How Big a Dehumidifier Do You Need? NRCan’s Sizing Chart
- NRCan’s capacity chart
- Efficiency: look for a high IEF
- Set the humidistat
- Setup tips from NRCan
- Reduce the load first
Natural Resources Canada (NRCan) says that if your space feels damp and musty, or there’s condensation on your walls or windows, it might be time for a dehumidifier. Size matters, and NRCan says plainly: “It’s better to oversize than undersize!”
NRCan’s capacity chart
Capacity depends on two things: the size of the space and how damp it is without a dehumidifier.
| Room conditions | Small–medium room (<185 m²) | Large room (>185 m²) |
|---|---|---|
| Slightly to moderately damp: feels damp, musty odour (50–75% RH) | 10–15 L/day | >15 L/day |
| Very damp: consistently feels and smells damp (75–90% RH) | 11–20 L/day | >20 L/day |
| Wet: walls or floor sweat; high loads such as laundry (90–100% RH) | 15–25 L/day | >25 L/day |
If a box lists capacity in pints, NRCan’s rule of thumb is that two pints equal about one litre.
Efficiency: look for a high IEF
NRCan says ENERGY STAR certified dehumidifiers use nearly 15% less energy on average than standard models. Efficiency is measured as the Integrated Energy Factor (IEF): litres of water removed per kilowatt-hour. Higher is better. For a whole-home (ducted) unit, NRCan recommends hiring a professional to size and install it.
For a cool basement below 18°C, NRCan suggests considering a model designed for lower temperatures.
Set the humidistat
All ENERGY STAR dehumidifiers have a built-in humidistat. You set the target RH, and the unit cycles on and off to hold it. NRCan calls 30–50% generally ideal, and says that in winter in colder climates RH should be around 30–40% to prevent condensation on windows. Health Canada’s 2025 guidance for indoor air quality professionals is a little lower: around 30% in colder weather (see our winter range article). A separate hygrometer lets you check whether the built-in humidistat is reading the room correctly.
Setup tips from NRCan
- Keep windows and doors closed while it runs. Outdoor air reduces efficiency.
- If the unit doesn’t discharge air from the top, keep it away from walls and furniture so air can circulate.
- Keep it away from dust and dirt, which can clog coils and grills, and clean the filters regularly.
- Some models can drain by hose to a floor drain or sump pump. Follow the manufacturer’s electrical warnings, and keep drain hoses away from cords and connections.
Reduce the load first
NRCan also suggests cutting moisture at the source: extend downspouts away from the foundation, keep gutters clear, don’t over-water plants near the foundation, vent the clothes dryer properly, use bathroom and kitchen exhaust fans, and fix leaky outdoor faucets.
Sources: Natural Resources Canada, Dehumidifiers (ENERGY STAR); Natural Resources Canada, Choosing the right dehumidifier; Health Canada, Guidance for indoor air quality professionals (2025). All read in full on 2026-10-14.
Originally published at https://dry-glass-notes.surge.sh/articles/dehumidifier-size-capacity-chart.html (AI-assisted, sources cited). If this helped, zaps go to hollisvarrow3753@coinos.io.
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