Bath vs Shower Calculator
Estimate gallons used, energy to heat water, and costs per session so you can choose the most efficient clean routine.
Average tubs hold 40–80 gallons.
Modern showerheads average 2.0–2.5 gpm.
Blend water + sewer charges. $0.01–$0.02/gal is common.
Groundwater ranges 45–70°F depending on climate.
Gas heaters convert to kWh automatically.
Per-Session Comparison
Bath
- Water used: 60 gal (227.12 L)
- Water cost: $0.9
- Energy cost: $0.92
- Total cost: $1.82
Shower
- Water used: 25 gal
- Water cost: $0.38
- Energy cost: $0.38
- Total cost: $0.76
How to Use This Calculator
Measure tub fill and shower flow
Time how long it takes to fill your tub or capture shower water for 15 seconds to determine flow (gallons per minute).
Check your utility rates
Review water/sewer bills or energy statements for accurate per-gallon and per-kWh costs. Enter blended estimates for best results.
Compare usage scenarios
Adjust shower length, bath fill level, and weekly frequency to see how small tweaks save water and money over a year.
Formula
Shower Gallons = Flow Rate × Minutes
Energy Cost = Gallons × (8.34 × ΔT ÷ 3412) × kWh Cost
Total Cost = Water Cost + Energy Cost
Example: 2.5 gpm × 10 min = 25 gal. With ΔT 45°F and $0.14/kWh, shower costs about $0.76.
Water-Saving Tips
Baths aren’t always wasteful and showers aren’t automatically efficient. Use this insight to match your routine to comfort, relaxation, and sustainability goals.
- Install low-flow showerheads (1.8 gpm) to shrink water and energy usage.
- Partially fill the tub or batch baths for kids to share warmth.
- Capture warm-up water in a bucket to water plants or mop floors.
- Heat water with solar or heat-pump systems to slash energy costs.
Frequently Asked Questions
Does a bath always use more water?
Not necessarily. Short showers or ultra-efficient heads can beat a partially filled tub. Run the numbers with your actual habits.
What about tankless vs tank heaters?
The calculator uses energy cost per kWh. If you know gas price per therm, convert to kWh (1 therm ≈ 29.3 kWh).
Should I include wastewater fees?
Yes—municipal bills usually charge water + sewer per gallon. Adjust the water cost input to represent combined charges.
How accurate is energy use?
It assumes all water is heated from incoming temperature to desired temperature. Actual heater efficiency and heat loss may vary, so treat it as an estimate.