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Earlier this year, , the company known for its��electric cars and its��, announced the , a residential battery system that charges via solar or when energy rates are low, then powers your home at night or when rates are higher.

Barely a week later, the $3,000-and-up devices (a Tesla spokeswoman recently said in an email that “more than 100,000 reservations have been placed”).

A few weeks later, Mercedes parent , indicating that demand for home energy storage solutions may��be high. Add in some lesser-known competitors, like , and others, and the home battery market seems to have sprouted overnight.

Not to be left behind, local firm was launched and hopes to surpass the others to become an energy storage force from its headquarters in downtown Honolulu. It��also hopes to edge out the competition by using newer battery technology from Sony that can last years longer than the competition’s batteries.

“The simplest way to put it is that we have way more energy being generated in the daytime than we know what to do with,” explained Gregg Murphy, a long-time solar salesperson (he started in the early ’90s) and now Blue Planet Energy’s vice president of sales.

“The problem is that we need fossil fuel during the evenings and overnight to keep up with demand when the sun’s not shining. The solution is to fill up these batteries in the daytime, for free, and use up that energy at night.”

Blue Planet Energy is aiming at customers of all sizes, from homeowners and businesses to utilities and investors.

With Hawaii’s goal of being off fossil fuels — sort of — by 2045, energy storage is likely to be a key factor. Wind and solar are expected to be our state’s main energy generation means, but the sun only shines half of the day and the wind occasionally stops. Being able to store that energy — whether at residential, commercial or utility-scale storage facilities — when it’s being produced is required to keep our lights on and refrigerators running when the wind stops or the sun goes down.

It’s also an attractive economic option, especially in Hawaii where the cost to buy electricity is high, yet the cost the utility is willing to pay for the excess your solar panels produce is lower.

“In markets like Hawaii in particular, where the price of electricity is significantly more expensive than the price a utility will pay a homeowner for excess solar production, Tesla is experiencing enormous demand,” the Tesla spokeswoman said.

Ion Cells vs. Iron Cells

Blue Planet Energy’s angle revolves around the technology inside the batteries at the heart of its system, which are supplied by Sony. While Tesla and the others use rechargeable lithium ion battery cells, similar to what’s in Tesla’s cars and your smartphone, Sony uses lithium iron phosphate cells. When asked to explain the differences, Murphy smiles and launches into his pitch.

“Have you ever felt your phone’s battery when you’re charging it? It gets hot because of the way lithium ion batteries work. You even see stories about them catching fire. And they store less energy as they get older. Lithium iron phosphate runs cool. That’s huge when you think about installing these in a home or garage. They’re very practical and they’re much safer all around.”

Heat might be an issue if the batteries are installed inside a home or building, but as we see around Hawaii, many appliances are situated outside. Drilling down, Murphy adds that there’s more to the Sony technology.

“There’s a term called ‘depth of discharge,’ and for lithium ion batteries, they can never be depleted below 30 percent. That means you’ll only ever get to use 70 percent of the battery’s stored energy. With iron phosphate, you can completely deplete the batteries. So for a customer, we can install 30 percent less��storage capacity and they’ll get the same amount of energy. Or, looking at it the other way, our competitors all have to install 30 percent more capacity than us, which makes them more expensive.”

Blue Planet Energy is aiming at customers of all sizes, from homeowners and businesses to utilities and investors. And while a greener future is always the focus, Murphy explains the three main needs it’s trying to address.

“First, there are customers who want to be completely off of the grid, so they install solar and storage and they never need to buy from the utility again. Second, there’s grid assist, which means you have solar and storage but you’re still connected to the utility’s grid in case you need more energy at certain times. Third is emergency backup, so during an outage, your home stays powered or the freezers at your restaurant stay cold.”

“Many people don’t realize that, if you have a solar photovoltaic system, it shuts down during a power outage,” Murphy said.��“You can’t run your home from your rooftop panels if there’s an outage, even if the sun’s shining.”

Battery Math Takes Some Thinkin’

For the typical homeowner, battery-based storage looks like an attractive option, but be warned that pricing isn’t trivial. Tesla’s Powerwall received a lot of press for its seemingly reasonable price of $3,000 to $3,500. What isn’t obvious is that most homes will require more than one unit. You’ll need 30 percent more than your expected energy needs, and lithium ion only lasts about 13 years, according to Murphy.

Blue Planet Energy’s units will cost quite a bit more at the outset, but they’re promised to last more than 20 years, don’t pump heat into your home, and will have their final assembly performed right here in Honolulu.

While Murphy declined to share prices, implying that every customer would be different, the cost of a system rises with the number of gadgets, lights, and appliances you’d like to run and how disconnected you want to be from the grid.

“Many people don’t realize that, if you have a solar photovoltaic system, it shuts down during a power outage. You can’t run your home from your rooftop panels if there’s an outage, even if the sun’s shining.” — Gregg Murphy, Blue Planet Energy

So, as points out, you’d need at least two $3,500 Powerwalls in order to run your oven while washing clothes. Adding in lights, laptops, and televisions, plus installation and other equipment, and the price easily hits tens of thousands of dollars for taking your home off of the grid. (For more math fun, of Tesla Powerwall versus Aquion and another supplier, Iron Edison.)

But it’s not all bad because you’re cutting back on your utility costs and Uncle Sam covers nearly a third of the system costs.

“Storage systems are also eligible for the 30��percent federal tax incentives, same as solar,” said Murphy. “As the economics of energy continue to change, it helps the return on investment of batteries make even more sense. Our systems offer the safest, longest life, and lowest lifecycle cost of any battery on the market.”

When pressed on the fact that the typical homeowner might not want to spend this kind of money, Murphy gets right to the point:

“Here’s what I tell people: For those without solar, we can take you totally off of the grid for cheaper than you’re currently paying the utility, and we’ll be less expensive than the other battery suppliers out there.”

Blue Planet Energy hopes to begin installing systems in the first quarter of 2016, and plans to expand to the mainland eventually. It’s��currently finalizing plans for a combined warehouse, assembly line and training space in Honolulu, with a showroom to allow people to see the technology in process.

“It’s a pretty exciting time to be in this space, like solar was 10 or 15 years ago,” said Murphy. “We’re starting in our backyard first, but this is going to be huge everywhere.”