The following summary is specific to Lethbridge.
(Most decisions to make a residential home ‘greener’ depend on the local climate, solar incidence, water availability, sources of electricity production, costs of energy, etc.)
Green Building
Compared to our standard home, we have:
- Insulated the basement walls 2×6 construction = 40 GJ
- Sealed the home = 16 GJ
- Added an HRV = 10 GJ
- Replaced old double-pane with triple-pane windows = 7 GJ
- Added insulation to the roof = 2 GJ
Initial Total Heat Loss = 128 GJ
Total Saved = 75 GJ
Greener Home Heat Loss = 53 GJ … a 58% reduction in heat loss (and emissions)
Savings: 75 GJ x $16.76/GJ = $1250/year
Emission reduction: 75 GJ x 50 kgCO2/GJ = 3.75 tonnes CO2 per year
A (very) rough estimate for this work is $11,200, which gives an emission reduction cost of about $100/tonne CO2 assuming a life-cycle of 30 years for these interventions.
Solar PV
Installing a solar PV array in Lethbridge to produce 7200 kWh of electricity each year:
The current cost of electricity on a 5-year plan will vary widely depending on your location and provider. I am paying $0.124/kWh. Currently, all array orientations and angles will produce electricity at a lower price for the life-cycle of the array (25 years). Though this is conjecture, with increasing electricity demand as we transition to a net-zero economy by 2050, it is unlikely that electricity prices will drop significantly over this period.
Air Heat Pump
An air heat pump in Lethbridge today will lower GHG emissions from 5880 kg CO2 to 4620 kg CO2 per year, a reduction of 1260 kg CO2 or 21%.
Air Source Heat pump will have cost of operation between $500 and $1250 more than a natural gas furnace in Lethbridge, Alberta given current prices.
For the next number of years, SAGE would recommend installing an Air Heat Pump if you are going to replace or install a new air conditioning system. New home building should install a heat pump (air or ground-source) in addition to using green building techniques. The current rebate for Air Heat Pumps makes this financially attractive, and you will be in a position to use the Air Heat Pump for heating if the emission intensity of Alberta’s electricity grid declines and if costs for electricity decline relative to natural gas. It will give you some flexibility in the future.
Many installers in Alberta recommend maintaining a natural gas furnace for backup home heating at lower ambient temperatures. This is good advice for the near future. Heating the home at temperatures below -20 C using electricity would be cost prohibitive.