Morning coffee thoughts

 As I was making my coffee this morning I was idly speculating on if I would save energy by putting hot water from the faucet rather than cold into my electric kettle.  Now, first, it is written that "Every big counts."  The energy in my morning coffee is probably below what I should be worrying about by a bit, if it wasn't fun.  

That out of the way, if I use cold water then all the energy I use comes in as electricity from the grid which then gets turned into heat in the water with near perfect efficiency.  In Massachusetts I'm emitting about 421 grams of carbon per kWh on that.

Or, lets say I use burning natural gas to heat my water directly.  That would typically be 185 g/kWh if I can do it perfectly efficiently.  If I was doing it on a stove top it wouldn't be that efficient but the boiler down in the basement should be about 95% efficient so lets say 195 g/kWh.  The water coming out of the tap isn't coffee making temperature but having part of the energy I'm using be more efficient is good.  Simple, right?  

Well, no.  A lot of water has to come out of the tap before it starts turning hot in the morning.  If I say that three times the volume of water I need has to flow before I get my hot water then suddenly we've got a factor of 4 efficiency penalty and now the hot water is at 780 g/kWh.   Pretty terrible, right?

But there's a bit more to it.  All that piping that was full of cold water is now full of hot water.  But before I go to make my next cup of coffee tomorrow morning it will be cold again.  That energy that was in those pipes went into heating the building.

In winter, this is great.  We would have been burning that natural gas to create heat anyways.  And since the heat that goes into the water from electricity ends up heating the building more we should discount the pure electrical option by 195 g/kWh down to 226 and count the hot water at 0.

In the summer, this is terrible and even worse than it looks since there's AC to factor in as well.  Pure electric kettle for me in the summer.

So there you have it, me sharing my morning noodlings with you all.