What % efficiency have you got from your solar panels?

[Tim Good]

I have 360w of solar on my boat. Today I got a max Output of 338w which is 94% efficient. Obviously that doesn't happen every day so I'm wondering what % others have managed to achieve. I run 3 x 120w in series via a victron MPPT in 4 x Trojan T-105.

 

[Yngmar]

That's not the solar panel efficiency. The efficiency of a solar panel is the percentage of the total solar energy the panel can convert into electricity, which is around 20% for typical current generation cells, and since panels aren't entirely made of cells (some of the panel area is frame or gaps), the panel efficiency is slightly lower than that, like 17 or 18%.

From that you have your nominal panel rating, the "360W of solar on my boat" people talk about. But that's just nominal, a value for a standard irradiance level at a certain temperature and ideal angle. Depending on location, atmospheric conditions and temperature (lower is better), you will typically get less than that, but can sometimes get more than the nominal rated power out of a panel too. For example our 600W nominal produced nearly 700W for a short while on a cool, clear and sunny day at noon.

 

[Richard10002]

How do you calculate it?

 

[Tim Good]

That's not the solar panel efficiency. The efficiency of a solar panel is the percentage of the total solar energy the panel can convert into electricity, which is around 20% for typical current generation cells, and since panels aren't entirely made of cells (some of the panel area is frame or gaps), the panel efficiency is slightly lower than that, like 17 or 18%.

From that you have your nominal panel rating, the "360W of solar on my boat" people talk about. But that's just nominal, a value for a standard irradiance level at a certain temperature and ideal angle. Depending on location, atmospheric conditions and temperature (lower is better), you will typically get less than that, but can sometimes get more than the nominal rated power out of a panel too. For example our 600W nominal produced nearly 700W for a short while on a cool, clear and sunny day at noon.

Thanks. I'll rephrase.

What's the max % of W you produce compared the the manufactures rating of the panels you have.

 

[RichardS]

I have 360w of solar on my boat. Today I got a max Output of 338w which is 94% efficient. Obviously that doesn't happen every day so I'm wondering what % others have managed to achieve. I run 3 x 120w in series via a victron MPPT in 4 x Trojan T-105.

I have 4 x 100W and the maximum I achieved in early August 2017 was only 244W which is only 61% even though the sun in Croatia was high in the sky.

When I went back to the boat in mid-September with a much lower sun, I changed the panel configuration from (2 in series) in parallel with (2 in series) to (2 in parallel) in series with (2 in parallel) and achieved 347W which is 87%.

Richard

 

[LadyInBed]

I've no idea. The sun shines and the batteries stay charged. (2×80W panels into 2x130ah banks).

 

[VicS]

I've no idea. The sun shines and the batteries stay charged. (2×80W panels into 2x130ah banks).

Solar panels are only around 20% or so efficient at converting the suns energy into electrical energy anyway!

 

[Pavalijo]

Based on the re phrased question (post #4) you need to restart the poll - I got a little over 100% the other day.
With 240w fixed and 107w roving panels at anchor we haven’t used the gas yet since launching last week - boiling our low wattage kettle and cooking on a portable single induction hob (not at full 2kw power) via the inverter.
Dull and raining this morning though, so the gas tap may be turned!

 

[alan]

Referring to Post#4 : 80%

 

[AntarcticPilot]

The efficiency as a percentage of rated output will depend totally on a combination of factors, most of which are out of our control. These factors include location - further south = higher efficiency and in the UK, further east = higher efficiency (less cloud). Domestic solar panel installers will show you maps of the expected best case efficiency. Then there are installation factors such as orientation with respect to the sun, shadowing and cleanliness of the panels.

Just for example, my roof top panels on my home near Ely never achieve more than 200 kW out of a rated 220 kW.

 

[wully1]

I've no idea. The sun shines and the batteries stay charged. (2×80W panels into 2x130ah banks).

My single 100 watt panel does that too! It must be some kind of magic.

 

[lw395]

Under standard test conditions, most brand new panels give around 110% to 120% of their nominal rating.
As they get older, this drops.
They are normaly spec'd to give something like 80% of nominal after 20 years.

The sun can be more powerful than standard test conditions.
Don't skimp on the wiring!

 

[TQA]

I have 3 x 135 watt panels. 405 watts total. The controller is a Blue Sky MPPT. I see a max of 22.6 amps under normal charging and as much as 26 amps when equalising. The panels are rigid Kyoceras and are at least 10 years old.

Assuming 13.8 volts then that gives 338 watts

 

[NormanS]

Life is too short to spend any of it staring at the voltage controller to see what the panel is producing. But I can say that over a period, my 100w panel regularly produces more 'tricity than my 714i windcharger. (The controller keeps a record).

 

[William_H]

The efficiency as a percentage of rated output will depend totally on a combination of factors, most of which are out of our control. These factors include location - further south = higher efficiency and in the UK, further east = higher efficiency (less cloud). Domestic solar panel installers will show you maps of the expected best case efficiency. Then there are installation factors such as orientation with respect to the sun, shadowing and cleanliness of the panels.

Just for example, my roof top panels on my home near Ely never achieve more than 200 kW out of a rated 220 kW.

Do you really have 220kw of solar panels? Or have you got the number wrong. I reckon that would equate to about 1000 panels each about 2m by 1 metre. Our Yacht Club has 40 kw and that covers an enormous roof . My home system is 1.5 Kw and that has 8 big panels. Re the poll. My home system delivers on a good day about 80 % of rating as KW into the mains at 240vAC. Typically about 8Kwhour ina good day. olewill
olewill

 

[Tim Good]

Based on the re phrased question (post #4) you need to restart the poll - I got a little over 100% the other day.
With 240w fixed and 107w roving panels at anchor we haven’t used the gas yet since launching last week - boiling our low wattage kettle and cooking on a portable single induction hob (not at full 2kw power) via the inverter.
Dull and raining this morning though, so the gas tap may be turned!

Interesting this. We have a decent inverter and should probably try and follow your lead in this as we regularly reach float in the batteries by midday.

Induction uses less electricity I presume? I'm also about to fit a new 60w panel on the coach roof. Would you recommend going to the effort of making it roving rather than fixing it down which is my easy option. I imagine roving you can probably make you 107w perform more like 150w or 200w in terms of total produced?

 

[AntarcticPilot]

Do you really have 220kw of solar panels? Or have you got the number wrong. I reckon that would equate to about 1000 panels each about 2m by 1 metre. Our Yacht Club has 40 kw and that covers an enormous roof . My home system is 1.5 Kw and that has 8 big panels. Re the poll. My home system delivers on a good day about 80 % of rating as KW into the mains at 240vAC. Typically about 8Kwhour ina good day. olewill
olewill

OOPS! You're right, it's 2.2 kW! I was thinking in watts...