Home Power Consumption
AC Appliance Watts X Hrs/Day = Wh/Day X Days/Wk = Wh/Wk
A. _____________________________________________________________
_______________________
B. _____________________________________________________________ _______________________C.
_____________________________________________________________ _______________________ D. _____________________________________________________________
_______________________
E. _____________________________________________________________ _______________________
Total the numbers in the last column. This is your AC power requirement. Total ______
1. Multiply the total by 1.2
to compensate for system losses during battery charge/discharge cycle. AC WH/WK ______
2. Enter the voltage of your battery
bank (usually 12 or 24 volts) VOLTS _______
3. Divide line 1 by line 2. This is your amp-hour requirement per week. AH/WK
_______
4. Divide line 3 by 7 days. This is your average amp-hour requirement per daythat
will be used to size your
battery bank and your PV module array. AH/DAY _______
Battery Sizing
1. Enter your daily amp-hour requirement. (From the Load Sizing Worksheet, line 4) AH/Day ______________
2. Enter the maximum number of consecutive cloudy weather days expected
in your area, or the number of days of autonomy
you would like your system to support. ______________
3. Multiply the amp-hour requirement by the number of days. This
is the amount of amp-hours
your system will need to store. AH ______________
4. Enter the depth of discharge for
the battery you have chosen. This provides a safety factor so
that you can avoid over-draining your battery bank.(Example:
If the discharge limit is 20%, use 0.2.) This number should not exceed 0.8. ______________
5. Divide line 3 by line 4.
AH ______________
6. Select the multiplier below that corresponds to the average wintertime ambient temperature
your
battery bank will experience. ______________
Ambient Temperature Multiplier
80ºF 26.7ºC 1.00
70ºF
21.2ºC 1.04
60ºF 15.6ºC 1.11
50ºF 10.0ºC 1.19
40ºF 4.4ºC 1.30
30ºF
-1.1ºC 1.40
20ºF -6.7ºC 1.59
7. Multiply line 5 by line 6. This calculation ensures that your battery
bank will have
enough capacity to overcome cold weather effects. This number represents the total battery
capacity
you will need. AH ______________
8. Enter the amp-hour rating for the battery you have chosen. ______________
9.
Divide the total battery capacity by the battery amp-hour rating and round off to the next highest
number. This is the
number of batteries wired in parallel required. ______________
10. Divide the nominal system voltage (12V, 24V or 48V)
by the battery voltage and round off to
the next highest number. This is the number of batteries wired in series. ______________
11. Multiply line 9 by line 10. This is the total number of batteries required. ______________