I queried the choice of inverter on my 3.92kW system as it limited output to 16 Amps (nominally 3.68kW). I got a standard answer from my supplier as above which I checked with Western Power (the local DNO). WP said they would have reviewed a higher than 16 amp  system for no cost (though at the time - prior to the FiT cut-off date they would not have had the time to meet the deadline).

On doing calculations of expected generation, though, I estimate I'll probably lose only about 15 pence a day (or 0.3kWatt-hour) on a good summer day if the actual summer peak would have reached 3.92kWatts, so unless I achieve more than the estimated output I'm not too concerned.

 Currently, looking at 5 minute data throughout December I've been peaking at around 2.4kW (sustained peaks). This is about 20% higher than I would have expected based on calculations of solar incidence taking into account estimates of transmission through the atmosphere. My current guess is either the panel efficiency is higher than the nominal figure (due to colder temperatures) and/or the air is clearer than average in Torquay. I'll know more by summer.

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There is no switching from PV power to grid electricity. The solar energy is converted to AC electricity and fed into your home via a consumer unit; in the same way as grid electricity. As a result you will never know which you are using - it is seamless to the end user or homeowner.

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I'm a 63 year old so a long pay back period for any green technology is a no-no.
I've just come across the 'rent a roof' scheme offered by Isis & Homesun & they seem an ideal solution for me.
I already run an air-source heat pump (5kW output) which draws, on average, around 1kW from the mains supply.  I use the heat pump to heat domestic hot water only (2x117 litre tanks; plus 1x117 litre preheat tank when demand is high) these tanks are normally heated in the morning.
My question is - how is the switching from solar PV power to mains power performed?  Is it an either/or solution ie drawing power from 1 source only or do both feed at the same time - ie if insufficient power is available from PV panel, is it topped up by the mains supply.
If it's either/or is the transition from PV to mains & back again rapid & smooth ie to all intents a continous supply without interuption?

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Dear Ben

The figure that the District Network Operators (DNO) quote is 16amps per phase which is about 3.6kWp into to the national grid.
So that would be 10.8kWp split across three phases.

This is for connections without prior warning; you might be able to install a larger array but you would need to send a notification prior to the install so that they can give you an estimate and see the connection points and transformers in the area.

Regards

Paul

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Hi - do you know what the maximum peak generating capacity a system can have when transmitting to the grid via a 3-phase 440V connection?

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We had a similar size system installed a couple of years ago with no problems. We used a Sunny Boy 3800 inverter and if your voltage is 240 then the maximum current is 15.833A, but your DNO might be pedantic and insist that the voltage is 220 which is 17.27A. Worth asking your installer if the output from the inverter can be limited to 3,500 Watts which is 15.909A?

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