Real world output from 4kWp?

Spies

I've been looking into panel specs and the advertised kWp assumes that you have 1000w/sqm hitting them, when you drop down to 800w/sqm you lose around 100kwp per panel!

Does that therefore make the real world output of a 4kWp system around 3000w max assuming you only get 800w/sqm of sunlight on a 10 panel system? 

Martyn1981

Hiya. The Wp of a panel represents its output at 25C. So on a cold clear day in April or Oct you may actually get more than 100%. On super hot summer days with no wind, the kind we just enjoyed, the panels will get hot and output will probably be around 75% of their rating. In more normal summer weather, on a nice clear day, you'll hopefully get around 80-85%.

For annual generation, if you go to the PVGIS site, the guestimates on there are extremely accurate, though a tad pessimistic as they use a default system loss figure which is a bit high. Over the last 10yrs, despite having some shading, we've generated roughly 95%-110% of the PVGIS estimate each year.

Regarding solar levels, obviously we are where we are, and we get what we get, and for south facing panels in England, a rough figure of 1,000kWh/kWp pa is fair. In Spain, it's more like 1,500, and some places 1,800. Although many places on the planet will get more than twice our sun hours, the drop in performance as panels get hot (and the gains we may see in poor, but cold weather) mean it's unlikely to see figures above 2,000kWh/kWp unless the panels track the sun's movement through the day, and then I think another 10-20% generation is possible.

Solarchaser

Just to add to Marts information there, basically if you are in South England and a South facing 4kw system you should expect around 4000kw a year, north England more like 35-3800kw a year, and into Scotland around 32-3400kw a year.

If the array is not pure South facing, expect to drop a little off

QrizB

There's a rough guide in my signature; over the 9.5 year life of my 2.72kWp system (pointing somewhat west of south) it has generated 24000kWh*, an average of around 2600kWh/yr, 7kWh/day.

If it had been 4kWp the equivalent numbers would be 3800/yr and 10/day.

* Should be 25000kWh by the end of September, barring awful weather or some sort of system failure.

Spies

I'm more interested in the peak power at say 1pm as I'm curious if 4kWp would give enough instantaneous power to run my dishwasher for example. 

QrizB

4kWp should be plenty for a dishwasher.

I can run my washing machine on 2.72kWp if it's a sunny day. Or boil my kettle, or run my toaster. But not all at once!

I've also got a poor man's solar diverter. I fitted a SCR controller to my 3kW immersion heater and get my son to turn the knob up and down depending on what the smart meter IHD says (He goes back to college in the autumn so I'll need to think of something else then).

Something like this although mine doesn't have a fan (it gets quite warm so I'd buy a fanned one if I needed another):
https://www.ebay.co.uk/itm/373617755321

Ectophile

4kWp of solar panels will give 4kW, when the sun is in the right place in the sky, relative to the panels, and if there are no clouds in the way.

If a cloud scuds across the sky at the wrong moment, you won't get 4kW.  In winter, when the sun is low in the sky, you won't get 4kW, and so on.

EricMears

We're a fortnight short of our panels' tenth anniversary and have generated a total of 36.206  MWh  so approx 3600kWh/year. Rest of details should be in 'auto-sig' below

ispookie666

Our 3.5KWp panels (suffolk) produces average of  3.7MW per year over the last 5 years with the peak generation of 3.3KW in spring.  

JKenH

Someone just down the road from me (Lincolnshire) with a SSE facing 4kwp installation has generated between 4 and 4.4 MWh p.a.

You can find other results on pvoutput.org

My 7.8kwp ENE/WSW system generates around 6MWh p.a. (Or rather it used to; currently I have some imbalance between strings and am getting on for 10% down on previous years.)

https://pvoutput.org/aggregate.jsp?id=42476&sid=44174&t=y

tim_p

4kWp system (16x250w panels across 3 roofs, south coast) has generated 4MWh or above for the last 6 years.  The worst year was 3921 and the best (last year) was 4251