« back to blog

What’s So Fun About Batteries?!

Chapter III. OMG, Batteries Are so Fun. Can I Get One?

“The energy storage revolution will grant individuals unprecedented control over their energy profiles.”

Welcome back, Friends of WSFAB! Apologies for the delay between chapters. Angelica, Richard, and I have been pretty busy with our day jobs – working with the Governor’s Office of Storm Recovery (GOSR) to deploy solar + storage systems[note] Solar + Storage (AKA Resilient Solar) – Shorthand for a paired solar photovoltaic (PV) and energy storage system. Most solar systems can operate during blackouts only if they are paired with energy storage. Therefore, in order to be considered “Resilient Solar,” a system must include energy storage.[/note] at community organizations around NYC. If you want to get really wonky, check out our first four sites!

We’ll talk more about the GOSR work soon – it’s exciting, groundbreaking stuff. But for now, please admire your friendly neighborhood energy geeks as they cool off between site walks at Birch Family Services:

We listen to our fans here at WSFAB. Here’s some feedback we’ve received from our treasured readers.

          • “Honestly, I really doubted the premise of this series. Like, they’re batteries, okay? They’re not fun. BOY was I wrong! Resilience?[note] Resilience – A power system’s ability to quickly and effectively bounce back from a service interruption. A section of the grid is “resilient” if it can quickly restore power after a blackout. A home, apartment building, or community center is “resilient” if it can provide its own power during a grid blackout, such as from a solar + storage system.[/note] Demand charge reduction? DOPE! Gimme batteries.” – Shane, 24
          • “Before I was a WSFAB subscriber, when I heard the word ‘battery,’ I thought of depleted cell phones. Now? I get so amped that I can’t think straight. It’s actually a little scary.” – Dolores, 36
          • “OMG, batteries are so fun. Can I get one?” – Glenn, 7


I feel the same way, Glenn. The answer is… maybe! Let me explain.

Why would you want a battery in your home?

For most people, the main appeal of a residential battery is its ability to provide backup power. If you pair it with a rooftop solar array, you can even recharge the battery day after day during an extended blackout, so you’ll have power when the sun’s not shining.[note]There are plenty of technical caveats to all of this, but I’ll spare you the details for now. Also, for safety reasons, a grid-connected solar array must turn off during blackouts, unless it is able to disconnect itself from the grid, and has a battery to which it can send excess power.[/note] You don’t need me to explain why you’d want backup power during a blackout. But big batteries tend to be expensive – certainly pricier than equivalent diesel generators. Why go with the more expensive option?

Demand charges.

But before I explain what these are, let’s talk about power.

A “kilowatt” is a unit of instantaneous electric power. A lightning strike, for example, carries about 10 million kilowatts in a given moment.[note]Yes, I know, a lightning strike isn’t technically an instantaneous event. (It lasts about 0.00003 seconds.)[/note] This isn’t a terribly useful metric for measuring your electricity consumption at home, though, since you (hopefully) never need nearly that much power at any particular instant. Instead, you draw far less power, but you draw at least some of it every second of every day. Therefore, you pay your electric utility by the “kilowatt hour” (kWh). A kilowatt hour is, you guessed it, a kilowatt of power exerted over the course of an hour.[note]Utility bills also include “fixed charges” – flat fees that cover the basic costs of providing service to a customer – but these make up a small part of your total bill.[/note] A kilowatt hour represents a volume of electricity consumed – you pay for kilowatt hours of electricity at home just like you pay for gallons of gas at the pump.

If you consume enough electricity, though, your utility will start billing you for kW in addition to kWh. Why? Because if you draw a lot of power in a split second – a “peak” in your consumption – they have to make sure they can provide all of that power instantaneously. If many customers peak at the same moment, the utility might need to rev up another power plant to provide enough power. To meet these needs, utilities bill their peakier customers “demand charges” by the kW. Every month, they bill each of these customers for their highest kW peak.


I’m sorry, I know this is a lot. The good news is, if you live in an apartment or a small house, you probably don’t need to worry about demand charges on your personal bill. But if you live in a large apartment building, the building itself probably does pay demand charges for its common area loads. These typically include lighting, heating, and air conditioning in hallways, laundry rooms, etc., plus elevators. If your building pays demand charges on its common area bill, then I’m happy to report, Glenn, that maybe you can get a battery!

Batteries are excellent at reducing demand charges. They do this by charging up when your building isn’t using much power, and discharging when your building needs lots of it. (A battery can charge up either from an onsite solar array or directly from the grid.) This can dramatically lower your building’s monthly peaks, leading to much cheaper electricity bills. In this scenario, a battery might be a fantastic investment.

But how can you tell whether your building fits the bill? Let’s get into specifics.

A good energy storage candidate:

      • Pays demand charges ($/kW), in addition to supply charges ($/kWh), on its common area electricity bill. If a building’s “SC” (Service Classification) on its Con Ed account is “EL” (Electric) 5, 8, 9, 12-demand, or 13, you know it pays demand charges. In NYC today, the only easily-accessible revenue stream for a battery is demand charge reduction. Generally speaking, if a battery can’t do demand charge reduction, it can’t pay for itself.
      • Has 200+ square feet available, either on a roof in good condition, in another outdoor space, or in a noncombustible indoor room. Lithium-ion batteries, the most versatile type currently on the market, cannot currently be sited indoors in NYC, so rooftop or other outdoor space is ideal. (If the plan is to power an elevator for multiple days, well over 200 square feet will be needed, unless the project includes solar.) However, advanced lead-acid batteries are nearly as useful, and can be sited in noncombustible indoor rooms.


If your building meets both of the above requirements, let’s talk! With utility data and some layout details, we can quickly estimate the size and type of battery you would need to meet your resilience needs, while still providing profitable demand charge reduction.

…but let’s not forget about solar.

After confirming that your building pays demand charges and has a good spot for the battery, the big remaining factor is your solar potential. The usefulness of solar to a battery depends on a few factors – most importantly, the size of your building’s critical load[note]The power loads you’ve decided are most essential during blackouts. These probably include lighting, elevators, device charging, refrigeration, etc.[/note] compared to the size of the battery. If the daily critical load is nearly as large as the battery’s capacity, the battery will only be able to power the building for roughly one day. To maintain power during an extended blackout, this building would need to add solar so it can recharge its battery day after day.

Plus, adding solar to the project will likely improve the quality of the investment, both because solar has a quicker payback period[note]The number of years it takes for a project’s revenues (e.g. demand charges savings) to surpass its costs (equipment, permitting, installation, etc.).[/note] than batteries in NYC, and because tax benefits on the solar can be extended to the battery if they’re deployed together. In other words, while solar is not always essential to a resilient battery installation, it really helps. So if your building meets the two battery viability requirements above, please also keep its solar potential in mind.

Believe it or not, I’ve skimmed over many important details here, but my spiel is already overlong. If you have any questions – or, better yet, building candidates! – shoot me a message at or on Instagram at @ResilientNYC.

Be sure to check in on WSFAB next week, when we’ll welcome a very special guest columnist. He’ll walk (trudge? heave?) us through some of the more whimsical methods of energy storage…


h1 { font-weight: regular; color: #ffd400; font-size: 40px; } body.category .inform h1 { display: none; }