Energy mass balanceCostingEquipment sizingHydrogen

Battolyser (nickel-iron battery-electrolyser)

TU Delft battolyser, a Ni-Fe battery that turns into an alkaline electrolyser once charged: pre-commercial, no current vendor offer, and no vendor cost data exists. Round trip, H2 output, specific energy, hours split, CAPEX, O&M, electrode replacement, LCOH and cost per MWh discharged, from lab cells and declared cost proxies.

Open Jack

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CurrencyEUR 2020
Battery limitex-factory
80 documented assumptions
Updated27 Oct 2026

Mass and energy balance

What the asset draws and delivers for the case and load you choose.

Electrolysis hours per year45.7 %

Hours a year at rated power in electrolysis mode (battery full, excess current makes H2 and O2). 4,000 h is the Observatory's cheapest-hours default for grid power. Charge + discharge + electrolysis hours must fit in 8,760 h; at 5 h and 365 cycles that caps electrolysis near 4,330 h, and above it the input is refused. At the defaults the LCOH goes from 7.63 EUR/kg at 4,000 h to 8.98 EUR/kg at 2,000 h.

Flows

Annual quantities at the current usage. Band width: share of energy in; non-energy flows are not to scale.

Rated power

Electrical power of the battolyser, used both for charging/discharging and for electrolysis. The slider runs 1,000-5,000 kW, the electrolyser capacity range Battolyser Systems says its cells are designed for ('1 to 5 megawatts', RWE press release, 3 May 2023); no larger battolyser is documented, and the only published performance data are lab cells of 3-10 Ah. CAPEX is per kW and per kWh at exponent 1: the cell stack is numbered up in identical modules (a 2.5 MW skid and 5 MW modules, Hydrogen Europe, 12 September 2024; a 'MW-scale, modular, containerized plant', KIVI, 2018), so size changes absolute flows and CAPEX but not the levelised costs. IRENA 2020 (p.71, after Bohm et al. 2020) gives a cost exponent of 0.6-0.75 for the balance of plant of conventional electrolysers: holding 1 on the electrolysis part (about 15 % of CAPEX) is prudent, it may overstate the CAPEX at 5 MW.

Usable storage capacity: — kWh
Hydrogen output at rated power: — kg/h
Electricity discharged: — MWh/year
Hydrogen produced: — t/year

CAPEX

Specific cost at this size, what backs it, and how it behaves with scale.

Specific CAPEX at this size

—

Reference size 1,000 kW

OpenJack modelling choice

CAPEX source

Model value: the Barton 2020 tested cell on a common cost base, 494.5 EUR/kWh battery part (Barton retail price) x storage duration + 420.2 EUR/kW electrolysis part (IRENA 2020), 2,892.7 EUR/kW at 5 h. Customized: your own equipment price per kW of rated power, applied as entered at every size, with no scale law. Either way the battery/electrolysis split, the electrode set (50 % of the battery part) and the fixed O&M (1.5 % a year) follow the CAPEX used.

CAPEX per kW by rated power

Ex-factory· this figure
Installed
Fully financed

CAPEX at the battery limit—

Installation, civil works, engineeringproject level

Working capital, contingencyproject level

Included

Equipment as delivered by the manufacturer

Not included

Installation, piping and electrical works
Civil works, buildings and land
Engineering and construction
Contingency

Added at project level

Every installation and indirect cost layer, from the project settings
Contingency, from the project settings

Lifetime and replacements

Costs this asset carries that project mode does not apply.

Not passed to project mode

LCOH electrode replacement component is left out of project results: project mode only replaces the whole asset at the end of its lifetime. Add it by hand until it does.

Project figures

Values passed to project mode when this asset is added to a project.

Battolyser (nickel-iron battery-electrolyser)Concept sketch, not to scale · drag to rotate

Electricity (charging and electrolysis) in: —
Water (stoichiometric minimum) in: —
Hydrogen outMain product: —
Electricity discharged (battery mode) out: —
Oxygen (stoichiometric) out: —
CAPEX to the battery limit: —
Fixed O&M: —
Variable O&M, excluding feedstocks: —
Asset lifetime: 15 years
LCOH electrode replacement componentNot applied by project: —

Levelised cost of hydrogen

A standalone indicator for a quick read. Project mode recomputes it for the whole system.

—

LCOH capital component—
LCOH O&M component—
LCOH electrode replacement component—
LCOH electricity component—

Linked to the balance above

Electrolysis hours per year45.7 %

Storage duration

Usable battery energy divided by rated power. 5 h is the C/5 rate Barton 2020 tested; Barton gives a maximum charge rate below 1C (duration at least 1 h, enforced by the guard). The slider stops at 2-6 h: the Ni-Fe battery part dominates CAPEX, and shorter durations push the LCOH below the Observatory market band at favourable settings.

