Estimated domestic hot water (DHW) useage
5 Person Household
If you plan to use a solar thermal system to
heat domestic hot water, an estimation of the building's consumption
must be made in order to properly size the system. We have done some
analysis to predict how much a 5 person household will use.
Summary
| Common uses |
Number of people (person) |
Number of cycles (cycles/person/week) |
Total cycles (cycles/week) |
Hot water (liters/cycle) |
Total hot water (liters/week) |
Average hot water (liters/day) |
Total energy (kWh/week) |
Average Energy (kWh/day) |
| Dishwasher |
5.0 |
1.4 |
7.0 |
31.4 |
219.9 |
31.4 |
8.9 |
1.3 |
| Clothes washer |
5.0 |
1.0 |
5.0 |
15.5 |
77.6 |
11.1 |
3.1 |
0.4 |
| Shower |
5.0 |
7.0 |
35.0 |
87.0 |
3045.0 |
435.0 |
123.4 |
17.6 |
| Miscellaneous |
5.0 |
7.0 |
35.0 |
0.8 |
29.0 |
4.1 |
1.2 |
0.2 |
| Total |
3,371.4 |
481.6 |
136.7 |
19.5 |
Temperature
Conditions
| Description |
Value |
Units |
| Cold water from the utility grid |
13.0 |
°C |
| Hot water from the domestic hot water
tank |
48.0 |
°C |
| Temperature difference |
35.0 |
°C |
Energy
Saving Considerations
| Reductions |
Normal use |
Energy savings use |
Savings per week |
Savings per year |
| Total hot water (liters/week) |
Total energy (kWh/week) |
Total hot water (liters/week) |
Total Energy (kWh/week) |
Total hot water (liters/week) |
Total energy (kWh/week) |
Total hot water (liters/year) |
Total energy (kWh/year) |
% Savings |
| Wash
dishes by hand, reduce dish washer cycles |
219.9 |
8.9 |
187.8 |
7.6 |
32.1 |
1.3 |
1,668.6 |
67.6 |
14.6% |
| Use
only cold water for a % of all clothes washing cycles |
77.6 |
3.1 |
69.8 |
2.8 |
7.8 |
0.3 |
403.4 |
16.4 |
10.0% |
| Reduce
time spent in the shower |
3,045.0 |
123.4 |
2,030.0 |
82.3 |
1,015.0 |
41.1 |
52,780.0 |
2,139.6 |
33.3% |
| No
change in miscellaneous use |
29.0 |
1.2 |
29.0 |
1.2 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0% |
| Total |
3,371.4 |
136.7 |
2,316.6 |
93.9 |
1,054.8 |
42.8 |
54,852.0 |
2,223.6 |
31.3% |
Calculation notes:
- Shower flow rate equal to 7 liters/minute for
15 minutes
- Dishwasher based on Whirlpool large capacity
model DU850SWP
- Clothes washer based on Whirlpool super
capacity model WTW5100S
- Miscellaneous uses might include hand washing,
coffee or tea making, cooking, etc.
- Liters/cycle indicates amount of hot water used
from the domestic hot water tank
- Total mixed temperature water used (not shown)
may be more than hot water used
- Temperature of cold water from the utility grid
and hot water from the DHW tank may vary based on climate and season
- Energy savings include reducing 3 dish washer cycle
per week, using only cold water for 10% of all clothes washing cycles,
and reducing shower length from 15 minutes to 10 minutes
Domestic hot water consumption will vary based
on many variables (number of occupants, habits of those occupants,
climate, appliances, etc.). In order to more accurately
predict domestic hot water production, you will need tweak this
estimation for your conditions. We have a spreadsheet available in
several file
formats to assist you.
|
|
