My roof is huge. Why can’t I install a bigger Solar Power System for my house!!? Why do I need Net Metering instead of using the battery bank!??

 

For Residential Solar Power projects or Solar Power systems for houses, the maximum size you allow to install is 4kWac (single phase) or 10kWac (three phase)... IF you intend to apply Net Energy Metering (NEM)!!

After we studied the client’s usage and proposed a certain Solar Power system (say 5kWp) for his house, using only a partial of his roof space…

The client wasn’t happy. He wanted to fully utilize his roof space. IF maximum is 10kWac, he wanted that..

He thought the bigger the system size, the more savings he can enjoy by selling Solar Energy to TNB.

Unfortunately, under the NEM program, we don’t sell Solar Energy to TNB. We can only export Extra Solar Energy that we can’t finish using to TNB. And use it as credit to offset our next month's TNB bill.

If you oversize your Solar Power system, you’re at the risk of wasting your money…

Here is the example of consequence of oversizing your Solar Power system...

Say your monthly usage is 500kWh per month for instance.

Assuming you maintain the same usage (500kWh per month), and day time and night time usage are as following:-

So, your total usage is 500kWh per month and 400kWh of it is your night time usage.

After Installed Solar Power System:

After installing the Solar Power system, your daytime power usage will be from the Solar Power System.

Hence, you aren’t using TNB power during daytime, and your total TNB power usage becomes 400kWh per month.. 

If you oversize your Solar Power system and generate said 900kWh per month, you will have 800kWh extra Solar Energy exported to TNB monthly (100kWh you use during daytime monthly).

The 800kWh extra Solar Energy exported to TNB will be used to offset the 400kWh (night time usage) you used during night time the previous month..

After offsetting the previous month night time usage, you still have a balance of 400kWh monthly.. 

This balance of credit only can be rolled over for 12 months. Meaning that if you oversize your Solar Power system like the above example, 4800kWh of credit or extra energy will be forfeited after 12 months.

Which is the reason why your Solar Power system should be designed in such a way that just matches your monthly power usage…

Use Battery Bank Instead of NEM

Some clients would think in that case it is better to install the battery bank to store the extra Solar Energy instead..

However, Battery storage isn’t cheap now and you will need a huge space to store your battery bank. 

The Capital Expenses for battery will shoot up the project cost. Let alone the maintenance cost, battery replacement cost after its lifespan etc.

Moreover, there will be losses along the charging and discharging of the battery. 

In fact, for NEM, TNB will be your battery bank to store your extra Solar Energy at no extra cost, maintenance cost etc. And most importantly the losses are much smaller compared to charging/ discharging the Solar battery banks.

Thus, it is a smarter choice to size the Solar Power system just enough for your usage, and go for NEM instead of the battery bank option…