This startup has a smarter way to make solar work for apartments

Allume Energy’s SolShare tech can divvy up solar output among apartment units however property owners choose, delivering more flexibility to an underserved market.
By Jeff St. John

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An Allume Energy SolShare unit installed between an apartment building rooftop solar inverter and individual apartment meters
Allume Energy’s SolShare technology can match a shared solar system’s output to the energy use of individual apartments. (Allume Energy)

For the past seven years, Allume Energy has been implementing a unique solar-sharing technology in its sun-drenched home market of Australia that helps make multifamily solar projects affordable. Now the startup is coming to the U.S. — but not the parts of the country best known for solar-friendly policies.

This week, Allume Energy unveiled its second U.S. project at the Madison Garden apartments in Jackson, Mississippi. The property’s eight units will share output from the 22-kilowatt solar array on its roof. But instead of averaging out that solar between tenants, as most multifamily solar projects do, Allume’s SolShare technology will measure and match solar output to each apartment’s energy usage on a second-by-second basis.

The SolShare is the only hardware technology — at this point, in the world — to do the work of splitting one single solar array into multiple meters,” said Mel Bergsneider, Allume’s executive account manager. That’s a bold assertion, but it’s backed up by the company’s patents, as well as by the fact that it’s the first technology to receive Underwriters Laboratories certification as a Power Division Control System” — a technology category created to match what SolShare does, she said.

This kind of unit-by-unit precision is far from standard for multitenant solar projects, mainly because it’s hard to do. Wiring individual solar panels and inverters to individual apartments is costly and impractical. The other option — connecting solar to a property’s master meter and averaging out production across tenants — works in some markets such as California that allow virtual net metering” or other methods that allow landlords and tenants to earn utility bill credits from power that’s imprecisely divvied up.

But that approach doesn’t work in many other markets, Bergsneider said, such as Mississippi’s, which has among the lowest rates of rooftop solar adoption in the country. That state’s net-metering regulations don’t include virtual net-metering options, and they offer customers relatively low payments for power that their rooftop solar systems export to the grid.

That increases the value of technologies that can match solar to on-site energy use as closely as possible to replace power bought from the utility. SolShare was designed precisely for this, Bergsneider said.

How solar sharing works

Australia has a national feed-in tariff regime that pays residential solar customers for the power they export back to the grid, but the value of the payments has phased down over time. That incentivizes solar-equipped customers to consume as much of the power they generate as possible.

Allume’s SolShare system is now installed at solar-equipped Australian apartment buildings and community-housing properties with hundreds of tenants collectively. The hardware consists of a power control platform installed between the property’s solar inverter and the meters serving individual apartment units or common areas. Sensors take subsecond readings of each meter to understand how much electricity each is using. Then its power division control system divides the amount of solar power available at that moment accordingly.

This graphic illustrates how SolShare would split up the power flowing to four different apartments to match rising and falling consumption. Studies of its deployments in Australia and the U.K. indicate that this demand-matching capability can lead to up to 50 percent higher consumption of solar generated on-site and up to 40 percent less grid power consumption than at comparable solar-equipped buildings that can’t perform this kind of optimization.

This chart shows how SolShare directs solar power to match individual apartment units' changing energy consumpt
A before-and-after demonstration of how SolShare directs solar power to match individual apartment units’ changing energy consumption (Allume Energy)

That’s the primary task for buildings trying to maximize self-consumption of solar power generated on-site, said Aliya Bagewadi, Allume’s director of U.S. strategic partnerships. But the SolShare system can do quite a bit more than that, she said.

Our software enables building owners to look into the performance of the asset, to see where the energy is being delivered, what’s the offset [of grid power consumption] for my tenants and the common areas, and toggle where the energy is going,” she said.

Property owners can use this flexibility to set up their preferred structures for distributing solar to tenants, Bagewadi said. That could include splitting up solar usage based on apartment square footage or other factors, or letting tenants choose whether they want to sign up under different terms that make sense for the property and the solar economics of the region. They can also redirect power away from vacant units to those that are still occupied — something that shared-power systems can’t do without shutting off the meter.

