We have a big bathtub, a standard bathtub, 1.85 gpm showers, and a sauna. When I’m feeling the need to soak my body in some serious heat over the winter, which is the most eco-friendly choice*?
- Showerhead: 1.85 gpm x 15 min = 27.75 gallons
- Standard bathtub, waist-deep: 20 gallons water
- Non-jetted spa-size tub (no heated recirculation), waist-deep: 30 gallons
- It takes 83,000btu (.9 gallons propane) to heat 100 gallons of water from 55 degrees to 120 degrees
- It takes 4.5 kwh (15,354 btus) to run one sauna session (heat for 40 mins to ~150 degrees, then residual heat only)
- 15-minute shower: 23,240 BTU + 28 gal water
- Standard bath: 16,600 BTU + 20 gal water
- Spa bath: 24,900 BTU + 30 gal water
- Sauna: 15,354 BTU + 2 gal water + 1000 BTU to heat water to 95 degrees (quick rinse shower after)
So – if what I want is to be very warm for as long as possible, the sauna is by far the best bet. Warmer than a standard bath, and I can stay in as long as I can stand and it’ll still be warm. Add to that the fact that my husband will usually join me in the sauna (but not the bath), and it looks like an even better option.
This is pretty much the opposite of how I thought this would pan out – I’m really glad I did the math!
* I am fully aware that doing any of these is a total luxury and “none” is the greenest answer…but if I’m going to do something, I want to know how these options compare