Home Solar PV System: How Much Can It Really Save?

 

Three months ago I wrote a post about installing a home solar PV system "Home Solar PV System: A No Brainer?".

Now, my home solar system has been up and running for more than 2 months.

It's time to share my short experience and how much money I can actually save.

Is residential solar system under NEM scheme really worth it?

As my average monthly electricity bill was approximately RM300, my contractor recommended a 6.40kWp solar PV system comprising 10 solar PV panels and 3 microinverters.

The overall price is RM16,000.

The brand and model of the solar panel is LONGi Hi-MO X10 640W Half cut Monocrystalline BC-Cell PV Modules (LR7-72HVH 630-650M). It comes with 15 years product warranty and 30 years performance warranty.

LONGi, a China brand, is one of the top 5 largest manufacturers of solar panels in the world in recent years.

As for the microinverters, the brand and model is China's Hoymiles HMS-2000. It has 12 years standard warranty but the contractor extends it to 25 years.

Each microinverter can be fit into one solar panel but for cost saving reason, only 3 microinverters are deployed for 10 panels in a 4:3:3 configuration.

There is a 5-year workmanship warranty which covers repair of defect, imperfections and water leakage. The warranty of aluminium mounting structure against corrosion is 10 years.

There will be 5 years of free insurance and 6 years of free annual maintenance service including non-scheduled on-call service.

However, after 6 years, the annual service fee (scheduled & on-call) is RM700 for the size of my solar system, which is not cheap.

It took more than 3 months for my home solar PV system to be commissioned which is quite a long time compared to what I expected.

I signed the quotation in the end of January, system installation was done in the end of March and TNB only came to change the meter in early May.

The delay was probably due to high demand since most people rushed to install it before the NEM 3.0 quota and SolarIS rebate ended.

My home solar PV system started on 5th of May. For the month of May from 5th to 31st (27 days), my TNB bill was RM8.90.

Subsequently for the whole month of June (30 days), my TNB bill was -RM2.80, with a "Baki NEM" of 80kWh. This means I sold more electricity than I used from the grid.

The "Baki NEM" of 80kWh should be the "credit" I earned by exporting excess electricity to TNB's grid. This credit will expire on 31st Dec 2025.

Lets look at the detailed break down of the TNB bill in June below. Please bear in mind that I'm not 100% sure how to interpret this bill and I might be wrong.

In the month of June, my electricity consumption from the grid "Anda Guna" was 390kWh, or RM123.44.

"Lebihan Tenaga Yang Dijana" or "Excess energy generated" in the bill was also similar at 390kWh or RM123.44. 

Both these figures are the same because there was excess electricity exported to the grid (Baki 80kWh) which was unable to be converted into cash, so it could not be more than 390kWh inside the calculation of TNB bill.

In reality, the electricity that my solar panels exported to the grid was 390 + 80 (Baki NEM) = 470kWh.

The TOTAL electricity generated by the solar panels should be 390 + 80 + the amount consumed by my house directly from solar panels during daytime.

Every solar system has a DTU (Data Transfer Unit) connected to WiFi to record the performance of the system via an app.

From the data, the total electricity generated by the solar panels in June was 650kWh, with an average of 21.65kWh per day.

This means my household consumed 650 - 390 - 80 = 180kWh directly from the solar panels during daytime in June.

My TNB bill in June became negative (-RM2.80) thanks to the ICPT of -RM7.80. ICTP refers to Imbalance Cost Pass-Through which allows TNB to adjust the tariffs based on changes in its cost.

Nevertheless, from 1st of July 2025 onwards, a new TNB billing structure will be introduced. There seems to be lots of non-energy costs.

I'm not sure how will it impact my electricity bill but I guess it probably won't increase much as my electricity usage is relatively low, especially after installing solar panels.

My 6.40kWp solar PV system produced 650kWh of electricity in 30 days, while my previous monthly consumption from Dec24 to Apr25 were 643kWh, 673kWh, 705kWh, 665kWh & 709kWh.

I feel that I should have installed 12 solar panels (7.68kWp) instead of 10... 

I'm not sure whether we are allowed to install more than average usage but I read that for single phase residential consumers, the maximum limit is 12.0kWp.

Anyway, so far I'm happy with this solar system and it's almost free of charge.

The whole system costs RM16,000. I paid 10% RM1,600 as down payment and got SolaRIS cash rebate of RM4,000 from TNB straight into my bank account.

It looks like I have "earned" RM2,400 to begin with.

The rest of the RM14,400 was paid through 48-month 0% credit card installment, which was RM300 each month.

There is also an option for 60-month installment but I think 48-month is enough.

My previous TNB bills was approximately RM300 per month, so I basically use the money supposed to pay for the TNB bills to pay for the solar system.

After 4 years when the installment is fully settled, I'll be able to enjoy huge electricity savings.

Now the NEM 3.0 has ended in the end of June 2025, which means we can't sell the electricity back to TNB anymore.

What's next? Will there be NEM 4.0? Or SELCO (Self-Consumption)?

I read that the government has published a new SELCO guideline which has taken effect from the 1st of January 2025.

It seems like it is meant for non-domestic high capacity users such as big businesses and factories. I'm not sure whether it can be applied to a small house.

If I'm not mistaken, SELCO is like "Eat Yourself", as your solar panels generate electricity 100% for your own use and you are not allowed to sell to TNB.

Thus, a Battery Energy Storage System (BESS) has to be installed in order to store the excess energy for use at night time.

It will be a big waste if no battery is installed under SELCO.

It seems like a good thing as you will still have electricity supply when there is power outage from TNB grid.

Nevertheless, the BESS seems to take up some space and it will definitely cost more to install and maintain.

In conclusion, I think installing solar PV system under NEM is a brilliant idea not only to safe money, but to save the earth.

Hopefully it won't give me any trouble at least in the next 10 years.