Surely the smart meter should/must be able to accurately measure usage/export figures, otherwise billing would be inaccurate?
I assume so, my comment wasn't a solution, it was more to prompt further thought and investigation. The laws of conservation of energy would imply that it hasn't been lost, more mis-measured. How is the number generated by the panels derived?
Interesting thread and something I’ve never looked into… likely I will at some point. Your generation and usage would be in Kw hours btw. Kw is an instantaneous rating.
The heatsink on modern charge controllers is to get rid of wasted energy in the MPPT converter. The 5% loss.. these days they just reflect the same voltage as the panel to reduce the power output to zero. In the olden days you would dump the excess energy in a shunt regulator equal to the whole solar array output, when the battery reached the correct voltage. Then you need a biig heatsink.
I think they're accurate for consumption but I have heard that, even though they measure Kwh exported, when calculating feed in payments the enery companies look at how much solar has been generated and simply pay half of that.
The inverter displays Kwh generated per day and there's also a generation meter fitted between the inverter and the consumer unit (basically a standard electricity meter wired backwards)
Well until you said it was less then I would have said I would trusted the DC number, after all it's much easier to calculate DC and there's no chance of current and voltage getting out of phase at DC.
The loss is in the inverter, it displays PV power going in and AC power coming out which is around 10w less
Ah, the AC is 10w less? I misunderstood. Then, I reckon the DC value is probably closer to ground truth than the smart meter.
@Fruitcake, I was just wondering how your system is performing, albeit over winter, I'd be interested in your learning, both good and bad.
Have a look at this site https://www.energy-stats.uk/blog-summary/ It contains tons of information including over 3 years of monthly solar generation and usage data.
I'm very pleased with how it's working, our bills have fallen considerably. I've also fitted a solar diverter that sends any surplus to the immersion heater which is giving us hot water most of the time without having to fire up the oil boiler. I've attached a graph showing the solar output against the generally used industry figures for 3.2 Kw. When I first installed it we were only using around 44% of the electricity but by changing habits such as using washing machine/dishwasher/tumble drier during the day when the sun is out has also helped.
Has anyone looked into the viability of sending the surplus output to a small storage heater to provide background heat during the day? They were originally designed to charge overnight but no reason why they cant be charged during the day, to release output late afternoon/early evening.
That's what the solar diverter does. It monitors the flow of current into and out of the house and diverts any surplus to the immersion heater. As it's a resistive load it can send anything from 50W to 3KW. It has 2 channels so it can be set to divert to another load once the tank is hot.
If we’re likely to get any surplus we plug the car in - the zappi charger is clever enough to power the house first then put any surplus into the car rather than lose it back to the electric company for buttons
