Switch to plug-in solar? My advice after testing DIY energy technology at home

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Highlights taken by ZDNET

• Plug-in solar uses microinverters to feed energy into the home system.
• So far, in the US, only Utah has passed legislation to allow such systems.
• These plans cost about $2,400 and will take years to pay off.

Ever since I owned my first solar panel a few decades ago, I’ve been impressed. The fact that a tiny piece of glass has the power to harvest energy from a giant nuclear orb 93 million miles away blew my mind then, and continues to blow my mind now. Since then, solar panels they have grown in size and efficiency and come down in cost to the point where it is economically feasible for you and me to buy panels and generate our own electricity.

But what do you do with that power?

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So far, you have two options. You can have a standard rooftop solar system, well connected to your home’s electrical system, or you can plug your panels into the grid. Portable power stationand use that to power devices in your home. The downside to the first option is the cost, as installing solar panels on your roof and connecting them to your electrical system is a professional job. The disadvantage of the second option is the limitation of having all the power flowing into the power station.

But what if you could connect your solar panels directly to your home’s AC system, and do it yourself?

This is what plug-in solar — also known as balcony solar or portable solar — promises.

What plug-in solar isn’t, and what it really is

Let me dispel the biggest myth right off the bat — plug-in solar is not an AC plug attached to your solar panels. Indoor power is AC, and solar panels produce DC (direct current), so the two are not compatible. If you try to plug the panels directly into the wall socket, many things can go wrong.

Plug-in solar is a new technology that allows solar panels to be plugged into a home’s electrical system. The idea is that the solar panels collect energy during the day, put it into the home system, and that energy is used to cover the home’s base load for the day, and maybe more (more on base load in a second).

Sitting between the solar panels and your outlet is a microinverter. This is a box that converts the DC power from the solar panels into AC that your home appliances can understand. It can then feed this AC power into your home’s electrical system through a standard plug and outlet (so that your outlet is an inlet). As well as converting DC power to AC, a microinverter must not only feed that power into your home’s power system, but do it safely.

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It’s that simple. You don’t need to find a professional because you can do it yourself. It also opens up solar to those living in rental properties or apartments. For example, in Utah, landlords cannot object to tenants installing solar systems that connect to an outlet and do not require permanent changes to the property.

What is base load?

Base load is the back load drawn by the house during the day when no major appliances are in use. It represents the continuous power draw from critical and standby devices, such as Internet and Wi-Fi routers, chargers, refrigerators, and freezers. As a ballpark figure, this is about 200 to 400 watts (or 4.8 to 9.6 kWh over 24 hours) for the average US home.

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How much power you can draw depends on factors such as the size of your solar panel setup in watts and how much sun you get in your area (called Peak Sun Hours, or PSH), and don’t forget to subtract losses due to inefficiency, fading, and dust and dirt from the panels (called derate).

The derate figure can vary, but I went for 0.77 (equivalent to a 23% loss), which errs on the side of unreliability.

Accumulated Energy (kWh/day) = Panel Output (kW) × Peak Sun Hours (PSH) × Derate Factor (0.77)

If you live in Alabama and get an average of 3.5 hours of sun per day, 1 kW (1,000-watt) of solar panels will collect:

1 x 3.5 x 0.77 = 2.7 kWh

Switch to a place like Arizona, which has about 6.5 hours of sun, and the number goes up significantly.

1 x 6.5 x 0.77 = 5 kWh

How does this work?

You put your solar panels in the garden or on the balcony (balcony installation is good for people who rent or live in apartments), connect them to the microinverter, connect them to the outlet, and that’s it, you are harvesting solar energy while the sun is shining. As long as you collect 200 to 400 watts, you cover the basic load.

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Okay, but what about the rest?

Well, you have options. The extra money can go into the grid (you’re unlikely to get paid for this, at least under current household electricity costs, but that could change), or you can push the excess money into a power station for later use. Adding a power station to the mix will increase the cost.

So, what’s stopping us from using plug-in solar?

Bottom line: Mainly government red tape.

While plug-in solar is available in some countries, such as Spain and Germany, where you can walk into a supermarket and buy a plug-in solar setup, the US and the UK are lagging behind. (Here in the UK, Anker recently unveiled the SolarBank 4 E5000 Pro — what a mouth! — before changes to the rules to allow these programs.)

Based on available data, it appears that Utah is the only state in the US so far that has mandated the use of plug-in solar units, with 29 other states pushing for legislation to make it legal. Utah allows systems up to 1.2 kW without a use permit or fees. As for the legislation that is still being drafted, most states seem to be sticking to that 1.2 kW limit.

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Another exception is the Colorado, which wants to push that limit to 1.92 kW. Compare this to the UK and Europe, which limit power to 800W.

Costs and benefits

Costs are also arguably holding back plug-in solar, as these systems can be cheap, especially when compared to the cost of electricity (which is, on average, about 17 cents per kWh).

1,200 W solar kit currently it will set you back around $2,400. I expect that as more states give plug-in solar the thumbs up and more players enter the market, prices will come down.

If you live in Utah and put $2,400 down on the program, how much will this save you? The best-case PSH for Utah is 7 hours, and plugging this into the above equation gives:

1.2 x 7 x 0.77 = 6.5 kWh

That’s a lot of energy, which costs about $0.86 a day (Utah’s electricity cost $0.1333 per kWh in February, based on state data), or another $315 a year. Assuming everything goes well, you will recoup your initial investment in 7.5 years.

If you only use a plug-in solar system to cover the base load during daylight hours, this figure gets worse. Assuming your base load is 400 W, your solar plug-in will cover 2.8 kWh during the day, but only cost $0.37 per day, or $135 per year.

That means it’s 17 years before you have to pay for the plan.

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Either you need to use more during the day than the base load — like running heavy appliances like AC or heating, or charging EVs — or pushing more power to the power station (which, as I said, greatly increases the cost of your setup).

Is plug-in solar safe?

Another concern raised by lawmakers in some states is that plug-in solar installations may not be safe. Anything can be unsafe (lithium batteries are now a major cause of house fires), so there is a risk that connected solar can be misused or damaged to the point of being unsafe. All connected solar systems must comply with National Electrical Code (NEC) regulations and require Underwriters Laboratories (UL) certification.

That’s about as safe as anything else we use.

I’ve had an EcoFlow PowerStream microinverter for over six months, running on an isolated test grid (plug-in solar isn’t legal yet here in the UK, so I’m limited to test systems), and I’ve had no problems with the hardware.

Do you need plug-in solar?

Currently, plug-in solar is a niche product, which means prices are high and it will take a long time to pay for itself. But as more countries and regions open up to plug-in solar, I expect competition to increase and prices to drop.

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My advice right now is that if you live in a sunny area and use a lot of energy during the day — maybe you charge an EV or have a Power Tower, like I do — you can pay for your expenses in a few years. But if you live in Alaska, where you get a few hours of sun a day, and your entire system will run on an internet router, it’s not worth it. At least for now.

But watch this space, because this is going to change a lot in the coming months and years, and prices can change a lot.