Power up: Installing solar panels on a shed roof – is it worth it?

Can I put solar panels on my shed roof? In a word, yes. But that “yes” comes with some “ifs” and “buts” attached. 

Solar Photovoltaic (PV) panels that generate electricity can effectively be installed on the roof of any structure that is robust enough to take their weight. But while a shed may seem like the obvious place to install solar panels, let’s remember that a typical garden shed is simply nailed together and often modest in size. What solar system you install on the roof will be determined by how sturdy and large the structure is. What you want to use the solar energy for will also influence your decision. 

When planning for solar PV panels on a shed roof, work out what you expect to use the energy for first. This will determine what type of solar panel system you’ll need. If you want to power electricity and small tools then a DIY solar panel kit, which can be moved and changed, would be a good solution.  

If you have more of a workshop setup, with multiple power tools that you’ll be using for longer time periods, as well as powering lighting and a computer, then opt for a PV panel system – like one you’d have installed on the roof of your home. This is a long-term home-style system that is fully installed and connected back to the home. 

A small shed that’s used for storing tools and general pottering may benefit from a DIY solar PV system, such as those used for camping or caravans. Although not as robust, and without as much oomph, they can be a lot less expensive and do not need formal installation, as they are not connected back to the grid. That means you won’t need to dig up the garden to run cables from the house to the shed either.  

Solar DIY kits can be picked up pretty easily online – a 20W lighting system could cost around £150. This type of system would typically have a solar panel and battery and four 5W bulbs. The panel would be able to charge the battery in around four to five hours in good sunlight and supply around six hours of light. Battery systems can indeed be used to power the system with no connection to a mains supply. 

If you are adding a few DIY panels and trickle charging a battery (which allows a very small amount of energy to flow over a very long period) and using a small inverter to run low–power lighting and small appliances, then there is no real need to be connected to the main electric grid. This is a good solution if you don’t need a great deal of power and the shed is a long way down the garden and you’re keen to avoid running mains cables down to it.  

A larger shed, perhaps a workshop, gym or garden office, would have heavier–duty electricity requirements such as better lighting, power tools and machinery, or even a heating system. It would therefore require a proper mains electric supply.  

Let’s breakdown the key measurements of a PV system. A 400W PV panel (as used on domestic home PV systems) is around 1m (3.3ft) wide by around 1.8m (5.9ft) long and weighs an average 20kg (40lb).   

A 10-panel installation – a typical installation size for an average home – would weigh around 200kg (440lb), plus the weight of the metal roof hooks that fix the panels to the roof securely. It’s a hefty weight to expect a garden shed roof to be able to hold, and therefore the structure of the shed would need to be reinforced to handle the stresses. 

Realistically, you’d only choose to have a 10-panel array on a shed roof if you were going to power your house with the renewable energy generated. This would mean a grid– connected system with underground cables running from the house to the shed. For this set–up you’d also be looking at having a proper workshop or garden room structure that could take this weight, rather than a shed. 

As such, it would then make sense to install as many PV panels on the roof as you can (up to 10 panels) and then install the inverter in the garden building. When the electric generation is not being used in the shed it can then go back to the home consumer board through the connecting supply wire and be used in the home. 

This kind of solar panel system might be worthwhile if the roof of your home isn’t suitable for solar panels – it faces north or the pitch isn’t suitable for the 10 panels you’d need, for example.  

But it will mean having your garden dug up to run the electricity cables. You’d need to pay a qualified electrician to do this work and wire it up. Costs very much depend on how long the job takes, but an electrician could cost around £300 to £500 per day. 

A 10–panel array would realistically be around 11x4m (36x13ft). Therefore it’s best to plan the shed with a mono-pitch roof (a lean-to style, with one sloping roof) so that you are using the full roof area.

Whether you opt for a solar PV system or a DIY kit, the best place to position your shed to get optimum sunlight is south facing. It should be pitched at around 30 degrees for optimum generation. If it faces east or west, then you lose around 20% of the potential power generation. However, it’s fine to have panels on both the east and west pitch if the shed is orientated this way, but this does sometimes need special wiring and inverter design to ensure optimum generation across the day.   

The PV panels can be placed in portrait or landscape orientation. It’s worth planning what size shed (or garden room) you would like and then checking what will fit. Different panels from different manufacturers have different dimensions and outputs. Ideally, it’s best to leave a margin of at least 30cm (1ft) around the edge, but you can also fit right to the edge and install a rim to avoid wind lift.