Introducing Bijli — Prepaid Smart Meter for Indian Societies

HiSociety Team13 May 20267 min read

Why sub-metering, why now

Most Indian housing societies that take a single-point electricity connection from the discom (DHBVN, BESCOM, BSES, Tata Power…) end up doing one of three painful things every month: photographing each flat's mechanical sub-meter, typing numbers into a spreadsheet, and arguing about the genset apportionment. None of these scale past ~80 flats, and none of them survive an audit.

We built Bijli to fix all three at once. Today we're announcing it as part of the HiSociety product family — and it's already in pilot with Haryana societies under the HERC Single-Point Connection Order framework.

The four questions every resident actually asks

Bijli's app is structured around the four questions a resident asks of any meter:

Do I owe money? A prepaid wallet with a real-time balance. ₹1,420 → 12 days at the current pace. Top-up via UPI / cards / net-banking through Razorpay.
What is my meter doing right now? A live consumption gauge that refreshes every few seconds, with kW and ₹/hr side by side. You can watch the AC kick in.
What will my next bill be? A projected-bill card that extrapolates the cycle-to-date burn rate against the days remaining. Move it down before bill-day, not after.
Can I do something about it? Appliance disaggregation — "your AC ate 49% of April". Source visibility — "DG ran 14 minutes last evening at three times the slab rate". Specific, actionable.

Each of those is one tap in the app. Mockup → [bijli-mockup.vercel.app](https://bijli-mockup.vercel.app/?theme=light).

What makes Bijli HERC-compliant

HERC's Single-Point Connection Order (revised 9 October 2020) is the operative regulation in Haryana. The hard requirements:

IS 16444 sub-meters only. Bijli ships only certified DLMS meters; the platform refuses non-compliant readings.
Annexure-A and Annexure-B as separate bills (HERC §6.1(e)). Energy charges (slab tariff × consumption) are billed under Annexure-A; CAE and DG premium are billed under Annexure-B. Critically, disconnection cannot be used to recover Annexure-B dues — a residents-rights protection HERC explicitly built in. Bijli enforces this at the engine level.
CAE methodology (HERC §6.1(e)(viii)): society total ÷ covered sqft × flat sqft. Implemented verbatim, with the inputs inline on every bill so any resident can replay the math.
Versioned, effective-dated tariffs (HERC §6.1(e)(vii)): every tariff change is a new database row with start/end dates. Bills regenerate identically from inputs, every time. No magic numbers.

For each of these, Bijli produces a regeneration-ready audit trail — every reading, tariff change, bill line, payment, and adjustment is SHA-256 hash-chained. A resident dispute is resolved by replaying the inputs, not by trusting a stored bill.

How the data flows

Each DLMS sub-meter (IS 16444, connected over RS-485) emits OBIS-coded readings to a per-society gateway. The gateway buffers up to seven days locally and pushes to AWS Mumbai over mTLS-authenticated MQTT (QoS 1, dedup on the broker). An ingest worker parses the OBIS payload, tags the source (grid or DG via a digital input wired to the changeover switch), and persists three ways: hot rows to Postgres for the society / flat / tariff / ledger / audit tables, a TimescaleDB hypertable for the 15-minute time-series readings (monthly partitions), and the raw DLMS frames to S3 with seven-year retention and Glacier IR migration after 90 days. From Postgres, the bill engine walks the slab tariff, adds FSA / ED / MTax / FC line items, and ships PDFs plus WhatsApp + DHBVN export packs.

Pilot fleet target: 200 societies × 200 flats × 100 readings/day = 4 million readings/day — generating ~12,000 bills/month. Everything is built for that scale from day one.

Grid vs DG, made transparent

The hardest fight in any society's sub-metering experience is the genset cost split. The grid kWh slab tariff in Haryana is roughly ₹4-7 per unit. The DG cost — fuel plus standby — can be ₹18-25 per unit. When residents see one combined number on the bill, they (rightly) assume something is wrong.

