The Short Answer
For new hardware purchases: Z15 Pro, always. For secondary market decisions: it depends on the price gap. The rest of this article explains the data behind both conclusions.
Specs Head-to-Head
| Specification | Z15 Pro | Z15 | Winner |
|---|---|---|---|
| Hashrate | 840 KSol/s | 420 KSol/s | Z15 Pro (+100%) |
| Power Draw | 2,780W | 1,510W | Z15 (lower) |
| Sol/W Efficiency | 302 | 278 | Z15 Pro (+8.6%) |
| Est. Daily ZEC | ~0.054 | ~0.027 | Z15 Pro (2×) |
| Power Requirement | 240V / 30A | 240V / 20A | Z15 (slightly easier) |
| Noise Level | ~75 dB(A) | ~72 dB(A) | Z15 (marginally) |
| Generation | 2024 | 2022 | Z15 Pro (newer) |
The Efficiency Gap in Real Money
The Z15 Pro's 8.6% efficiency advantage over the Z15 translates directly into electricity savings. At $0.10/kWh running both machines for equivalent hashrate output (i.e., comparing one Z15 Pro vs two Z15 units):
- One Z15 Pro: 2,780W × 24h × $0.10 = $6.67/day in electricity
- Two Z15 units (same 840 KSol/s): 3,020W × 24h × $0.10 = $7.25/day in electricity
- Annual saving with Z15 Pro: approximately $212/year per 840 KSol/s of capacity
That $212/year electricity saving is a tangible ROI advantage for the Z15 Pro that grows with every dollar of electricity cost and every year of operation.
When the Z15 Can Win: Secondary Market Pricing
The Z15's only realistic advantage over the Z15 Pro is acquisition cost on the secondary market. Used Z15 units often trade at significant discounts to new Z15 Pro pricing. If you can buy a Z15 for 45% of Z15 Pro new price, the lower capital outlay may justify the efficiency gap - depending on your electricity cost and ZEC price assumptions.
The break-even analysis works like this: take the hardware price difference between the Z15 Pro and Z15, then divide by the annual electricity saving ($212 at $0.10/kWh). That's your additional payback period for the Pro. If the Z15 Pro costs $800 more than a used Z15, the electricity saving pays that back in about 3.8 years - which is borderline over a typical 3-year depreciation horizon.
At lower electricity costs ($0.05/kWh), the annual saving halves to ~$106, making the payback period 7.5 years for the same $800 premium - clearly tilting toward the used Z15 in that scenario.
The Power Infrastructure Angle
One often-overlooked difference: the Z15 draws only 1,510W vs the Z15 Pro's 2,780W. If you have a limited electrical panel and can fit two Z15 units in the same circuit capacity that supports one Z15 Pro, you're getting the same aggregate hashrate with lower individual unit risk and potentially better redundancy. Two machines mining rather than one also means continued operation if one unit has a hardware failure.
Verdict by Scenario
| Scenario | Recommendation |
|---|---|
| Buying new hardware today | Z15 Pro - no question |
| Used Z15 at <50% of Z15 Pro new price, electricity <$0.08/kWh | Z15 - reasonable value |
| Already own Z15 units, profitable | Keep running - no need to upgrade yet |
| Already own Z15 units, marginal profitability | Evaluate co-lo or Z15 Pro upgrade |
| Limited electrical panel capacity | Consider two Z15 units vs one Z15 Pro |
Model Both Miners at Your Electricity Rate
Use our calculator with the Z15 Pro preset (840K Sol/s, 2,780W) and Z15 preset (420K Sol/s, 1,510W) to see exact monthly profit for each at your electricity cost.
Compare in Calculator →