On or Off the Grid

One of the biggest decisions you need to make about your new PV system is whether or not to tie it to the mains power grid. Obviously, if you live in a rural home that is not connected to the grid this is not a concern. But for most people there are a number of factors to this decision that will affect the energy savings of your PV system.

Of course one of the main factors will be cost. All things being equal in terms of the type and amount of solar panels, a grid-tied system will be cheaper than a battery-tied system that is off the grid. The reason for that is the added cost of the batteries themselves.

Other factors that will influence your decision are the amount of roof space you have available and ease of installation. A system that supplies half of a typical home's energy needs uses roughly 10-15 m2 of solar panels. If you have less space, a battery-tied system may be able to make more efficient usage out of the smaller amount of energy created by your solar panels by directly powering one or two smaller electrical devices in your home. Then again, having a battery-tied PV system will involve higher maintenance costs over the long term than a grid-tied system.

If you do decide to go with a grid-tied system, it may pay to shop around the different energy providers in your area. Currently, there is no fixed rate that energy providers are obliged to pay to people with PV systems for the excess electricity created and supplied to the grid. In fact, some suppliers will not pay you for your excess electricity at all! A study performed by the Energy Saving Trust found that the average PV system customer only uses half of the energy that they generate. That means that the average PV system will generate 700 kWh of energy per year that your supplier should pay you for.

The second thing to be aware of for a grid-tied system is that you need either a mechanical meter that cannot run backwards or a full import/export meter to monitor your PV system's output to the grid. This meter can be installed by your energy supplier, but discuss with your PV system installer the kind of meter that is best for you. Some meters are much more expensive than others and your energy supplier will simply try to install the one that they normally use.

Now if you do decide on a battery-tied system, you have to think about batteries. Most PV systems will use lead acid batteries for their deep-cycle capability and cost effective energy density, but NiMH batteries are also available. What you will have to discuss with your installer is the number of batteries that you require. That will be determined by the size of your solar panels, your energy usage, how much electricity you can achieve from other microgeneration methods such as generators, and cost.

Now that you have a good idea of the kind of system that is right for you, the next step is to find a PV system installer.

Next: Finding an Installer for Your PV System