Guide To Solar Panel Efficiency

Overview: What You Need To Know About Solar Panel Efficiency

This is a 10-minute long guide. Feel free to bookmark this page for an in-depth read later, and read this overview instead…

The average efficiency for solar panels is around 20%. However, there are plenty of panels that offer higher levels of efficiency, such as the Longi Hi-Mo 9, sitting at 24.43%. 

There are dozens of factors that affect a solar panel’s efficiency including: 

Want to jump right in and get the most efficient solar panel system for your property? 

Click over to our solar panel page here; our clickable tool will do all the hard work so you don’t have to!

Average Solar Panel Efficiency

When looking at panels from different manufacturer’s you’ll notice multiple ratings for efficiency. A typical solar panel efficiency measure will take into account how much natural light your units can convert into usable electricity in your home. 

Average solar panel efficiency currently sits at around 20%. Manufacturers now produce panels that sit anywhere in the 15%-24% range when it comes to efficiency. 

At the lower end you’ll have panels included in cheap DIY kits, achieving efficiency ratings of nearing 15%. These are suitable for setups such as those to power an external workshop, or to power basic appliances in a motorhome. 

However, if you’re looking for a solar panel system with higher efficiency ratings to power your home, you’ll want panels from a leading manufacturer. As an example, a panel like the LONGi Hi-Mo 9 will hit a much higher efficiency rating of 24.43%.

We only fit high efficiency panels from the best brands in the business. To spec your high efficiency solar panel system, jump over to our solar panel page here. 

What Affects A Solar Panel’s Efficiency?

To achieve efficiency levels that manufacturers suggest their solar panels can achieve, you’ll need to have your solar panel system carefully designed. 

Below, we’ll cover the most common things that affect the efficiency and electricity production of your system. 

Roof Pitch & Orientation

Both the tilt angle of your panels and the direction they face has a huge bearing on how much electricity they can produce. 

On average, the best tilt angle for solar panels is 30°. And for direction, you'd want them to be facing due south. 

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However, if you're not able to direct your solar panels due south, you may have to adjust your solar panel's tilt angle to maximise their efficiency. 

As you can see in the Energy Saving Trust’s table above, solar panels might be more efficient when set to an angle other than 30°, depending on which way your roof is facing. 

Not sure if your roof pitch and direction is suitable for your solar panels? 

Jump over to our solar panel installation tool here, or if you’ve got any questions, you can speak to our experts here. 

Age & Degradation Rate

Age and degradation rate both affect solar panel’s efficiency to produce electricity. 

Whilst cheap DIY solar panels may seem like a bargain initially, they’ll generally have a much worse efficiency rate on day 1, and this reduces exponentially as the years pass by. 

On average, solar panels see a degradation rate of 0.5%-1% each year, with a common degradation rate being around 0.7%. This is something that’s important to consider when purchasing panels. 

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A solar panel with a 1% degradation rate over 25 years will be working at around 78% of its original efficiency towards the end of its lifespan.

However, buying solar panels that have a lower 0.5% degradation rate would mean that during the same 25 year period, the panels will still be producing around 88% of what they were originally!

Our systems are carefully designed and only incorporate panels with a low degradation rate. 

Get prices on your system by jumping over to our solar panel page here. 

Inverter Type

Solar panels absorb sunlight and essentially, produce direct current (DC) electricity. 

However, properties in the UK use alternating current (AC). The job of the inverter is to convert DC to AC power, so it's usable in your home. 

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The type of inverter you use will affect your solar panel system's efficiency dramatically.

A common type of inverter is a string inverter. This takes the power produced by a "string" or group of solar panels at once. If one panel in the string is lacking in efficiency, it could reduce the efficiency of the whole string. 

A much better option is to use a micro inverter. This allows each panel to produce its electricity individually. 

Have a panel that's degraded faster than another, or shaded by trees? 

A micro inverter ensures panels don't see a huge drop in efficiency overall, simply because one panel isn't operating efficiently.

Our solar panel tool here can spec your system, incorporating an inverter that maximises solar panel efficiency throughout your system’s lifespan.

Shading

When designing your system, you’ll need to determine if any panels will be shaded. This could be from: 

For systems using a micro inverter, any reduction in efficiency and energy production will be limited to the shading on an individual panel. 

However, if your system uses a string inverter, one panel being shaded can affect your whole system!

Read our detailed guide to solar panel inverters here. 

Or, use our solar panel quote tool on this page to determine what type of inverter you need, and what your electricity production is likely to be by installing solar panels. 

Temperature

Believe it or not, sometimes it’s “too hot” for solar panels to work efficiently. They work based on absorbing sunlight rather than heat. 

According to most manufacturers, any temperature above 25 °C is going to mean that the efficiency of your solar panels reduces. 

However, various tests show that the real efficiency loss comes at temperatures above 30 °C.

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Either way, the message is clear; high temperatures don’t help when it comes to optimising solar panel’s efficiency. 

Typically, higher quality (but more expensive) panels will be affected less by rises in temperature. And the same goes for installing monocrystalline rather than polycrystalline; monocrystalline panels will be less affected by any variation in temperature.

Put simply, investing in high quality panels that can withstand higher temperatures pays for itself in the long run. 

Type of Solar Panels

For UK installations, there are two main types of solar panels that are used; monocrystalline and polycrystalline. Choosing the right type of panel is going to affect the overall efficiency and energy production of your system.

Polycrystalline may seem like the best option due to their low price. However, they have a range of disadvantages including: 

• Don't work well in high temperatures (efficiency drops considerably)
• Short lifespan
• Low efficiency (approximately 15%)

A much better option is a system that incorporates monocrystalline solar panels. The upfront cost is higher, but you'll benefit from: 

• A panel that is much more efficient, especially in higher temperatures
• Longer lifespan

Jump over to our solar panel page here, our tool will determine which type of panel is the most efficient and cost effective for your installation. 

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