Should we use our solar energy or feed it to the grid ?

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Re: Should we use our solar energy or feed it to the grid ?

Postby zzsstt » Tue Nov 20, 2012 6:07 am

Smurf1976 wrote:The basic concept is that the fixed network costs of having a line to your house in the first place are payable in full regardless of actual consumption.


I understand the concept of a high fixed charge. I was questioning how 17c, or any other figure, could be seen as an acceptable price for 1:1 PV FIT when the network charge would still be applied before that energy could be resold? If the fixed cost ("daily charge", "service charge", "metering fee" whatever it is called) was increased to cover all the network charges such that energy was charged as energy, then 1:1 at the "normal" cost works fine, but whilst there is a network charge imposed by the kwh on the delivery of power, no 1:1 price can ever be anything less than a large loss to the power company.

Tracker wrote:I charged in the OP.. supplied a special cct during the peak... measured everything in and out, and found a 50% savings but this excluded the costs of the batteries. The other moderating issue was the inverter/charger, which had terrible losses..


Offpeak power is more or less 50% of the cost of peak power (under my suppliers fee scale). I suppose that if offpeak was far cheaper it might work, but at 50% it doesn't - by the time the charger has lost 10-15%, and the batteries have only returned 80-90% of their charge, and the inverter has lost another 10% (all cumulative losses) the price of that offpeak power would have risen dramatically. Add in the long term costs of batteries and the lost "return" on capital invested and I would be much better leaving the money in a term deposit!

Tracker wrote:Another moderator, is the belief that off peak will be raised in proportion to peak as more folk take advantage of OP rates.


This cannot fail to happen! Whether or not people are taking advantage of that power is largely irrelevant. Whether or not people are using PV to ossfet their peak usage is irrelevant. The point is that privately owned companies want to make money in ever increasing quantities. Under a state owned scheme, selling price reflects cost, but in a commercial environment selling price simply reflects what the market will tolerate. Off peak power is a lost opportunity for profit, and it won't stay that way for long!

offgridQLD wrote:So how low are you running your battery's every night? Do they have a conservative cut off or are they just going to live a short life?


At present I have the cutoff set at 60% SOC, but I'm still experimenting!
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Re: Should we use our solar energy or feed it to the grid ?

Postby Tracker » Tue Nov 20, 2012 7:17 am

Sorry... I had intended to say the op offpeak would rise disproportionately to peak,

Remember that we in Sydney, had TOU rates like 11c, 23c, and 42c., so the saving came from using the 11c inefficiently to replace the 42c.. the actual cost ended up more like the shoulder rate of 23c... That's a win.
Remember that I actually metered all the power.. it was not a case of estimating the various losses..
As it was accurately time switched, I could relate all to the tou rates.

One problem was that I did not have any SOC control, and so I likely wasted power during the recharging.

Again I stress that this took no account of the cost of the setup..
..
.
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Re: Should we use our solar energy or feed it to the grid ?

Postby zzsstt » Tue Nov 20, 2012 4:56 pm

Tracker wrote:Sorry... I had intended to say the op offpeak would rise disproportionately to peak,


I thought that was what you intended, so my answer was written with "disproportionate" in mind!!

Tracker wrote:Remember that we in Sydney, had TOU rates like 11c, 23c, and 42c., so the saving came from using the 11c inefficiently to replace the 42c.. the actual cost ended up more like the shoulder rate of 23c...


That makes sense, you had a nearly 4:1 ratio between peak and off peak. We buy offpeak at about 50% of peak (peak and shoulder are charged at the same price) and there is no saving in using batteries because the losses are so great. As I said:

zzsstt wrote:I suppose that if offpeak was far cheaper it might work, but at 50% it doesn't
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Re: Should we use our solar energy or feed it to the grid ?

Postby evadsiv » Wed Jul 10, 2013 2:35 pm

Jackie wrote:[Moderator - moved from Solar Analyser Support]


We have a new 4.8 kw system installed and running. We are on a 1:1 on the 25c rate and live in the Sunraysia area which is supposedly one of the most solar friendly climates in Australia.

Are we better off using off peak power at night @ 12c to run our pool pump and dishwasher or should we run them during the day using the solar power generated ? Some peole have suggested we are better off getting 25c back from the grid and clean the pool at night for 12c ?

Others say that we should clean the pool during the day as it wouldn't use all the solar power generated (on a sunny day) and the grid could still be fed 10-15c at the same time as we are using it ?


For shifting from off peak power to day time power.
If it takes 10kWh at say 2kW to clean your pool.
If you do it after hours it will cost you about $1.20 (10 x 12c) but you will not be using that 10kWh during the day so you can export it to the grid thus making $2.50 - $1.20 = $1.30 to you in total
If you do it during the weekday there will be no direct grid cost (as long as it is not cloudy) but you will lose the $2.50 that you would export to the grid and if it is cloudy then your grid cost will increase but you would not be exporting as much to the grid either.
0kWh charged but -10kWh exported to grid 0-2.50 so -$2.50 to you.

So time shifting to off peak power is of financial benefit.

This is as long as your grid peak cost and off peak costs stay the same. It becomes a much more difficult equation as off peak and peak costs raise. Because the only one that will not go up is the feedin price ;)
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