Frequently Asked Questions (FAQs)
The amount of solar (or "PV") that you need will depend on your goals, your electrical loads, and other factors. For example, if your goal is merely to reduce your energy bills in the summer, you may not require very much solar. If your goal is to depend entirely on solar during the winter, that will require much more solar.
If you want your home to remain connected to the grid, many utilities will limit the amount of solar you install and connect. The Backup Power Calculator defaults to recommending enough solar to offset around 100% of your expected consumption, based on your selected loads. Most utilities will allow at least that much solar, and a local, licensed solar contractor should be familiar with those policies.
A consultation or a local, licensed solar contractor may help you determine how much solar is necessary to help you reach your goals.
This will depend on your goals and other factors. The number of batteries required may be dictated by either the power or the available energy.
POWER: Use the Backup Power Calculator report to estimate how much continuous power and peak power you may need. Check with your licensed solar contractor to confirm that the proposed system will be able to deliver that much power. Most batteries are able to discharge in 1-2 hours, which means that if you need 5kW of continuous power, you may need 5kWh – 10kWh of energy in order to deliver the 5kW of continuous power.
Air conditioners and other electric motors typically require a lot of power, especially peak power on startup.
ENERGY: Use the Backup Power Calculator report to estimate how much available energy you may need. Keep in mind that many batteries only recommend actually using 70% - 80% of the nominal energy, meaning a "10kWh" battery may only have 7kWh – 8kWh of available energy.
Air conditioners tend to consume a lot of energy, but also tend to consume more during the day, while solar is also producing.
CONSULTATION: A consultation or a local, licensed solar contractor may help you determine how many batteries are necessary to help you reach your goals.
This too will depend on your goals and other factors. If your only goal is to reduce your energy bill, then burning fuel to run the generator doesn't usually result in any net savings. If, however, you are in a local climate with poor solar production, and you're preparing for long term outages, it may be wise to include a generator in your system design.
If you do choose to install a generator, make sure it will deliver enough continuous power and peak power to meet your needs (see page 1 of the Backup Power Calculator report). Make sure you also pair it with a fuel source will allow it to run for a sufficient length of time.
This will depend on the available energy of your batteries, the energy production of any attached solar, and the consumption of your various loads.
Some combined solar and battery systems are designed to power only critical loads for weeks on end, whereas some combined systems are designed to power a whole house for only a few hours.
Use the Backup Power Calculator and perhaps a consultation to determine if a particular system will meet your needs.
Some batteries can power an entire house, but most whole house backup systems require multiple batteries, often because of air conditioners and other large electric motors.
(See also: "How many BATTERIES do I need")
This will depend on the cost to install the battery, along with your local laws and utility company policies. Without solar, most batteries can only offer very limited financial benefits. Paired with solar, most energy storage systems will allow you to do at least some "peak shaving", which is to use your battery during times of day when energy prices are highest.
Some utilities allow you to sell back large amounts of energy to offset most or all of your consumption from earlier in the day (net energy metering). Many utilities (especially in California) are instituting policies that greatly undermine the financial benefits of owning an energy storage system (a battery).
A local, licensed solar contractor should be familiar with local utility rates and policies.
That said, there are some government programs which can help with the initial cost of installing a battery. A local, licensed solar contractor should be familiar with those programs.