Solar Panel, Power & Battery Discussion

[tgh]

We are currently on 48c…..

 

[Quickstatus]

blackout protection is necessary.

It's like the spare tyre question.

Most ?all modern battery systems have inverters that can operate in an off grid mode

In order to operate in a blackout the system needs to be automatically electrically isolated from the grid. This is a safety related issue as you don't want parts of a de-energised street to be still supplied from someone's solar panels. Many existing solar inverters are grid tied meaning they need to see AC power in the street to work - they need it because whatever AC power they generate from solar needs to be in sync with the AC frequency from the street. . When there is a blackout they don't see the AC and will turn off as a safety requirement.

New systems have hybrid inverters meaning amongst other things. they can operate without needing the AC reference from the street . This poses a problem as per the above safety issue. So the way around it is to install a Gateway which is a box of high power relays/contactors that sit between the street and the inverter. When the relay senses the street has no power, it trips and isolates the house from the street. The hybrid inverter can then happily works as though nothing has happened and the house can continue to be supplied by solar /battery.

There is a changeover which is normally in the milliseconds as the inverter goes from using the AC from the street as a reference to generating its own AC frequency

Any thoughts on what the payback time for this might

Give me the cost of battery and the amount of kWh the warranty guarantees over the warranty period, and the warranty period

sense to have a manual changeover ??

Auto changeover better and while in off grid mode you can dump non critical loads such as aircon - these can often be operated by an app. Or you can wire the system such that when in Off grid mode only critical circuits are automatically supplied.

 

[VPS]

It's like the spare tyre question.


Give me the cost of battery and the amount of kWh the warranty guarantees over the warranty period, and the warranty period

Auto changeover better and while in off grid mode you can dump non critical loads such as aircon - these can often be operated by an app. Or you can wire the system such that when in Off grid mode only critical circuits are automatically supplied.

Thanks

I have a 6.64 kW solar panels set up.

I have a quote for a solar battery for $8.2k for a 20kw battery but need to check whether that includes blackout protection.

My electricity bill is around $2k pa but I recently installed a new aircon and it's much cheaper to run.

---

System details
Your custom design
Battery size
20 kWh (20 kWh usable)
Battery storage1
1 × Alpha ESS SMILE-M-BAT-5P IV · 20kWh

Warranty

https://static.getpylon.com/warranties/storage/AlphaESSWarranty_30102024-AU.pdf

Data sheet

https://static.getpylon.com/datasheets/storage/AlphaESS_SMILE-M-BAT-5P-AU.pdf

 

[AuSammy]

We are in Brisbane suburbs.

We have 13.5 in the roof with no overshadow and twin 5 inverters installed.

Supply from Energex is single phase and retailer is Origin with FIT of 4c

Been in this place 2.5 years and not paid for electricity yet, partially due to gov and retailer credits. However credits are gradually being eaten away with each quarterly bill.

If the gov rebates dry up and if we have a really hot wet season I expect we may go from credit to start paying.

While any energy costs are likely to be insignificant in the near term, there is no real financial incentive to install batteries.

However, there are couple of reasons I have been toying with installing batteries.

1. Blackout protection. Although we haven't had one at this place (we have had in the past elsewhere in Brisbane), the increasingly unstable weather patterns make it more likely in the future.
2. Still contemplating purchasing an EV within a couple of years.

Oh and 2 person (adults, one senior) household.

Anyone would like to comment if they were in this position.

 

[Quickstatus]

I have a quote for a solar battery for $8.2k for a 20kw battery

So:
Battery $8200
Warranty 10 years
Warranted kWh in that 10 year period 3120kWh per installed kWh. Tot = 62400kWh. Meaning you can take 62400kWh out of the battery during that 10 years

Let's assume you use all of that 62400kWh in the 10 years. If you use all of that in less than 10 years it will be cheaper per kWh

Let's also assume the opportunity cost is the interest rate of a home mortgage = 5%

So 10 years of $8200 actually cost you $10436
Because it was not earning an income elsewhere.

