Energy Audit-Common and Not So Common Appliance Energy usage

During an energy assessment or audit, I often test household equipment and appliances for energy usage.  Over the years, many people have been surprised that some devices use the amount of energy they do.  This weeks blog will be all about how much it costs to operate the electrical stuff in a home.

The average home uses more energy for heating and cooling than any other energy using devices.  This energy may or may not be in the form of electricity.  Lets look at heating first.  Forced air systems use fans to move heat through ductwork and some use fans to move exhaust from the combustion process to the outside.  The average furnace fan I test used to move air through ductwork consumes 500 watts of power.  In my area, that is about $.06 per hour for each hour the fan operates.

Hot water heating systems can use less electricity, depending on whether the boiler is electric or gas.  Most I see are gas, but I have seen electric boilers as large as 27 kW, which on the general service rate, will cost around $3.25 per hour to operate.  Off-peak electricity programs can reduce this cost by more than 50%.  Hot water heating systems need pumps to move the heated water through a home or in a floor.  Most of these pumps use less than 100 watts, and some newer models containing electronically commutated motors (ECM’s) use substantially less electricity to operate (around 15 watts).  Some systems may have several pumps used to control the heat needs in different parts of the home.

I still occasionally see homes heated only with electric baseboards, usually on the general service rate.  (In my area, that rate is around $.125 per kWh.)  This is one of the most expensive ways to heat a home.  I wrote a blog about heating fuels which you can read here.

An electric baseboard heater.

Cooling is another large electricity user.  Air conditioner electricity usage is based on the size of the unit, rated in tons or Btuh’s and the efficiency of the unit, rated in SEER or EER’s, depending on whether it is central air or a window/wall unit.  Read a blog posting I wrote last year about AC here.  Some of the most efficient air conditioners will be air source heat pumps.

Electric domestic water heating can use substantial amounts of electricity, depending on household habits.  A typical water heater draws 4500 watts, which on the general service rate in my area, will cost around $.55 per hour for each hour the water heater operates.  $30 to $40 per month for domestic water heating is not uncommon in my area.  Reducing hot water usage is a low cost way to reduce costs.  Installing low flow aerators and shower heads, limiting shower times, and washing clothes in cool or cold water will help.  Purchasing more efficient water heaters and/or placing the water heater on a reduced rate program (if available in your area) will also reduce costs.  In my area, an off-peak water heating storage program in conjunction with a higher efficiency water heater can reduce water heating costs by more than half.  I often see homes utilizing this system with water heating costs of under $10 per month.

105 Gallon Marathon water heater. This type and size of water heater is commonly used for utility controlled programs.

Traditionally, one of the larger users of electricity is lighting, but this has moved lower in the past several years because of the increased use of LED light bulbs.  An incandescent light bulb might use 60 watts, new LED’s use 9 watts for the equivalent amount of light.  Turning off lights when not needed, or using occupancy sensors, timers or photo eyes that automatically turn on and off lights is the best way to save money on lighting.

Household appliances are typically the third largest user of electricity in the average home, with refrigeration being one of the largest in this category.  The age and style of the refrigerator are determining factor.  A fridge purchased before 1990 will use around 140 kWh per month, costing $16.  That same fridge purchased between 1990 and 2000 will use 85 kWh, costing $10.  This fridge purchased after 2000 will use 45 kWh and cost a little more than $5 to operate.  Purchasing a new energy star rated unit will drop consumption to 35 kWh and the cost to around $4 per month.  I have been in many homes where the homeowner purchases a new, more energy efficient refrigerator and moves the old unit into the garage for the beer and sodas.  AAGH!  Style of fridges can also affect the cost of operation.  The most efficient tend to be top freezers, followed by bottom freezers and lastly, side by sides.

Another appliance that can use a lot of energy is a dehumidifier.  Most that I test range between 350 watts and 750 watts.  Many run continuously during the summer months.  A 500 watt unit running non-stop will cost nearly $45 per month.

A dehumidifier.

Coffee makers often surprise homeowners.  The modern single brew units such as Keurig are more efficient and do not use much electricity.  Coffee makers that brew entire pots instantly, such as a Bunn, can use larger amounts of electricity.  These coffee makers work similar to a water heater, by maintaining hot water in a reservoir and have nameplate ratings of 550 to 1200 watts.  The best way to gauge energy use on an appliance is by using a recording watt meter.

My Kill-o-watt meter

Clothes washing is another household chore that can use a substantial amount of electricity.  How you wash clothes and the efficiency of the washer matter.  Do you use hot or cold water?  Do you use a clothes line to dry your laundry or an dryer?  Have you cleaned the lint out of the dryer vent recently?  The average home uses around 100 kWh on a washing and drying clothes per month, costing around $12.  (Much higher in my household.)  The $12 per month does not include the cost for water heating.

A lot of the energy assessments I conduct are in rural areas.  Most of these homes have their own wells and sewer systems.  All wells and some sewers have pumps.  Occasionally I see these pumps stuck on.  A recent assessment I completed found a well pump which must have had a bad pressure switch.  The pump was stuck on, and was drawing 1900 watts, or nearly $.25 per hour.  I’m not sure why this pump was drawing so much electricity, most well pumps are under one horsepower.  (A one horsepower motor draws 746 watts.)  It could be the pump is nearing the end of it’s operation.  Both wells and sewers with pumps that are operating continuously will not be noticed until a homeowner receives an unexpected elevated electric bill.

The rural area assessments I conduct sometimes have a hobby farm.  These very small farming operations typically supplying the family with home-grown food.  Other hobby farms may have livestock, such as horses.  Frequent garden watering usually will require a water pump, which will increase an electric bill.  Raising chickens in a northern climate will require keeping them warm during the winter.  Heat lamp use is common.  Some of these lamps draw 250 watts, costing around $.03 per hour to operate.  That adds over $20 to an electric bill, per bulb.  Tank heaters that are designed to keep livestock water from freezing often use 1200 watts.  Many times these heaters also run non-stop, which will cost over $100 per month.  And then there’s the place I visited a few years ago that had around 20 aquariums filled with spiders, snakes and lizards, each with their own heating lamp.

These are just some of the things I see on an average energy assessment or audit.  I could write a book on what I’ve seen over the past 10 years.  Rarely a boring day!

Leave a Reply

Your email address will not be published. Required fields are marked *