How a Bukit Tunku household with EV charging, heat-pump pool, and four split ACs achieved near-zero TNB bills with Huawei SUN2000 + LUNA2000
tCO₂ offset annually
“We were on TNB's highest tariff block — RM 0.571 per kWh for everything above 600 units. Between the EV, the heated pool, and four inverter ACs running at night, we were spending RM 2,400 a month. Trexon sized the system properly around our actual consumption pattern, not a generic quote. The LUNA2000 battery means we run on stored solar until nearly midnight. Four months in, our TNB bill has averaged RM 118. The FusionSolar app is genuinely satisfying to watch.”
Malaysia's TNB domestic tariff has a progressive block structure. Once you cross 600 units per month, every additional kWh costs RM 0.571 — the highest residential tier. For most Malaysian households that rate is theoretical. For a Bukit Tunku bungalow with four large-capacity split ACs, a 10,000-litre heated pool running a heat-pump circulation system, two EV chargers in the covered porch, and a home office drawing continuous load, it is the predominant rate. This household was reliably consuming 4,200–4,600 units per month, with the top-block consumption accounting for more than 60% of its bill.
At RM 2,400 per month — RM 28,800 per year — the financial motivation for solar was self-evident. But the homeowner had deferred the decision twice. A previous quotation in 2023 had proposed a standard 10 kWp grid-tied system: adequate for a modest Malaysian semi-detached but undersized for this load profile. A second quotation in 2024 had recommended a larger system but without battery storage, which meant the EV charging and pool heat-pump — both predominantly evening-to-midnight loads — would continue to draw fully from TNB.
Trexon's engagement in late 2025 started with a different question: not "how big a rooftop array do you want" but "when does each load actually run?"
A standard TNB smart-meter data download for the previous 12 months, combined with a smart plug survey on each circuit, produced a granular hourly consumption map. Key findings:
The evening and overnight loads totalled 2,550 kWh per month — 58% of total consumption — and were entirely outside normal solar generation hours. Any system that ignored this would deliver a technically impressive daytime performance number while leaving the homeowner's biggest cost driver (TNB's top-block evening units) completely unaddressed.
Inverter Selection: Huawei SUN2000-12K-MAP0 Hybrid
The Huawei SUN2000-12K-MAP0 is a single-phase hybrid inverter rated at 12 kW AC output with 18 kW DC input capacity. Its selection was driven by three factors. First, its native LUNA2000 battery integration via Huawei's proprietary DC-bus architecture (no AC-coupling conversion loss). Second, its EV-charging intelligence: the SUN2000-MAP0 series supports direct communication with Huawei's SEMATE EV charger for solar-first EV scheduling, automatically diverting surplus solar generation to the car before exporting to the grid. Third, its ability to operate in backup mode during TNB outages — relevant for this household, which had experienced two prolonged outages in the preceding 18 months.
PV Array: 25 × Trina Vertex 720W
Twenty-five Trina Solar Vertex 720W monocrystalline PERC panels were mounted on the main residential roof (south-facing, 20-degree pitch) using a low-profile aluminium racking system with concealed cable management. Total DC capacity: 18 kWp. The Vertex 720W was chosen for its high power density — this allows the 18 kWp system to fit within the available roof area without extending onto the north-facing sections, preserving both aesthetics and yield efficiency.
Battery Storage: Huawei LUNA2000-15-S0 (15 kWh)
One Huawei LUNA2000-15-S0 battery module (15 kWh usable, 90% DoD) was installed in the utility room adjacent to the main distribution board. The LUNA2000 is a DC-coupled lithium iron phosphate (LFP) chemistry unit — safer for indoor residential installation than earlier NMC alternatives and rated for 6,000 cycles at 80% capacity retention. At 15 kWh, the battery is sized to cover approximately five hours of typical evening AC load (4 × 3 kW inverter ACs in eco mode ≈ 8 kW combined draw at light load), bridging the gap between solar cut-off (around 19:30) and the household's typical midnight sleep time.
