Off Grid Solar Power Systems can be dramatically decreased in size by addressing various aspects of a building, the appliances in the building and usage patterns.
The Heating System
One of the largest consumers in a home is the heating system. There are various items that relate to this.
- The energy efficiency of the home. The more energy efficient that the home is, the less fuel and electricity it will take to heat. The investment in energy efficient measures such as wall insulation and type of insulation, ceiling and floor insulation and most importantly, the windows and doors will greatly reduce the amount of energy that the Solar System needs to supply. For example, having a wall system that has an "R" value of 25 but only using standard double pane windows having an "R" value of just over 2 for the center of glass is going to result in a lot of heat loss through the windows.
- The type of heating system also has a large impact on the amount of electrical energy consumed. Generally, a Hydronic heating system (also known as hot water or floor heat) is the most efficient in terms of the amount of electrical energy required, as the pumps usually take less energy than a fan and liquid transfers heat better than air because of its mass. Within the subtypes of Hydronic heating, choosing a simple "Primary – Secondary" system would be preferable to a system that uses injection and/or outdoor reset controls. The major problem with "outdoor reset" controls is that they are designed to run the whole system 24 hours a day, 7 days a week. Outdoor reset heating is based on the principle of trying to match the heat delivered to the home with the heat loss of the home. So as the temperature outside warms up, the temperature of the water used to heat the home is reduced, thereby causing the pumps and boiler to run much longer. This can increase the power usage tremendously.
Choose appliances that have the lowest KWH per year rating when you purchase them. A good modern energy efficient fridge is likely in the 365 KWH per year range (1 KWH per day)
While electricity can be used in an "Off Grid" home for cooking and baking as we do, it will take a larger system to accomplish this. Generally, "Off Grid" homes use either natural gas or propane for cooking.
Clothes dryers would also use a lot of power, so consider hanging the clothes up to dry on a clothes line or indoor drying rack. If a dryer is going to be used, a natural gas or propane dryer would again be preferable.
Computers & other devices
Devices such as computer that are left on for long periods of time can use considerable power, even more than a fridge. For example, I had a computer that would use 170 watt of power, so if it was on for 10 hours a day, it used 1.7 KWH per day. My present laptop uses about 35 watts and with the second monitor it is about 53 watts of energy, so less than 1/3 of the desktop. If just the laptop is used without the second monitor, even more energy can be saved. Additionally, the operating system such as Windows 7 has the computer ready to go in just a few seconds compared to the XP system where it was a matter of turning the computer on, having breakfast and then it would be ready to go because of all the updates going on. This way the computer only needs to be turned on when it is required and can be turned off again right away.
Other devices that are plugged in but not turned on may use power all the times as well, so consider adding switches or power bars to turn them off when not in use.
Another way to increase the efficiency of the whole system is to use power when it is coming in and during the final charging phase of the battery bank. If you use the power while it is coming in from the Solar array, then it does not go to the battery first and then back out (with the resulting efficiency loss of the battery). Also, if you can use the power when you need to "waste" some at the end of the charge cycle, you will then be able to utilize the power better.
Heat Recovery Ventilators
When a house has been designed and built very efficiently, one of the largest contributors to heat loss is the ventilation, so check out the HRV efficiencies and choose the best one that you can in terms of heat transfer efficiency and electrical energy consumption.
In our climate, if vehicles are outside in the winter, they will need to be plugged in. Ideally, they will be put into a heated or at least an insulated garage to reduce the amount of power required. If they do need to be outside, consider installing a timer so that the block heater will only come on for a few hours prior to being started.
If possible, adjust your lifestyle so as to utilize the power when there is lots of sunshine. This would involve cooking, baking or laundry on sunny days and just doing the minimum on overcast days.