Running The Numbers: Surving the Winter With Unorthodox Heating Techniques

 

TL;DR synopsis: this is a non-religious, math-heavy, dad-centric, boring Saturday night post. 

Due to the war and the skyrocketing cost of energy, a quarter of those living in the UK do not plan to turn their heat on at all this winter.

I feel their pain. Our neighborhood does not have a natural gas line; we heat with oil (hydronic baseboard). I have played around with the idea of various alternatives; my neighbor switched to propane, one friend supplements with a wood stove, others extol electric heat pumps.

Because we got a new oil boiler 7 years ago, I'm not inclined to switch to propane for a nominal savings in fuel cost. I did get a quote on a wood stove + install ($9,500) which was too rich for my blood. Plus in talking with my friend who has one, he gets cold outside the 75 degrees he keeps his house, so it might soften us inadvertently.

With temps dropping below freezing this week, our family is acclimating to the cold, both outside the house and inside of it. Thankfully, we have a two-zone heating system (separate thermostats for upstairs and downstairs) which saves on fuel. In a typically heating season in the Northeast, we will go through approximately 300 gallons of heating oil for a 2,000 square foot house. 

I am currently figuring the cost/benefit of a single head ductless mini split install + operating costs in order to offset oil usage versus using...a series of simple 1,500w space heaters. People rave about the superiority of heat pumps, but the issue is not as straightforward as you might think. 

The estimate I received from an HVAC guy who stopped by is $6k per head/condenser for a ductless mini-split heat pump. 15 year average lifespan (versus 20-25 for a boiler). That's $400/yr avg (without the cost of electricity)

Heat pumps are 2.5x more efficient than electric space heater, (250% efficiency for heat pump vs 100% efficiency for space heater). So to run a space heater for 8 hrs/day x $.16/kWh is $1.92/day during the heating season. These units are extremely uncomplicated and reliable. If it croaks for whatever reason, I would just buy another one for $10 or so. There is (or at least should be) an inherent advantage and consideration in ease of use, reliability, and simplicity.

HOWEVER, there are three additional factors when it comes to heat pumps that I think many of the green-folks either don't admit or don't take into consideration:

1) heat pumps lose efficiency below 32 degrees F

2) heat pumps use a 'ghost load" of approximately 150 watt-hours during defrost cycle to keep the condenser coils from freezing.

3) heat pumps need to run 24/7, they don't do well "turning them down" at night. It's "set it and forget it"

An unorthodox practice that I have been employing experimentally for the past week is "heat the person, not the house." It's actually been working well, surprisingly, and is incredibly efficient. The idea is to have a series of ceramic space heaters in each room, and turn them on and off as I work, or as we relax in the family room, etc. Basically, only heat where you are. The upstairs and downstairs thermostats would be set to 55 (an acceptable temperature to ensure pipes don't freeze during very cold weather).

The things that get overlooked in the total cost comparison with heat pumps is a) the cost of the unit and installation averaged over it's lifespan; and b) annual maintenance servicing costs

So, I could zone heat during day with space heater downstairs in the family room for 8hrs/day during waking hours and turn off at night for $1.92/day. A heat pump would cost about the same ($1.54) for 24 hrs, and would obviously produce more BTUs, but would unnecessarily be heating at night. Factor in yearly service costs as well ($125/yr?) and you are looking at $400 unit+installation cost/yr averaged; +$125/yr service; +$275 cost of electricity for six month heating season. For a total of $800/yr

The space heater cost me $10. Cost of running it for 8hrs/day for six months is $345. It does not lose efficiency depending on ambient external temp. No maintenance. So, the total cost per year is $345. With oil at $5.50/gal and our oil boiler 87% efficient, electric space heating (which is 100% efficient) is on par price wise with oil now, per equivalent BTU. So, if I got a single heat pump I would be more efficient from an energy usage standpoint, but it would still cost me $445/yr more than running a space heater at this point, apples to apples.

Anyway, just one way to think outside the box this winter; zoned space-heating may not work for everyone, or even be preferable; take it for what it’s worth. But for some families, it may just help them survive the winter without going bankrupt.