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Can Energy Efficiency Be Bad?


A January 19 article by Michael Davenport in the Vancouver Sun caught my attention.  The article title was Energy efficiency bad for Environment?  The article’s sub-title summarizes the basic premise: “A switch from incandescent light bulbs to compact fluorescent light bulbs could up carbon dioxide emissions”.  My initial impression was that the article’s conclusions seemed wrong, however I decided that the article deserved closer scrutiny.

The real issue: gas heat vs electric heat.

First, I should point out that the question being asked in the title of both my and Michael Davenport’s articles is provocative and somewhat of a misdirection.  The real question can be restated as follows:

Does replacing heat from a gas furnace with electric heat reduce greenhouse gas emissions?

So, let’s review the article’s arguments which I would summarize something like this:

  1. In BC we have lots of hydro-electricity which has no carbon emissions.
  2. Heating with natural gas leads to 220 grams of CO2 per kW-hr.
  3. Electric light-bulbs, appliances and electric heaters are 100% efficient at converting electricity to heat (all of the light eventually ends up as heat).
  4. In gas-heated houses, using energy-efficient light-bulbs results in less light-bulb related electric heating requiring more gas heat to compensate.

So, summarizing the arguments, if we use electricity for heating in place of gas in houses with gas heating we will be replacing 220 g CO2 with no emissions for each kW-hr used.  Let’s take a closer look at this line of reasoning.

Carbon footprint of electricity generation.

In today’s world all forms of electricity, even hydro-electric, have a carbon footprint.  Hydro-electricity may not result in emissions during generation, however dam and generator construction have footprints that need to be amortized over some period of time into the cost of generated power.  The distribution network also has a footprint that should be factored in and the day-to-day operations of BC Hydro will contribute as well.

A 2006 report from the UK Parliamentary Office of Science and Technology titled Carbon Footprint of Electricity Generation compares the ‘cradle-to-grave’ footprint for various forms of electricity generation using LCA (Life Cycle Assessment or Life Cycle Analysis).  They estimate a footprint of between 10 and 30 g CO2e per kW-hr for storage based hydro (using reservoirs) and a smaller 5 g CO2e per kW-hr for ‘run-of-river’ systems.  Both of these are small compared to the 220 g CO2 when gas is directly used for heating.  Therefore the assumption that hydro-electricity has zero emissions, while inaccurate, is accurate enough for the purposes of this discussion.

The UK report also gives footprints for electricity generated from coal-burning at 800 to 1000 g CO2e per kW-hr and from burning gas at around 500 g CO2e per kW-hr.  I mention these values now because they will turn out to be useful later on.  I will assume that, while these results from this report may not exactly apply to British Columbia or other regions of North America, they should still be close enough for ballpark calculations.

Where does the additional electricity come from?

Let’s return to the question of whether replacing gas with electricity for heating reduces greenhouse gas emissions  To answer this we must first answer a different question:

Where does the additional electricity required for the additional electric heat come from?

The assumption in the article seems to be that the extra power comes from clean hydro-electricity and hence results in no (or very little) carbon emissions.  British Columbia does not have an unlimited supply of clean hydro-electricity that can be called upon at any time, so this assumption is not consistent with how the BC electricity supply is managed.  In fact, BC is part of a larger electricity trading network that covers much of North America (The Canadian Electricity Association has some good information on the North American electricity trading network).  Within this network it is usual to use hydro (as well as solar, wind and nuclear) to capacity as part of the base load and top up the supply using fossil-fuel generation to meet total demand.  Gas-fired generation plants are particularly well suited to handling fluctuations in demand.  Hydro coming from a storage reservoir system can also be used to manage short-term fluctuations but since the yearly amount of water is fixed, any extra power used today is an equivalent amount of power that will not be available tomorrow.

So, to answer our question of where our extra demand comes from, consider the following “thought experiment”.  Imagine that we can make 2 identical copies of the universe that behave the same for period of 1 year with the following exception.  In universe-A, you heat your house using a high efficiency gas furnace while in universe-B, electric heat is used instead.  Let’s assume that you now need a total of 1 kW of heating for a total of 1000 hours over the year.  As a result, in universe-A, 220 kg of GHG emissions would result from using the gas furnace.  In universe-B, 1 MW-hr of extra electricity is required that someone must supply.

Over the year in the two universes the sun, wind and water supplies are the same so the extra demand cannot be satisfied by solar, wind or hydro power assuming that we use all available supply from these use-it-or-lose-it sources.  Nuclear power is most efficient at full power and so is probably not be the source of the new demand either.  So, the extra 1 MW-hr will almost certainly be supplied by burning extra natural-gas or coal at an existing generation plant.  If a typical gas-generator is used that behaves as per the UK report then around 500 kg CO2e will result – more than double the emissions saved by turning off the gas-furnace.  If it turns out that a coal-burning plant is used then 800 – 1000 kg CO2e are released.  That’s roughly 4 to 5 times the gas-furnace emissions.

So, in universe-B using electric heat, there would be two to five times the emissions of greenhouse gases released compared to universe-A where gas heat was used!  These emissions might not be in BC, but we all share the same atmosphere so it is definitely not better for the environment as a whole.

BC Hydro admits energy-saving program could lead to higher emissions.

 Another article in the Vancouver Sun dated February 17, 2009 by Scott Simpson has the equally provocative title:

Energy-efficient bulbs increase greenhouse gases: BC Hydro

Apparently BC Hydro itself was admitting what appears to be a confirmation of Michael Davenport’s original assertion that I claim makes no sense when carefully scrutinized.  This time, however, the article provides its own clarification.  The following is a direct quote from this article:

However, Hydro also states that lighting regulations “will increase GHG emissions in Hydro’s service territory by 45,000 tonnes due to cross effects” of a switch to cool-burning bulbs.

