Lim Ah Pin Road Solar Installation: 12 kWp on a Ballasted Flat Roof, $3,720 a Year

25 black monocrystalline panels on aluminium ballast frames, zero roof penetrations, commissioned and exporting within a single day. Here's what was actually installed at this Lim Ah Pin Road home, and what it saves.

What was actually installed at this home?

25 black monocrystalline panels totalling 12 kWp, mounted on aluminium ballast frames sitting directly on the existing flat concrete roof. No drilling, no sealant, and no structural modification to the roof itself, a flat concrete surface in this Hougang estate being one of the more straightforward roof types to fit this approach to.

Why ballasted mounting instead of a penetrating one?

A flat concrete roof is a genuinely clean candidate for ballasted mounting: the panel frames' own weight, distributed correctly across the roof, holds the array in place without bolts through the waterproofing membrane. This removes an entire category of leak risk a penetrating mount has to actively manage through sealant and flashing instead.

See how ballast weight actually gets calculated for the real standard, SS EN 1991-1-4, governing how much weight a specific roof and system size actually needs.

How does a one-day install actually happen on a roof like this?

A flat, unobstructed roof with no penetration work removes several of the steps that usually stretch an installation timeline: no waterproofing repair sequencing, no drilling and re-sealing, no waiting on a structural sign-off for penetration points. Placing and connecting ballasted frames is comparatively fast work once the roof and layout are confirmed.

This isn't universal. A roof with obstructions, multiple orientations, or a more complex electrical run to the inverter would extend even a ballasted installation's timeline meaningfully beyond a single day, and confirming with an installer upfront whether a single-day timeline is realistic for your specific roof avoids setting an expectation the property's actual layout can't support.

How much does this system actually save?

Around $310 a month, roughly $3,720 a year, based on Sunnify's projection for this 12 kWp system at the Q3 2026 EMA regulated tariff of S$0.3478/kWh, 25% self-consumption, and an SCT export credit of S$0.2581/kWh. These are the same real-world assumptions applied across every documented Sunnify installation, regardless of roof type or mounting method.

How does this compare to a similar-sized system on a pitched roof?

At the same 12 kWp size, a bifacial system on a pitched metal roof at Tai Keng Avenue projects an essentially identical savings figure, which is the useful takeaway here: mounting method and roof type shape installation complexity and cost far more than they shape the underlying generation and savings math at a comparable system size.

What would a similar flat concrete roof need to consider?

Confirm the roof's structural load capacity supports the ballast weight before assuming this approach transfers directly, since it's a real engineering calculation specific to each roof, not a universal yes for every flat concrete surface. This is worth confirming through an actual structural assessment rather than a visual estimate, since two flat concrete roofs that look similar can have genuinely different load capacities depending on their age and original construction.

See waterproofing considerations for a solar installation for how ballasted and penetrating approaches compare more broadly.

Run the full roof suitability checklist to assess your own roof, and the Sunnify solar estimate to see what a similar system could save on your property.