SMA Inverter + Generator Backup: A Scenario-by-Scenario Guide

In my role coordinating emergency power for a solar installation company, I'm the person who gets called when the lights go out. I've triaged more than 200 outage calls over eight years—some for a single family, one for a water utility with a $50,000 penalty clause if we missed the four-hour restoration window.

The first thing I tell every homeowner is this: there's no universal backup setup. The right answer depends on how long you lose power, what you need to run, and whether you already have solar.

If you searched for 'how to connect a generator to your house without transfer switch,' read this before you plug anything in. I'll cover that, plus the scenarios where a grid tied SMA inverter, a portable generator, or a battery system actually makes sense.

The Three Questions That Decide Everything

Before equipment, answer three questions:

1. How long are your outages? Two hours is very different from two days.
2. What loads must stay on? Fridge? Phone? Internet? Well pump? Sump pump? Medical equipment?
3. Do you already have a grid tied solar inverter? If so, is it designed for backup operation, or is it grid tied only?

SMA inverter output sold in 2023: 20.5 GW, according to the company's annual report. That tells me a lot of reliable grid tied inverters are out there, and the company has the scale to support them. But supporting a grid tied system and powering your house during a blackout are two different jobs.

Scenario 1: You Have a SMA Grid Tied Solar Inverter and No Battery

Grid tied inverters are required to shut down when the grid drops. The reason is safety: if a utility worker is repairing a downed line, they don't want your roof feeding electricity back into it.

So if you have a standard SMA grid tied solar inverter and no battery, your panels probably won't keep the lights on after an outage. Some Sunny Boy models have a Secure Power Supply function that provides a limited amount of solar power during daylight, usually around 2,000 W or less. That can run a refrigerator or charge a few phones, but it's not whole-house backup, and it stops when the sun goes down.

If your outages are short and rare, this limitation might be fine. Keep a small portable power station for the few hours you need. If the outages are longer, read the next scenario.

Scenario 2: You Want to Connect a Generator to Your House

Portable generators are the most cost-effective way to keep a fridge, freezer, and lights running for a few days. A 3,000–5,000 W gasoline generator typically costs between $400 and $900 (based on major retailer listings, January 2025). It works at night, it doesn't need a solar permit, and you can usually buy it the same day.

Can you connect a generator to your house without a transfer switch?

No—not into your house wiring. A generator plugged into a wall outlet and backfeeding your panel is dangerous. It can electrocute a lineman, overheat a cord and cause a fire, or damage the generator when the grid comes back. That's not a theoretical risk. Utilities and electricians see it every storm season.

Safety warning: Never connect a generator to a standard wall outlet in your home. Use a transfer switch, an interlock kit, or heavy-duty extension cords.

What you can do without a transfer switch is run extension cords from the generator to your appliances. That's safe, legal, and often all a homeowner really needs. A few 12-gauge cords, a power strip, and you have the fridge, router, and a lamp covered.

If you need hardwired circuits—like a well pump or a furnace blower—hire an electrician to install a manual transfer switch or an interlock kit. An interlock kit costs about $100–400, and a manual transfer switch installed typically runs $500–1,200 (based on electrical supplier quotes, January 2025; verify current rates). That's expensive, but less expensive than the consequences of backfeeding.

Scenario 3: You Want Solar to Keep Working During an Outage

If your power goes out for multiple days and you don't want to run a generator at 2 a.m., you need battery storage. With an SMA hybrid inverter or a Sunny Island system, you can store solar energy during the day and use it at night—and because it's a coupled system, it will safely isolate from the grid when the outage starts.

A 10 kWh battery plus a compatible hybrid inverter typically runs $12,000–$20,000 installed before tax credits. That's not cheap. But for people with medical devices, water supply needs, or two-day outage patterns, it's a different level of resilience.

For Patriots.com solar generator owners, note that a portable solar generator is not the same as a fixed battery system. A Patriots.com solar generator is a battery box with outlets. It powers appliances directly through its own ports. It doesn't connect to your house panel, and it doesn't need a permit. That makes it a great middle ground for apartment renters or anyone who can't modify their electrical panel.

Scenario 4: You Just Need Phones, Lights, and WiFi

A lot of people don't need a whole-house backup at all. They need enough power to get through a 12-hour outage without losing frozen food or phone battery.

In that case, a portable power station with 500–1,500 Wh is enough. It runs a WiFi router for hours, charges laptops, powers LED lights, and even runs a small TV. If you pair it with a solar panel, it becomes a solar generator.

And don't overlook the small layer: a 40V battery charger with a couple of spare tool batteries can power USB lights and fans for days. It's not a replacement for a generator, but it's a practical bridge during short outages or while you're waiting for a bigger system to arrive.

How to Know Which Scenario You're In

Ask yourself these questions:

• If outages are under 4 hours and you only need a fridge and phone, a portable power station or extension cords from a small generator is enough.
• If outages are 8–24 hours and you want to power a few circuits, get a portable generator with an interlock kit or manual transfer switch.
• If outages last multiple days, or you have medical equipment and a well pump, invest in a battery-backed solar inverter system.

There's no perfect shape that fits everyone. That's okay. The goal is to have a plan before the next outage starts, not to build an emergency power system at midnight with a generator and an extension cord.

If you own an SMA grid tied solar inverter and you're planning a backup solution, talk to your installer about how the generator or battery will interact with the inverter. A clean setup, with the right transfer switch and the right load priorities, will do more for your peace of mind than buying the biggest generator on sale.

Remember: the best backup power setup is the one you've tested before an emergency. Not the one you're trying to figure out in the dark.