In some rural locations, the cost of bringing power to
the home is prohibitive. The cost of power poles and easements,
and the labor to string the wires and install the poles
can be quite costly. Not to mention that often people
chose the rural life to get away from such things.
Less frequently, a homeowner has the resources and inclination
to be self-sufficient, even when a grid tied system might
be more cost effective.
In either case, some portion of the power generated during
the day must be stored for use at night. This almost always
involves rechargeable batteries.
To power a house requires a lot of battery. The batteries
usually require some amount of maintenance, and do not last
as long as the solar panels, and so the cost of replacing them
must be taken into account.
To reduce the number and size of the batteries required,
some measures can be taken to limit the night-time load
the house requires.
Freezers can often be turned off at night, as the frozen
contents are well insulated and will not thaw inside the
freezer before the power comes on the next day. Several
days worth of cloudy weather can usually be tolerated if
the freezer is kept full. A partially empty freezer can
be filled with plastic bottles full of water to make a
large ice supply to keep things cold.
Very efficient refrigerators can also be turned off at night,
since they are extremely well insulated.
Using direct current lights at night can save some of the
inefficiencies of the inverter.
In rural areas where an electric well pump is used, the
water can be pumped up into a storage tank during the day,
allowing gravity to maintain water pressure at night, instead of
a booster pump and air bladder.
Non-solar power sources can be used at night, such as wind
or micro-hydro power. Lastly, a generator can be used at
night if the power demands are occasionally greater than the
battery power can support. This adds flexibility, so the
homeowner can choose a smaller battery system for normal use,
and run the generator when company comes.