How to Size a Home Battery for Your Singapore Landed Home
10 kWh is right for most Singapore landed homes. Here is the sizing logic: daily solar surplus, evening household load, EV charging needs, and the one calculation that ties them together.
Why should this article concern you?
- 1
A 10 kWh battery is the practical starting point for most Singapore landed homes: it covers evening peak consumption for a household using 15 to 20 kWh per day and matches the daily surplus of a 10 to 15 kWp solar system
- 2
Oversizing wastes money: a battery larger than your daily solar surplus will spend most cycles partially charged. Undersizing wastes solar: a battery smaller than your evening load leaves export credits on the table
- 3
For households with an EV, add 8 to 15 kWh to cover overnight EV charging from solar, bringing the recommended battery to 18 to 25 kWh for a typical Singapore EV owner with a 15 kWp solar system
Battery sizing is the question most Singapore homeowners get wrong twice: once by undersizing because the upfront cost is high, and once by oversizing because the installer recommended the largest option. The right size is the one that matches your actual solar surplus to your actual evening load. The complete battery storage guide covers cost and ROI; this article covers the sizing logic.
The Two Numbers That Size Your Battery
You need two numbers. First: daily solar surplus, meaning how much your panels generate beyond what you consume during the day. Second: evening load, meaning how much your household draws from 6pm to midnight.
For a typical Singapore landed household with a 15 kWp solar system generating 16,590 kWh per year (45 kWh per day on average) and daytime self-consumption of 25% (11 kWh during generating hours), the daily solar surplus available for battery storage is approximately 34 kWh.
But most Singapore households use 15 to 20 kWh per day total, with roughly 8 to 12 kWh consumed in the evening after solar stops generating. A 10 kWh battery covers that evening load comfortably. A 20 kWh battery would store twice as much, but only if your evening load and overnight consumption actually demands it.
The EV Adjustment
A Singapore EV (Hyundai Ioniq 5, BYD Atto 3, Tesla Model 3) typically needs 5 to 10 kWh per day for an average commute of 30 to 50 km. If you want to charge the EV overnight from stored solar, add that to your evening load.
For a household with one EV: evening load 8 to 12 kWh plus EV charging 8 to 10 kWh = 16 to 22 kWh total. The recommended battery size is 18 to 25 kWh: two BYD HVS modules, a Sungrow SBR at 19.2 kWh, or a Tesla Powerwall 3 (13.5 kWh, slightly under but covering most of the load).
The Sizing Rule of Thumb
Start with your daily solar generation (kWp x 1.106 for Singapore conditions). Subtract daytime self-consumption (roughly 25% of generation for a household that is partially away during the day). The remainder is the maximum battery storage that makes sense. Then check your evening load; there is no point storing more than you will actually use overnight.
Most Singapore landed homes land on 10 kWh without an EV, and 18 to 25 kWh with one EV. Beyond 25 kWh, a second EV or a very high-consumption household (pool, multiple air conditioner units running overnight) is needed to justify the additional cost.
Oversize the solar. Rightsize the battery. A bigger solar system always pays back better than a bigger battery, because solar generates at S$0.00 per kWh and the ROI compounds for 25 years. Size the battery to what you actually use overnight.
For the full battery brand comparison and cost breakdown, see Tesla Powerwall vs BYD vs Sungrow. The complete financial case is in the battery ROI article.
Further reading: battery storage ROI and payback in Singapore · battery brand comparison for Singapore homes · battery storage cost and sizing guide.
What does this mean for your home?
- Calculate your evening load before your installer quotes a battery size. Pull three months of SP Group bills and estimate how much you use between 6pm and midnight. That number is the upper bound on the battery size that will actually pay its way.
- 10 kWh covers most Singapore landed homes without an EV. If your household uses 15 to 20 kWh per day and the solar system is 10 to 15 kWp, 10 kWh stores enough evening load to lift self-consumption from 25% to 60-70%. Going to 20 kWh adds cost without proportional return.
- If you have or plan to buy an EV, size up to 18 to 25 kWh. Overnight EV charging from stored solar at S$0.00/kWh instead of grid charging at S$0.3478/kWh saves S$600 to S$900 per year for a typical Singapore commute. Run the Sunnify estimate with EV charging included to see your combined system ROI.
What is the right battery size for a Singapore terrace house?
For a Singapore terrace house without an EV, a 10 kWh battery is the practical sweet spot. It covers 8 to 12 kWh of evening household load, matches the daily surplus of a 12 to 15 kWp solar system, and is the standard size offered by most Singapore installers. With an EV, size up to 18 to 25 kWh to cover overnight EV charging from stored solar.
Can I add more battery capacity later if I need it?
Yes, if you choose a modular battery like BYD Battery-Box HVS, Sungrow SBR, or Huawei LUNA2000. These systems allow you to add capacity in increments later. Tesla Powerwall 3 is not modular in the same way, though multiple Powerwalls can be stacked. The key is to ensure your hybrid inverter supports the expanded battery capacity at the outset; confirm the inverter's maximum battery input rating with your installer before deciding on the initial size.
