Guides · Faisalabad, Lahore, Punjab
Should You Charge Your Solar Battery From the Grid at Night?
Short answer
For most solar homes in Punjab, the answer is no: let the sun charge the battery and keep grid charging switched off or limited to emergencies. Charging from the grid buys a unit at your full tariff, loses part of it in conversion, and adds a battery cycle. Grid charging does make sense in a few cases: before expected load-shedding after a cloudy day, when your battery is about to hit its low limit, or where cheaper off-peak units can replace more expensive peak units.
This guide explains the setting, the arithmetic and the cases where grid charging is worth it.
The setting: charger source priority
Most hybrid inverters have a charger source priority setting, separate from the output mode (SBU, SUB and so on). Typical options are:
| Option (names vary by brand) | What it does |
|---|---|
| Solar first | Solar charges the battery; the grid charges only when solar is not available, depending on model |
| Solar and utility | Solar and grid charge together at the same time |
| Solar only | Only solar charges the battery; the grid never does |
The letters on the screen differ by brand, and on some models a code that means "solar first" on one series means "solar only" on another. Check your own manual. Many inverters also let you set a grid-charging current limit and a time window for grid charging.
How this setting works together with the output mode is explained in our guide to SBU, SUB and utility-first modes.
Charging from the grid at night
Off-peak night
Grid can top up the battery
Evening peak
Battery runs the house
Daytime
Solar recharges the battery
Why grid charging usually costs you money
A battery does not create energy. It moves energy from one time to another. Every grid unit you push through it:
- Is billed at your normal tariff when it comes in.
- Loses some energy in charging, storage and the inverter. You get back less than you put in.
- Uses one charge cycle of the battery's life.
So, if the unit you buy to charge the battery costs the same as the unit you would otherwise buy later, you lose money on every cycle.
Example arithmetic
These numbers are round and illustrative, not your tariff and not a forecast.
Say your tariff is Rs 50 per unit at all hours, and you charge 10 units into the battery from the grid at night. If about 15% is lost in the round trip, you get back about 8.5 units.
| Units | Cost | |
|---|---|---|
| Grid units bought to charge | 10 | 10 × 50 = Rs 500 |
| Units delivered later from the battery | 8.5 | They replace 8.5 × 50 = Rs 425 of grid units |
| Result | Rs 75 worse off, plus battery wear |
With a flat tariff, grid charging only makes sense for backup, not for savings.
When grid charging can make sense
1. Before expected load-shedding
After a cloudy or foggy day, the battery may be low at sunset. If you know outages are coming at night, topping up from the grid gives you backup when you need it. Here you are paying for reliability, not saving money. Fog and smog days in winter are the usual case; see do solar panels work at night, in fog and in smog?
2. Protecting the battery from sitting empty
A lithium battery left at a very low state of charge for long periods is not good for it. Most inverters automatically use the grid to bring the battery up to a minimum level, then stop. That small, automatic top-up is sensible. Keep it.
3. Peak and off-peak tariffs
If you have a time-of-use meter, your bill shows peak and off-peak units at different rates. Peak hours fall in the evening. In that case, charging from cheaper off-peak units and using the battery during expensive peak hours can pay, but only if the gap is large enough.
Example, illustrative only: say off-peak units cost Rs 40 and peak units cost Rs 55. You charge 10 off-peak units (Rs 400) and get back about 8.5 units in peak hours, avoiding 8.5 × 55 = Rs 467.50. That is a gain of about Rs 67, before battery wear. If the peak rate were Rs 45, the same cycle would avoid only Rs 382.50 and you would be worse off.
A quick rule: grid charging pays only if the off-peak rate divided by the round-trip efficiency is clearly less than the peak rate. In the example, 40 ÷ 0.85 ≈ 47, which is below 55. Then subtract something for battery wear.
Our guide to reading your electricity bill shows where peak and off-peak units appear.
