Not mentioned . Should be 10KWac

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Why.? = Please show your calculations for around 6 years ROI.
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This is wrong

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Please show the right.
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I don’t recall Bess will be 6years in my calculation. It’s about 7.5-8 years. Coz the saving really fluctuates especially when u have afa. Maybe in best case scenario it will be 7 years. Or if u do those diy stuff with cheaper parts.

what was the reference price u made before?

at 39k the ROI will be faster, also, the elders are at home all the time so daytime consumption will be 20% plus, 32kwh just ok for storage, may work like 90% NEM

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According to the above Solar company, Trdenergy, it's more like your calculation of around 6 years ROI may not work like 90% NEM (after contract ends) and the new ATAP.
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i dont read wall of text, give summary please

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The summary is in the highlighted and/or bolded parts. Please read.
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So, under ATAP with BESS, if the household uses most of its electricity (90% or more) at night, which is most households, the ROI for the above RM39k Solar system is about 7 years, ...
.... but if the household uses some of its electricity (>20%) at daytime, eg got elders at home, the ROI is about 6 years. Correct.?
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AFAIK, most households with Roof Solar use most of their electricity at night, eg cooking dinner, bathing with water heater, using Internet, TV, computers, etc in aircon living room, charging EV car overnight, sleeping in aircon rooms, etc. Correct.?
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For battery, a 32kwh battery will theoretically provide 960kwh at night. But after factoring 90% DOD, it’s only about 860kwh, and also there are days when you ar unable to fully charge due to low production. In good months for example, there will be 15% - 20% of the days when u get lower than expected yield and unable to fill up ur battery. This hasn’t include the conversion efficiency which will eat up a few more kWh along the way.

Plus, if battery is fully charged by noon on good days, all those extra generation will only be paid 20cent (if under atap) or go to waste if not under atap.

Then we have negative afa on certain months. Electricity tariff is lower with the new calculation, so it will also drag the ROI a bit too.
For example, in the past , the before solar and after solar bill has a bigger difference, but even under nem, the gap narrow a bit.

The good thing about the Bess is the possibility to get the eei incentive as the import is lower significantly compared to nem.

The best scenario for ROI will be those with over 1500kwh usage, and with the system will be able to reduce the import figure to just a few hundreds units. If your bill is around this usage, then it’s possible to have quicker ROI as what u mention, (6years).

I would think 6 years is always on paper. Expect some delay in ROI coz lots of factors might affect it unlike nem, which is quite straight forward.

Keyword= most

Say there are 100kwh under generation in total for some days and 100kwh over generating on some days

Total battery storage 760kwh, total day use 8kwh x30 or 240kwh, total export 300kwh @ 20sen. Day use should probably be higher because everyone in the house during weekend

Total generation in a month 1300kwh

Total saving about 500 a month

Roi about 6.5 years

Afa is fluctuating so just ignore coz there maybe certain time afa is positive

It’s not that straight forward. Coz you can’t total the 100kwh jsut like that. It’s on daily basis. If you have more days of lower generation, expect to be hit with higher bill. A 100kwh could be just due to 3 day low yield but also it can be due to 6-7 days of low yield. This could also affect.

To achieve 500 saving, it would be easier if usage is above 1500kwh, coz ur bill before solar is based on 37 cent per kWh excluding other charges instead of 27 cent. This is also one thing that can speed up the real ROI.

Going solar has been a long term commitment. Even under nem, it’s about 5-6 years. So Bess at 7 years is very acceptable. Who doesn’t want free solar setup and battery from Tnb right? Instead of jsut paying for electricity.

This post has been edited by bee88: Oct 30 2025, 07:39 AM

Just rough estimation say 10 days of under generation of 10kwh each day, 10 days of normal generation, 10 days of over generation

If usage above 1500kwh will easily cut roi for 1 year

First thing to do now is to install a power meter with data logging. After checking your hourly usage, you know your house hourly electricity usage and day-night use distribution. Then, you can size your solar and BESS accordingly.

Something to take note:

Energy import and export are calculated separately for each phase, not as a combined total across all three phases.

Example:

Phase A consumes 3 kWh

Phase B generates 2 kWh

Phase C generates 2 kWh


This is not treated as a net export of 1 kWh (3 − 2 − 2 = −1 kWh) ❌.
Instead, TNB records it as 3 kWh imported and 4 kWh exported ✅ — calculated per phase.

These values are then accumulated over the month and reflected in the billing cycle.



This post has been edited by RicoT: Oct 30 2025, 08:15 AM

Half hourly consumption is available in mytnb website but of course not in real time, but you get the historical data there

As to minimize the issue of importing in one phase but exporting in the other, this is where the inverter with load balancing feature play a significant role. It can be optimized to prioritize self consumption. I am mainly using only phase A and sometime phase b and c except when i charge my ev using a 3 phase charger



The system always prioritize self consumption and adjust the output on each phase based on demand. The graph above is showing current output from the inverter itself.


The graph below shows when there almost zero usage except for the fridge and some small consumption from multiple cctv and ups
All output spread evenly among 3 phases



This post has been edited by backspace66: Oct 30 2025, 09:41 AM

yeah ROI of 7 years are acceptable, furthermore although battery warranty is 10 years, it wont drop dead at 10 years + 1 day, just the capacity degrade to 80% or so, still can use for very long time for further saving down the line

just like some idiot worry about the 8 years EV battery warranty

Hi Sir, can you recommend such power meter?
I assume it is install at DB?
Does it give live reading of consumption from tnb? Thank you

He’s using Shelly iinm u can do that if u want. But not really necessary info for nem users. Good for tinkering around though.