Battery backup, with or without solar

Yes. Storage without generation is a complete project and a common one, because the problem being solved is usually an outage rather than an electricity bill. The battery charges from the grid when power is available and carries your chosen circuits when it is not. It still needs an electrical design, a building permit and, in most areas, a utility notification or interconnection application — because the equipment is capable of energising circuits and the utility and the jurisdiction both care about that regardless of whether anything is generating. What changes without PV solar is that nothing recharges the battery during a long outage, which makes the runtime question sharper rather than less important.

That is set by the loads you put on it, not by the battery alone, and it is the calculation worth doing before you choose equipment. A modest essential set — a refrigerator, lighting, internet, phone charging, a furnace fan — is a small continuous draw and can last a long time. Central air conditioning, electric resistance heat, an electric water heater, a range, a dryer or a vehicle charger are in a different class entirely and can turn days of runtime into hours. This is why any answer that comes as a number of hours without first asking what you want backed up is not an answer.

Both are legitimate and they are different projects. Essential-circuit backup means a subpanel that holds the loads you chose, with the labour to move those circuits into it — smaller, cheaper, and it forces the useful conversation about what actually matters. Whole-home backup means the entire service is carried, which needs enough capacity and equipment to handle the largest load that might start up, and usually more of both. A middle path exists too: whole-home backup with managed loads, where certain heavy circuits are automatically shed during an outage. Which is right depends on what you are protecting and what you are willing to spend, and it should be settled before equipment is quoted.

In almost all cases, yes to the permit and usually yes to some form of utility notification. The permit is because this is electrical work and, depending on the equipment and location, sometimes structural work as well. The utility involvement is because a system capable of energising circuits has to be incapable of backfeeding their lines while a crew may be working on them — which is a safety matter, not a formality. Adding storage to an existing PV solar system generally requires a new application rather than an amendment, because it changes what the system can do. Requirements vary by jurisdiction and by utility, so it is established for your address rather than assumed.

Usually, but it is a design question rather than a straightforward addition. A standby generator already owns the single transfer point where your house switches between sources, and two sources must never be able to energise the same circuits simultaneously unless the equipment is specifically listed for it. So the design has to state which source keeps the transfer point and what the other one does during an outage. There are several arrangements in common use and they differ in cost and complexity. This is worth resolving on paper before either piece of equipment is ordered.

The on-site work is typically one to two days, and where a subpanel is being added and circuits moved into it, that is most of the labour. As with any permitted electrical work, the schedule is set by the approvals rather than the installation: a permit has to be issued, the utility notification or application processed, and an inspection passed. Where storage is being added to an existing PV solar system, the utility review is often the longest single item.

That depends entirely on your utility's rate structure, and for many homeowners the honest answer is that backup is the benefit and any bill reduction is secondary. Where a utility charges materially different rates at different times of day, storage can shift consumption and that has a value. Where it does not, a battery installed for outage protection is insurance rather than an investment, and it is more useful to price it that way than to build a savings case that depends on assumptions about future rates. We would rather set the expectation correctly than quote a payback figure we cannot stand behind.