Bijli wires a digital input on the changeover switch directly into the gateway. Every reading is tagged grid or DG at the device. Bills then split the kWh between the slab tariff and the DG premium — line by line, transparent, with the kWh count for each source. Disputes drop to nearly zero within a cycle of moving to this model.

There's also a Sankey diagram in the resident app showing how each kWh flowed from source (grid / DG) to appliance (AC / lights / geyser / refrigeration). "Your AC ate 32 kWh of DG last month, which is why your bill jumped" reads very differently from a flat percentage increase.

What you get as a committee member

Cycle dispatch in one click. Preflight checks run automatically — missing readings, tariff edge cases, unconfirmed DG hours — surfaced before the run, not after the disputes arrive.
DHBVN export pack: a CSV bundle generated per cycle, formatted for the discom portal. Annexure compliance is one click.
Defaulter actions: prepaid wallets mean *the meter itself* enforces non-payment. No more chasing 8 flats by WhatsApp.
Audit log: every committee action (tariff change, manual adjustment, dispute resolution) is logged and SHA-256-hashed. When the next AGM asks "who approved that ₹2,400 adjustment for Flat 2-203 in March", the answer is one query away.

What it costs and what's next

Bijli is available now for pilot in Haryana — the easiest path is a single-tower deployment (30-60 days, 50-100 flats). Cost depends on existing infrastructure (MCB cabinet retrofit, DG changeover wiring) and flat count. Reach out at admin@hisociety.in for a quote.

Maharashtra (MERC) and Karnataka (KERC) are next on the regulator-coverage roadmap; the architecture is regulator-agnostic and the bill engine is config-driven, so other states follow the Haryana rollout pattern.

Try the resident app mockup at [bijli-mockup.vercel.app](https://bijli-mockup.vercel.app/?theme=light). Full product page at [/bijli](/bijli).

Every unit, accounted. Every meter, live. हर यूनिट का हिसाब.

Frequently asked questions

Is Bijli only for Haryana?▾

The pilot is in Haryana because the HERC Single-Point Connection Order, the DHBVN export format, and the CAE methodology are all Haryana-specific. The architecture itself is regulator-agnostic — Maharashtra (MERC) and Karnataka (KERC) are the next planned states. Email admin@hisociety.in if you'd like your state prioritised.

What sub-meters does Bijli support?▾

Only IS 16444-certified DLMS/COSEM sub-meters. We've validated meters from L&T, Genus, HPL, and a handful of regional vendors. RS-485 wiring connects up to 50-200 sub-meters per gateway. Existing mechanical meters need to be replaced — they cannot be retrofitted with smart heads to HERC standards.

How is the prepaid wallet enforced — does the meter actually disconnect?▾

Yes for the energy supply (Annexure-A side). When a resident's wallet drops below the auto-warn threshold (default 20%, configurable), they receive WhatsApp / SMS / push alerts at 20%, 10%, and 0%. At zero, the meter relays disconnect for the energy supply. Importantly, per HERC §6.1(e), disconnection cannot be used to recover Annexure-B (CAE / DG) dues — Bijli enforces that legal protection at the engine level.

Who has access to the data — committee or resident?▾

Residents see only their own flat's readings, bills, and disputes. Committee members see society-wide aggregates and can drill into any flat's bills for dispute resolution, but the raw 15-minute meter readings are exposed only on legitimate audit access (with the access itself logged in the hash-chained audit trail). DHBVN gets the export pack — not the raw readings.

What happens during a network outage?▾

The DLMS gateway has 7 days of on-device buffer. Readings are queued locally and replayed when connectivity returns. The MQTT client uses QoS 1 with deduplication on the broker side, so no readings are lost or double-counted. Long-distance outages (rare in Indian cities) can buffer up to 30 days with a flash upgrade.

How does this work with HiSociety's existing maintenance billing?▾

Bijli is a HiSociety module — it shares the same society, flat, member, and unit records, the same login, and the same committee permissions. Electricity bills appear alongside maintenance, sinking fund, and other charge heads. Residents see a unified bill PDF when they choose, or per-product breakdowns when they need them. No separate platform to manage.

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