When designing an offgrid (not connected to utility power) solar or wind
power system, it's very important to have an accurate estimate for how much
energy you need. Off the grid systems must utilize batteries to store DC
power from the solar panels and convert it to AC power with an inverter. If
you are not storing enough energy, you will decrease the life of your
batteries, possibly ruin your batteries and most importantly, your power
will eventually go out. An electrical system does you no good if it can't
provide you with the necessary energy to properly run your home, RV or boat.
This is why we do a load evaluation. The
computation
helps us
determine roughly how much energy your home will need. If a
device is drawing energy, no matter how small, it will have an impact on
your solar system. Lets examine some electrical loads as an
example.
The behaviour of every family and familymembers differs sgnificantly. Some
like to work at nighttimes on computer or do the daily cores like washing
and cleaning. Some others sleep early while they have to get up early
morning. Normally these loads by themselves would probably not adversely
affect your system, but if they all get used in the same day, it could have
a large impact upon your stored energy. In the morning, you may use the
microwave oven before the sun rises and the microwave has
dropped the battery storage below 50% capacity. This is when batteries start
becoming damaged and it's irreversible. Damaged batteries will significantly
reduce the overall performance and storage capacity of your system which
will only exacerbate the problem. Batteries are far too expensive to allow
them to be needlessly damaged or ruined. We will add in a
buffer amount of capacity to the design to account for inefficiencies and
small phantom loads like a digital clock on your microwave and the idle
power draw of the inverter.
Technical Note: Many people have a difficult time understanding how watts
are calculated and how that relates to energy. Basically, the amount of
power a device consumes is rated in watts. This is most easily seen with the
oldfashioned incandescent light bulbs. Those have the wattage rating listed
on them: 25W, 50W, 100W, 150W etc. The new LED bulbs, witch are included in
our packages, do not
draw nearly as much power as their incandescent equivalent but they often
list the incandescent equal in light output. So if you have a LED bulb that puts out the same level of light as a 50 watt
incandescent, that does not mean that the compact fluorescent consumes 50
watts of power. It probably uses about 3 or 9 watts compared to the 50
watts. The packaging will normally tell you exactly how much wattage the
compact fluorescent actually consumes or it may even be listed on the base
of the bulb. If you need to know the rated wattage of other electrical
devices, such as your T.V., you can often find that information listed
somewhere on the device. If it does not list the wattage but tells you the
amperage and voltage, you can calculate the total watts. This is done by
using a formula derived from Ohms Law. If you can't find the watts, voltage
or amps listed on the device, we have included a basic wattage chart with
the computation for most devices and appliances. Your device may consume a
little more or less than what is listed on the chart, but it will give you a
pretty good estimate. For those that want a very accurate energy or power
measurement for a device, we can measure it with a
watt
meter.
Here is how you can calculate the watts if you know the voltage and amperage
of a device.
Watts
=
Volts
x
Amps
If your T.V. plugs into a standard 220 volt receptacle and uses 1.2 amps, the
total watts is calculated by multiplying 220 volts x 1.2 amps. That equals
264 watts.
220
Volts x 1.2 Amps = 264 Watts
Watts is an instantaneous value. Knowing the wattage of a device is
necessary, but it does us no good unless we know the length of time that the
device is turned on. When you multiply time by watts, that is called energy
and it is measured in watthours. To be clear, 1 watt is NOT equal to 1
watthour or 1 watt per hour. If you have a device that consumes 1 watt and
use that device for 1 hour, that is equal to 1 watthour. If you powered
that same 1 watt device for 2 hours, that would equal 2 watthours. It's
simply watts multiplied by hours which calculates the energy needed. Once we
know how much energy you use, we can then design you a system that will meet
all of your electrical needs. We are here to help!
