How much solar irradiation W/m2 in South UK

I am trying to calculate what maximum instantaneous power I can expect from my PV panels in the summer.
The datasheet for panels gives output with 1000 or 800 W/m2 at particular temperatures and windspeed.
All I can find online is average irradiation which for my situation is 3.1 kWh/m2/day
My installer used 1050 kWh/kWp per year in payback calculations.
Where can I find estimated peak instantaneous W/m2 for my location ?
Is it likely to be more than 1000W/m2 ?
I am asking because GE portal shows PV current and power well above what seems reasonable.

EricIoW Instantaneous insolation doesn't help you to calculate how much energy you will harvest from your PV system over the course of a day or year. The averages quoted by your installer should be typical for your location and are in the right ball park, from my experience (except it should be 1050Wh/kWp or 1.05kWh/kWp). We are further north, on the same latitude as Liverpool and last year we harvested about 0.9kWh/kWp over the whole year. That did include a fair amount of clipping which we can't do much about other than micromanage our electrical appliances and battery charging to reduce it. Other years will see higher or lower figures, but that's the ball park. HTH

Thanks Tim but I am trying to calculate maximum current and power from panels at any instant not an average. I am seeing currents 20% above what I expect.

EricIoW I'm not best placed to explain how the MPPT works but my (very limited) understanding is that the MPPT will shift the input impedance of the string to modulate current and therefore voltage to get the most power out of the panels while charging the batteries. As long as the string voltage is within the operating envelope and the line current is within the maximum for the inverter string (and panels), I wouldn't be too concerned. You could monitor the data and also ask others what they are seeing in terms of line current per string.

I have a link here which I use for Terravolt - live (as best as it can) and forecast in W/m2
https://www.windy.com/-Solar-power-solarpower?solarpower,54.743,-2.142,5

Tim The issue I have is the panel datasheet states 1000W/m2 current at peak power point is 10.8A with 239V (for my string of 7) Short circuit current is 11.3A. GE portal is showing 12.6A and 240V giving over 6kW from 14 panels rated at 5.1kW !!

hoggy Thanks, that shows about 750 W/m2 today at noon and nearly 1000W/m2 south of me. The scale stops at 1000W/m2, presumably it never goes above that.

EricIoW it can go over 1000, currently in Peru its 1032W/m2.
How often that happens here (if at all) I've never really given much thought.

If your panels are cool (it was very windy between clouds today) your panels will produce more than rated. The best time of year for peak output for mine is usually March/April with cool weather and clear skies where my 6.1kW install will do 7+

EricIoW I can see why you would be concerned, but as @hoggy says, the panel output is for a standard insolation at a standard temperature. If your panels are receiving more light at lower temperature, they'll be performing better. My only question would be why your installer put 5.1kWp PV in with a HY3.6 rather than HY5? Having said that, if he was looking for a simple G98 installation, then popping on a couple of extra panels to make sure your solar harvesting season is as long as it can be isn't a bad thing.

Tim I am not convinced that my panels are outputting almost 10% above short circuit rating with temperature around 20 deg. 8 weeks or so after Summer solstice.
About 3.6 vs 5 inverter, I was told it takes a long time to get the go ahead from network to use more than 3.68kW to grid. Also I asked specifically for the extra panels to boost power out of season / when cloudy !

EricIoW They do seem to be overperforming. Are you sure that the actual panels installed aren't a slightly higher rating than specified? It can take longer to process a G99 application (which would be needed for an HY5). I guess it depends on how well resourced that part of your DNO is. And yes, asking for additional panels to be fitted is always a useful move. I've not yet found anyone wishing they hadn't put so many panels on their roof.

Tim I have photos of panel labels so 100% sure about rating (from datasheet).

My panels will regularly show as a higher current than listed as the short circuit current (data taken from home assistant), they also at that point are producing more than their 'rated' power. It is always when there is a break in clouds though, so they are receiving full direct sun and also a lot of additional reflected light from the underside of the clouds which I believe is why they are going higher in terms of output. If I have clear blue skies and a nice generation curve then the peak is within the ratings (this may change in mid winter when they are nice and cold but I've only had the system since March).

In terms of how much higher they go I have max power current of 10.8 and short circuit current of 11.35 but reported peak of 12.9 just over the last 2 days. Array as a whole is 4.1kW and spikes of 4.7 are not uncommon, have on a couple of occasions seen >5.

Not sure how useful solar radation figures would be. Panel angle vs. sun angle changes the effective 'square meterage' of your panel in terms of solar radiation to ground area.

For example, If both sun and panel have 45 degree elevation, a 1 sq M panel is receiving the radiation for 1.414 sq metres of ground.