How much battery do I need with a solar system in Bangalore (2026)?
TL;DR: How much battery you need depends on what you want to power at night. For typical Bangalore homes in 2026:
- •Basic backup (lights + fridge + router): ~3–4 kWh usable → buy a 4 kWh nominal pack.
- •Fridge + lights + a couple of fans: 5–6 kWh usable → buy a 6–7 kWh pack.
- •Run a 1.5-ton AC for ~4 hours at night: ~6 kWh usable → buy ~6–8 kWh nominal (allowing headroom).
Installed residential battery costs in India in 2026 are roughly ₹18,000–₹30,000 per kWh (installed), so a 6 kWh usable system typically adds about ₹1.1–1.8 lakh to the project (range depends on brand, BOS, inverter & warranties).
1) Battery basics - useful words (no jargon)
Nominal capacity
The number printed on the battery (e.g., 10 kWh).
Usable capacity
How much energy you can actually use (depends on battery settings / DoD). This is what matters for your needs.
DoD (Depth of Discharge)
How much percent of the battery you allow yourself to use (many modern Li-ion/LFP batteries safely use 80–100% DoD; installers commonly plan 80–90% for longevity).
Round-trip efficiency (RTE)
Energy you get out divided by energy you put in (Li-ion/LFP batteries are typically ~90–95% efficient).
2) The simple battery sizing formula (use this every time)
You want X kWh usable at night → battery nominal kWh =
required_nominal_kWh = usable_kWh ÷ (DoD_fraction × round_trip_efficiency)
Where:
- •DoD_fraction = e.g., 0.90 for 90% depth-of-discharge, or 0.80 for 80% (pick what your vendor recommends).
- •round_trip_efficiency = e.g., 0.90 for 90% RTE.
We use conservative working numbers in examples below: DoD = 90% (0.90), RTE = 90% (0.90) → combined factor = 0.9 × 0.9 = 0.81.
3) Exact examples for Bangalore - step-by-step math
Example A - basic backup (usable need = 3 kWh)
We want 3.0 kWh usable at night.
Combined factor = 0.90 × 0.90 = 0.81
Raw nominal = 3.0 ÷ 0.81 = 3.7037037037 kWh
→ round up to 3.71 kWh → pick a 4 kWh nominal battery
Cost estimate (installed): using ₹18,000–₹30,000 per kWh installed:
Low = 3.7037 × 18,000 = 66,666.67 → ≈ ₹66,667
High = 3.7037 × 30,000 = 111,111.11 → ≈ ₹111,111
So expect ≈ ₹67k–₹111k for a 3 kWh usable solution (installed), depending on vendor & warranties.
Example B - fridge + lights (usable need = 5 kWh)
Raw nominal = 5.0 ÷ 0.81 = 6.1728395062 kWh
→ round up to 6.2 kWh → pick a 6–7 kWh battery
Cost low = 6.17284 × 18,000 = 111,111.11 → ≈ ₹111,111
Cost high = 6.17284 × 30,000 = 185,185.19 → ≈ ₹185,185
Expect ≈ ₹1.1–1.85 lakh installed.
Example C - 1.5-ton AC for 4 hours at night (usable need = 4.8 kWh)
From AC power 1.2 kW × 4 h = 4.8 kWh needed
Raw nominal = 4.8 ÷ 0.81 = 5.9259259259 kWh
→ round up to 6 kWh nominal recommended
Cost low = 5.92593 × 18,000 = 106,666.67 → ≈ ₹106,667
Cost high = 5.92593 × 30,000 = 177,777.78 → ≈ ₹177,778
So ≈ ₹1.07–1.78 lakh installed for ~6 kWh usable capability - this matches typical market examples for small AC backup.
Example D - whole-home partial backup (usable need = 10 kWh)
Raw nominal = 10 ÷ 0.81 = 12.3456790123 kWh
→ round up 12.4 kWh → pick 12–15 kWh system
Cost low = 12.34568 × 18,000 = 222,222.24 → ≈ ₹222,222
Cost high = 12.34568 × 30,000 = 370,370.40 → ≈ ₹370,370
Expect ≈ ₹2.2–3.7 lakh installed for a robust ~10 kWh usable system.
Notes on these numbers
The installed cost per kWh we used (₹18k–₹30k/kWh) reflects typical residential installed costs in India in 2026 (pack + inverter/BMS + installation & BOS). Different reports show slightly different ranges; developers and grid-scale projects may negotiate lower unit costs. Use vendor quotes to lock in exact pricing.
4) Practical tips - real-world things installers will check
🔋Chemistry & efficiency
Prefer LFP (Li-FePO4) chemistry for home backup - it's safer, cycles more, and has high round-trip efficiency (~90–95%). Ask vendors for chemistry & cycle life.
📋DoD & warranty
Some vendors advertise 100% DoD; others recommend 80–90% daily to extend life. We use 90% DoD & 90% RTE in examples - conservative and realistic. Ask for warranty terms tied to cycle count and retained capacity at X years.
⚡Inverter & surge handling
If you want to run AC compressors, confirm the inverter or hybrid inverter has sufficient surge rating to handle compressor starts. Some systems use batteries to support the surge. Ask for short-term surge numbers (e.g., 2–3× continuous power for a few seconds).
🌤️Temperature & monsoon in Bangalore
Batteries perform best at moderate temperatures - Bangalore's climate is moderate, but battery enclosures should be ventilated and protected from heavy rains. Good installers provide thermal management and IP-rated enclosures.
🔧Service, maintenance & replacements
Expect battery life of 8–15+ years depending on cycles and DoD; LFP systems often offer long cycle warranties (thousands of cycles). Factor replacement costs into long-term planning.
5) Quick decision guide for Bangalore homeowners
6) How to get an exact quote - checklist to ask installers
Ask each installer to provide, in writing:
- ✓Battery chemistry & nominal kWh and usable kWh (explain DoD used).
- ✓Round-trip efficiency assumed in the quote.
- ✓Inverter / hybrid inverter model and surge rating.
- ✓Cycle life warranty & capacity guarantee (e.g., 70% capacity after 10 years).
- ✓Line-item installation costs, and whether quoted ₹/kWh is pack-only or fully installed (BMS, inverter, thermal, labour).
- ✓Service & replacement costs and response time in Bangalore.
Compare line-items, not just the final number.
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