Commercial Pool Cover Savings Calculator

Evaporation is calculated from the difference in humidity ratio between air saturated at your water temperature and the ambient air, at a sheltered surface air velocity of 0.1 metres per second. That is deliberately conservative: an exposed, windy site evaporates considerably more, and therefore saves more.

• An unoccupied-pool activity factor of 0.5 is applied, as the cover is on when the pool is closed

• Latent heat of vaporisation taken at 2.26 MJ per kilogram

• The cover is credited with blocking 95% of evaporation while it is on the water, and nothing while it is off

• Outdoor pools use 9am relative humidity, which overstates the daily average and again understates the saving

The cover is modelled as adding R0.15 m²·K/W in series with an R0.09 m²·K/W surface film, applied to the temperature difference between the water and the air while the cover is on. No credit is taken for daytime solar gain through the cover.

• Indoor pools are modelled at a hall air temperature 1°C below the water and 60% relative humidity

• Heat saved is converted to fuel at your stated efficiency or coefficient of performance

• Unheated pools return no heating saving

Water saved is the evaporation avoided, charged at your volumetric supply rate. Chemical saving is modelled at half your annual spend, scaled by the share of the day the cover is on — a deliberately cautious treatment, as chemical loss varies widely by plant and bather load.

• Natural gas at 54.29 kg CO₂-e per GJ, commercial use

• Grid electricity at 0.0787 kg CO₂-e per kWh, 2025 annual average

• Payback is undiscounted and excludes GST