BC Hydro is only counting emissions from its service territory, that is, from the province of British Columbia.  These are the only emissions that it is responsible for in its own carbon accounting.  The emissions produced on the other side of the BC border have been exported elsewhere and do not directly make the overall BC emissions look worse.  If my calculations are right, however, those 45,000 extra tonnes emitted in BC probably saved in the ballpark of 100,000 to 200,000 tonnes of emissions in the US or Alberta.

Unfortunately, this single line quote appears to be widely abused.  Do a web search with your favourite search engine for the phrase will increase GHG emissions in Hydro’s service territory.  This quote has become wide-spread, often used to support the argument that compact fluorescent bulbs are bad for the environment.  More than a few of these articles use this to support that the “carbon-footprint” of these bulbs is higher than that of incandescents.  These clearly either missed the four words “in Hydro’s service territory” or they do not understand that carbon footprints take into account all emissions regardless of where they occur.  A few articles do highlight that increasing electricity demand requires more dirty electricity but I suspect that overall this one small quote has done more harm than good to the cause of electricity efficiency.

Better heating with electricity.

You can do significantly better than a baseboard heater if you want to heat with electricity.  Heat pumps do not generate heat directly but move heat from a colder area to a warmer area.  This can be used to either heat or cool a space.  Air-source heat pumps are well suited to heating in the warmer areas of BC as they usually work best when outdoor temperatures are around the freezing point or higher.  Typical efficiencies of these units fall in the range of 2.5 to 3.0 units of heating for each 1 unit of electricity used (1 kW-hr of electricity will provide the equivalent heating as a baseboard heater using 2.5 to 3.0 kW-hr of electricity).  Returning to our example where we replace our gas furnace with a heat pump with a factor of 3 efficiency might result in slightly fewer emissions if the best gas-generating plants are used for the extra demand but if the extra power comes from coal the heat pump would still probably result in more emissions.  I have to admit that I was disappointed by this discovery because I am a big fan of heat-pumps.

It is possible to do better than an air-source heat pump.  Ground source, or geothermal, heat pumps can have a better efficient factor, also referred to as the coefficient of performance (COP).  Efficiencies between 3 and 5 are often attained and at these efficiencies, emissions from the heat pump may be lower than those of the gas furnace, even when using coal-generated electricity.  Ground source units are typically much more expensive to install and frequently cannot be installed on the typical small lot in most residential areas.

An informative article entitled Strategic GHG reduction through the use of ground source heat pump technology written by J Hanova (Institute for Resources, Environment and Sustainability, University of British Columbia) and H Dowlatabadi (Resources for the Future, Washington, DC) and published in Environmental Research Letters in 2007 has a detailed analysis of the greenhouse gas emissions of heat pumps in various scenarios.  They analyze the contitions under which replacing gas heat with heat from a heat pump either increases or reduces greenhouse gas emissions.  The article can be viewed by going to the IOP Publishing web site and searching for articles with the keyword GSHP.

My Conclusions

In my opinion, the best way to reduce emissions is to reduce all types of energy use.  In other words, generate more Negawatts!  Indeed, BC Hydro’s goal for the next few years is to account for up to 50% of new demand through energy efficiency.

If your electricity comes from the North American electricity grid and you have to choose between a gas-furnace and a baseboard heater, take the gas-furnace (and get the most high-efficiency model that you can afford).  A heat-pump might be ower-emitting than the gas-furnace but try to do the math to find out.

Energy efficient light-bulbs, such as compact fluorescents, will actually reduce overall global greenhouse gas emissions not increase them as many seem to believe.

End Notes

Data from BCStats shows BC imports and exports of electricity for the past few years.  In 3 of the last 4 years reported, BC was a net importer of electricity, a trend that is expected to continue.

A recent article reported in The Huffington Post indicates that, according to new EPA calculations, natural gas may not be as clean as previously thought.  Note that I have not yet seen any related EPA data.  This does mean that the emissions are probably higher, both for the gas furnace and for electricity generated by burning natural gas.

I used Michael Davenport’s 220 g CO2 per kW-hr for greenhouse gas emissions from burning natural gas for heat.  Another estimate by PG&E (California electricity supplier) uses a value of just under 240 g CO2 per kW-hr.  As suggested by the above Huffington Post article, these estimates may actually be low compared to actual emissions taking into account all greenhouse gas emissions including methane leaks during production and distribution.  I am still looking for a good source of information on this.

BC Hydro provides actual transmission flow data for power between BC and Alberta and between BC and the US.  As I write this sentence, BC is exporting about 500 MW into Alberta and, at the same time, importing about 500 MW from the US.

The BC Hydro Service Plan has a lot of interesting information on BC Hydro’s supply and demand projections, greenhouse gas emission strategies, etc.

The current Wikipedia page for Carbon Footprint has a table summarizing estimatee of emissions for electricity from different energy sources.  One of the references, a report from the University of Sydney entitled “Life-Cycle Energy Balance and Greenhouse Gas Emissions of Nuclear Energy in Australia” has a lot of useful data for electricity from sources other than nuclear including an analysis of various types of hydro.  There is a large variation in the carbon footprint estimates for electricity.

BC Hydro is clearly aware of the issues associated with the carbon accounting of electricity imports.  In a section on GHG emissions in their latest Service Plan they state:  Emissions from imported electricity are not included, subject to clarification of Western Climate Initiative (WCI) mandatory reporting protocols.  The WCI document COVERING EMISSIONS FROM IMPORTED ELECTRICITY: AN ADMINISTRATIVE APPROACH describes proposals for handling electricity import emissions.

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