With solar control comes valuable data 

The data coming from the system also has value, Bergsneider said. We’re working with major real estate companies that need to report on carbon footprint reductions, but they literally don’t know how much the rest of their building is using because they only control the common area or have access to the common-area bill,” she said.

That kind of data is increasingly important to property owners trying to improve the overall energy efficiency of their buildings, she said. It’s also important for those seeking to manage their carbon emissions profiles to meet city-performance benchmarks such as New York City’s Local Law 97, or to assess their portfolios’ performance toward environmental, social and governance (ESG) goals, she noted.

That’s the case for Renu Communities, the subsidiary of Taurus Investment Holdings that worked with Allume to install SolShare on its first U.S. sustainable-retrofit project, the 296-unit Canopy Apartment Villas complex in Orlando, Florida. Chris Gray, Renu’s CTO, said the company takes a holistic approach in its multitenant buildings, which often includes submetering individual units to track and improve energy performance.

At Canopy Apartment Villas, that included heat-pump space and water heaters and LED lighting, as well as SolShare’s unit-by-unit energy management capabilities. Renu plans to implement Allume’s technology at a 360-unit multifamily community in Orlando and a 280-unit complex in Tampa, Gray said.

The split-incentive challenge for clean energy equity 

A growing number of companies are looking to bring solar, batteries, electric-vehicle chargers, grid-interactive water heaters and other clean-energy technologies to apartment buildings. Beyond the potential to reduce energy bills and carbon footprints, these kinds of investments are increasingly seen as ways to attract and retain tenants, Bergsneider said.

But multifamily properties need all the help they can get in making solar economics work, she said. Apartment buildings and rental housing have been largely left out of the rooftop solar revolution.

That’s mostly because of the split-incentive” problem — the fact that property owners pay to install solar panels, while tenants usually reap the rewards of lower electricity bills. 

Even in Australia, where more than one in four single-family homes have solar — the highest per capita rate of adoption in the world — less than 1 percent of apartments are solar-equipped, according to Bagewadi. These ratios are similar in California, which leads the U.S. in single-family rooftop solar. The result is that low- and moderate-income families, who make up a larger portion of renters in the U.S., are being left out of the benefits of solar, she said.

While SolShare doesn’t necessarily solve the split-incentive problem, it does make it possible for multifamily properties to structure a solar installation that can work in territories that don’t offer virtual net metering, she said. At the same time, the technology could be used in states where existing net-metering regulations are changing in ways that reward solar-equipped customers for consuming more of the power they produce on-site versus sending it back to the grid, as is happening in California.

The appetite for workable models for multifamily solar is growing in response to state and utility incentives that reduce the cost of solar for lower-income customers, as well as the bonus tax credits, grants and loans being made available for clean-energy investment in low-income and disadvantaged communities under last year’s Inflation Reduction Act.

Climate First Bank, a Florida-based community bank that’s working with Allume to develop more projects in the state, noted that rising utility rates are putting more pressure on multifamily building owners and tenants alike. Solar power provides greater economic stability to residents” and, for owners, a clean energy source that reduces operating expenses” from common-area electricity usage and increases the value of their investment property,” Chris Cucci, the bank’s chief of staff, said in a statement.

Allume has raised AUD $16 million (USD $10.7 million) to date. Backers include Hawaii-based nonprofit investor Elemental Excelerator and The Clean Fight, an accelerator funded by the New York State Energy Research and Development Authority and New Energy Nexus, both of which are focused on extending clean-energy options to lower-income communities, according to Allume’s Bagewadi.

That’s the reason we’re trying to bring solar to multifamily buildings,” she said. It’s very important to be able to create affordable clean energy for low- to moderate-income families who have contributed to climate change the least and who are suffering from it the most.”

Jeff St. John is director of news and special projects at Canary Media. He covers innovative grid technologies, rooftop solar and batteries, clean hydrogen, EV charging and more.