Use of PV power

[greyt]

I recently had a 3.9KW system installed. I have linked my home automation system to the Inverter to see real time output it reports and I can see real time house consumption.

The house never uses less than 1.1KW/H. At the moment the inverter reports 1.8KW output, I know the house is consuming 1.3KW but 0.3KW is still being used from the national grid.

I am manually working out by using the generation meter readings what the margin of error is on the inverter stats, but my question is I understand the consumer unit has two feeds, the electricity grid and the PV unit. How does the PV power take priority over the electricity grid to ensure that 100% of the PV power is used before the national grid power, or is that the whole point, this isn't expected.

Thanks!

 

[greyt]

Just had a thought. My house power reading is via a clamp around the incoming utility power cable. I guess this is going to be reporting on exported power as well and hence giving me false readings....

 

[langstroth2]

I think you've answered it. I'd be very surprised if your house was consistently showing a demand of 1.3kw at any point - typically we only go over a demand of 1kw when there's some form of electric heating element on (kettle, dishwasher etc). Otherwise demand hovers between 200 and 800w.

 

[greyt]

We use alot of computer equipment 24/7, hence the 1.1KW minimum usage. That figure is accurate since we also use First Utility with online power usage reporting. Also one of the reasons I went for solar panels.... the FITS payback combined with our high usage should make a good return on investment.

I will just need to change the power reading module from a clamp to one that counts the LED pulses on the electricity meter. Still looking for an ideal piece of kit to link into. I currently use RFXCOM kit, but their LED pulse meter is end of life and not being replaced until next year. I can tap into the broadcasts from the savometer kit but they only support pulse reading for Gas meters and I doubt they will read the rapid pulsing from an electiricty meter reliably. I could modify the kit available from airsensor.co.uk but I would rather invest my time in a close to ready made solution......

 

[stuart99]

Have a look at Home | OpenEnergyMonitor

It will do all this and a lot more!

 

[greyt]

Thanks, that looks like some interesting kit. It needs a little R&D to get the best out of it. If I was starting over again it would be my first choice, but I think I will hold out a little while and see if I can get a slightly simpler solution to integrate.