📖 How To Use
How to Use This Calculator
This tool compares the total cost of continuing water deliveries against buying and owning a storage tank. Here's how to get your personalised break-even result:
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Enter your current delivery costs
Input the price you pay per delivery order and how many times per month you receive deliveries. The calculator works out your monthly spend automatically.
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Add the tank investment total
Enter the tank purchase price and any installation costs separately. Include plumbing, fittings, and labour in the installation field for an accurate total.
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Include ongoing tank costs (optional)
Add any monthly maintenance cost (cleaning, inspections) and a projected annual delivery price increase percentage — defaults to 3% if left blank.
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Review your results
The calculator shows your break-even month, 10-year savings, and a bar chart comparing delivery costs at 1, 2, 3, 5, and 10 years versus tank ownership at each stage.
Tip: Include all hidden delivery costs — minimum order surcharges, emergency delivery premiums, and fuel levies. These can add 15–30% to the base price and significantly shorten your break-even period.
📐 The Formula
Water Delivery vs Tank Cost Formula
The calculator solves for the month at which cumulative delivery costs exceed the total tank investment plus running costs:
Monthly Delivery Cost = Cost Per Delivery × Deliveries Per Month
Total Tank Investment = Purchase Price + Installation Cost
Cumulative Delivery (Year N) = Σ Monthly Costs × (1 + Annual Increase%)^Year
Break-Even Month = Month when Cumulative Delivery > Total Tank Cost
10-Year Savings = 10yr Delivery Cost − (Tank Investment + 10yr Maintenance)
Annual delivery price increases are compounded yearly. If your deliveries cost $100/month today and prices rise 3% per year, you'll pay approximately $134/month in Year 10 — which is why the long-term savings often look dramatic.
Sample Break-Even Scenarios
| Monthly Delivery | Tank Cost | Price Rise/yr | Break-Even | 10-yr Savings |
|---|
| $60 | $800 | 3% | ~14 months | ~$6,200 |
| $100 | $1,200 | 3% | ~13 months | ~$10,700 |
| $150 | $2,000 | 5% | ~14 months | ~$17,500 |
| $200 | $3,500 | 3% | ~18 months | ~$18,700 |
| $300 | $6,000 | 5% | ~21 months | ~$29,000 |
Estimates assume zero maintenance costs. Your actual figures will vary based on delivery frequency, tank type, and local price trends.
💡 When to Use
When Does Buying a Tank Make Sense?
This calculator is designed for anyone currently paying for recurring water deliveries who is weighing the investment in permanent storage.
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Rural & Off-Grid Households
Not connected to mains water. Deliveries are the only option — until you own a tank and only need top-ups occasionally.
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Construction Sites
Sites paying for multiple weekly deliveries often find a hired or purchased tank pays back within two to three months.
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Farms & Agricultural Land
Livestock water, irrigation, and seasonal demand make reliable large-volume storage a financial necessity.
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Commercial Properties
Restaurants, laundries, and commercial kitchens in low-pressure areas can dramatically cut costs with dedicated storage.
Rule of thumb: If your annual delivery spend exceeds the tank purchase price, you'll likely break even in under 12 months. Use this calculator to confirm the exact number.
❓ FAQ
Frequently Asked Questions
How long does it take for a water tank to pay for itself?
It depends on your monthly delivery spend and total tank cost. Most households paying $80–$150/month see payback within 12–24 months on a standard tank. Use the calculator above to find your exact break-even month based on your real numbers.
What should I include in the "installation cost" field?
Include all one-time costs beyond the tank itself: plumber labour, pipework, inlet/outlet fittings, overflow diverters, base preparation or slab pouring, and any council application fees. These are typically 20–60% of the tank purchase price for larger domestic installations.
What is a realistic annual water delivery price increase to use?
Historically, water delivery prices in most regions track between 3–7% per year due to fuel costs, driver wages, and infrastructure. Using 3% is conservative; 5% is more realistic in areas with rising transportation costs. The calculator lets you enter your own figure for accuracy.
Does this calculator account for the cost of water to fill the tank?
This calculator compares delivery costs versus tank ownership costs. If you'll still need periodic deliveries to fill the tank (rather than using mains water or rainwater), enter a lower number of deliveries per month to reflect reduced frequency. For example, if you currently get 4 deliveries/month but would only need 1 after installing a tank, use 1 in the "after tank" scenario.
What is the calculator for water delivery vs tank cost?
This is a financial break-even tool that compares two scenarios: (1) continuing to pay for regular water deliveries, and (2) purchasing a storage tank. It calculates the exact month your delivery spending would have paid for the tank, and shows projected savings over 5 and 10 years.
Is buying a bigger tank better value than a smaller one?
Generally, larger tanks offer better cost-per-litre value and reduce refill frequency, lowering long-term delivery costs further. However, a larger tank has a higher upfront cost, which extends the break-even period. Use the water storage cost per litre calculator alongside this tool to compare tank sizes before deciding.
How do I compare plastic vs steel tank costs for this decision?
Plastic (polyethylene) tanks have lower upfront costs and near-zero maintenance, making them ideal for shorter break-even calculations. Steel tanks cost more initially and may have corrosion maintenance costs, but often have longer lifespans. Enter each scenario separately into this calculator and compare. You can also use our plastic vs steel tank cost calculator for a detailed material comparison.
🔗 Related Calculators
Related Cost & Comparison Tools
Use these calculators alongside the break-even tool for a complete picture of your water storage investment: