Recently, the top honchos of two top solar firms in the US, SunPower and SolarCity, echoed a similar view: Seeking complete independence from the grid through the use of rooftop solar is naïve (http://storage.pv-tech.org/news/sunpower-ceo-grid-independence-is-naive ).

It is not just in the US that industrial and commercial users are keen on using solar, especially rooftop solar, to get independence from the grid.

A similar trend is taking place in India as well.

In one of the first rooftop solar projects Solar Mango worked on, the CEO of the company putting up the plant had a rather idealistic ambition – he wanted some portions of his company to work completely independent from the grid.

There were reasons for his ambition – the main one being the fluctuating voltage of grid power, and his aspiration to rely as much as possible on sustainable power.

No one can deny that his intentions were in the right direction.

But were his aspirations realistic? Unfortunately, not.

The fact is, except for some select cases, it will be next to impossible for commercial or industrial enterprises to get completely off the grid using rooftop solar power, even if they have sufficiently large rooftops.

Sure, if you are lucky, it is just about possible that rooftop solar could replace 50-60% of your connected load, but it is more likely to be in the range 20-30% of your total power consumption.

The extent to which solar can replace your grid power depends on the following:

• Your load
• Your total rooftop space
• Total electricity consumption
• When you are using this electricity

You can easily visualize scenarios when rooftop solar (with little or no battery storage) will be able to replace only a small part of your electricity consumption:

A factory with a small rooftop space, with heavy machinery and high connected loads, with many of the machines running on night shifts.

At the same time, you can also visualize scenarios when rooftop solar could satisfy a large part of a commercial rooftop:

A company in the software or services industry, with large rooftop area, with the main loads being laptop and server loads and using minimal air conditioning owing to a green building construction, and working mainly day shifts.

For the first scenario, solar might replace less than 10% of total electricity consumption. For the second scenario, solar might be able to replace upto 50% of the total electricity consumption.

But I can visualize few industrial or commercial settings where solar can replace 100% of their loads all the time. Perhaps, just perhaps, it is possible if they use tons of battery backup, but they are not going to like the quote for batteries. I am sure of that.

So, here’s the bottom line. Rooftop solar is not a silver bullet for your grid woes, but to some commercial and industrial units, it could get you half way there.

That’s pretty good news.