A solar battery is a significant investment and one that shouldn’t be made lightly. If you’re an existing solar power system owner and want to determine if such a purchase may be right for you, try SolarQuotes’ new battery calculator.
SolarQuotes has had a spiffy solar and battery calculator for years, which is great for getting an estimate on savings and simple payback for just a solar system, or a combined solar and battery setup. While it separates savings/payback figures for solar and energy storage, SQ Founder Finn wanted to create a dedicated and easy-to-use calculator for adding a battery to an existing solar system – and the job’s now done.
But read on before you scoot over there to check it out.
You’ll Need An NEM12 File (Don’t Panic)
In order to provide you with solid estimates, you’ll need to upload what’s called an NEM12 file to the calculator. The information in this file is generated by your home’s smart meter. If you’re in Victoria, or on a time-of-use-tariff or had solar panels installed in the last three years, you’ll have a smart meter.
An NEM12 file contains consumption and export information at 30-, 15- or 5-minute intervals and is sent to electricity retailers for customer billing and calculating your feed-in tariff. It’s this granular data that enables the new SolarQuotes battery calculator to provide a good estimate of savings and simple payback based on your household’s electricity profile.
If you don’t have this beastie handy (and many wouldn’t), here’s how to access your smart meter NEM12 data. Getting access should be straightforward in most cases, but if you couldn’t be bothered doing so or don’t have time right now, here’s a sample file with real world data you can use to try the calculator. This was provided by one of our beta testers who has 12kW of solar panels and a 10kW inverter.
Ready, Steady, Calculate!
With the NEM12 file sorted, you’re ready to rock. Head out to the battery calculator, where you’ll need to enter your postcode, select the electricity plan you’re on and adjust the pre-populated tariff rates where necessary, choose a battery, upload the NEM12 file and then hit the calculate button.
Using the sample data file, selecting a Tesla Powerwall and our home’s electricity plan, here’s a summary of the battery calculator’s results:
- Bill before battery: $1,126/year
- Bill after battery: $-85/year
- First year savings: $1,211
- Simple payback: 10 years, 6 months
- 10-year savings: $14,320
- 20-year savings: $34,602
The results page will also will show you other detailed information including the impact on seasonal bills, cumulative savings and more.
But the good times don’t end there. You’ll also be able to email/print the results and have the option of sharing them with others. You can even request home battery quotes from trusted installers directly from the results screen if you wish.
We hope you find the new solar battery calculator useful. If you have any questions or comments, or come across a bug, please submit your feedback below – we’d appreciate it! By the way, if you don’t have solar panels yet or can’t access your smart meter NEM12 data, give our original solar calculator a whirl.
About Michael Bloch
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REAL RISK OF FIRE. CHEAPER FOR ME TO IMPORT THEM!!
Hi Dave,
What are you yelling about exactly?
Think his cheap a*e e-scooter has just set fire to his apartment.
FYI – your NEM12 data file needs to cover at least 12 months worth of data ( I guess that is what the “12” stands for)
Hi, downloaded 12 mths csv but calculator said sorry no go as need 12 mths data.
mmm
Might come back when gremlins sorted..
Ron, thanks for trying it out. Some DNSPs don’t seem to conform to the standard, so if you can send the csv to [email protected] we can investigate.
Cheers!
What is the assumption re daily rate charge currently $1.17 per day irrespective of whether I use the grid or not?
Hmmmm. Perhaps your battery calculator is a work in progress. I can’t see where my retailer is on your dropdown list.
It’s a very small retailer. Perhaps you haven’t heard of them before.
They currently go by the name AGL.
Any reason they’re not on the list????
What is your postcode?
I also just checked and AGL is missing from the list, Postcode is 3802.
This is odd because I found this calculator 2 weeks ago and AGL was in the list then.
We’re looking into why AGL is now missing.
AGL is back on the list now. Apologies for the inconvenience.
One thing to note about the results: the calculation assumes your battery will only be charged with excess solar. Some batteries can be configured to charge with off peak electricity – during the day – if there’s not enough solar. And some can also charge at night from off peak electricity. The next version of this calculator will let you see the savings from off-peak charging, which can improve payback.
My battery, for example, cycles twice per day using a combination of solar and off peak grid electricity:
While you have an option for different rates at different times, which I guess could be utilised for Sun Tax periods in affected areas, you don’t factor in solar plans which offer premium rates for the first 10 kWh etc. This skews the data, though I’m uncertain how much.
The calculator also assumes recharging to max as soon as the sun starts providing power meaning those affected by a Sun Tax likely fill their battery before the peak\taxed period starts and then start earning the reduced rate. This seems sub-optimal.
I’m assuming there’s also no factoring in bad days\weeks such as of late where the solar isn’t enough to cover household demand, let alone fully refill a battery.
“The calculator also assumes recharging to max as soon as the sun starts providing power” – yes – that’s how almost all current battery software works if you are on a flat tariff.
“I’m assuming there’s also no factoring in bad days and weeks such as lately, when the solar isn’t enough to cover household demand, let alone fully refill a battery.” the calculator uses your actual 12-month, 30-minute import and export data to determine how much solar you had spare to charge the battery every day of the year. That’s why this calculator is different – it uses your smart meter data.
Hi there,
This is of great interest to me as I recently commenced the battery process (via getting installers from solar quotes).
