How Many Solar Panels Do You Need? Guide to Calculating Solar Panel Requirements

When it comes to renewable energy options there is no denying that solar power is a firm favourite for residential properties. In fact, walk down any street in the UK and it would seem unusual if you didn’t spot at least a few houses with solar panels proudly positioned on their rooftops.

This popularity is for several reasons ranging from the reliability and flexibility of solar panels to cost efficiency, the generous guarantees offered by governments, and increased home value.

If you are considering getting solar panels for your home, you may be asking yourself: “How many solar panels do I actually need?” Well, you are in luck. Because in this guide, I will walk you step-by-step through everything you need to know to calculate your solar panel requirements.

How many solar panels do I need?

Here’s a quick table with how many solar you may need based on your annual energy consumption:

Annual Energy ConsumptionNumber of Solar Panels
(250W each)
Number of Solar Panels
(400W each)
Consumption Level
1000 kWh32Very Low
2000 kWh64Low
3000 kWh96Average
4000 kWh127Average
5000 kWh1510Medium-High
6000 kWh1812Medium-High
7000 kWh2114High
8000 kWh2415High
9000 kWh2717Very High
10000 kWh3019Very High
Number of solar panels needed based on annual consumption and panel capacity

However, there are many additional factors to consider when calculating the number of solar panels you will need for your home. Let’s have a look at everything you need to know to size your solar system!

Understanding Solar Panels and Their Capacity

When it comes to solar panels there are several options available on a commercial basis. For electricity production, these include monocrystalline, polycrystalline, and thin-film panels. 

Which is right for you will depend on several factors. 

For example, monocrystalline panels are made from a single silicon crystal. This helps to produce a panel that is highly efficient. However, producing these panels is relatively expensive and panels tend to be considerably smaller. This makes monocrystalline panels ideal for those with less space, but reasonable budgets. 

Polycrystalline use a mix of silicon crystals, this makes them cheaper to manufacture and allows for panels to be larger. However, they are less efficient compared to monocrystalline panels. Typically, these are ideal for those with plenty of space for solar panels. 

Thin-film panels use a mix of different materials. Although these types of panels have come on considerably in recent years and have many benefits, they are rarer to find on residential properties due to their lower levels of efficiency.

Solar panel capacity

Solar panel capacity is typically measured in kilowatt-hours (kWh). This number simply shows how many kilowatts a solar panel could produce in an hour. Although the number can vary vastly based on factors such as materials used and panel size, an average commercial solar panel produce around 0.25 and 0.4 kWh. 

Evaluating Your Energy Needs

You cannot assess how many solar panels you may need before you know how much power you use or may use in the future. Once you know this you can make a much better judgement on just how many solar panels you need. 

Your energy usage will depend on a whole range of factors. Some of these include: 

  • How big your home is
  • How many people live in your home
  • How much time each resident spends in the home
  • How efficient are your electrical appliances
  • How many electrical appliances you have
  • How often you use your electrical appliances
  • How well insulated your home is (if you use electric heating)

Here are some examples of common household items and their typical energy requirements: 

  • Refrigerator: 100 to 400 kilowatt-hours (kWh) of electricity per year
  • Washing machine: around 400 to 1,200 kilowatt-hours (kWh) per year
  • Dryer: around 1,800 to 5,000 kilowatt-hours (kWh) per year
  • Dishwasher: around 1,200 to 2,400 kilowatt-hours (kWh) per year
  • Oven: around 2,000 to 5,000 kilowatt-hours (kWh) per year

Of course, you need to be as specific as possible when calculating your own energy consumption, as this will help better inform your calculation.

Here are 3 good methods to help you do this: 

  • Check your energy bill, as this will often outline how much energy you have used in that month
  • Check your smart meter to see how much energy you are currently using 
  • Use a free online energy usage calculator

Estimating Solar Panel Output

How much energy you need your solar panels to generate directly correlates to how much energy your home uses – that should come as no surprise. 

So, let’s use an average UK household as an example. According to OVO Energy, the average UK home uses 3731 kWh of energy per year. So, as a general rule, you will want to install panels that cover this need. 

However, several other factors come into play. For example, factors such as your geographic location, the orientation of your panels and angle can impact the efficiency of solar panels. 

So, if you have a south-facing roof that is suitable for panel installation, you could see much greater energy production compared to the same panels if they were mounted on north facing roof. 

It is important to remember that even though a panel has the ability to capture a certain amount of the sun’s energy, doesn’t mean it will. If conditions for you your solar panels aren’t optimal, you may need to invest in further panels in order to help you reach your desired capacity.

NOTE: Typically it is best to slightly overestimate your energy needs when installing solar panels. This will help cover you for future growth in energy requirements. Plus, the surplus energy created can either be stored in batteries for use with an inverter during nighttime hours or sold back to the grid. 

Calculating Solar Panel Requirements

Here is your step-by-step guide for calculating exactly how many solar panels you may need: 

  1. Calculate your daily energy consumption in kWh using the methods outlined above (we will use 10 kWh as an example here).
  2. Multiply this number by the peak sunlight hours for your area, this will vary throughout the year, but you can use the UK average (which was 4.9 hours in 2022)
  3. Calculate the daily output of your chosen solar panels by multiplying the panel’s watts by the average daily hours of peak sunlight (you can use 300 watts as an average if you haven’t yet chosen a system):

    300 watts x 4.9 hours = 1470 watts

  4. Factor in potential lower efficiency based on factors such as position. You can use 0.75 as an average:

    1470 watts x 0.75 = 1102.5 watts

  5. Divide the daily energy consumption by the total daily kWh:

    10 / 1.1 = 9.09

This final number is the total number of panels you will need. So, in the example above you would need about 10 panels to cover your daily needs. 


It is clear that there is a lot to consider when calculating how many solar panels you may need for your home. After all, it isn’t always that easy to calculate exactly how much energy you may need in the future. 

Luckily, with government schemes such as the Smart Export Guarantee (SEG) you minimize the potential for wasting the energy you don’t use. This can make slightly overestimating your requirements less risky. 

If you are still a little confused, don’t worry! Any quality solar panel installer will be able to offer you bespoke advice on how many panels you need based on your unique circumstances.

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