Price a gas heater using input energy units
A home uses a gas heater with sample efficiency of 80%. A sample fuel charge of USD 2.344 per therm is about USD 0.08 per input kWh using 29.3 kWh per therm.
Open CalculatorInputs and calculation
| Tool input | Value |
|---|---|
| Currency | USD |
| Volume or billing unit | liters |
| Volume (L) | 100 |
| Temperature rise (°C) | 40 |
| Heating method | Fuel heater |
| Efficiency (%) | 80 |
| Energy price (USD per input kWh) | 0.08 |
| Water price (USD/L) | 0 |
Heat delivered = 100 × 40 × 0.001163 kWh. Divide by 0.8 to get about 5.815 input kWh. Multiply input energy by 0.08, add 100 × 0 for water, then round to USD 0.47.
Tool result · USD 0.47
| Tool input | Value |
|---|---|
| Currency | USD |
| Volume or billing unit | liters |
| Volume (L) | 150 |
| Temperature rise (°C) | 40 |
| Heating method | Fuel heater |
| Efficiency (%) | 80 |
| Energy price (USD per input kWh) | 0.08 |
| Water price (USD/L) | 0 |
Heat delivered = 150 × 40 × 0.001163 kWh. Divide by 0.8 to get about 8.7225 input kWh. Multiply input energy by 0.08, add 150 × 0 for water, then round to USD 0.70.
Tool result · USD 0.70
What the comparison shows
The extra draw adds about 2.91 input kWh. Dividing by efficiency accounts for fuel energy that does not reach the water.
Assumptions and limits
Use the fuel conversion and price basis from the bill. The tool accepts a price per input kWh, and fixed gas charges are separate.