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My roof is shaded. Is solar still worth having?

My roof is shaded. Is solar still worth having?

You like the idea of solar, but you’re concerned that there’s too much shading on your roof for a solar panels system to work properly.

If this sounds like your situation, keep reading. 

This article explains:
  • The different types of shading and impact of solar output
  • Actions you can take to minimise shading
  • Why most solar panels systems don’t work well in the shade
  • Understanding which solar technologies work in partial shade
  • The best solar panels system for a partially shaded roof

 

Before we start – completely shaded solar panels aren’t worth it!

First things first… If your roof is fully shaded between the hours of 10am and 4pm for most of the year, then forget it.  Rooftop solar is not a viable option for your home.  Solar panels need sunlight to work.  No sunlight = no solar power.

If this is your situation, you might like to invest in a community solar bank (when these start to popup in your region) Note: potential to link on this to an article on this topic or purchase green power from your electricity retailer to offset your carbon emissions.

But if your roof is partially shaded only some of the time, solar may be worthwhile.  That’s because there are some clever solar technologies that minimise the impact of shading on the performance of your solar panel system.

 

Different types of shading and impact on solar output

There are different types of shade, with some having a more detrimental impact on solar output than others. In the same vein, there are some types of shading you can do something about and others that are beyond your control.

  • Clouds: A solar power system can still generate some energy on a cloudy day. That’s because some sunlight will still reach the solar panels in the form of diffuse radiation. With a high quality shade-tolerant solar panels system installed, the loss of solar energy from cloud cover can be minimised.
  • Trees: Depending on the density of the trees, some light may still reach the solar panels. Shading from trees is something you can control (more on this later).
  • Nearby buildings: This is ‘hard shade’ (i.e. zero sunlight) and is virtually impossible to do anything about. If you’ve got neighbouring properties that shade your roof during the peak sunshine hours, solar probably isn’t for you.
  • Objects on your roof: Antennas, chimney, an evaporative air conditioner (aka swampy) – these types of objects create hard shade which is bad for solar. The good news is that – as these ‘sunlight-blockers’ are your property – you can do something about them!

Actions you can take to minimise shading

  1. Get shade mapping from a good solar installer

The first step is to get shade mapping for your rooftop from a qualified solar installer.  This will determine how much shading there is on your rooftop for each hour of the day and at different times of year. With this information, the solar installer can estimate the impact of shading on the solar yield – i.e. the amount of solar energy that your solar panels system will produce.

  1. Avoid installing panels where there’s shading

If possible, install solar panels on those parts of the roof that aren’t shaded – or a shed if you have one. If your north-facing roof is shaded but your east and west roofline isn’t, installing solar panels on the east and west could result in a higher solar yield.

Adding a few more panels to make up for the reduction in solar energy production caused by partial shading is another option.  This can be a cost-effective way to generate more solar energy – as the additional cost of the solar panels is likely to be less than the extra electricity bill savings you could achieve with a bigger solar system.

  1. Remove the object that’s shading your roof

If we’re talking about your neighbour’s house, this clearly isn’t possible.  But if your neighbour is planning an extension, have a chat to them and ask to see the shading analysis diagrams.

If the object is something on your property, try to remove it or minimise the impact.  Trim trees, remove antennas, remove your evaporative air conditioner (aka swampy) and get a split system with the unit installed under your house.

Why most solar panels systems don’t work well in the shade

Most solar panels systems use string inverters. They’re a great option is your roof is in full sunlight and they can perform at high levels of efficiency. They’re also the most cost-effective type of solar panels system.

However, when it comes to shading, string inverters struggle. That’s because when even one panel in a string inverter solar system is shaded, the entire array (or string) of solar panels will drop in output to the level of the worst performing panel. This means that if the worst performing panel is at zero output, the entire array will be at zero output.

Fortunately, new solar technologies have been developed that minimise the impacts of partial shading and generate good levels of solar energy.

Which solar technologies minimise the impacts of shading?

Shade resistant solar panels

Purchasing high quality solar panels – like LG and SunPower – that have clever shade-resistant technology can help to alleviate the impacts of small amounts of shading. Often these panels combined with other solutions – such as microinverters and power optimisers (see below) – give the best outcome in terms of maximising output in partially shaded conditions.

Microinverters and power optimisers

Microinverters and power optimisers are little boxes that are installed at the back of each solar panel.  They both minimise the impact of shading by limiting the loss of power output to just those panels with shade on them.

Microinverters have a mini-inverter on the back of each panel, performing the conversion of DC power to AC power at individual panel level.  Whereas power optimisers require a string inverter for converting DC power to AC power.

Differences between Power Optimisers and Microinverters

 Power OptimisersMicroinverters
Little box installed at the back of each panelYesYes
Loss of power output from shading restricted to shaded panels onlyYesYes
Inverter locationOne central string inverter located on an exterior wallMicroinverters attached to the back of each panel.

No central string inverter

 

The best solar panels system for a partially shaded roof

Which is best, power optimisers or string inverters?

In our opinion, power optimisers are the best solar solution for partially shaded roofs. They have the same advantages when it comes to shading as microinverters – at a lower price point.

Pros and cons of power optimisers versus string inverters

Power optimisersMicroinverters
ProsAllow each solar panel to work independently from every other panel

 

Effective in combatting the loss of power output from partial shading

 

Monitoring will show power output for each panel individually

 

More cost effective than microinverters

Allow each solar panel to work independently from every other panel

 

Effective in combatting the loss of power output from partial shading

 

Monitoring will show power output for each panel individually

 

 

 

ConsWhen it comes to minimising the impact of shading, Power Optimisers don’t have any consMore expensive than Power Optimisers

At Solar Run, we recommend SunPower SunPower shingled panels as the best solar panels system for partially shaded roofs.  The SolarEdge solution comprises of:

  • shade-resistant, high performance solar panels
  • built-in power optimisers on the back of each panel
  • a high efficiency solar inverter

The benefits of SolarEdge are:

  • More power
    • Shading on one solar panel does not affect other power output of other panels
    • When half the panel is in shade, the other half will continue to work
  • Greater control
    • Includes panel-level solar monitoring – so you can see exactly how much power each panel is producing at any time of day
  • Lower installation costs
    • Power optimisers are pre-installed on the back of each panel by the manufacturer (so no work involved by the solar installer)
  • Industry leading warranties
    • Better than industry-average warranties on panels, inverter and optimisers
  • Lower purchase cost and faster payback
    • SunPower shingled panels Inverter is a more cost-effective solution than a microinverter solar system. What’s more, the solar yield – i.e. the amount of solar electricity that the system will generate – is comparable. The bottom line for you is a faster payback on your solar dollar!

 

Interested in getting a quote for SolarEdge?  Would you like advice on solar and shading? Get in touch and we’ll be glad to help out!

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