Solar Panel, Power & Battery Discussion

[exceladdict]

Sigenergy 3 phase 48kWh/25kW (battery capacity/inverter capacity)

In operation for 31days
Total 1.75MWh (1700kWh) have been sent through the battery

Cost of electricity going into battery:
10% at a cost of 8c/kWh (overnight tariff)
2% at a cost of 6 c/kWh (foregone solar FiT plus capital cost of solar + cost of capital , amortised over 20years)
88% at a cost of 0c/kWh (free tariff)

Cost of storing electricity:
=Capital cost of battery+ cost of capital amortised over warranty period and expressed as cents per warranted kWh. = 21c/kWh

Cost of electricity coming out of battery:
= cost of electricity to charge battery plus cost of storing electricity. So add 21c to the cost of electricity. Smaller capacity Sigenergy battery cost more on a c/kWh basis

Have a couple of acquaintances who have negative Amber experience so have left that provider.

I like the way you simplify this to cost of charging + cost of storage, makes it easy to decide if to sell when feed in tarriff exceeds the sum of these.

 

[Quickstatus]

makes it easy to decide if to sell when feed in tarriff exceeds the sum of these.

I only use the battery for the house , I don't export from the battery, only solar excess.

But yes people forget that there is a cost of storage. Some even think the battery produces free electricity.

 

[clifford]

But yes people forget that there is a cost of storage. Some even think the battery produces free electricity.

As a pensioner, I've looked at the cost of solar and batteries and have decided it's not for me (at the moment). However, my son has the works.

I'm finding it hard to see that I'd be better off with solar in my lifetime (whatever that might be) rather than continuing to pay the lowest standard electricity tariff (minus the senior etc, etc rebates). As I get older, I can't see this equation changing. When (if) my kids inherit the house, it may be a different equation for them.

 

[Quickstatus]

it may be a different equation for them.

Gotta do the sums to cut through the weeds.

 

[exceladdict]

As a pensioner, I've looked at the cost of solar and batteries and have decided it's not for me (at the moment). However, my son has the works.

I'm finding it hard to see that I'd be better off with solar in my lifetime (whatever that might be) rather than continuing to pay the lowest standard electricity tariff (minus the senior etc, etc rebates). As I get older, I can't see this equation changing. When (if) my kids inherit the house, it may be a different equation for them.

Where abouts are you in Australia and/or what's the effective seniors discount?

The general rule seems to be that a right sized (for your consumption) solar system pays itself back long before the warranty is up, but batteries are marginal and more dependent on your individual use case.

Of course YMMV e.g. if you use zero energy while the sun is up there will be little to no benefit!

 

[Quickstatus]

f you use zero energy while the sun is up there will be little to no benefit!

Actually, there might actually be a case for battery only and no solar - it depends on the retail tariff

For example
OVO free 3 hours plus 8c/kWh overnight for if the resident also owns an EV (6 hrs)
A battery would charge during the 3 hours - and sized appropriately and or depending on average consumption, it might be enough to cover the non free and 8c/kWh overnight = 15hrs.

A battery depending on size might cost anywhere between 20c/kWh and 30c/ warranted kWh (converting capital cost to cost of electricity coming out of battery and smaller capacity batteries generally cost more than larger capacity batteries on a cents /warranted kWh basis)

So if someone is on a single tariff which is >30c/kWh, something like OVO or similar which gives free electricity period plus a battery might be worthwhile.

 

[Buzzard]

We have had solar panels for a few years, since we purchased the place. I'm not keen on getting a battery as I doubt it would be beneficial. How many more years have I left on this mortal coil? Will we decide to sell up and move to the beach? It's not necessarily an easy decision when it comes to installing a battery.

 

[exceladdict]

We have had solar panels for a few years, since we purchased the place. I'm not keen on getting a battery as I doubt it would be beneficial. How many more years have I left on this mortal coil? Will we decide to sell up and move to the beach? It's not necessarily an easy decision when it comes to installing a battery.

Definitely. That's why I'm working this maths so hard. Payback won't land til year 9 or 10 based on current numbers so want to be sure we count it correctly

 

[Quickstatus]

Payback won't land til year 9 or 10 based on current numbers so want to be sure we count it correctly

I think that is an incorrect method.
The better method is to convert the cost of battery to cost of storing electricity in cents/kWh

The numerator depends on
Capital cost of battery
Cost of capital
Period of warranty

For example if cost of battery is $21000
Cost of capital is say 6%.
Period of warranty is 10 years as most batteries have a 10 year warranty.

Over a 10 year period the total cost of battery = $28,000
(Think of this as paying back a $21,000 loan with monthly payments over 10years )

The denominator is the number of warrantable kWh over that 10 years. This can be found in the warranty battery. In the $21,000 battery example above the warrantable kWh is 142000 kWh

So the cost of battery is $28,000/142,000 =20 cents/kWh.

Using this figure, add in the cost of charging the battery. This is the cost of importing electricity from the grid. I also use a similar calculation to work out cost of electricity produced by solar. But the warranty is 20 years.

So as long as you only charge the battery such that the combined cost of battery + cost of charging is less than the tariff at the time, you are ahead.

The problem with using a payback period is that the retail electricity plan for houses with batteries is quite different to retail plans for non batteries. It's not comparing like for like.