Separate water and heating costs for a tub fill
A tub fill costs money for both metered water and heating. Compare 100 L with 80 L at the same temperature, using separate water and electricity prices.
Open CalculatorInputs and calculation
| Tool input | Value |
|---|---|
| Currency | USD |
| Volume or billing unit | liters |
| Volume (L) | 100 |
| Temperature rise (°C) | 25 |
| Heating method | Electric resistance |
| Efficiency (%) | 100 |
| Energy price (USD per input kWh) | 0.25 |
| Water price (USD/L) | 0.004 |
Heat delivered = 100 × 25 × 0.001163 kWh. Divide by 1 to get about 2.9075 input kWh. Multiply input energy by 0.25, add 100 × 0.004 for water, then round to USD 1.13.
Tool result · USD 1.13
| Tool input | Value |
|---|---|
| Currency | USD |
| Volume or billing unit | liters |
| Volume (L) | 80 |
| Temperature rise (°C) | 25 |
| Heating method | Electric resistance |
| Efficiency (%) | 100 |
| Energy price (USD per input kWh) | 0.25 |
| Water price (USD/L) | 0.004 |
Heat delivered = 80 × 25 × 0.001163 kWh. Divide by 1 to get about 2.326 input kWh. Multiply input energy by 0.25, add 80 × 0.004 for water, then round to USD 0.90.
Tool result · USD 0.90
What the comparison shows
For 100 L, water costs 0.40 and energy about 0.73. A smaller fill reduces both components in the model.
Assumptions and limits
Use USD 0.004/L for a water price of USD 4/m³. Fixed fees, sewer surcharges and tank losses are excluded.
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