How many batteries do I need to run a 1.5 ton AC for 8 hours?

A 5-star 1.5 ton inverter AC consumes ~900W average. For 8 hours: 7.2 kWh needed. With LiFePO4 (80% DoD): 9 kWh bank (2×5kWh). With Lead Acid (50% DoD): 14.4 kWh bank (12×150Ah at 12V). LiFePO4 is strongly recommended for overnight AC use.

What is the difference between LiFePO4 and Lead Acid for solar battery backup?

LiFePO4 offers 80% usable depth of discharge vs 50% for Lead Acid, meaning same kWh rating delivers 60% more backup hours. LiFePO4 lasts 3,000–5,000 cycles vs 500–1,000 for Lead Acid. While 2–3× more expensive upfront, LiFePO4 costs less per cycle over its lifetime.

What size battery bank do I need for a 2 ton AC overnight?

A 5-star 2 ton inverter AC draws ~1,400W average. For 8-hour overnight backup: 11.2 kWh needed. With LiFePO4 (80% DoD): 14 kWh battery bank. With Lead Acid (50% DoD): 22.4 kWh bank. A 15kWh LiFePO4 system is the practical recommendation for overnight 2-ton AC backup.

Can a solar system charge the battery and run AC simultaneously?

Yes, with a hybrid solar inverter (like Growatt, Solis, Deye). During daytime, solar charges the battery AND runs AC directly. At night, the battery powers AC. A 3–5 kW solar + 10 kWh battery is the standard setup for 1–2 ACs in Indian power-cut areas.

What is DoD (Depth of Discharge) and why does it matter?

DoD is the percentage of battery capacity you can safely use. LiFePO4 allows 80% DoD — so a 10 kWh battery gives 8 kWh usable. Lead acid allows only 50% — same 10 kWh gives only 5 kWh usable. Exceeding DoD drastically shortens battery life.

How long does a battery last for daily AC backup use?

LiFePO4 lasts 3000–5000 cycles at 80% DoD, roughly 8–13 years at one cycle/day. Lead acid lasts 500–800 cycles at 50% DoD, roughly 1.5–2.5 years with daily use. For areas with daily power cuts, LiFePO4 is far more economical over 10 years.

Is a 5 kWh battery enough for 1 AC overnight?

Depends on tonnage and hours. A 5 kWh LiFePO4 (4 kWh usable) runs a 1T 5-star inverter AC (~850W) for ~4.7 hours. For 8 hours, you need at least 8 kWh usable — so 10 kWh LiFePO4 or 16 kWh lead acid. Use our calculator above for your exact AC.

What inverter do I need to run an AC from battery?

You need a pure sine wave solar inverter with battery support. For 1–2 ACs up to 3 kW total load, a 5 kVA hybrid inverter (like Growatt 5000-ES or Deye 5kW) is standard. Make sure the inverter supports your battery voltage (48V is most common for 5–15 kWh systems).

Does adding more ACs linearly reduce backup time?

Yes, exactly. If 1 AC gives 8 hours, 2 identical ACs give 4 hours from the same battery. Battery capacity needed scales proportionally with load. Running multiple ACs overnight requires significantly larger battery banks — our calculator shows the exact math.

What about PM Surya Ghar subsidy for battery systems?

PM Surya Ghar subsidy (up to ₹78,000) applies to grid-tied solar systems without batteries. Off-grid and hybrid systems with batteries may qualify for partial benefits depending on state government schemes. Check your state DISCOM for battery-inclusive subsidy eligibility.

LIVE: 2026 Battery Prices Updated

Battery Backup — Off-Grid & Power-Cut Ready · India 2026

Solar Battery Backup Calculator (2026)

Enter your AC tonnage, star rating, and backup hours needed — instantly get exact battery bank size, overnight AC sizing, and a comparison between LiFePO4 and Lead Acid options for Indian homes.

Overnight Sizing

8-Hr Power-Cut Mode

LiFePO4 + Lead Acid

Both Types Calculated

±10% Accuracy

BEE Load Data

Instant Results

No Login Needed

Calculate My Battery Backup Size My Solar System First

LiFePO4 gives 80% usable depth vs just 50% for lead acid — meaning same kWh rating delivers 60% more actual backup hours for your AC.

Real AC Load Calculation

Inverter ACs draw far less than rated wattage. We use BEE-based average consumption by tonnage and star rating — not peak nameplate values — for realistic backup estimates.

Overnight 8-Hr Sizing

Power cuts in India peak during 10 PM–6 AM in summer. We calculate exactly what battery bank keeps your AC running all night without grid power.

LiFePO4 vs Lead Acid

We size both battery types and show the full cost vs backup comparison — helping you decide whether the lithium premium is worth it for your use case.

Solar Battery Backup Calculator

Add your ACs below — results update live as you adjust.

Your Air Conditioners

AC Group

1150W total

Units

Tonnage

Star Rating

Type

1150W each · 1150W total

Add Ceiling Fans?

