The last show of the year is behind Sonnenbatterie and we are definitely looking forward to 2016. But we still have a few exciting things up our sleeves that will be revealed before the holidays are upon us. ESNA was a very different show than the SPI and ISNA I attended this year with Sonnenbatterie. The attendees were definitely a more educated bunch who asked more thought provoking questions than the obligatory, “Will your battery system withstand an EMP blast?” (It won’t, by the way), but there was still the lingering and ever present question of, “How long will this battery run my house?”

If battery systems are the next big thing (and we all know they are) then the industry needs to catch up to the guys that have been designing and sizing battery systems for the last 30+ years. We need well informed solar companies who can intelligently talk about battery sizing and relay the importance of load calculation spreadsheets or other battery system sizing tools. But I fear this will not really happen based on the explosion of new PV installers who jumped on the micro/optimizer bandwagon- installers who don’t want to have to deal with the “hassles” of PV system string sizing because it takes an extra 5 minutes and/or math kicks their ass and they will want a tool that they can just plug (no more than) 2 variables into and get a system size. For the old timers and people who have an intimate knowledge of battery systems, we know where this will lead- bad system designs that will not meet customer expectations which result in many service calls to the site. Ask me how I know…

I finally found a not-so-hidden nugget a few years ago on a backup generator website that revealed why people ask the questions, “I have a 2000 square foot house. How big of a battery system do I need?” (of course, my fans already know my answer to this one). The Generac website has a page to help customers determine how big of generator they need. It is basically an oversimplified load calculation spreadsheet that asks if the back up application is for a whole home backup or just essential loads. Yes, it even asks for the square footage of the house.

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When I clicked the submit button for both applications, Generac speedily gave me my 3 options

1. A 16kWh generator for the whole house backup
2. An 11kWh generator for a bit more than just the essentials
3. An 8kWh “budget friendly” generator for just the essentials

This rough sizing might be good enough for a generator but it simply won’t do for a battery backup system for one simple reason- it doesn’t give an idea of autonomy. Sure, for a generator the autonomy is equal to the number of gallons of fuel the homeowner has in his garage- which is still a finite value. But there are more variables to consider for battery based systems, like how much PV is on the roof. For the people who just want a quick answer for battery backup, here’s one for you:

“Any size battery bank can power any amount of house loads.” -Greg Smith

That’s a true (self quoted) statement- that 16kWh battery system might only power the pool pump, EV, well pump, freezer, fridge, disco ball and AV system for 30 minutes during an outage, but it would still power the house.

Perhaps home owners and inexperienced installers have the same mindset as the backup generator sizing webpage- “This Sonnenbatterie 16kWh battery bank will be able to power my house since that is how big of a generator I was told use.” Again, that battery system will indeed power that Beverly Hills 3500 square foot home when the grid goes out, but they might want to turn off the pool pump, Jacuzzi(s) and other non-essential loads if they want the battery to last longer. This is when the homeowner (and then the installer) will get upset.

It will take some consumer education on our part to get people to understand how much autonomy they will get with their battery system instead of the industry trying to accommodate the insane amount of loads the homeowner wants to power. It might have to come down to a very frank conversation. Something like this:

Homeowner: How long will this power my house?

Installer: This system will power your house for about 3 hours with all the loads on. If you want it to last longer then turn some of the loads off.

Homeowner: But I want them all to run when the grid goes down. I like to use my glass kiln and my pottery is my life. I need the battery to last at least 3 days.

Installer: Ok, then. You will need a bigger battery bank, more solar and a larger battery inverter.

Homeowner: How much will that cost?

Installer: About 4x the quote I gave you.

Homeowner: That’s ridiculous! I knew this battery stuff was a rip off.

Installer: If you can go without making pottery and just survive with a few lights, some outlets for charging your laptop and cell phones, your freezer and a few other essential loads, then I can get you to your 3-day autonomy. Possibly even more. But I would have to install a protected loads panel and you would only be able to power those loads in an emergency, not the whole house.

This conversation could go on for hours, and I know a lot of you have had this EXACT discussion with your customers. I don’t know, maybe those generator guys are on to something. Maybe the battery guys should just give a round number using the square footage of the house and add a disclaimer written by a few lawyers explaining that “Results may vary.”

Why go through all the trouble of nuking out a correctly sized system if a fast and simple calculation seems to be what the homeowners (and installers) want anyway? Those of us with an appreciable amount of time in this battery business already know the answer to this.

What about the people who were raising hogs 3 months ago who now want to get into the storage industry?