Backing Up Your Home: Transfer Switches, Integration Kits and Sizing

The power goes out and you want the fridge, the router and a few lights to keep running. Plugging a battery into a wall outlet is not the way to do it, and there are safer routes that cost less than you might fear. This page walks through them, then helps you pick which circuits to back up and how much battery that takes.

Option one: a manual transfer switch

A transfer switch sits beside your main panel and physically isolates the home from the grid before the battery feeds it. A manual one is the simplest version. You flip it yourself when the lights go out. It suits people who are home during outages and want a low-cost, easy-to-understand setup. The 100A manual switch below is described as a maintenance switch, so check its listing for what it is meant to pair with before you plan around it.

Option two: an integration kit for a portable-style battery

If you already like the idea of a movable power station, a home integration kit is the neat middle path. It is a bundled way to connect an AC300-class system to your home wiring, so the battery can feed selected circuits without extension cords. These bundles suit renters of the idea, not of the house: people with a modest list of essentials who want a system they can still take camping. The kits are listed as 120V for the AC300 bundles. The older EP500PRO kit lists both 120V and 240V.

Option three: a whole-home style system

Bigger homes, or people who want the house to carry on with little fuss, look at the EP800 and EP900 families. These are sold as home battery backup systems with stacked B500 batteries, and a bracket is sold to support the inverter and batteries. Expect a larger budget and a proper installation. Two units can be paired for more output and storage, which suits a larger house or heavier loads such as a well pump or central air. Look at how the listings are built: the single-unit options start smaller, and the paired ones double up.

Sizing the battery

Two numbers matter. Inverter output tells you how much you can run at once. Battery watt hours tell you how long. Add up the running watts of your essentials for the first, then multiply by the hours you want to cover for the second. Solar can top the battery up during the day, which stretches a long outage. Smaller AC300 bundles with one B300 suit a short essentials list. Adding more B300 batteries extends the hours. The AC500 pairings and the Apex 300 kit sit in between.

If you want to recharge during the outage, bundles that include solar panels save you matching parts later.

Why you never backfeed an outlet

Backfeeding means pushing power from a generator or battery into your house wiring through a regular outlet, using a cable with a plug on both ends. It sends live voltage back up the lines, and it can leave plugs or wires live where nobody expects it. It can also fight with the grid when the power returns. Do not do it, however tempting a double-ended cable looks. The safe options all do one thing: they make sure your home is fed by either the utility or the battery, never both at once. Follow the manual and use a qualified electrician for anything that touches your panel.

Deciding which circuits to back up

Do not try to back up everything. Walk round the house and list what you would truly miss in a long outage: fridge, freezer, internet, a few lights, phone charging, perhaps a gas furnace fan or a CPAP. Leave out the electric oven, dryer and water heater. They draw a lot and are easy to live without for a day or two. A short list means a smaller battery, a smaller bill and a simpler panel job. Then check each item's label for running watts, and note anything with a motor, which pulls more for a moment at start-up.

How to choose

• Pick your circuits first, then the battery. Not the other way round.
• Check voltage: 120V kits cover most essentials, while 240V loads need a system or kit that lists it.
• Match inverter output to your biggest single load, and battery capacity to the hours you need.
• Check the bundle contents. Many ship in separate packages that may arrive on different days.
• Look for "Discontinued" in a name before you count on support or restocking.
• Plan for solar if outages in your area run long.

Questions people ask

Can I just use a double-ended cable into an outlet?

No. That is backfeeding. Use a transfer switch or an integration kit so the house is isolated from the grid.

Do I need an electrician?

For anything wired into your panel, yes. Local rules vary, so ask a licensed electrician and follow the product manual.

Can a portable power station back up a whole house?

Usually not the whole house. It can carry a chosen set of circuits. Larger stacked systems are made for wider coverage.

Will the same battery still work for camping?

The AC300 and AC500 style bundles are built as separate units, so they can leave the house. The EP series is designed as a home installation.