Smart Home Integration via FusionSolar
The FusionSolar AI Energy Management System was configured with the household's specific appliance schedule: - Pool heat-pump: shifted to 10:00–14:00 (peak solar hours) where possible; evening override maintained for temperature top-up - EV charging (Huawei SEMATE AC Wallbox): solar-priority mode charges from surplus generation during the day; after-midnight grid-tariff charging as secondary (TNB midnight rate applies under the commercial ToU framework, though this household remains on domestic tariff) - Battery charge strategy: fill from 09:00–15:00 solar peak; preserve 30% reserve for backup; discharge 19:00 onwards prioritising AC and lighting loads
Under Malaysia's Solar Accelerated Transition Action Programme (ATAP), gazetted as GP/ST/No.60/2025 and effective 1 January 2026, residential solar systems operating under NEM 3.0 export excess generation to TNB at the Displaced Cost rate. For residential consumers, the self-consumption value of solar is therefore paramount: every kWh consumed directly (or via battery) from the solar system avoids RM 0.571 of top-block TNB cost; every kWh exported recovers only the Displaced Cost rate, which is materially lower.
This makes battery storage financially decisive for heavy residential consumers. The LUNA2000's 15 kWh of usable capacity increases the system's self-consumption rate from an estimated 61% (PV-only) to 84% (PV + battery) — translating to a RM 8,400/year improvement in annual value over the PV-only scenario, which more than justifies the battery's incremental installed cost over the system lifetime.
The installation was completed over three working days in March 2026. Trexon's residential team operates with a strict no-damage policy for bungalow roofworks: all penetrations sealed with polyurethane foam and butyl tape over butyl flashing, camera-documented before panel installation. The homeowner was provided a post-installation waterproofing guarantee.
The LUNA2000 battery was installed in the utility room on a dedicated wall-mount bracket with 30 cm clearance on all sides for ventilation, in compliance with Huawei's installation manual and Malaysia's Uniform Building By-Laws fire safety provisions for lithium battery storage.
TNB NEM 3.0 (ATAP) application was submitted on the installation completion date. Grid-energisation and import/export metering was completed 21 days later — within the ATAP stipulated timeline of 30 working days for residential applications below 25 kWp.
Generation performance:
Monthly generation averaged 1,840 kWh — a specific yield of 1,022 kWh/kWp/year, slightly above the P50 design estimate of 990 kWh/kWp for KL's irradiance profile. Bukit Tunku's elevated position relative to the Klang Valley floor results in marginally lower ambient temperature and reduced soiling compared to valley-level sites, contributing to the above-estimate yield.
Consumption and savings:
Monthly self-consumption (solar consumed directly + via battery): 1,550 kWh (84% of generation). Monthly export to TNB at ATAP Displaced Cost: 290 kWh. Total monthly TNB bill: average RM 118 — compared to RM 2,400 before installation. Monthly saving: RM 2,282 (95.1% reduction).
EV charging:
The homeowner charges a battery EV (estimated 1,000 km/month). Under the solar-priority EV scheduling, approximately 320 kWh per month is supplied from direct solar and battery storage rather than TNB — a fuel-equivalent saving of approximately RM 183/month versus the previous grid-charged approach, included within the overall bill reduction figure.
Environmental:
The system displaces approximately 26 tonnes of CO₂ equivalent per year, using Malaysia's 2024 grid emission factor of 0.694 kg CO₂/kWh. For a household that tracks its carbon footprint as part of broader sustainability commitments, this is the equivalent of taking 1.4 average Malaysian cars off the road annually.
A standard grid-tied inverter of equivalent DC capacity would have cost approximately RM 9,000 less than the SUN2000-12K-MAP0 hybrid. The additional expenditure purchased four capabilities: battery integration (eliminating a separate battery inverter), EV-smart-charge scheduling, seamless backup power on TNB outage (sub-20ms switchover), and the FusionSolar AI energy management that enables appliance-level scheduling optimisation.
For a household where the evening load — pool, EV, AC — is both the dominant cost driver and the primary reason for choosing solar, those four capabilities are not optional extras. They are the reason the system achieves 95% bill reduction rather than 60%.
Note: Financial figures represent indicative modelling based on Trexon installation data and TNB domestic tariff schedules. Specific client details are anonymised per residential confidentiality.
Get a free consultation and see how much you can save with solar.