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You would need to unplug it or switch it off for a year to save as much energy as it takes to have one-and-a-half baths. Maybe something is lost in tr

You would need to unplug it or switch it off for a year to save as much energy as it takes to have one-and-a-half baths. Maybe something is lost in translation but what on earth are they comparing? The energy cost to heat the water in a bath?

wuputah 16y ago
Presumably, yes. Although there are formulae to convert water use to an amount of energy consumption (which takes into account processing, pumps, etc), they are probably referring to the energy to heat water. 1 watt for 1 year is (1W * 24h * (365d/year)) * (1Wh/1000kWh) = 8.76 kWh, or ( * 3412 BTU/kWh) about 30k BTU. The average bath is about 50 gallons, or ( * 8.35 lb/gallon) 417.5 lb. 30k BTU is enough energy to raise that much water by about 70°F (30k BTU / 417.5 lb). By that measurement, the Guardian takes baths 46.6°F hotter than their tap water. If that is too cool for you, you can take a smaller bath. It's worth noting that the conversions here assume you can transfer the kWh with perfect efficiency to heating water, while in actuality, all heating systems will be somewhat inefficient. It will actually take more energy to heat the water, regardless of the energy source used by the water heater. Edit: whoops, I originally misread and used 1.5 years and 1.5 baths. Calculations changed.
- kragen 16y ago
  A couple of points: - It's a lot easier to heat your bath with solar energy than it is to run your phone charger. So if you have a solar hot water heater, a different comparison would be in order. - The inefficiency of the water heater is probably relatively small (under 50%, maybe under 10%) and so can be neglected for the purpose of round-number figures like "one and a half baths".
barkingcat 16y ago
what if you have cold water baths? The comparisons are really unclear - really poor use of language. And they assume too many things. What if you don't take any warm/hot baths AND turn off lights? Would that save energy?

wuputah 16y ago

Presumably, yes. Although there are formulae to convert water use to an amount of energy consumption (which takes into account processing, pumps, etc), they are probably referring to the energy to heat water. 1 watt for 1 year is (1W * 24h * (365d/year)) * (1Wh/1000kWh) = 8.76 kWh, or ( * 3412 BTU/kWh) about 30k BTU. The average bath is about 50 gallons, or ( * 8.35 lb/gallon) 417.5 lb. 30k BTU is enough energy to raise that much water by about 70°F (30k BTU / 417.5 lb). By that measurement, the Guardian takes baths 46.6°F hotter than their tap water. If that is too cool for you, you can take a smaller bath. It's worth noting that the conversions here assume you can transfer the kWh with perfect efficiency to heating water, while in actuality, all heating systems will be somewhat inefficient. It will actually take more energy to heat the water, regardless of the energy source used by the water heater. Edit: whoops, I originally misread and used 1.5 years and 1.5 baths. Calculations changed.

kragen 16y ago
A couple of points: - It's a lot easier to heat your bath with solar energy than it is to run your phone charger. So if you have a solar hot water heater, a different comparison would be in order. - The inefficiency of the water heater is probably relatively small (under 50%, maybe under 10%) and so can be neglected for the purpose of round-number figures like "one and a half baths".

barkingcat 16y ago

what if you have cold water baths? The comparisons are really unclear - really poor use of language. And they assume too many things. What if you don't take any warm/hot baths AND turn off lights? Would that save energy?