Solar Panels On Pergola – Is it a good idea?

Solar pergola roof

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Designing a DIY solar pergola

Can You Put Solar Panels On A Pergola?

A pergola is an structure with a roof and four or more pillars supporting it. In some circumstances it can be a great idea to use that extra roof space for mounting solar panels, either to supplement home energy usage or as an outdoor off-grid solar system.

The size and type of solar power system you install depends on what you want to do with it.

What this post covers:

  • How many solar panels do you need?
  • How much solar power can you get from your pergola roof area?
  • Are solar panels too heavy to mount on a pergola?
  • What type of solar panels are best for pergola mounting?
  • What can the panels be used to power?
  • What sort of controller and other equipment is need for a solar pergola?

DIY solar pergola design – Can you put solar panels on a pergola?

I’m going to fit solar panels on an existing pergola roof that’s pretty old, so I need to check that it can support solar panels at all!

DIY solar panels on pergola design

The author’s DIY solar pergola roof

Solar panels on a pergola seems a great way to use that extra space. This particular pergola is currently used as a carport, which I also use for storing an inflatable kayak equipped with an electric motor.

I use a lithium iron phosphate battery for the electric kayak – I also have solar panels mounted on the kayak as well – I like solar!

In addition, I have a spare car battery and a lead-acid deep-cycle battery for home energy storage backup, so in total I have 3 big batteries.

The lead-acid are heavy so it make complete sense to leave them all in one place and charge them with solar panels on the pergola roof.

How many solar panels do you need?

If you have a particular task to perform, like recharging a number of batteries, then I would work this out from the battery capacity in watt-hours in this way:

  • Battery capacity needing recharge at 50% discharge = 100Ah = 1200 watt-hours (Wh)
  • A 100 watt solar panel generates on average 400Wh/day
  • Number of solar panels needed = 1200/400Wh = 3 x 100 = 300 watts

So for building my solar charging station I need three 1oo watt solar panels to make sure my batteries recharge in a day.

Is my pergola roof big enough?

Solar panel sizes and wattage

The average size of a 100 watt panel is 1005mm x 670mm (39.5″ x 26.5″) which gives an area of 0.673 square meters, or 7.25 sq ft.

Typical 100 watt solar panel size

What are the dimensions of a 100 watt solar panel?

As my pergola roof is 15m2 (161 sq ft), I’ve no worries there!

I like 100 watt panels because they are easy to handle. I almost always use the flexible solar panels, but more of that later. Of course, there many sizes of panel to choose from – see the size chart below:

Table – Solar panel size and wattage chart

Rated Watts

Length (inches)

Width (inches)

Weight

50

29.9

27

6.6 lbs

100

39

26.4

17.6 lbs

160

58.3

26.4

22.9 lbs

200

52

39 

32 lbs

300

65

39

40.1 lbs

400

81.4

41.2 

56 lbs

What if you wanted to use all of the roof area to add to your home grid-tie solar power system?

Renogy Flexible Solar Panels

How much power can you generate from your solar pergola roof?

The average garden or home pergola roof size is 12 feet by 12 feet, so 144 square feet.

How many 100 watt solar panels will fit on 144 square feet? Let’s use the dimensions of a a 100 watt panel, which is 39.5 inches long by 26.5 inches wide.

12 feet is 144 inches, so we can comfortable fit 3 panels lengthways – and how many wide?

Divide 144 by 26.5 inches and we get 5.4, so 5 panels.

The total number of 100 watt solar panels we can fit on a 12ft by 12 ft pergola roof is 3 x 5 = 15 panels.

How to calculate solar power generation

The amount if energy any solar panel can generate depends on how much of the sun’s energy falls on its surface. It’s called irradiance.

Although this value varies according to location, professional installers use an average value of 4 kWh/m2/day for estimating purposes.

This value is also known as peak-sun-hours – find yours for your location here.

Find peak sun hours in historical irradiance data

How much power can a solar pergola produce?

From the previous section we found that 15 x 100 watt panels would fit on a pergola roof size 12ft by 12ft, and that a 100 watt solar panel can generate 400 watt-hours per day at an average peak-sun-hours of 4.

Energy from 1500 watt solar = 1500 x 4 = 6kW per day.

