Short answer: the same EN-EL15 that reaches over a thousand frames by the official CIPA measure in a D850 delivers only three to four hundred in a Z7 II or Z6 II. The pack has not degraded — the viewing method has changed. A DSLR can keep the sensor and screen unpowered while framing, whereas a mirrorless body runs the sensor continuously to feed the EVF and LCD, and in-body stabilisation draws power the whole time. Once that is clear, planning spares stops being a matter of buying more packs.
Why CIPA figures only show a trend
The CIPA test is a restrained one: 23°C, flash off, one frame every 30 seconds, a playback every other frame, and a zoom lens worked at a fixed rhythm. That routine favours a DSLR, which spends most of the time waiting and draws almost nothing while it waits. It is less kind to mirrorless in a way that is not even realistic — in real use, mirrorless shooters keep the EVF running for long stretches, review constantly and leave Bluetooth file transfer on, drawing far more than the test conditions allow for.
The practical reading is that CIPA’s relative relationships are trustworthy while the absolute numbers need discounting. The ranges below come from experience and are meant for planning how many packs to carry, not for predicting an exact frame count.
| Body type | Representative models | CIPA reference range | Typical street range | Video |
|---|---|---|---|---|
| Full-frame DSLR | D850, D780, D500 | About 1200-2200 shots | About 800-1500 shots | Not the main use |
| APS-C DSLR | D7500, D7200 | About 900-1200 shots | About 600-1000 shots | Limited by clip length |
| Full-frame mirrorless | Z6 II, Z7 II, Z8 | About 300-450 shots | About 250-500 shots | About 1-2 hours continuous |
The last row is the important one: the mirrorless weakness is not stills but video. A 16Wh EN-EL15c running continuous 4K usually hits empty a little past the hour mark, and that figure decides how many packs leave the house more than the stills count does.
Why a DSLR sips power
A DSLR draws in pulses. Framing goes through the optical finder, when the main sensor is unpowered and only the metering and AF modules run at low consumption. The sensor powers up for the exposure when you press the shutter, then goes down again. For the whole sequence, the most expensive part of the chain runs for less than a second.
That is also why DSLR runtime tracks shooting rhythm so closely. Waiting quietly for the light and shooting slowly, a single pack can last two or three days. Switch on bursts, constant review and live-view video, and runtime drops straight to mirrorless levels. If your DSLR runtime has suddenly worsened, ask whether you have started using live view before you rush to buy a pack.
Another DSLR advantage is that it draws nothing when switched off. Leave one for a month and the charge is essentially unchanged. A mirrorless body keeps a clock, a Bluetooth standby circuit and background firmware tasks running, so it drains slowly even in storage.
Where a mirrorless body spends its charge
Mirrorless has no optical bypass, so framing is itself a major load. The Z6 II and Z7 II run a bright EVF at 60fps or even 120fps with screen and finder both on standby; the sensor must read out continuously; the electromagnetic mechanism of five-axis stabilisation is always working; and on top of that sit dual processors plus Wi-Fi and Bluetooth standby. Base consumption is an order of magnitude above a DSLR.
A few factors get overlooked:
- The EVF costs more than the LCD. Many assume switching the screen off and using the finder saves power; on mirrorless it is often the opposite, especially at high refresh settings. If you want to economise, try dropping the EVF to 60fps.
- Stabilisation left on. It has to work when you shoot handheld, but switching it off on a tripod saves a little, though not much.
- Wireless connections. SnapBridge left connected with auto transfer keeps drawing without you noticing.
- Cold. Below freezing, ion activity falls and voltage sag triggers the shutdown protection earlier. The method in this minus 10°C battery test applies here, and the mechanism is independent of the pack model.
Building the spare kit
- Work out the scene, then the count. A day of city street shooting — eight thousand steps, three hundred frames — needs one EN-EL15c in a Z6 II plus one spare. For weddings and events where you cannot stop, budget one pack every three hours.
- DSLR owners need not stockpile. A D850 or D780 with two packs will rarely use the second on a normal day. The money is better spent on a lens or a card.
- Mirrorless owners should weigh charging over buying. A 30W-plus USB PD power bank and a C-to-C cable can add a substantial amount during a half-hour break, and weigh less than two spare packs.
- A vertical grip is a hidden battery bay. The MB-N11 and MB-N12 hold two packs, doubling runtime, and allow a single pack to be hot-swapped mid-shoot.
- Rotate old packs. Using one and leaving the other idle means the idle one fails sooner through self-discharge and ageing. Alternating them evens out the wear. When restocking, choose packs that state 7.0V and a clear capacity; single-model specialists such as YO tend to label their specifications properly.
For which generation to buy, see the EN-EL15 category; if your body is a Z8 or Z6 II, the functional limits of older packs deserve a separate read. Anyone travelling between cities or countries should also check the airline rules — see whether camera batteries can fly.
FAQ
Why does my D850 fall well short of the official figure?
Check whether you are using live view, whether a Wi-Fi accessory is attached, and whether lens stabilisation is left on. All three pull a DSLR close to mirrorless consumption. A pack over two years old and several hundred cycles in will also have lost 15-20% of its capacity, which is normal.
How many packs does a full day of mirrorless shooting need?
For a Z6 II or Z7 II, three to five hundred stills in a day is usually covered by two EN-EL15c packs. If video or wireless transfer is involved, take three, or bring a PD power bank.
Is an EN-EL15c longer lasting in a DSLR?
Yes, because it holds about 20% more. But a DSLR is not short of runtime to begin with, so the absolute gain is modest and the money is better put toward a spare card.
How should packs be stored when not in use?
Charge to around 60% before storing, keep them somewhere cool and dry, and top up every three to six months. Storage at full charge or completely flat both accelerate ageing.