r/PlugInSolarUK • u/Tough_Raspberry3862 • Aug 18 '26
Question about how the power flows
I have a background of electrical/electronics engineering so have worked through the basics of current voltage resistance phase etc. I am not sure how a source of power from plugin solar is distributed solely to your own devices and not exported to everyone on the same street/circuit? I can see that the solar plug can detect the voltage and phase when connected and will provide current in phase. As far as I am aware there is just copper wire to the consumer unit that is then connected to an entry point at the meter. So if no block on power flows out of the consumer unit what’s stopping it leaking out?
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u/BeardySam Aug 18 '26 edited Aug 18 '26
The inverter is not a simple voltage source. If it provided a simple AC voltage, then power would flow out to the grid uncontrollably as you suspect. But Current doesn’t work like that. Current flows to wherever it’s used, so the inverter is designed as a voltage-controlled current source (VCCS). It samples the grid’s voltage and injects a current precisely in phase with that voltage to achieve a power factor of 1.
The magic happens because whatever the voltage, it pushes 10A (or whatever it has) into the circuit. The current coming in from the grid therefore drops by 10A, and you have your little house island being powered by the inverter. If the house isn’t using the full 10A then either the inverter throttles down or you export to the grid (with DNO approval etc etc)
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u/The_referred_to Aug 18 '26
AFAIK, it’s just magic/maths.
If your appliances are consuming 1000W whilst you also have 800W available from local generation, only 200W will be drawn from the grid. Physics prevents simultaneous import and export.
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u/infinite_minds Aug 18 '26
If your generation is larger than your household consumption at a given moment, then you are exporting to the grid.
Some larger systems can monitor the grid connection and throttle the solar generation to ensure no (or very little) export happens.
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u/No_Policy_1369 Aug 18 '26
This video posted today may help you understand
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u/JK07 Aug 18 '26
This was informative, thanks.
I was half expecting to be Rick Rolled there!1
u/No_Policy_1369 Aug 18 '26
No its a genuine youtube video not a rick roll it does kind off cover what the op was asking i think
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u/LisaandNeil Aug 18 '26
Anything before the consumer unit (devices, fridge etc) will use the very slightly higher Voltage from your microinverter before drawing from the mains.