For the next iteration, i think the following would be useful;
1. The ability to add more than 1 battery. E.g. I might want 2 or 3 5kWh batteries, but if i choose such a battery, I end up with a capacity of 5kWh only.
2. Tariffs: As the NEM data is historical, you should be able to choose the plan that is applied to that data. However an option to have a different plan post battery should be there. E.g. I am currently on a flat rate plan, but if/when i get a battery, i will be switching onto a time of use plan.
I can work around the above 2 items by choosing a different battery and then doing 2 separate calculations with the different plans, but it would be nice if I didnt need those work arounds.
Keep up the good work!
Regards
Jon
Hi Jon,
We’re working on better versions all the time but yes different capacity option is coming. I’ve used it to check the winter surplus of my existing system against different batteries.
Cheers
Given we’re back into the era of actually having reasonable earning rates on savings – perhaps also doing a Net Present Value calculation is a lot more relevant than payback period.
Especially if you allow us to enter the discount rate to be used in the calculation.
For example for some people it would be appropriate for them to use the rate they pay on their mortgage.
At 4% PA, semi annual then a $400 saving in ten years is worth just over $269 today, quite a big difference for assessing the financial worth of investing in a battery.
At 5.5% interest though the $15,000 battery system you don’t buy will have earnt you close to $11,000 after 10 years. Of course much of that ‘profit’ will be lost to paying for grid power so I guess break even but keep your capital for a newer and better option? 🙂
Hi Michael
I put the data in as requested – uploaded a csv file, but your calculator keeps telling me I must have 12 months of data. My data is 01/07/23 to 30/06/24? Is that not enough?
cheers, Tom
Hi Tom,
I had the same thing so I downloaded a fresh data file and it worked.
Some retailers aren’t providing it in the correct NEM12 format so you may need to take it up with them. For mine (from SAPN) they have a couple of simplified options but the full detailed file is the one you need.
Thanks Anthony I will give that a shot.
Does it factor in the cost of capital to buy the battery? For example, if I pay for it using cash from my offset account, then my home loan interest payments will go up by approx $700 per year ($14k * 5% mortgage rate). Taking that extra annual cost into account significantly changes the payback period of the investment.
no it’s simple payback only
Isn’t the current battery life only 7 years? If correct that puts a dent in any longer term (10 years or more) savings
Hi Ross,
My two EVs have a lithium battery which is 13½ years old and still going. Warranties on house batteries are ten years with a “mileage” figure of megawatt hours delivered generally.
Ross,
Domestic LFP battery banks warranted to 8,000 cycles are now quite cheap – so cheap that I put in 46 kWh, resulting in around 2 battery cycles per month. Even at 4 cycles per week, that would be 40 years for capacity to fall to 80%. The nominal 20 year calendar life is up first.
There are Teslas out there which have done more than half a million km, and The Electric Viking says the battery warranty on the MG4 has been extended to a million km in Thailand. Dunno if that’s coming here.
And after that million km of driving, the EV battery can still be used for domestic energy storage, as 80% capacity on an 80 kWh battery is still quite useful. There are a lot of slow learners missing out on the current opportunities, but demonstrated benefits become obvious over time.
Finn mentioned this in: https://www.solarquotes.com.au/blog/home-battery-saver-mb2940/
Unfortunately it looks like batteries are only relevant for particular kinds of households. In my case the payback period was 17 years, so I’d be better off leaving my money in a low interest transaction account than buying a solar battery – yes obviously there’s much better investment options.
Barring a shift to off grid, a massive increase in power prices, or a massive collapse in FiTs – they’ve just dropped 20% and there’s no Sun Tax being applied yet, I can’t see the battery maths working for me.
What are the assumptions for batteries becoming useful? From memory – I can’t remember if it was SQ data or calculations I did ages ago, you need a very large system and high usage of said system to bring the cost per kWh down low enough to justify the investment.
Or as my solar installers said when I asked for a quote, they just aren’t worth it if you’re looking for a Return on Investment.
An interesting tool, but a dead end for most?
Hi George,
Some people have made batteries into just what they need because they don’t have enough roof space. https://www.solarquotes.com.au/blog/install-second-powerwall/
Hi Michael, a great calculator thank you for your efforts on this front. It’s very welcome. One question about the results: why would they show grid usage when the battery hasn’t yet reached its 20% reserve limit? Maybe there is a simple answer to this but it’s not clear to me. Thanks, Robert
Thanks for putitng the calculator together! Unfortunately it doesn’t seem to like Jemena’s CSV file – claims no interval data but it’s all there… Happy to provide the file if it helps unpick any bugs.
shoot the file to [email protected] and we’ll have alook
Reading some trade journals out of China. BOM cost per kWh for lithium phosphate oxide cells is down to 340 yuan. That’s about $70 Australian or $47 US. This is one of those tipping points, where using batteries to run a constant load from battery backed solar (in Australian conditions) becomes cheaper than using grid power.
The other side of the coin, is it is now viable to use them at grid scale to timeshift otherwise curtailed renewables, turning the duck curve into something a bit flatter, perhaps increasing solar feed in prices.
In the near future, we are going to have to rethink the electricity market once again. Thermal (Fossil fueled or Nuclear…) generators will move from load following into a residual role. Making up the gap between the day’s VRE generation, and demand, not in power, but bulk energy.