How to Size a Solar System

With traditional forms of energy-depleting, and scientists advising that the Earth is suffering from pollution, there has been a concerted effort to find greener and cheaper alternatives to fossil fuels. Of the ones that have become the most successful, solar power and wind power are seen as the most effective.

These types of alternative energy are also a good way for homeowners to make a difference to the environment as well as saving money on their energy bills. Although wind energy may not always be effective, especially if you live in an area that doesn’t get high winds, solar energy is far easier to collect and store.

This article will look at the types of solar systems you can get, and how you should size your system to get the best results.

Setting the Starting Point

Buying solar panels for your home is a big investment, so it is important that you consider all the factors before you start. A good place to begin is to set your limits first, that way, you can set your goals relative to those limits. There are three main points that you need to consider:

  1. Your Budget
  2. The Available Space
  3. How Much Energy it Will Offset

Your Budget

Because installing solar systems can become expensive, you need to know from the beginning how much you are willing to spend. This should be a realistic figure and one that you are going to stick to. It can be easy to stretch the budget once things progress but ensure that you are always within your means.

Space Available

The amount of space that you have to place panels will directly influence how much energy you are going to produce. Although a number of properties will have their panels on the roof, this option might not be available to you, so you need to assess where and how many panels you can have.

Energy Offset

This relates to the amount of energy the solar system will offset towards your usual energy use. You obviously want to offset as much as possible, however, the previous two factors will play a part in this. There are also other factors that will impact on this, and they will be covered later in this article.

Calculate Your Home’s Energy Usage

To find out how much energy your home is using, you need to calculate the average monthly figure. To do this, you need to collect the electricity bills for the previous 12 months. Add together the total kWh on each bill and divide this number by 12. This will give you the average for each month. You can then divide this number by 30 to work out your daily usage. Although some smart meters now do this for you, it is always a good idea to check for yourself as well.


When you have reached this figure, you need to find the solar insolation table that relates to the nearest location to you. This table will provide you with the average number of hours per day that the sun produces peak sunlight in your area.

Calculate Your Energy Needs

Once you have the averages from your home usage and the insolation in your area, you can use the following calculation:

Daily kWh / Insolation hours = number of kW

You can then use the following calculation to work out how much your solar system needs to produce for your home.

Number of kWh x 1.3 = Number of kW

For example, if your first calculation resulted in 3 kW, then this would be 3 x 1.3 = 3.9 kW. This would be the amount of kW your solar system would need to produce to meet your home’s needs.

Number of Solar Panels

Now that you have calculated how much energy your house uses, and how much your solar system needs to produce, you need to see how many solar panels it will take to produce that energy.

To find out how many panels you need, you take the daily kWh requirement for your home, and divide it by the efficiency of the solar panel, this will give you the number of panels that you need. The next step, is to find out if you have enough space to accommodate all of the panels you need.

The space you have available depends on a number of factors, for example, the slope of your roof needs to be facing in the right direction to get the maximum level of sunlight. This also relates to the angle of the roof you will be using.

Another factor is the roof area available. If there is not enough room to accommodate all of the panels, then you will need to think about alternative locations. Other areas that you can place panels are on the ground but this will take up space on your land.


Solar systems come with various lengths of warranty depending on the type you buy and the company you use. In general terms, warranties can vary between 10 to 25 years, so this is an important factor to consider.

If you don’t have the budget to factor in a longer warranty system, then you need to ensure that the system will provide enough energy to cover the cost of the system you choose.

Government Schemes

Before you buy your solar system, check with your local government to see if there is a scheme that will help with the cost. Many governments have an incentive scheme to help homeowners switch to solar energy.

There are many factors to consider when choosing a solar system, but the benefits of using solar energy on the environment are worth the effort. It is always important to consider many solar system companies before deciding on the one that is right for you.

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