Mechanicals-Electrification of Heating Systems

Did you know, there are a few areas in the country where a homeowner no longer has the option to hook to a gas line when building a new home?  These communities have banned all gas installations in new construction.  A growing trend or community overreach?  Time will tell.  That said, I’ve been hearing a lot of noise lately about electrification in new construction.  Homeowners and builders are giving some consideration on how to condition, that is heat a home using only electricity as the fuel source.
Can this be an effective option in a cold or very cold climate? 

Can an all electric option work?  It can, but I’m going to stick a * next to the answer.  *An all electric heating source can work in a cold and very cold climate, but electric heat will work best in low load houses.  (This is true of all heating systems and sources, but especially important in all electric homes.)  Well insulated and air sealed homes require less heat and they tend to keep the heat that is produced inside the space longer than the typical home.  In a nutshell, that’s the biggest trick to using electricity as the heat source, build a house in such a way it doesn’t require as much and is slow to loose heat.

Heating requirements of a home.  How much heat a home will require has many variables.  Insulation and air sealing are a couple, but more important is where the home is located.  Two identical homes, one is Austin, TX and one in Grand Rapids, MN will have huge differences just based on the difference between inside and outside temperatures during the heating season.  Exposure to wind and the overall design of the home also influence heating needs.  We need to talk a little about heat, what is a BTU?  A BTU is a British Thermal Unit and one BTU is roughly the equivalent of one wooden match stick burning, simply, it’s a measurement of heat.  A typical code built home in my climate might have a heating load of 40,000 BTU’s, that load is based on the coldest outdoor temperatures of the year.  A home that moderately improves insulation and air sealing levels might reduce that load by 50%.  A very high performance home might drop to 10,000 BTU’s.  Heating needs of a home have many variables, but they can be fairly easily reduced.

Into the weeds!  Lets look at a few different fuel types and their heat output.  Each fuel source produces a specific amount of heat per unit of fuel.  Natural gas, for example, produces roughly 100,000 BTU’s of heat per therm of gas.  A gallon of propane produces around 91,500 BTU’s.  1 kilowatt hour of electricity produces 3412 BTU’s.  Each of the fuel sources has a cost associated with it, as I’m writing this, the cost of natural gas and propane is roughly $2 per unit.  I’m hearing rumblings about fuel shortages this winter which may drive these costs substantially higher, but let’s use the $2 cost.  In natural gas, we can convert this to $.020 per 1,000 BTU’s.  Propane is $.022 per 1,000 BTU’s.  Electricity costs on the general service rate in my area are around $.13 per kilowatt hour, so 1,000 BTU’s has a cost of $.038.  What?, why would anyone even consider electric if the cost of equivalent BTU’s is nearly double the cost of natural gas?

Electricity provider programs and efficiency.  Electricity providers in my area (and hopefully yours) have been playing with peak electrical loads for decades.  These providers want to see a steady use of electricity, the same demand all the time.  Unfortunately, this is seldom the case, there are peaks and valleys in demand which sometimes forces a utility to go on the open market to purchase power.  This typically ends up being very expensive for the utility, often they have to purchase power in the dollars per kilowatt and then sell it back to their customers in pennies.  A business isn’t going to be successful if it looses money every time there is an unexpected demand on their system.  To combat this, the utilities in my area have designed several off peak control programs to control different electricity using appliances in a home.  The electric water heater is one commonly controlled example.  The electricity provider is given permission to turn on and off (control) someone’s water heater, and in return the homeowner receives a special rate, usually 50% less than the normal rate for the power consumption of the water heater.  The power company now has a way to turn on and off the electric water heaters on it’s system that are enrolled in the program to help reduce peaks in usage.  The water heater is just one example, imagine if there was an electric furnace that could also be controlled.  Well…

This is an electric thermal storage furnace or ETS, manufactured by a company in North Dakota called Steffes.  This furnace is loaded with a ceramic brick, (the unit weighs in the thousands of pounds), the brick is heated by electric resistance elements, but only takes a charge over night.  The heat that is stored by the brick is then released during the day.  My local electricity provider has a special off-peak storage heat rate of $.0535 per kWh, this ends up being $.0157 per 1,000 BTU’s, substantially cheaper than natural gas.  This furnace isn’t new technology, I remember installing room units manufactured by Steffes, which operate similarly, back in the mid 1990’s, all on load control programs.  Something to know about this furnace, it radiates a lot of heat which typically increases the temperature of the area where it’s located by several degrees.  (A great place to install a heat pump water heater, move some of the excess heat to the water).  Where you could really make this system shine is if you pair it to an air source heat pump.  Spring and fall heating loads, along with AC would be addressed by the heat pump, the storage furnace would take over during colder temperatures, December through March in my area.