Let's assume that each kWh you see is actually 95% of the kWh that goes into the battery. Charging and discharging incur some losses so your 62400kWh is actually 59280kWh

So 10436/59280 =0.176
= 17.6c/kwh. This is the cost of discharging the battery of power on a per kWh basis

However there is a cost to charge the battery. The cost of this electricity is either your solar panels or cost of electricity from the street. Add this to the 17.6c/kWh. Let's say the cost of solar to charge the battery is the greater of Feed in tariff and 5c/kWh approximate

So let's round up the cost of battery to 20-22c/kWh for arguments sake

Your payback period depends on the cost of your street power that the battery replaces.
If the cost of street power is less than 20-22c/kEh cost of charging you are losing money.

The idea is to use all of the warranted kWh before the 10 year period because the amortisation period is then not 10 years but less - you are not paying "interest" once it is fully amortising.

So it is important to dimension the battery size appropriately..

 

[VPS]

So:
Battery $8200
Warranty 10 years
Warranted kWh in that 10 year period 3120kWh per installed kWh. Tot = 62400kWh. Meaning you can take 62400kWh out of the battery during that 10 years

Let's assume you use all of that 62400kWh in the 10 years. If you use all of that in less than 10 years it will be cheaper per kWh

Let's also assume the opportunity cost is the interest rate of a home mortgage = 5%

So 10 years of $8200 actually cost you $10436
Because it was not earning an income elsewhere.

Let's assume that each kWh you see is actually 95% of the kWh that goes into the battery. Charging and discharging incur some losses so your 62400kWh is actually 59280kWh

So 10436/59280 =0.176
= 17.6c/kwh. This is the cost of discharging the battery of power on a per kWh basis

However there is a cost to charge the battery. The cost of this electricity is either your solar panels or cost of electricity from the street. Add this to the 17.6c/kWh. Let's say the cost of solar to charge the battery is the greater of Feed in tariff and 5c/kWh approximate

So let's round up the cost of battery to 20-22c/kWh for arguments sake

Your payback period depends on the cost of your street power that the battery replaces.
If the cost of street power is less than 20-22c/kEh cost of charging you are losing money.

The idea is to use all of the warranted kWh before the 10 year period because the amortisation period is then not 10 years but less - you are not paying "interest" once it is fully amortising.

So it is important to dimension the battery size appropriately..

Thanks for that analysis.

I already have solar but FIT is 2c

Minimum I'm paying at the moment for electricity is 19c but that goes up to 51c which is peak time and probably when I would use the aircon most and the electric stove the most so with all of that I think it's probably worth it and payback of around 10 years but whether I'll still be here or not is another matter

 

[Pushka]

Thanks for that analysis.

I already have solar but FIT is 2c

Minimum I'm paying at the moment for electricity is 19c but that goes up to 51c which is peak time and probably when I would use the aircon most and the electric stove the most so with all of that I think it's probably worth it and payback of around 10 years but whether I'll still be here or not is another matter

April next year is when current plan ends. Not hopeful then. Interestingly just looking at plans if I changed today I can see the 2c FIT amd the daily charge plus usage charges are cheaper than if I opt for the highest which is 8c FIT. They'll get us either way.

 

[Brissy1]

We are currently on 48c…..

Likewise; bizarre but installing a battery would likely increase your electricity bill.

 

[Buzzard]

Thanks for that analysis.

I already have solar but FIT is 2c

Minimum I'm paying at the moment for electricity is 19c but that goes up to 51c which is peak time and probably when I would use the aircon most and the electric stove the most so with all of that I think it's probably worth it and payback of around 10 years but whether I'll still be here or not is another matter

I hear you. Exactly what I'm thinking, will I be here at 80?

 

[Brissy1]

...work out what to do

Insurance?

 

[RAM]

We are in Brisbane suburbs.

We have 13.5 in the roof with no overshadow and twin 5 inverters installed.

Supply from Energex is single phase and retailer is Origin with FIT of 4c

Been in this place 2.5 years and not paid for electricity yet, partially due to gov and retailer credits. However credits are gradually being eaten away with each quarterly bill.

If the gov rebates dry up and if we have a really hot wet season I expect we may go from credit to start paying.

While any energy costs are likely to be insignificant in the near term, there is no real financial incentive to install batteries.

