How to Calculate Your Singapore Electricity Bill Before Solar

Your own SP Group electricity bill is calculated as monthly kWh usage multiplied by the current tariff, currently S$0.3478 per kWh including GST for Q3 2026 specifically. Working this out yourself takes under a minute if you have a recent bill on hand, and gives you the real, concrete, actual baseline figure to compare against any future solar savings estimate you are handed later.

What's the actual formula?

Monthly bill = kWh used x S$0.3478. For a household using 500 kWh in a month, that is 500 x 0.3478, or roughly S$174. This is a simplified estimate, since a real bill can include minor additional charges, but the energy component, the part solar actually offsets, follows this formula directly.

Where do you find your actual kWh usage?

Two reliable sources: your SP Group online account, which shows usage history by month, or the physical or digital bill itself, which states total kWh consumed for that billing period. This is the most accurate starting point, since it reflects your household's real consumption pattern rather than a generic estimate.

Does this simplified formula match your real bill exactly?

Very closely, for most households on SP Group's regulated tariff, which is the default for homeowners who have not actively switched to an Open Electricity Market retailer. The formula above captures the core energy charge, which is the large majority of a typical residential bill, though your specific figure may differ by a small amount from minor items depending on your account, which is why comparing your calculated estimate against last month's actual total is always worth doing once, just to confirm the two line up closely for your own account.

Does this calculation differ if you buy electricity from an OEM retailer instead of SP Group?

Yes, potentially by more than the SP Group formula alone would suggest. A homeowner who has switched to a retailer through Singapore's Open Electricity Market may be on a fixed-rate plan, a discount-off-regulated-tariff plan, or another pricing structure entirely, none of which is guaranteed to track SP Group's own quarterly S$0.3478 figure directly. If you buy from a retailer, your own contracted rate, not the SP Group regulated tariff used in the table above, is the number to actually multiply your usage by.

How does this formula change once solar is actually generating?

It splits into two separate pieces rather than staying one multiplication. Self-consumed solar generation offsets usage at the full retail tariff rate, effectively reducing the kWh figure you are paying for at S$0.3478.

Exported surplus generation instead earns a separate, lower SCT or ECIS credit rate against the bill, covered in full in how solar export credit works in Singapore. Knowing your pre-solar bill precisely, using the formula above, is exactly what makes the post-solar comparison a real, grounded number rather than an abstract percentage claim.

What if you don't have a recent bill to check?

Estimate from your major appliances. Air-conditioning is typically the largest single factor in a Singapore landed home's electricity use, followed by water heating and general lighting and appliances. A rough estimate built this way will not be as precise as an actual bill, but gives a workable starting figure while you locate your real usage data.

What does a worked example actually look like, start to finish?

Take a household using 800 kWh in a month, a realistic figure for a landed home running air-conditioning regularly. The pre-solar calculation is straightforward: 800 kWh multiplied by S$0.3478 comes to roughly S$278, matching the table above.

With a well-sized solar system self-consuming, say, 25% of its own generation directly and covering a meaningful share of that 800 kWh usage, the portion still drawn from the grid at S$0.3478 shrinks accordingly, while any surplus the system exports earns the separate, lower SCT or ECIS credit on top. Running your own real numbers through the Sunnify solar estimate turns this worked example into your household's own actual figure, rather than a generic illustration built on someone else's usage pattern.

Why is this the right first step before estimating solar savings?

Because it turns an abstract percentage, solar could cut your bill by 60 to 90%, into a concrete number specific to your household. Knowing you currently pay roughly S$278 a month makes a projected post-solar bill of S$50 to S$110 a real, comparable figure, rather than an estimate with no baseline to anchor it.

Further reading: see the Singapore electricity tariff tracker for the current rate this calculation uses, and will I still have an electricity bill with solar for what changes after installation. Run the Sunnify solar estimate to see your own specific, fully worked-out post-solar bill.