Your Battery Setup

Battery Type

Battery Capacity (installed)5 kWh

1 kWh10 kWh20 kWh30 kWh

Usable: 4.0 kWh at 80% DoD

Overnight Target Hours8 hrs

4 hrs6 hrs8 hrs10 hrs12 hrs

1.15 kW

Total AC Load

1150 watts running

5 kWh

Battery Capacity

4.0 kWh usable (80% DoD)

3.5 hrs

Backup Duration

Not enough for 8-hr night

9.2 kWh

Overnight Need

Your battery covers it

Your 5 kWh battery handles overnight AC use

With 80% usable DoD, your 4.0 kWh available comfortably exceeds the 9.2 kWh overnight need.

Load Breakdown

Total AC load

1150W1.15 kW

Battery type

LiFePO4 Lithium80% usable DoD

Usable capacity

4.00 kWhout of 5 kWh installed

8-hr overnight need

9.20 kWh1150W × 8 hours

Actual backup time

3.5 hrsFull night covered

Recommended Battery Banks

Based on your 1.15 kW load and 9.2 kWh overnight need

Best for 1 AC

LiFePO4 5 kWh Bank

100Ah × 48V (1 battery)

Total capacity5 kWh

Usable (80% DoD)4.0 kWh

Backup hours3.5 hrs

Price range₹1.2L – ₹1.6L

Insufficient — need 11.5 kWh installed

80% usable depth
Lightweight & compact
3000+ charge cycles
No maintenance

LiFePO4 10 kWh Bank

200Ah × 48V (2 batteries in parallel)

Total capacity10 kWh

Usable (80% DoD)8.0 kWh

Backup hours7.0 hrs

Price range₹2.4L – ₹3.2L

Insufficient — need 11.5 kWh installed

Full overnight for 2 ACs
80% usable DoD
Solar rechargeable
Stackable system

Budget Pick

Lead Acid 7.2 kWh Bank

150Ah × 48V (4 batteries × 12V)

Total capacity7.2 kWh

Usable (50% DoD)3.6 kWh

Backup hours3.1 hrs

Price range₹55K – ₹75K

Insufficient — need 18.4 kWh installed

Budget-friendly
Easy local service
Proven for inverters
Widely available spares

Heavy Duty

Lead Acid 14.4 kWh Bank

300Ah × 48V (8 batteries × 12V)

Total capacity14.4 kWh

Usable (50% DoD)7.2 kWh

Backup hours6.3 hrs

Price range₹1.0L – ₹1.4L

Insufficient — need 18.4 kWh installed

Maximum lead-acid capacity
Handles 2–3 ACs overnight
Robust for high loads
Good cycle life if maintained

LiFePO4 vs Lead Acid — Which Should You Pick?

LiFePO4 (Recommended): 80% usable depth means a 10 kWh bank gives 8 kWh real backup. Lasts 3000+ cycles (~8–10 years). No maintenance. Compact. Best for daily power-cut areas like UP, Bihar, Maharashtra rural.

Lead Acid (Budget): Only 50% usable depth — a 10 kWh bank gives only 5 kWh real backup. 500–800 cycles (~3–4 years). Requires water top-up. Cheaper upfront but higher cost over lifetime. Suitable for occasional backup only.

Quick Reference — Battery Need by AC Setup

Minimum battery installed capacity for 8-hour overnight backup

AC Setup	Total Load	LiFePO4 Need (80% DoD)	Lead Acid Need (50% DoD)	5kWh Battery	10kWh Battery	Scenario
0.75T 5★ Inverter, 1 AC	650W	6.5 kWh	10.4 kWh	6.2 hrs	12.0 hrs	Small Room
1T 5★ Inverter, 1 AC	850W	8.5 kWh	13.6 kWh	4.7 hrs	9.4 hrs	Bedroom
1.5T 5★ Inverter, 1 AC	1150W	11.5 kWh	18.4 kWh	3.5 hrs	7.0 hrs	Most Popular
1.5T 3★ Inverter, 1 AC	1400W	14.0 kWh	22.4 kWh	2.9 hrs	5.7 hrs	Common
2T 5★ Inverter, 1 AC	1550W	15.5 kWh	24.8 kWh	2.6 hrs	5.2 hrs	Living Room
1.5T 5★, 2 ACs	2300W	23.0 kWh	36.8 kWh	1.7 hrs	3.5 hrs	2-Room Home
1.5T 5★, 3 ACs	3450W	34.5 kWh	55.2 kWh	1.2 hrs	2.3 hrs	Large Home
1T + 1.5T 5★ Mix, 2 ACs	2000W	20.0 kWh	32.0 kWh	2.0 hrs	4.0 hrs	Typical Home

Battery hours shown with LiFePO4 (80% DoD). Actual runtime varies with inverter efficiency (90–95%) and temperature. Add 15% buffer for real-world sizing.

Battery Backup FAQs

Everything you need to know about running ACs on battery in India

A 1.5T 5-star inverter AC draws ~1.15 kW on average. For 8 hours, you need 9.2 kWh of usable energy. With LiFePO4 (80% DoD), install 11.5 kWh. With lead acid (50% DoD), install 18.4 kWh. A 10 kWh LiFePO4 pack is the most practical choice for one 1.5T overnight.