Anywhere you look on the internet you will find people and articles slating mirrorless cameras because of their battery life. This may certainly have been the case with some early mirrorless cameras, but it sure isn’t the case with the Nikon Z6II and Z7II from my experience. It's no secret that a mirrorless camera works differently to a DSLR camera, and this does have an impact on battery life, but it isn't all doom and gloom as it's made out to be.

The main factor that leads to mirrorless cameras using more power than DSLRs is the lack of an optical viewfinder. In a mirrorless camera, using the EVF (Electronic Viewfinder) or the rear LCD screen for live view involves using the CMOS sensor, which is the single part of the camera which draws the most power. This is not the case with DSLRs as they have an Optical Viewfinder, and look through the lens, as opposed to looking ‘through the sensor’. Taking this into consideration, it makes perfect sense that mirrorless cameras eat through batteries a little quicker than DSLRs do. 

So where did the Myth come from?

Sony was the first manufacturer to really commit to mirrorless cameras and have been manufacturing them for a while now. Their earliest mirrorless cameras were notoriously bad with battery life, ask anyone who shot with the A7R and A7RII! Sony ofcourse, tried to downplay the problem by shipping 2 batteries with their A7RII, this probably exaggerated the issue and made it seem worse than it actually was. That being said, I have never owned a Sony camera, so it wouldn't be fair to form an opinion around the subject. 

What are CIPA Ratings?

All cameras are given standardised battery life ratings by CIPA. The way CIPA calculates and rates battery life seems a bit of a mystery to me if I’m honest, from what I found on Nikon’s website though: ‘One photograph taken at default settings once every 30 seconds‘. This means there is a lot of idle time between images. Nikon also states that this is done in a controlled environment (Measured at 23 °C/73.4 °F with a tolerance of ±2 °C/3.6 °F. They also specify the lens used for the tests (NIKKOR Z 24–70mm f/4 S lens) and the memory card used (SONY CEB-G128 memory card), hinting that all these factors potentially have some impact on battery life. 

The definition of a CIPA rating is as follows:

‘A measurement of the number of images a digital still camera can take on a single battery charge. The procedure for determining this rating comes from the Camera & Imaging Products Association in Japan.’

Below are the different CIPA ratings for the Nikon Z6II and Nikon Z7II:

The Nikon Z7II and Z6II

Interestingly, the Z6II and Z7II specified battery life is not the same, even though these cameras are almost identical (The only differences between the Z6II and Z7II are the the Sensor (25Mp Vs 46Mp and Base ISO), the Frame rate (14 FPS Vs 10 FPS), The number of focus points (273 Vs 493) and the AA Filter(Z7II doesn’t one). 

According to above CIPA ratings, the Z6II can take 20 more shots than the Z7II with energy saving enabled, but it can take 20 shots less than the Z7II with energy saving disabled - Strange isn’t it?

Both cameras are rated to take more shots using the monitor only (Rear LCD). Once again, the Z6II can take slightly more shots than the Z7II with energy saving enabled (10 more), but it can take 10 less shots than the Z7II when energy saving mode is disabled.

Real World Use

The CIPA ratings don’t paint a very pretty picture. According to them, the Z7II can only manage 440 shots on a full battery. That’s certainly not the case, the number varies significantly and it depends on how you use your camera. I managed to get over 1600 shots on a single fully charged Nikon EN-EL15C battery back in September at the Malta International Airshow. This included a lot of time spent in playback mode chimping and checking my focus as it was the first time using my Nikon 300mm F4 with the FTZ Adaptor and my Z7II. The remaining battery at the end of the shoot was still 17%. The high number of shots obtained on a single battery was due to a lot of fast shooting and turning off the camera when not using it. 

Landscapes and Astro

Naturally, when shooting astro and landscapes, the batteries do not last as long. Shooting in low light requires much longer shutter speeds, from several seconds to a few minutes. I only ever use live view on the rear LCD when shooting landscapes and astro because I like to be able to zoom in to key areas of the frame to check sharpness and my composition. 

What are the main factors that reduce battery life?

There is plenty you can do to get the most out of each battery, below is a list of the main culprits behind reduced battery life:

• EVF / Rear LCD Screen

• Eye detect EVF/Monitor switching

• Image Stabilisation (Body)

• Image Stabilisation (Lens)

• Autofocus (Especially Continuous AF)

• Exposure Delay

• Timer

• Menu Sounds (Beeps)

• EVF / Monitor brightness

• Long Exposures

• Long Exposure Noise Reduction

• Wifi

• Leaving camera on standby

Luckily, for landscapes and astro I don’t use many of the above functions such as Eye detect EVF/Monitor switching, Image Stabilisation (Body), Image Stabilisation (Lens), Autofocus (Especially Continuous AF), Menu Beeps or leaving the camera on standby. I do sometimes use Wifi to control the camera from my phone instead of a remote trigger release, however this is not done often and is done for a short period of time.

What can you do to put your mind at rest?

• Always head out with fully charged batteries

• Invest in spare batteries - How many do you need? Add an extra one on top of that - just in case!

• Invest in a portable charger - Ideally one capable of charging multiple batteries at once from a powerbank (I use the Nitecore UNK2 Charger which is compact and lightweight - You can see my review here)

• Label your batteries and use them in order so that you know how many you have left

• Don't store batteries long term inside your camera

• Replace old / sub-optimal batteries 

• Always use original batteries (I’ve heard horror stories about 3rd party batteries and frankly I don’t think it’s worth the risk to save a few euros!)