However, there are couple of reasons I have been toying with installing batteries.

1. Blackout protection. Although we haven't had one at this place (we have had in the past elsewhere in Brisbane), the increasingly unstable weather patterns make it more likely in the future.
2. Still contemplating purchasing an EV within a couple of years.

Oh and 2 person (adults, one senior) household.

Anyone would like to comment if they were in this position.

Charging up a home battery (loses typically up to 25% of the kWh input depending on what battery you have as it converts it from DC to AC (panels to inverter) and then from AC to DC (inverter to battery and then back again when you draw out the power). A term quoted for batteries is 'round trip efficiency' but this only refers to the power lost (kWhs) getting it into & out of the battery.

If you were to then draw from the battery to charge an EV battery you face another loss. Your EV is a mobile battery - so depending on your usage (how often and how far you drive) will dictate (had written generate) the outcome.

For example if you drive the typical distances a week (less than 300km) then you may well be able to charge it fully by leaving it plugged in to a household socket during the day(s) over the weekend. Especially (without the need to get a special charger installed) if you have capacity on your existing power supply to added say a 30 Amp circuit. Going by the rule of thumb that it should not operate continuously at more than 80% of capacity (so 24 Amps) then at peak charging (managed by your car's software during charging) you can add up to around 5.28 kWh per hour plugged in (24 * 220 volts = 5,280 watt hours or approx 5.28 kWhs). How much it charges will depend on the season & conditions BUT it will always be worse if you're double dipping and charging by using a household battery to supply it.

Also given a household battery typically has a fraction the capacity of an EV - you cannot come close to fully charging it - so you are required to leave it parked at least some of the time during the day when your roof is generating power. As you can see from the above example you'd need to be generating well in excess of say 7 kWs to be able to charge IF you do not have AC or other high draw running in your home. So in summer this would likely require 10kWs of panels on the roof, and in June more than 20 kWs.

If you do less distance per week and have the car parked at home more then the figures are more favourable. Many EVs allow you to set a max draw when charging so despite having a capacity to supply 24 Amps (in the example) you could set it to draw a lesser amount (due to lower solar generation during Autumn/Winter) say down to 3 or just 2 kWhs.

Yes, lowering the draw will lengthen how long it takes to charge BUT most EVs have a charging cycle which starts off high and as the battery fills the draw (in kWs) declines. Some quite rapidly - meaning that you may find that despite say halving the draw that the time taken to charge to the level wanted (typically no more than 80% for most battery types to ensure longevity) is much less than 2x.

Even better, as move brands/models start to allow V to Grid, V to Load etc - then you can use your EV to power your house (or a subset of it) when the sun isn't shining. In the US when Ford introduced the F150 Lightening (nearly 100kWh battery) with VtG or VtL - it has forced other manufacturers to allow the same. Tesla is about to enable it for the Cybertruck and its only a matter of time (due to competitive pressures) before it can be done on any Tesla. With Teslas it is virtually a software switch (toggle on/off) to be able to do it. People have been 'jailbreaking' the software to enable it but if you do so it voids the warranty from Tesla.

Must protect Tesla Powerwall sales mustn't we? They get about 9x the margin on the battery capacity vs the effective cost of it in a Tesla vehicle. hence why Tesla is being dragged kicking & screaming into doing so BUT they built their vehicles for years being able to do so simply by getting a software update over the air.

Shame the software with the Ford Lightening is so buggy/pathetic.

If your car stays at home some days during the week then the equation can be even more favourable

 

[exceladdict]

I have a 6.64 kW solar panels set up.

Now down to FIT of 2c

I have a quote for a solar battery for $8.2k for a 20kw battery but need to check whether that includes blackout protection.

What are people's thoughts on whether blackout protection is necessary.

My electricity bill is around $2k pa but I recently installed a new aircon and it's much cheaper to run.

@exceladdict are you still interested in running some numbers

Any thoughts on what the payback time for this might be?

Absolutely, I'll DM you, have the web app almost at alpha stage if you have interval data to use. Will just need to grab your retailer and tariff details too for comparison, I only have a couple configured at the moment.