If your HDB has a System 4 aircon, you have one outdoor unit on the ledge and four indoor units inside: usually the three bedrooms and the living room. Buying it was a one-time number. What nobody gives you is the yearly number: what should you set aside to keep four indoor units clean and the system running?
This guide works that out using only the prices published on our pricing page, so you can check every figure. It also shows something that catches people out: how you split the units across visits changes the bill more than which service you pick.
First, what a System 4 is (and why it matters for the bill)
A System 4 is one outdoor unit serving up to four indoor units. We cover how it compares with a System 3 and a System 5 in our guide to which system fits your HDB. For upkeep, two things follow from that layout:
- Cleaning is priced per indoor unit. Four indoor units means four units on the servicing and chemical wash tables.
- Gas is priced per outdoor circuit, not per indoor unit. Our pricing page says indoor units that share one outdoor unit share one circuit. A System 4 with one outdoor unit pays for one gas top-up, not four.
The three jobs and what each costs for four units
These are the published prices for a visit covering four wall-mounted indoor units. The price you see is the price you pay, and the 9-point pre-check is included with every service booking.
| Job | 1 unit | 4 units | How often (as published) |
|---|---|---|---|
| General servicing | $45 | $115 | Routine 3-monthly maintenance |
| Chemical wash | $135 | $425 | Every 6-12 months |
| Chemical overhaul | $200 | $640 | Every 2-3 years, or for severely fouled units |
Look at the general servicing line: four units cost $115, which is $28.75 a unit, against $45 for a single unit. A System 4 is already the cheaper way to buy servicing per unit, because the price drops as you add units to the same visit.
What a year can look like: three worked examples
These are straight additions of the published prices for four units, not packages we sell. We do not sell annual packages or take money upfront. Each visit is booked when you need it.
- Light upkeep: general servicing every 3 months. 4 visits x $115 = $460 a year.
- Balanced: 2 general services plus 1 chemical wash. 2 x $115 + $425 = $655 a year.
- Thorough: 3 general services plus 1 chemical wash. 3 x $115 + $425 = $770 a year.
The overhaul sits outside the yearly cycle. At $640 for four units, once every 2 to 3 years works out to between about $213 and $320 a year if you spread it out ($640 divided by 3, and by 2). If your units are heavily fouled, or it has been years since anything beyond a filter rinse, our guide on whether to overhaul or replace helps you decide.
Which example suits you depends on your home, not on a rule. A flat that is lived in all day and run every night is a different case from one used only in the evenings. Our guide to how often to service your aircon goes through the factors.
The part that changes the bill: do all the units in one visit
Because the price per unit falls as the unit count in a single visit rises, splitting your units across visits costs more than doing them together. Here is what that looks like using the published tables.
| Scenario | General servicing | Chemical wash |
|---|---|---|
| All 4 units in one visit | $115 | $425 |
| Split 2 + 2 in two visits | $70 + $70 = $140 | $245 + $245 = $490 |
| Split 3 + 1 in two visits | $95 + $45 = $140 | $345 + $135 = $480 |
Splitting 2 + 2 costs $25 more for general servicing and $65 more for a chemical wash than doing all four in one go. For a flat doing three or four services a year, that adds up.
We cover the other side of this, whether every unit really needs a wash or just the worst one, in chemical wash for every aircon or just one unit. The short version of the pricing: washing one unit is the most expensive way per unit, and washing only the worst unit is only worth it if the others are genuinely clean.
If you have a fifth unit, bring it too
Some flats have a System 4 plus a separate single split in the study or a bedroom, which makes five indoor units. The published tables switch to a flat per-unit rate from five units: $25 per unit for general servicing, $100 per unit for a chemical wash, and $150 per unit for an overhaul.
- General servicing: 5 units together is $125. Doing 4 first ($115) and the fifth on its own ($45) is $160, which is $35 more.
- Chemical wash: 5 units together is $500. Doing 4 ($425) plus 1 ($135) is $560, which is $60 more.
- Overhaul: 5 units together is $750. Doing 4 ($640) plus 1 ($200) is $840, which is $90 more.
The fifth unit costs only $10 extra on a general service when it joins the visit. On its own it costs $45. If one unit is always the odd one out on your service schedule, change that.
The costs that are not on the yearly plan
Some bills are not scheduled. For a System 4, here is how the published prices behave:
- Gas top-up: priced per outdoor circuit. R22 is $115, R410A is $130 and R32 is $170. Check the sticker on the outdoor unit for the refrigerant type. With one outdoor unit that is one charge, not one per room.
- Leak or pressure test: $180 per FCU, which is per indoor unit. If you needed a dedicated test on all four indoor units, that is 4 x $180 = $720, so it is worth the pre-check pointing at a real reason. If a repair is approved on the same visit, the test fee is offset against that repair. Piping replacement is $450 per FCU, with concealed pipe work quoted after the test. Before you approve any leak quote, read what to check before you approve a gas leak repair.
- Standard repair (drainage, electrical): from $80.
- High-floor ledge access: we do charge extra for this on a case-by-case basis, and there is no fixed figure because it depends on your block. The fee is confirmed for your specific block before work starts.
A well-kept system is the best protection against the large items. A choked drain, a coil full of grime and a blower wheel loaded with dirt are the kind of problems a regular service and an occasional wash are meant to catch early.
Contract or pay as you go?
Maintenance contracts sell the idea of fixed annual savings. We do not sell annual packages or take money upfront, so the examples above are simply what happens if you book when due. If someone offers you a prepaid plan, our guide on what to check in a prepaid maintenance contract lists what to ask, including whether the price per unit is better than the published rate above.
Before you book: a short checklist
- Count your indoor units, including any separate single split. Give us the full number.
- Book all of them in one visit so the multi-unit rate applies.
- Note the last time each unit was serviced. If one has been skipped for years, tell us. It may need a wash rather than a general service.
- Check the refrigerant type on the outdoor unit sticker.
- Ask for the price before work starts. You see the finding and the price first. Repair work carries a 90-day workmanship warranty.
Every figure on this page comes from the pricing page, so if our prices change the page there is the one to trust.
WhatsApp us on 9107 2601 with the number of units and when each was last serviced, and we will confirm the visit price.