electricity, expecially if using reversible AC units. The US average is about 30 kWh per day but the usage per state can vary wildly.

### Table – Compare kWh usage per day for 20 US States

 State Average kWh used per month Ave kWh used per day 1211 40 632 21 557 18 723 24 1078 35 1088 36 1005 33 1273 42 551 18 1220 40 860 28 629 21 602 20 1205 40 1142 38 602 20 1124 37 1174 39 894 29
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## How Many kWh Does A Solar Panel Produce Per Day?

#### Discover your solar saving potential

Solar panel output is determined to a great extent by the irradiance at a particular location. Once you know this irradiance value, it’s quite easy to work out how many kWh any size panel will produce each day.

Power output = solar panel size in watts x peak-sun-hours

### Table – How many kWh does a solar panel produce per day in different locations?

 City New York, NY Birmingham, UK Lisbon, PT Brisbane, AU Nairobi, KN Irradiance (peak-sun-hours/day) 4.086 2.165 5.163 5.275 3.955 100W solar panel output per year (kWh) 149.1kWh 79kWh 188.5kWh 192.5kWh 145.8kWh 100W solar panel output per day (kWh) 408.6 watts 216.5 watts 516.3 watts 527.5 watts 395.5 watts
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## How Much Does A 1000 Kw Solar System Cost?

Installation costs for domestic solar are reducing all the time, spurred on by healthy competition, but there are still differences between the US States. Here’s a list of several States, with average costs per solar kW installed:

## How Many kWh Does A 12kW Solar System Produce?

The exact amount of kWh generated by a 12kW solar power system depends mostly on the irradiance in the installation’s location.

### How Many kWh Does A 12 kW Solar System Produce In San Francisco, Ca?

The irradiance value in San Francisco is 2089 peak-sun-hours per year, so the calculation is:

Energy generated 12 kW solar in San Francisco = 12000 x 2089 = 25.68 kWh per year (68.7kWh/day)

### How Many kWh Does A 12kW Solar System Produce In Glasgow, UK?

In Glasgow it’s a very different story, as the irradiance is very low at 678.8 peak-sun-hours/year.

Energy generated by 12 kW solar in Glasgow = 12000 x 678.8 = 8.1246 kWh per year (22.3 kWh/day)

## How Many Solar Panels Does It Take To Make 2000 kWh A Month?

This depends heavily on your location, because the sun’s energy varied according to geographic location.

For example, in Las Vegas the irradiation is 7.492 kWh/m2 per day, or put another way, 7.492 Peak-sun-hours. 2000kWh per month equates to 65.75 kWh per day, which is a lot of power!

The solar power required = 65,750 watt-hours/7.492 peak-sun-hours = 8.776 kW

### How many 300 watt solar panels to make 2000 kWh/month in Las Vegas?

8776 watts/300 watts = 28 solar panels of 300 watts each.

### How many 300 watt solar panels to make 2000kWh/month in London, UK?

London’s irradiance is 2.398 Peak-sun-hours, so the equation becomes:

The solar power required = 65,750 watt-hours/2.398 peak-sun-hours = 27.418 kW

As you can see, this is a massive difference!

Number of solar panels required = 27418/300 = 91 solar panels, each 300 watts.

### Table – How Many 300W Solar Panels Needed for Monthly Loads Between 300 Watts and 1500 Watts.

The following table assumes an average irradiance value of 4 peak-sun-hours and individual solar panel size of 300 watts.

 Home load in kWh Number of 300 watts solar panels required (irradiance of 4 peak-sun-hours) How Many Solar Panels Do I Need For 300 kWh Per Month? 8 solar panels of 300 watts each How Many Solar Panels Do I Need For 400 kWh Per Month? 12 How Many Solar Panels Do I Need For 500 kWh Per Month? 14 How Many Solar Panels Do I Need For 800 kWh Per Month? 24 How Many Solar Panels Do I Need For 700 kWh Per Month? 20 How Many Solar Panels Do I Need For 1500 kWh Per Month? 42 How Many Solar Panels Do I Need For 20 kWh Per Day? 17 How Many Solar Panels Do I Need For 100 kWh Per Day? 83
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