Compare equal water volumes over the same number of months. Include bottle prices and delivery on one side, and upfront spending, recurring payments, filters, service, energy and consumables on the other. Neither option is automatically cheaper or suitable for every water-quality need.
Compare your own costs
All defaults are illustrative, not market prices. Replace them with actual quotations and your household use. Each comparison month is 30 days.
Start with litres, not people alone
Review a normal shopping cycle. Count how many bottles or cartons are finished, how much water goes to work or school and whether another source supplies some drinking water. The amount your household uses matters more than the number of people at home.
Divide the pack price by total litres. A hypothetical RM12 pack containing 12 litres costs RM1 per litre before delivery. A smaller pack may look cheaper at checkout while costing more per litre.
The calculator uses a 30-day comparison month. Its default 6 litres per household per day is an editable spending example, not a recommended intake. Use the same daily water amount for both options.
Enter the full purifier commitment
Include purchase and installation as upfront spending. Enter rental or other recurring payments separately. Add filter and service costs only when they are not already included in the plan. An annual RM240 service expense becomes RM20 a month for this simplified comparison, even if it is paid in one instalment.
Electricity, feed-water costs, reject water where relevant and other consumables belong in the calculation too. A refundable deposit is money tied up, not automatically an expense; record it separately unless it will not be returned.
The rental-versus-buying guide covers the payment and ownership decision. This comparison takes your chosen arrangement and compares it with bottled-water supply.
A worked example with visible assumptions
The illustrative defaults use 6 litres a day for 30 days: 180 litres monthly. At RM0.80 per litre, bottled water costs RM144 a month. Over 36 months, with no delivery fee, the total is RM5,184.
The example purifier costs RM2,000 upfront, RM20 monthly for filters and service, RM10 for electricity and RM2 for water or consumables. With no rental payment, the 36-month total is RM3,152. The difference is RM2,032 in favour of the purifier under these inputs only.
These are illustrative calculations, not current market quotations or measurements of a particular product. At lower water consumption, a lower bottle price or a higher purifier commitment, the difference can narrow or reverse.
Choose a realistic comparison period
A longer comparison period spreads the purchase cost across more months. That can make buying look cheaper even if you expect to move sooner. Start with the period you reasonably expect to use the arrangement and check obligations extending beyond it.
If a rental contract lasts longer than your comparison period, include unavoidable remaining payments or use the full contract period. Add financing charges to the relevant input if applicable. Resale value, interest and unexpected repairs are excluded unless you account for them.
The monthly average is total spending divided by the comparison months. It is not necessarily the payment due each month. The output shows both the upfront amount and recurring purifier cost so the difference remains clear.
Cost does not establish water quality
A cost calculator cannot identify what treatment your source water needs. Products and bottled-water supplies differ. Check the exact claims and supporting evidence instead of assuming that any cheaper option gives equivalent treatment.
Use the water-purifier buying guide for the wider decision and the electricity guide for power estimates. A plumbed purifier is also not an unlimited reserve when the supply stops; use the disruption checklist to plan backup water.
Consider the routine behind the figures
- Can someone receive and store bottled-water deliveries?
- Is purifier installation practical in the current home?
- Who arranges filters and servicing?
- What happens on relocation or early cancellation?
- What backup supply is available during downtime?
Keep your inputs with a date and written quotations. Revisit them when household use or contract terms change. The more useful option is one the household can afford and maintain, with appropriate evidence for its intended use.
Frequently asked questions
Are the default inputs current Malaysian prices?
No. They are illustrative values. Replace them with actual bottle prices, a written purifier quotation and your running-cost estimates.
Can I compare a rental purifier?
Yes. Enter the rental payment and upfront costs. Avoid counting included filters or servicing twice, and account for the full contract commitment.
Does the cheaper result mean better drinking water?
No. This tool compares entered costs, not water safety or treatment performance.
Sources and further reading
Sources checked on 11 September 2026.
