Reduce Your Electric Bill: Solar and Battery Calculations for Home Use

It’s that time of the month again. You open your mailbox (or, for the more progressive, your email) and find the most dreaded bill: your Hydro bill.

Many homeowners accept the fact that they will still have to pay for this service. However, there is another group that is quietly exploring alternatives. These people are looking for ways to generate their own power and reduce, or in some cases eliminate, their reliance on the power grid.

The solution explored in this article is the combination of photovoltaic (PV) solar energy and small-scale battery storage to generate and store the energy needed by the home. To be honest, there is a cost to exploring this alternative; however, it is one that will benefit you and your family in the future. By installing a solar array (or if you have the ability) near your home, you can generate power. This energy is then stored in a series of batteries that can be “called” when needed. Through inverter technology, your array can prioritize demand to draw from batteries before the grid is used.

Depending on the amount of energy you use and the number of solar panels and batteries you install, the payback on investment can come in as little as 6 years if you use equipment that will work for more than 20 years (which means approximately 14 years of ‘free’ energy through the installation of a system). Sounds interesting, doesn’t it? But where do you start?

If you’re trying to figure out how much “solar” you’ll need, there are some simple calculations you can do. If you look at your utility bill, you will see how much energy you used. This is displayed in kWh. Your bill can also show you your usage in kWh for the last year.

There are two ways to see this. First, there is the average usage over the twelve months. Using this method will result in designing a system that will result in periods where the power generated will not be enough to power your entire home, but will be averaged out over the year. The second way is to design for ‘peak’ use: in most residences, this will be during the summer, when air conditioners and swimming pools drive up electricity costs. In this case it may produce too much power and end up ‘giving back’ some power to the utility once the batteries are fully charged. In both cases, you want to calculate the average daily usage in kWh. As an illustration, let’s say you need to produce an average of 30 kWh per day.

To determine the number of panels, we need to take the daily kWh usage and divide it by the number of hours of sunlight. If we use seven hours for the calculation, we would have 30 kWh divided by 7 hours or 4.29 kW from your solar panel. If you are using 250W panels as a whole, the following formula would apply: 4.29 (kW) divided by 250/1000 (kW) or 17.1 panels would be needed to offset 30 kWh per day under *ideal* conditions.

At this point you need to make sure that your roof or “area” can accommodate 18 (cannot have 17.1) panels and that it receives seven hours of sunlight a day and that there are no obstacles blocking the panels.

The best thing to do after performing these simple calculations is to find someone who can help you with the engineering and calculations as well as the implementation of your project. Completed correctly, this solution could eliminate, or at least drastically reduce, your energy bill.