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10 Rooftop Solar and Storage Predictions for the Next Decade

California solar veteran Barry Cinnamon lays out his predictions for home solar and batteries in 2020 — and the decade ahead.


Predicting the future is easy; getting the exact timing is very hard — especially with all the emerging technologies and requirements facing the solar and storage industry.

So this year I’m giving myself a whole decade to get these behind-the-meter energy system predictions mostly right.

1. Storage will be standard with solar....

Solar-only installations will become the exception rather than the rule. Changes with net metering, unreliable utility power, lower battery costs, grid-services capabilities and energy management features will drive customers toward selecting more full-service solar and storage offerings. By necessity, the skill set of solar contractors will expand to backup panel and communications cable wiring, as well as complicated commissioning and configuration procedures.

2. ...Which means new cost metrics will be needed

For 20+ years, the solar industry has been measuring costs based on dollar-per-watt capacity and dollar-per-kilowatt-hour generation. But adding batteries to a PV system increases the cost and confuses the energy savings calculations. I’m waiting for the gurus at NREL and LBNL to figure these new metrics out.

3. Do you have an app for that?

Cellphone apps are the standard for customer system monitoring. For these apps to work, reliable inverter communications to a server somewhere in the cloud is a necessity. Although Wi-Fi, ZigBee and Bluetooth protocols are convenient and relatively cheap, they are dependent on customer’s router and internet connections — not exactly the pinnacle of reliability. Hard-wired Ethernet or high-bandwidth cellular protocols are better for the reliable communications needed for customer apps.

4. Software is the price of admission

Experienced solar and storage contractors will select systems based on software capabilities: customer app, installer commissioning, management interface and fleet level/utility interface. Regardless of the caliber and capabilities of the hardware, great software is the price of admission.

5. Net costs going up, not down (for now)

Labor, inverter and racking costs are up. Building departments are increasing storage system permitting fees and safety requirements. Building codes are more restrictive (especially for batteries). And customers expect additional integration work with existing electrical systems. To make matters worse, the Investment Tax Credit's phase-down will effectively increase costs by 4 percent in 2020, 4 percent in 2021 and 12 to 22 percent in 2022. Lower hardware costs will not offset these higher soft costs. 

6. One brand for batteries and inverters

Unlike solar modules — which are interchangeable with virtually all inverters — battery systems will be designed and branded by the inverter company. Cells may be a commodity, but the integration between the battery and inverter is specific in order to maintain warranty integrity, performance and installation ease. Contractors want one point of contact for the entire solar and storage system.

7. No standard energy system interface

There is a lack of coordination between various home energy systems (solar, storage, EVs, HVAC, lighting, etc.) and the major home app providers Google and Apple. Security requirements and a lack of industry standards mean that we are at least five years away from integrating these devices. Meanwhile, dedicated apps for every major device will continue to clutter our phone screens.

8. Predicting battery performance will remain challenging

Reliability and projected performance of solar-only systems are well documented. However, performance of battery systems depends on many more variables (temperature, utility rates, building consumption, battery reliability, operating characteristics), making it easier to oversell the benefits of these systems — and almost impossible to predict savings. Heck, one cannot even trust the lifetime of branded batteries from Amazon.

9. Still waiting for vehicle-to-grid

These intuitively obvious capabilities will continue to be delayed as automakers strive to reconcile their miles-driven warranties with the extra demands of providing on-demand power to buildings. The technology is available now, but the automakers will take another five to 10 years to provide stationary power access to their batteries.

10. The dawn of commercial and industrial storage

Residential battery storage began to take off about two years ago when leading inverter and battery companies released well-integrated turnkey solutions. The benefits were initially time-shifting energy use — and then the blackouts happened. The same growth will happen for C&I customers when leading inverter companies release their own storage systems based on existing solar inverters.