Monthly domestic hot water profiles for energy calculation in Finnish apartment buildings

• The annual mean DHW consumption rate was 43 L/person/day.
• Variation of consumption rate and DHW ratio were observed during calendar months.
• Most of cases common consumption rate were in between 20 and 70 L/person/day.
• Smaller apartments had higher specific consumption by factor of about 1.5.
• DHW profile increased delivered energy use by 4.7% compared to constant profile.

Domestic hot water (DHW) profile is required to estimate energy use and system design. Few onsite data and simulation-based studies are available in literature focusing on hourly profile, individual consumption with seasonal variation and occupant number. This paper investigated onsite DHW daily consumption in 182 Finnish apartments with 379 occupants during two consecutive years. DHW monthly consumption rates and monthly consumption factors for full week, weekdays, and weekend were derived allowing of calendar months variation. The average consumption was 43 L/person/day whereas maximum and minimum consumptions were noted, respectively in November and July. The variation was observed between weekdays and weekend too, being mostly in the range of 20–70 L/person/day and DHW ratio varied from 0.3 to 0.5. Higher consumption trend during November to February were noticed whereas opposite behavior was observed during May to July. Apartment's size affected specific consumption and smaller apartment consumption was higher by factor of about 1.5. The obtained profiles effect on the energy use was tested with dynamic simulation of solar thermal system. The derived monthly profile increased delivered energy by 4.7% compared to simulation without monthly variations. The weekday and weekend consumption variations did not have significant effect on delivered energy.