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my power bill

PostPosted: Tue Jun 27, 2017 10:53 am
by solar1957
Hi... could someone please explain ,
I have 6kw on roof 5kw inverter grid tied .
During none peak production, if i am producing say , just 1500w and i'm using a 3kw aircon , would this mean i am drawing 1500w from grid and 1500w from solar ?
And if i'm producing 4.2kwh and running 3kw air con i would be sending 1.2kw back to the grid and my air con is running for free ?

Re: my power bill

PostPosted: Tue Jun 27, 2017 11:17 am
by Gordon-Loomberah
solar1957 wrote: if i am producing say , just 1500w and i'm using a 3kw aircon , would this mean i am drawing 1500w from grid and 1500w from solar ?


yes, if you have no other loads.

And if i'm producing 4.2kwh and running 3kw air con i would be sending 1.2kw back to the grid and my air con is running for free ?


yes, as above

This is assuming that by "3kW aircon" you mean that your aircon actually draws a 3kW load, not does 3kW of cooling.

Re: my power bill

PostPosted: Tue Jun 27, 2017 12:04 pm
by solar1957
well i don't understand why my power bill, shows i send back to grid roughly the same amount of power as i take from the grid . eg this bill paid february 2017

anytime 962 kWh = $255.99
Off peak 596 kWh = $126.17
Solar rebate 1539 kWh @ 6c = $92.34

my daily average is 16.23 kWh don't use grid power for lights , stove (gas), ceiling fans

if i use 3kw air con 10 hrs per day and produce say 20 kWh per day from solar i don't understand my bill ?
I thought i would have used ...all... my solar energy and had none to send back to grid

Re: my power bill

PostPosted: Tue Jun 27, 2017 12:15 pm
by Gordon-Loomberah
It would be very unusual for you to be able to match your loads to solar production all day every day, so it is inevitable that you will be exporting energy to the grid, as well as importing some of the time.
In SE Qld I'd expect you would be producing ~25kWh/day on average, but you will be producing a lot more than that in summer, so more exports, and less in winter, so more imports. You'll be exporting more on sunny days, and importing more on cloudy days.
How do you heat your water? Do you use electric kettle/jug, toaster, oven, microwave etc?

Re: my power bill

PostPosted: Wed Jun 28, 2017 8:23 am
by APR
solar1957 wrote:if i use 3kw air con 10 hrs per day.....


Is the air con a split system or is it a ducted system?

If the system is a split system of 3kW cooling capacity, or a box type air con of 3kW cooling capacity, and is working at capacity, I would expect it to use somewhere between 7 and 10 kWh a day when operated for around 10 hours per day. So, a 90 day consumption of very roughly 600kWh to maybe 900kWh by the air con if operated around 10 hours a day for 90 days. If it is a ducted system drawing 3kW in normal operation, all bets are off.

If you are looking at a billing period of 90 odd days covering March to May I would expect your 6kW system to generate, roughly, somewhere around 2,000 to 2,200 kWh over that period if the panels are oriented to the north.

I can see your export being around 1,500kWh after deducting 3kW cooling capacity air con use from your generation, but unless, as Gordon queries, you have a resistive element hot water heater that is chugging through the power outside solar generation hours, your grid draw seems excessive. Are you running any water pumps? You are not by any chance on gross electricity metering?

If you do have a resistive element HWS, I would check that the pressure/temperature valve is not dribbling hot water and wasting energy.

To get a better handle on what and when electricity is being used and what is being generated, I would be installing an in-home energy monitor. They can cost a couple of hundred dollars, but you will have the info you need to maximise the use of your solar generation. Cheaper units give you energy coming in from the grid only, better units will give you grid usage, solar generation, and whether you are importing or exporting electricity.

Do a google search on "home energy monitors".

Re: my power bill

PostPosted: Wed Jun 28, 2017 8:54 am
by solar1957
thanks guys , i am using a 125ltr electric hot water system ,my electricity bill problem has been a long term thorn in my side , when i look back at power consumption before solar install my grid consumption was very similar to now ?
I have placed a timer on the hot water system so i control when and if power is supplied to heater.
i try to use sunlight hours , and only run for 30 mins at a time and maximum 6 times out of 24hrs ? ie 3hrs per day. turned on and off buy industrial timer and contactor not by temp or off peak installed by electrician , still cant seem to change the looks of my bill. Maybe i,m just trying to get blood out of a stone :D

Re: my power bill

PostPosted: Thu Jun 29, 2017 12:05 pm
by Gordon-Loomberah
If you are using some of your PV production and the imported usage is the same as before you installed your system, then you must be using more electricity since installing it.

Re: my power bill

PostPosted: Thu Jun 29, 2017 12:14 pm
by Alex Morrow
By "Off peak 596 kWh", you don't mean the controlled supply normally used for hot water, do you? This is the one at a lower tariff, that guarantees a certain number of hours of supply a day.

Re: my power bill

PostPosted: Mon Oct 02, 2017 12:33 pm
by solar1957
Hi all thanks again for comments on my last question , it now seems my solar system performance ended up with no Solar System Performance. My system was installed by Solar Freedom in August 2015.
B&B SF5000TL INVERTER AND 6KW X 250W SUNRISE PANELS
The inverter warning light keeps coming on , keeps going into self check , sometimes will produce 10kw per day other days will produce no solar energy at all.
My problem is , what would be the best process to start looking into problem , for example , repair companies want $180 travel time just to turn up , how do i trust a diagnosis , what should be a ball park $ figure on repairs , i've called 2 sparkies they wont touch solar!

Re: my power bill

PostPosted: Mon Oct 02, 2017 12:39 pm
by solar1957
Also would buying a second hand inverter same size different brand be an option ?