Lately I have noticed some spikes on my graphs that occur about every 2 hours 15/30 minutes. If I zoom in on the spikes, they seem to last about 10 seconds. I have no pumps starting up during this time. I suspect it is one of the fridges kicking in. I can probably switch off one fridge at a time when going to sleep and see if the spikes still occurs. It might be something else? How do I determine what is causing the spikes? 

Put an Efergy plug-meter on the fridge and check the peak? I'm not sure how accurate it is, but the one I have seems to record a peak value that "feels" sort-of right.

Rule of thumb says an induction motor needs 5 times nominal to start. So a 250W fridge (fairly common non-eco-model size) will need 2.5kw.

It also seems spaced around 2 hours apart? By the time I replaced my fridges with better units, they were running 12 hours out of 24, they would literally turn on every half an hour and run for almost half an hour.

Thanks @plonkster. I don't have an Efergy meter. If I don't come right, I will go buy one. 

I would do as you suggested in your original post. Turn the fridges of one by one (at least for one night each) and check ICC in the morning. You'll soon find the culprit. 

My old Pascali booster pump spiked at almost 4Kw (0.75Kw motor) with ICC constantly showing daily max usage figures of 5000w+.

I decided to replace it with a tankless unit which I got from Builder's(box say's JOJO so not sure what make it actually is. It's got a 0.35Kw motor on the pump and with half the flow (40l/min) of the Pascali it's still more than enough to even supply 7 pop-up sprinklers. I've installed the smaller pump almost three months ago and can clearly see a difference. Average daily usage is down by roughly 2Kwh, and that by only installing a more efficient pump. Spikes are now never above 3000w (except when I start welding)

PS: I did find that the old (6 months old) Pascali pump was very stiff. You could turn the impeller by hand, but only just. That would explain my excessive spikes

Hi Don, which computer program are you using to record your data from the Inverter or is it a brand designed for a specific inverter make only ? 

Hi Des that looks like an Emoncms feed. I think Don uses ICCpi.

@Don's display is Dashboard2 of @Manie's ICC-Pi program. It was added a few realeses ago. The runtime display of over 200 hours on Don's system is a clear indication of how stable ICC-Pi is. I cannot envisage running my 2 x Axpert cluster without it and the matching MQTT Dashboard on my Win10 PC.