Do you really need a battery along with your solar panels?

In Palomar Solar’s opinion, not yet.

Batteries seem to be the talk of the solar industry right now. I’m hearing radio ads and seeing infomercials that are incredibly misleading to the consumer.

What many homeowners do not understand is there are only two purposes for purchasing a battery for a solar system. One is to have power in the event of an outage, and the other is for peak-load shifting (trying to offset the new time-of-use rates).

What do you think your battery is going to power?

Most companies selling batteries are giving the false impression your whole home is covered in the event of a power outage. This scenario is possible, but only if you scale back your usage accordingly. An average residence uses 30–40kW per day and power consumption is minimal when you are out of the house, and overnight while you are sleeping. So how much power is being used at the busiest times of the day in an average household? Realistically, maybe 10kW per hour.

How long will the charge last?

It all depends on the size of the battery and what you are trying to power. If you are considering a backup system, your consultant should be asking you “In the event of a power outage what do you want to be able to use?” We typically hear “Everything!” After a little discussion, we end up at “a couple of lights, the TV, computer, and the refrigerator.” Powering your entire home for a significant period of the day could take a room full of batteries, and that cost would be substantial.

The only way to power your “must-haves” is to isolate those circuits and relocate all essential loads to a new sub panel. This will allow your 10 kWh battery (brands such as LG and Tesla 2 are a nominal 10kWh) to provide back up for an extended period. Of course, if you are committed to go outside and turn off all the breakers to non-essential loads when the power goes out, you could avoid this additional $1,000 expense. The issue I’m seeing is that many companies are not installing the essential loads panel resulting in frustration when their customers are joining their neighbors in the dark after a couple of hours.

Can a battery cope with peak-load shifting?

With the new time-of-use (TOU) rates coming from the power companies, everything you have been conditioned to do needs to be reversed. Off-peak rates (the lowest) are now 9 pm until 4 pm. That’s right! Midday is now when the utility companies want you to use power. Peak rates are between 4 pm and 9 pm, so when you come home from work and do laundry, the dishes, watch TV, etc. you’ll be incurring more cost rather than less.

To combat the TOU rates, we use batteries to implement peak-load shifting. The battery will charge during the day when the power is less expensive and then in the evening (during peak hours) power will be drawn from the battery. You’ll be using solar power past sunset even though your solar system is no longer producing.

This benefit sounds great, but at today’s battery costs, it makes zero financial sense. In fact, we believe the best-case scenario is that you may recoup your battery investment around year 11 or 12.  Unfortunately, your warranty expires in year 10!

Does a battery purchase make sense?

At Palomar Solar, we believe batteries are only for the early adopters who want the latest and greatest, not those looking at it from an investment standpoint. We think for the majority of solar consumers, waiting another 1-3 years will be worth it.

Batteries are an exciting idea, but not ready for “prime time.” In a few years, prices will drop significantly, and the technology will become more advanced. When we see a 5-7 year payback, that’s the time to buy.

It’s essential to have an in-depth conversation with your consultant about battery expectations. We are more than happy to install them as long as the expectation is fully understood. Some companies are merely using batteries as another revenue stream, and the sales pitch misleads their customers. Unfortunately, they won’t find that out until the next outage when their battery is drained in less than an hour.

If you are concerned about back up in the event of another outage such as the recent wildfires, we believe a generator makes the most financial sense and provides the reliable backup you are expecting.