Reducing Battery Count

Reduce Energy Consumption

Of course, reducing energy consumption is the best way to reduce your battery count. Here are some ideas:

Use LED bulbs. LED bulbs can reduce energy consumption quite a bit. A typical LED bulb that outputs light equivalent to a 60 watt incandescent bulb consumes less than 10 watts
Turn off lights that are not needed
Buy efficient appliances

Move Night Energy Consumption to the Day

Moving energy consumption to the day saves on battery array size because all of this energy is being used during the day, when the solar array can power these things directly. As a result, this energy will not need to be stored in the batteries.

Run the washing machine during the day
Run the dryer during the day (or better yet, use a clothes line)
Run the dishwasher during the day (or hand-wash the dishes)
Turn off lights when not in use, particularly at night
Run well pumps during the day (use reserve tanks for night-time use)

It is not uncommon, if you use a well, to fill reserve tanks with water and use the reserve tanks to provide water to the house. Ideally, these tanks will be elevated, so supplying water to the house is done by gravity and the pump will not be needed during normal water use. In this case, schedule your pump to fill the reserve tank during the daylight hours when direct energy can be used.

Moving energy use to daylight hours will only reduce your battery count for the carry-through part of the array. It will not help if you are not generating power every day.

Add Auxiliary Power Sources

One of the leading contributors to the size of the battery array (besides energy consumption) is the fact that there is nothing supplying energy to the house, except the batteries, once the Sun goes down.

Adding some other power source would further reduce the size of the battery array. It would also increase reliability since you have multiple sources of power.

Consider these:

Wind Power

Wind generators help fill some of the gap in solar power generation. They work at night, they work in the daytime, and they can help fill the cloudy-day gap. Imagine a dark cloudy day without wind. These have moving parts, so their mechanical reliability will be less than that of solar panels

Micro-Hydro Power

If you have moving water available, you may be able to add a micro-hydro generator to your energy plan. They are as stable as the water supply. These have moving parts, so their mechanical reliability will be less than that of solar panels. Additionally, they are typically constantly exposed to a wet environment, so they may be less reliable than wind turbines.

Backup Generator

A backup generator is always a good idea, even if you are tied to the grid. But it can help fill in gaps in case no solar energy is available. The big advantage is they are relatively cheap, with a Generac 6500 watt generator running about $1000. You could use it to charge your batteries and get you through the rest of the design time of your battery array.

Grid-Tie

Of course, you could also tie into the grid and use grid power when your batteries ran low. In some areas, you might even be able to bank energy on the grid or sell it to the energy provider.

Why does it Matter?

There are several reasons to reduce your battery count

Batteries are expensive, both in purchase price and shipping costs
Batteries have a finite life that varies based on how you use them
Batteries are heavy
Some battery types require maintenance.
Some battery types may require active heating in cold weather.

Even if you move enough load to daylight hours to warrant buying more solar panels, that is still better than adding more batteries. Solar panels are very reliable and last for 20+ years with only a slight degradation in performance.

In short, batteries; while probably a requirement, are the least reliable and most expensive part of your system AND they are a recurring cost. So to lessen their impact, reduce your reliance on them as much as possible.

Robby Casteel - Solar Power