Under Pakistan's net billing framework, exported solar units are bought at a much lower rate than the price you pay for grid units. This has made batteries a serious option for many solar homes. Here's how to think about it.
Why batteries are more attractive now
- Without a battery, midday surplus is exported at a low buyback rate.
- In the evening, you buy grid units at the full tariff — often during peak hours for TOU consumers.
- A battery stores the surplus and uses it in the evening, turning a low-value export into a high-value saving.
How a hybrid system works
- Solar powers your home during the day.
- Surplus charges the battery.
- Only when the battery is full is power exported.
- In the evening and at night, the battery supplies your home until empty, then the grid takes over.
- The battery can also provide backup during load-shedding (depending on the inverter setup).
Sizing a battery
Look at your evening and night consumption. If you use about 10 units between sunset and midnight, a battery with around 10 kWh of usable capacity could cover most of that on a sunny day. Your inverter must support the battery's power and voltage.
Battery types
- Lithium-ion (LiFePO4): longer life, deeper discharge, more expensive upfront; now common in Pakistan.
- Lead-acid / tubular: cheaper but shorter life and limited usable capacity.
Is a battery worth it?
Compare:
- Extra cost of battery (and any inverter upgrade)
- Annual value = units shifted from export to self-use × (grid price − export price)
Example: shifting 8 units a day × 365 × (Rs 50 − Rs 11) ≈ Rs 113,880 a year (illustrative). If the battery costs Rs 450,000, simple payback is about 4 years — check this against the battery's expected life and warranty.
Practical tips
- Buy from reputable suppliers with clear warranties.
- Install in a cool, ventilated place — heat shortens battery life.
- Set inverter priorities correctly (solar → load → battery → grid).
These figures are examples; actual savings depend on your tariff, usage and current buyback rates.