Home heating cost calculator for Lethbridge

1. The heat your house needs

We start from NRCan's measured heating need per square metre for Ontario houses of each age and scale it to Lethbridge's climate:

• Before 1946: 1 GJ per m²
• 1946–1965: 0.7 GJ per m²
• 1966–1980: 0.6 GJ per m²
• 1981–1995: 0.45 GJ per m²
• 1996–2010: 0.4 GJ per m²
• 2011 or later: 0.3 GJ per m²
• Semi-detached ×0.9, row or townhouse ×0.8 (our assumption for shared walls).

This reproduces NRCan's published typical loads (Heating with Gas, Table 4) within 10% for Ottawa and Toronto, and within 20% for every other city in that table. Degree-days come from NRCan's HOT2000 climate data, the same file EnerGuide evaluations use.

2. Your bills, if you give them

Your yearly use (or monthly bill ÷ average price × 12) is turned into heat delivered. For gas, oil or propane we count 80% of the fuel as space heating when the water heater uses the same fuel (NRCan: space heating is 63.6% and water heating 17.2% of an average home's energy) and 95% otherwise. For electric heat we take off your summer use × 12, or, without it, assume 54% of the electricity heats the house (Hydro-Québec's figure for electrically heated homes; 67.5% if your water heater isn't electric).

Every result is then multiplied by the calibration, and labelled “calibrated to your bills” or “based on a typical house”.

3. What each system costs

• Energy per unit (NRCan): natural gas 37.5 MJ/m³, oil 38.2 MJ/L, propane 25.3 MJ/L, electricity 3.6 MJ/kWh, hardwood 30.6 GJ per full cord, wood pellets 19.8 GJ per tonne.
• Efficiencies (NRCan): old gas furnace 60%, mid-efficiency 80%, condensing 95%; oil 60–86%; propane 82–93%; electric 100%; certified wood stove 75%, older stove 62%, pellet stove 68%, older outdoor wood boiler 40%.
• Heat pumps at 4,274 degree-days: standard 1.9, cold-climate 2.2, ground-source 2.8 (seasonal COP, backup heat included). These are set a little below modelled results because field studies in BC and Yukon came in lower.

4. Two prices, on purpose

“Cost a year” uses the average price, including fixed charges, because that is what your bill shows. Every saving, and the “change vs yours” column, uses the price of one more kWh, m³ or litre, which leaves fixed charges out. That makes savings smaller and is the conservative choice. Where the winter step price for electricity is higher than the average (Hydro-Québec, BC Hydro), we use the step price for heating.

5. Hot water

NRCan's 75 L per person a day; cold water at the annual mean air temperature + 3.3 °C (9.2 °C here before the 5 °C floor), the ANSI/RESNET shortcut. Then divide by the heater's efficiency: gas tank 0.58, condensing gas 0.81, gas tankless 0.87, electric tank 0.92, oil tank 0.55, heat pump 2.2 (a conservative field value). A heat pump water heater takes heat from the house in winter; we add (1 − 1/2.2) × ⅔ of its output as extra space heating.

6. Air conditioning

The first part is NRCan's formula; the 0.8 reflects that most households don't run AC around the clock, and puts the result for our Ontario cities near NRCan's measured average of 1,321 kWh per central unit. Default size: NRCan's rule of thumb of 200 Btu/h per m², rounded to a half ton.

What this leaves out

Maintenance, equipment life, a gas meter's fixed charge if you leave gas entirely, and future price changes. Prices change (Ontario electricity on November 1, gas quarterly), so check your own bill. An EnerGuide evaluation replaces every assumption here with measurements of your house.