Comparing Solar System Sizes

Five typical sizes of system:

  • 1kW
  • 2kW
  • 3kW
  • 4kW
  • 5kW

This is based on the size rating of one of the two main parts of any solar system; the inverter. The power capacity of the solar panels themselves tends to vary depending on which panel brand you choose to go with. For instance, you may choose a 1.5kW inverter and then the closest value you can get with your selected panels is 1.6kW.

So how do you best select which of the five typical sizes suits your needs? It usually comes down to three main factors; price, physical space and energy requirements.


Despite the fact that the government rebates on solar continue to drop, the affordability of solar is actually increasing. The reason being that a large scale global uptake of solar has driven down manufacturing costs to the point where solar systems now are under half the price they were when the largest government rebates were being offered.

How much you are willing to pay for a solar system can be the limiting factor for the size that you invest in. The table below shows the current price range you’d expect to see for each system size.

Prices (£)
System Min Max
1kW Solar System £2,500 £3,500
2kW Solar System £3,000 £4,000
3kW Solar System £4,000 £5,500
4kW Solar System £5,000 £6,500
5kW Solar System £6,500 £8,000

Physical Space

The average 190W solar panel is about 1.6 m x 0.8 m. That is about 1.3 m2 per panel, which equates to approximately 6.8 m2/kW. You will want to ensure that whatever system size that you are considering, is going to be able to physically fit on your roof.

For 1W and 2kW systems especially, all panels are going to have to be facing exactly the same way, both in terms of direction and angle. This means that you can not have any of the panels facing north, some facing east.

For 3kW and above you can get away with two different roof faces for your panels, because the inverter will more than likely have the proper number of ports to support doing this.

Most importantly, when measuring up your roof, be aware that optimally you will want the panels to be pointing somewhere north of due west or due east. As soon as they start facing south, you start to lose potential solar production, which means less energy that you can make from your system.

Energy Requirements

So, hypothetically you can afford to spend ££11,000 and easily have the space for a 5 kW system. Is this the best option for you financially? The rule of thumb is that the best rate of return on that solar investment comes when you most closely match the power generated from your system to your actual usage.

As a rough guide, you can use the table below to assess which size system most closely matches your energy needs. The numbers are for a 1kW system and so can be multiplied by whatever system size you are looking at e.g. 2kW system multiply the numbers in the table by 2. To compare, your average daily consumption per billing period should be given on your electricity bill.

1 kW System Total Average Daily
Month kWh (units) kWh (units)
Jan 181 5.8
Feb 155 5.3
Mar 152 4.9
Apr 132 4.4
May 107 3.4
Jun 94 3.1
Jul 101 3.3
Aug 120 3.9
Sep 137 4.6
Oct 167 5.4
Nov 171 5.7
Dec 184 5.9


The best way to determine what size solar system best suits you is to look at the three key factors of price, physical space and energy requirements. You can use the numbers given above as a rough guide but note that prices will change as time goes forward.

Additionally the figures given for number of units generated per day are heavily dependent on what direction the panels are facing and where you live.

Getting a Solar Power Quote from a MCS certified installer in your local area is easier than ever.

Proceed to get a quote now!

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