Another all electric option, heat pumps.  This is the “efficiency” end of the conversation.  There are two different types of heat pump, air source and geothermal.  I’m going to stay out of geothermal for now, I will have a dedicated blog on the subject in the next few months.  Air source heat pumps, another all electric option that both heat and cool.  Are they right for cold and very cold climates?  Yes, but…I have a not so good experience to tell that I’ll get to in a minute, but before that, how can they replace fossil fuel heating sources?  By being very efficient.  The biggest advantage that an air source heat pump (ASHP) has over other fuel sources is they move heat instead of burning a fuel to create heat (technically transform energy).  They work by taking a fluid that boils at a very low temperature, almost -50°F.  Move the fluid through an area with higher temperatures than -50°F and the ambient heat will transfer to the colder fluid, warming it.  Compress the fluid and the temperature will greatly increase.  This is called the refrigeration cycle.  The big advantage in moving heat instead of burning something to transfer heat is efficiency.  For every dollar of electricity, an equivalent of around $4 in heat is moved.  This is called the COP or coefficient of performance, it’s the relationship between the heat moved and the energy used in the move.   A COP of 4, which isn’t uncommon in air source heat pumps operating at a specific temperature, means that for every dollar in energy, $4 in heat is moved.  This example is simplified, but hopefully you get the point.

This is the central ducted air source heat pump at the Concreteless Slab on Grade Home.  There are also versions called mini-splits which have a wall hung head instead of a central duct system.  The drawback with ASHP’s in a very cold climate, there are times when the outdoor temperatures become so cold, the heat pump no longer operates.  At that point, a second source of heat is needed.  This heat pump has an integrated electric strip or plenum heater that takes over the heating needs when temps drop to around -15°F.  At that point, the COP becomes 1, one dollar of energy in equals one dollar of heat out, and at the cost of $.038 per 1,000 BTU’s.

Here is my not so good experience with ASHP’s in a very cold climate.  The amount of condensate produced by the outdoor unit at the Concreteless Slab on Grade Home has been excessive over the past two heating seasons.  The ice builds up against the home and spills over the customer’s driveway.  I believe I’ve come up with a solution, stay tuned about a posting on this subject.

Other electric sources.  Through the years working as an electrician, I’ve been involved with several all electric heat sources along with many dual fuel systems.  Some of the all electric have been electric cables and mats installed under concrete slabs, a type of radiant heat.  Straight up electric baseboard heat, much like the first picture on this posting.  Electric baseboard is usually the choice when cost of the system or installation accessibility is an issue.  Dual fuel systems are usually some sort of electric heat that is the main source with a gas back-up.  The electric source is typically controlled by an electricity supplier, the gas system comes on automatically when the electric system is being “controlled”.

Why make the change?  We could get into the discussion of climate change, but I’m not going to go there.  To some, it’s a polarizing subject.  I’ve got a good argument without that discussion, that reason is cost stability.  Energy costs are always going to rise over time, it doesn’t matter if it’s electricity, heating oil or gas.  The thing with electricity, it’s more stable.  You don’t see the big rate swings like you can with fossil fuel sources.   I believe this winter will be a good example of that.  I become very busy conducting energy audits when propane and natural gas costs have a big increase, costs are already higher very early in this heating season than they have been over the past few years, and the costs are expected to rise. We saw this a few years ago when propane hit $4 per gallon, that’s $.044 per 1,000 BTU’s, it was cheaper to run an electric space heater on a general service rate than operate a propane system.

Can an all electric heating system work in a cold climate?  It can, but it would work best if the heating load of the home is addressed first.  This should be done regardless of the heating source, but it’s more important in the all-electric home.  In the distant future, gas and oil heating systems will be as foreign as burning coal to heat a home is today, people will not be comfortable with open flames inside their homes, that day is coming.