Battery cycles per year

Full charge-discharge cycles a year. 365 = one diurnal cycle a day (derived from Barton 2020's long-duration, diurnal role). Mulder 2017 shows more than 500 deep cycles over 18 months in the lab; 15 years at 365 cycles is about 5,500 cycles, far beyond anything demonstrated. Each cycle wears the electrodes and is paid through the replacement provision.

Electricity price

Average price paid for charging and electrolysis electricity. 51.11 EUR/MWh is the Observatory's wholesale average over the 4,000 cheapest hours (Spain, ENTSO-E 2023). The model buys power for 6,607 h at the defaults (charging plus electrolysis), more than those 4,000 hours, so the default leans low. Hourly arbitrage is not modelled: discharged electricity is not credited at a different price, it carries the same levelised cost as the hydrogen.

Electrode and electrolyte life

Equivalent deep cycles one set of electrodes and electrolyte lasts before replacement. No battolyser end of life has been measured. Mulder 2017 saw no loss after more than 500 deep cycles (slider floor; lower values are refused); Barton 2020 quotes 20-25 years for conventional Ni-Fe batteries (7,300 cycles = 20 years at one a day, slider top) but saw electrode damage under repeated overcharge. Default 2,000 = the geometric mean of 500 and 7,300 (1,910), rounded: a declared modelling assumption, evidence low.

Discount rate (real)

Cost of capital for the annuity. 6 % is the Observatory's default. All costs are constant, un-escalated euros, so the rate is applied as a real rate; at 0 % the annuity falls back to 1/lifetime.

Economic lifetime

Annuity horizon. 15 years is Jenkins 2022's analysis horizon, not a demonstrated durability: Mulder 2017 shows 18 months and more than 500 deep cycles in the lab. Electrode and electrolyte replacements within it are paid pro-rata from the electrode life input.

Levelised cost of hydrogen by electrolysis hours per year

All results

Every model output at the current settings, grouped, with the sensitivity charts.

65 outputs · 7 groups · 16 also shown above, dimmed

Levelised costs

Levelised cost of hydrogen: ComputingEUR/kg
Cost per MWh discharged (joint allocation): ComputingEUR/MWh
Levelised cost of battolyser output (LCOWB): ComputingEUR/MWh
LCOH capital component: ComputingEUR/kg
LCOH electricity component: ComputingEUR/kg
LCOH O&M component: ComputingEUR/kg
LCOH electrode replacement component: ComputingEUR/kg
Electrolysis-mode power cost per kg: ComputingEUR/kg
Charging cost per MWh discharged: ComputingEUR/MWh

Electrolysis mode

Specific energy (electrolysis mode): ComputingkWh/kg
Stack specific consumption: ComputingkWh/kg
Balance-of-plant penalty: Computing%
Implied electrolysis cell voltage: ComputingV
Electrolysis voltage above battery OCV: ComputingV
Specific energy vs Jenkins 58.8 kWh/kg: Computing%
Hydrogen system efficiency (HHV): Computing%
Hydrogen output at rated power: Computingkg/h
Hydrogen produced: Computingt/year
Hydrogen energy (HHV): ComputingMWh/year

Battery mode

Usable storage capacity: ComputingkWh
Charge rate (C-rate): Computing1/h
Electricity discharged: ComputingMWh/year
Electricity charged: ComputingMWh/year
Battery losses: ComputingMWh/year
Standby loss, low: ComputingkWh/day
Standby loss, high: ComputingkWh/day

Operating schedule

Charging hours: Computingh/year
Discharging hours: Computingh/year
Total operating hours: Computingh/year
Idle hours left in the year: Computingh/year
Device utilisation: Computing%
Electrolysis capacity factor: Computing%
Electricity into electrolysis: ComputingMWh/year
Total electricity bought: ComputingMWh/year
Useful output: ComputingMWh/year
Heat and losses: ComputingMWh/year
Hydrogen share of useful output: Computing%
Annual output efficiency (HHV): Computing%

Electrode wear

Electrolysis charge in battery capacities: Computing1/year
Charge throughput: Computing1/year
Charge per deep cycle in Mulder's test: Computingratio
Electrode wear: Computingcycles/year
Electrode set life at this duty: Computingyears
Electrode sets used over the life: Computingsets
Replacements paid over the life: Computingsets
Lifetime wear vs demonstrated cycles: Computingratio
Cost of one electrode and electrolyte set: ComputingEUR
Electrode and electrolyte replacement provision: ComputingEUR/year

CAPEX and O&M

CAPEX (equipment price level): ComputingEUR
CAPEX per kW: ComputingEUR/kW
Model CAPEX per kW: ComputingEUR/kW
CAPEX, battery part: ComputingEUR
CAPEX, electrolysis part: ComputingEUR
Battery share of CAPEX: Computing%
CAPEX per kWh of storage: ComputingEUR/kWh
Capital recovery factor: Computing1/year
Annualised CAPEX: ComputingEUR/year
Fixed O&M: ComputingEUR/year
Electricity cost: ComputingEUR/year
Total annual cost: ComputingEUR/year

