Solar Battery Backup Calculator Pakistan
Solar battery backup calculator Pakistan — size an inverter and battery bank for load-shedding backup from your appliances and backup hours.
Solar Battery Backup Calculator Pakistan
Size an inverter and battery bank for load-shedding backup: tell it what you want to keep running and for how many hours, and it works out the inverter size and the battery capacity you need. All calculations run in your browser. This is an estimate, not a quote — real backup time varies with battery age, temperature, and the loads actually running.
What do you want to run?
Tip: check the wattage on the appliance label. A fridge does not run its compressor all the time, so its average draw is lower than its rated watts — if you add a fridge, size generously or measure it with a plug meter.
How long the outage usually lasts in your area — e.g. 2, 4 or 6 hours.
Assumptions (all editable)
25% headroom so the inverter never runs flat-out.
Inverters are rated in kVA; kVA = kW / 0.8.
90% of battery energy reaches your appliances; the rest is lost as heat in the inverter.
Lead-acid: 50% usable (deeper discharge shortens life). Lithium LiFePO4: 90% usable. Changes automatically with battery type.
Used only to count how many batteries you need — e.g. 200 Ah tubular batteries are common in Pakistan.
Your backup sizing
Peak load
470 W
everything running at once
Energy needed
1.88 kWh
1,880 Wh over 4 hours
Recommended inverter
1.0 kVA
computed 0.73 kVA, rounded up
Battery bank
175 Ah
at 24 V (4.18 kWh total)
Estimate only, not a quote. A new battery delivers close to its rated capacity; an old or hot battery delivers less, so backup time shortens over the battery's life. Motor loads (fans, fridge compressors) draw a brief start-up surge — the 25% safety margin covers normal surges, but a large motor starting at the same moment as everything else can still trip a small inverter. No prices are shown because inverter and battery prices in Pakistan move with the dollar rate and vary by brand; get a written installer quote before buying.
About our Solar Battery Backup Calculator Pakistan
The solar battery backup calculator Pakistan sizes an inverter and battery bank for load-shedding backup from the appliances you want to keep running and for how many hours. It works out peak load, the energy needed, a recommended inverter size with a 25% safety margin, and the battery capacity in kWh and in amp-hours at your chosen system voltage, using standard stated assumptions: inverter efficiency 90%, power factor 0.8, usable depth of discharge 50% for lead-acid and 90% for lithium (LiFePO4). It also shows how many 12 V batteries you need and what the same backup would take with the other battery chemistry, so the lead-acid versus lithium trade-off is visible in one place. Every result is an estimate, not a quote: real backup time varies with battery age, temperature and the loads actually running, and no prices are shown because inverter and battery prices in Pakistan move with the dollar rate and vary by brand.
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Frequently Asked Questions
How big an inverter do I need for load-shedding backup?
Add up the watts of everything you want running at the same time, then add a 25% safety margin and convert to kVA by dividing by 0.8. For example, a 470 W load becomes 587.5 W with margin, which is 0.73 kVA, rounded up to a 1 kVA inverter. The calculator does this for you from your appliance list.
How is battery size calculated?
Energy needed equals load in watts times backup hours. That energy is divided by inverter efficiency (90%) to get the usable energy the battery must deliver, then divided by the usable depth of discharge — 50% for lead-acid, 90% for lithium — to get total battery capacity. Bank amp-hours equal total watt-hours divided by system voltage. For a 470 W load over 4 hours on lead-acid at 24 V, that is 1,880 Wh, 2,088.89 Wh usable, 4,177.78 Wh total, and 174.07 Ah, rounded up to 175 Ah.
Why does lead-acid need a much bigger battery than lithium for the same backup?
Because only about half of a lead-acid battery's rated capacity is usable without shortening its life, while a lithium (LiFePO4) battery can use about 90%. The same 470 W, 4-hour backup needs 175 Ah of lead-acid at 24 V but only 97 Ah of lithium. Lithium costs more upfront but lasts far more cycles, so compare lifetime cost, not just the sticker price.
What system voltage should I choose?
12 V suits small setups (a few lights and fans). 24 V is typical for home backup. 48 V suits larger homes and hybrid solar systems, and keeps currents and cable losses lower. The calculator counts batteries for your voltage: at 24 V with 12 V batteries, two batteries in series make one string.
Does my existing solar reduce the battery I need?
Only during daytime outages, when panels can power loads directly. This calculator sizes for the worst case — a night outage with no solar input — so the battery is never undersized. If you enter your solar kW, it shows how much load your panels can cover during sunny hours.
Is this an official quote?
No. This is an estimate for planning only. Real backup time varies with battery age, temperature and the loads actually running, and motor start-up surges can trip a small inverter. No prices are shown because they move with the dollar rate and vary by brand — get a written installer quote before buying.