4. Sites where backup is critical
For clinics and some businesses, a full battery at all times matters more than the cost of a few grid units, so grid charging to a set level is part of the design.
When to keep grid charging off
- Flat tariff, sunny season. The sun will refill the battery tomorrow for free.
- The battery is used in SBU mode every evening. Grid charging at night simply refills it with expensive units before the sun can.
- Your solar array barely fills the battery. Fix the sizing instead. Grid charging hides the problem but increases the bill. See our battery size guide.
Net billing makes the solar-charged unit more valuable
Since February 2026, new connections are on net billing, where exported solar earns much less than imported units cost. Storing surplus midday solar in the battery and using it in the evening is now one of the best uses of a battery. If the battery is already full from the grid when the sun rises, there is no room for that surplus, and it is exported at the lower rate instead. That is another reason to let solar do the charging. Our net metering and net billing guide explains the rates.
Battery wear: the hidden cost
Each charge and discharge uses part of a lithium battery's cycle life. Lithium iron phosphate handles daily cycling well, but there is no reason to spend cycles on grid units that neither save money nor protect your backup. Our guide to lithium battery lifespan and care covers depth of discharge and heat.
A sensible setup for most homes
- Charger priority: solar first or solar only, depending on what your model offers.
- Grid charging: allowed only to keep a minimum state of charge, or in a short window before expected outages.
- Grid charge current: set low, so grid charging is gentle.
- Output mode: SBU with a reserve, or SUB in heavy load-shedding areas.
- Check the app. Your monitoring app shows how much energy the battery took from the grid. If that number is large, review the settings. See our monitoring app guide.
How we set it up for you
At commissioning, our engineers set the charging and output priorities to match your tariff, outage pattern and battery size, and explain them at handover. If your tariff or load-shedding pattern changes, we can review the settings. Battery options are on our lithium battery price page.
Get today's price or a free site survey
- WhatsApp or call: 0336 666 4321
- Email: info@solarworks.pk
- Head office: Main Boulevard, Sargodha Rd, Block F FDA City, Faisalabad
- Lahore branch: 2nd Floor, Jeff Heights, Gulberg, Lahore
- Hours: 9:00 AM to 6:00 PM, daily
We serve customers throughout Punjab. See our Faisalabad and Lahore pages, or contact us with a recent bill and a screenshot of your inverter settings. Site surveys are normally free.
Frequently asked questions
Is it cheaper to charge my solar battery from WAPDA at night?
Not with a flat tariff. You pay full price for each unit and lose part of it in the battery round trip, so you get back less than you paid for. It can only pay with a large enough gap between off-peak and peak rates.
Should I turn off grid charging on my hybrid inverter?
For most homes, set the charger to solar first or solar only, and allow grid charging only to keep a minimum level or before expected outages. Leave the automatic low-battery protection on.
Why is my battery charging from the grid at night?
Your charger priority is probably set to "solar and utility" or a similar option, or the battery fell below its minimum level. Check the setting in the inverter menu or app.
Does grid charging damage lithium batteries?
Not directly, if the current and voltage are set correctly. It does add cycles, which uses up the battery's life faster without saving money in most cases.
When should I charge my battery from the grid?
When you expect load-shedding after a cloudy day, when the battery is close to empty, or when off-peak units are cheap enough compared with peak units to cover the round-trip loss.
Does charging from the grid affect net billing?
Units used to charge the battery are imported units billed at your tariff. A battery already full at sunrise also has no room for surplus solar, so more of it is exported at the lower rate.
Sources
- Power Forum, "Axpert Max 72: problem in SNU charging" (charger priority labels differ by model): https://powerforum.co.za/topic/13632-axpert-max-72-problem-in-snu-charging/
- WKS hybrid inverter configuration manual (PDF, French; charger priority and grid-charging options)
- Daily Pakistan, "Peak electricity hours cut to 11pm" (21 Aug 2025)