Use the table below to find the amount of solar energy your pergola could produce per day, month and year:

Table – How much solar power from various pergola roof sizes

Pergola Dimensions (feet)

Energy per day (kWh/day)

Energy per month (kWh/mth)

Energy per year (kWh/yr)

8 x 8 (64 sq ft)

3.5

106.5

1277

10 x 10 (100)

4

121.6

1460

12 x 12 (144)

6

182.5

2190

13 x 13 (169)

7

213

2555

14 x 14 (196)

8

243.3

2920

15 x 15 (225)

9

273.75

3285

17 x 17 (289)

12

365

4380

18 x 18 (324)

13.5

410.6

4927

20 x 20 (400)

16.5

501

6022

Are solar panels too heavy to mount on a pergola roof?

The average weight of a commercially available 100 watt panel is between 17 and 20lbs, and for my pergola that means total weight would be 15 x 20 = 300 lbs.

How much weight can a pergola support?

A good rule of thumb for pergola loading is between 250 and 300lbs, so if I mounted panels on the total roof area I would be pushing that upper limit, if I used rigid panels.

What type of solar panels are best for pergola mounting?

For many applications I use flexible solar panels instead. A 100 watt panels weighs about 5.5lbs instead of 20lbs, so quite a big difference. 15 solar panels at 5.5lbs weight is only 82.5lbs, so there’s a comfortable margin for safety.

Use flexible solar panels for mounting on pergola roofs

Flexible solar panels are much lighter than rigid.

Flexible solar panels have the same area and are just as efficient, but they are much thinner at just a few millimetres. For roof-mounting I build simple aluminium frames to keep them rigid – see image below:

Deatil of solar panel DIY frames

‘Rigidize’ the flexible solar panels with aluminum angles. Total weight is less than 10% of rigid solar panels!

What kind of controller do I needed for a solar pergola?

If charging batteries with your solar setup, a charge controller is needed.

For my 300 watt installation I’m using a 30A rated, up to 60 volt input MPPT (Maximum Power Point Tracking) controller.

The open circuit voltage (Voc) of my 100 watt panels is about 21 volts, so I’ll simply connect them up in parallel, taking two wire to the controller input terminals.

MPPT 30A solar charger - how to connect

MPPT controllers are much more efficient than than standard PWM controllers

I use MPPT controllers in most of my projects for two reasons:

  1. MPPT controllers are up to 30% more efficient than the cheaper PWM charge controllers
  2. They produce more power when the solar panels may be partially covered with clouds, for example.

What can a solar pergola be used to power?

Outdoor lights supplied from a solar pergola

Solar panels mounted on a pergola roof can power light, charge batteries and operate water pumps

If used as a stand-alone, off-grid system the solar panels can power typical garden items, such as garden lights, electric lawnmowers, water pumps and swimming pool lights.

A small system like mine (300 watt) would need a 50Ah battery with an appropriate solar charger for devices with no batteries (like water pumps), while most others will just have their batteries charged direct.

If you intend to use the whole pergola roof area to supplement an existing home solar system, this is easily done.

I recommend fitting panels with micro-inverters connected to each panels. Micro-inverters convert DC to AC at the panel level so DC losses are minimized.

AC cabling would then run to the house solar control board and tie in to the AC circuit breaker.

Note: Make sure that existing component capacity can take the extra current from the new solar supply.

Authors solar battery charging system

My charging system showing solar panels mounted on pergola roof, lithium battery and MPPT control board

How much does a DIY solar pergola cost?

Installing solar panels on pergola doesn’t cost the earth, particularly if you mount and connect them yourself.

This is easily doable and there’s plenty of detailed guides on the internet to help with system sizing. The costs for purchasing the components for my own DIY solar pergola roof were as follows:

  • Three 100 watt flexible solar panels – $200
  • MPPT solar charge controller (30A rating) – $70
  • Cabling and junction boxes – $10
  • Aluminum angles and sundries for making solar panel frames – $15

In total, just $305 with no labor, as I mounted and connected everything myself. If this system was to feed any AC appliances, then a 50Ah lithium iron battery would be required at a cost of $250.

Total cost with battery = $555

If I covered the whole roof of my pergola with solar panels to add to an existing grid-tie system, the cost would be:

  • Solar panels = 15 x $161 = $2430
  • Micro-inverters (5 required) at $150 each) = $750
  • Alu. angle iron to make frames for flexible sola panels = $55
  • AC isolating breaker and AC cabling to existing solar grid-tie board = $70

Total DIY cost for adding 1500 watts of solar pergola supply to existing grid-tie = $3305 ($2.2/watt)

The average current price for professional installation is about $3/watt, so a DIY solar installation represents quite a saving.

Related:

How many solar panels do you need to power your home?


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