How to choose a plug-in solar kit: size, certification, mounting

Choose in this order: what your state allows, what size your home can use, which certification to require, and how it will mount. Brand comes last.

1. Check your state’s limits

Most plug-in laws cap output at 1,200 W, but the details differ. Vermont counts the combined inverter capacity per meter, so two smaller devices are fine. Connecticut and Maryland allow only one device or system per meter. Maine requires a licensed electrician above 420 W. Find your rules on the state map.

2. Size it to your always-on load

Because exported power usually earns nothing, the best size is close to what your home draws all the time during the day.

Your always-on daytime load	Sensible kit size
Under 150 W (small apartment, efficient fridge)	300–400 W
150–300 W (fridge, router, standby, a dehumidifier)	600–800 W
Over 300 W (home office, aquarium, second fridge)	800–1,200 W

To find your load, look at your smart meter’s lowest daytime hourly reading on a mild day, or run the calculator and watch the self-use percentage.

3. Require the right certification

Buy a kit whose microinverter or system is listed by a nationally recognized testing laboratory to the standard your state names. Vermont and New Jersey name UL 3700; Connecticut names UL 1741. As of September 2026, Solar.com listed the Hoymiles HiFlow Pro, APsystems EZ1 and Mango Power S kit as UL 3700 certified. Details in our UL 3700 guide.

4. Choose a mount that fits your railing

Railing hooks or clamps for metal railings. Check that they are rated for the panel’s weight and wind load.
Tilting brackets angle the panel outward and can lift yearly output by a third or more over vertical. See orientation.
Ground or deck stands for patios and flat roofs, at 20–35°.
Lightweight or flexible panels reduce load on railings, but usually cost more per watt and age faster.

5. Compare on price per usable watt

Typical plug-in kits ran $600 to $1,500 in Solar.com’s September 2026 survey. Compare the full system price (panels, microinverter, mounts, cable) against the yearly kWh the calculator predicts for your setup, not against panel wattage alone.

Buyer’s checklist

Within my state’s wattage cap and per-meter limit
Microinverter or system certified by an NRTL to the standard my state names
Plug goes directly into a wall outlet on a circuit without heavy loads
Mounting hardware rated for my railing and local wind
Landlord or HOA notified or approved, in writing
Utility notified, if my state requires it
Warranty covers the microinverter for at least 10 years

Common questions

What size balcony solar kit should I buy?

For most apartments, 400 to 800 W. Size it so the kit's midday output is not much more than what your home draws all the time, since exported power usually earns nothing.

Can I connect two kits?

It depends on the state. Vermont allows several devices up to a combined 1,200 W per meter. Connecticut and Maryland allow one device or system per meter. Never daisy-chain units unless the product is certified for it.

Should I buy a kit with a battery?

Only if you have little daytime load and the price difference is small. A battery stores midday surplus for the evening but adds cost, weight and another device that needs certification.