How much does it cost to keep my Ottawa pool heated through an unusually cold August week?

Great question, and one that catches a lot of Ottawa pool owners off guard. A cold August week — the kind where daytime highs sit around 15 to 18°C and nights dip toward 10°C — can easily drop an unheated pool from a comfortable 28°C down to 20°C or colder, which is genuinely unpleasant for swimming. The cost to fight that temperature drop depends heavily on what type of heater you have, your pool's volume, and how aggressively you want to maintain your target temperature.

If you're running a natural gas heater, expect to burn through roughly $30 to $80 in gas over a cold week, depending on pool size and how hard the heater is working. A standard 400,000 BTU gas heater on a 14x28 foot pool maintaining 28°C against cold August nights might run 4 to 8 hours per day during a cold snap — gas heaters are powerful but not cheap to operate. The upside is they respond quickly and don't care about air temperature, which matters when Ottawa throws you a grey, cool week in August.

Heat pumps are far more efficient but have a critical weakness in Ottawa's climate — they extract heat from ambient air, and their efficiency drops sharply when air temperatures fall below 15°C. During a cold August week, your heat pump may struggle to keep up and will run almost continuously, pulling $20 to $50 in electricity over the week while doing less work than it would on a warm day. If nights are dropping to 10°C, a heat pump alone may not hold your target temperature without a solar cover helping to retain heat overnight.

A solar cover (liquid or blanket style) is your best cost-control tool regardless of what heater you have. A good thermal blanket can reduce overnight heat loss by 50 to 70 percent, which means your heater runs far less during the day to recover lost temperature. If you don't already have one, a quality solar blanket costs $200 to $600 depending on pool size — it pays for itself in a single cold season.

The honest reality is that heating an Ottawa pool through a genuinely cold August week is manageable but not free. Budget $30 to $100 in energy costs for the week depending on your heater type, pool volume, and whether you're using a cover at night. If you're running a gas heater without a cover and trying to hold 30°C during a 12°C night, you could push toward the higher end of that range.

One thing worth knowing: Ottawa's cold August weeks are often followed immediately by a return to hot weather, so it's usually worth maintaining temperature rather than letting the pool cool and reheating from scratch — reheating a cold pool costs significantly more than maintaining a warm one.