Materials

Active nickel: Computingt
Active iron: Computingt
Cell volume at lab energy density: Computingm3
Oxygen co-produced: Computingt/year
Water consumed (minimum): Computingt/year

Sensitivities

4 charts

LCOH vs electricity price

LCOH vs electrolysis hours

LCOH vs storage duration

LCOH and electrode replacement vs battery cycles

Sources

80 documented assumptions · 13 sources

About

Calculator context

Screening techno-economics for a battolyser: one nickel-iron cell stack that works as a battery and, once full, as an alkaline electrolyser making hydrogen and oxygen from the same electrodes (concept of Mulder et al., TU Delft, 2017). The calculator gives the storage capacity and round-trip losses in battery mode, the hydrogen output and specific energy in electrolysis mode, the annual split of hours between the two modes, CAPEX, O&M, the electrode and electrolyte replacements, the levelised cost of hydrogen (LCOH) and the cost per MWh discharged under the same joint allocation.

STATUS: this is a pre-commercial technology with no current vendor offer. No company sells a battolyser today (Battolyser Systems merged into Alquion, whose Flexolyser is a flexible alkaline electrolyser with no battery function and no printed specs; this vendor status comes from the brief and was not re-verified). There is no datasheet and no vendor price: no vendor cost data exists. The physics comes from peer-reviewed lab cells: Mulder 2017 (10 Ah, 18 months) and Barton 2020 (3 Ah). Every cost is a declared approximation, evidence LOW: the battery part is a UK retail Ni-Fe battery price (Barton 2020), the electrolysis part a conventional alkaline electrolyser (IRENA 2020), the fixed O&M an electrolysis rate (IEA 2019) and the electrode replacement a declared share of the battery price.

Method. Battery mode: cycles x usable kWh discharged, divided by the round-trip efficiency for the energy charged. Electrolysis mode: specific energy = 39.37 kWh/kg HHV / (voltage efficiency x 100 % faradaic x 95 % balance of plant). The efficiencies are values of the reference case, not inputs: Barton 2020's tested 3 Ah cell, about 70 % round trip at C/5 and 70 % as an electrolyser at 2.11 V (59.2 kWh/kg). Barton prints that point at 83 mA/cm2; the model runs electrolysis at the rated power of C/5 charging, about 8 mA/cm2, so 70 % leans conservative. Barton's 'typically 50 %' is tied to no current (the cell falls below 40 % only near 10 A and 3 V, about 200 mA/cm2) and is not used. The faradaic efficiency (100 %) is Mulder's, not Barton's 87 %: the one value of the case that comes from another cell, declared as a modelling assumption. Jenkins prints 58.8 kWh/kg for an alkaline battolyser at 2.1 V (about 70 %) with the same construction (a check of construction, not a validation). Charge + discharge + electrolysis hours must fit in 8,760 h, or the inputs are refused. CAPEX = kWh x battery-part price + kW x electrolysis-part price, linear in size: the battolyser is scaled by numbering up identical modules (2.5 MW skids and 5 MW modules, company statement 2024), and the size slider is held to the 1-5 MW range its cells are designed for (RWE 2023). A Customized CAPEX per kW (EUR 2020, ex-works, 1,190.4-3,842.5 EUR/kW) replaces the model value at every size; the battery/electrolysis split, the electrode set and the O&M then follow the entered total. Electrode wear = the larger of the battery cycles and the charge throughput / 2 (Mulder's test passed more than 1,000 capacities of charge in more than 500 deep cycles); sets used over the life = lifetime x wear / electrode life, the replacements beyond the first set are paid pro-rata at 50 % of the battery-part CAPEX each (project mode does not replace them, so this line is what a project figure omits), with no lump at the end. The annual cost is CAPEX x CRF + fixed O&M + replacement provision + electricity (Hydrogen Observatory LCOH manual eq. 1, 8-14). It is divided by electricity discharged plus hydrogen HHV, adapted from Jenkins' LCOWB (eq. 7, where charging power is free and the wind farm sits in the capital; here power is bought and no generator is costed). The cost per MWh discharged is that LCOWB, a joint allocation and not Jenkins' eq. 5 LCOS; LCOH is the same cost per kg (x 39.37/1000).

Defaults: 1 MW, 5 h (5,000 kWh), 365 cycles, 4,000 electrolysis hours, 51.11 EUR/MWh (Observatory, Spain 2023), electrode life 2,000 equivalent cycles, 6 % real, 15 years. Reference case 'Barton 2020 (Loughborough, 3 Ah cell) on a common cost base': RTE 70 %, electrolysis 70 % HHV (2.11 V) and 494.5 EUR/kWh (GBP 440 retail at the ECB 2020 rate) from Barton; 420.2 EUR/kW electrolysis part (IRENA's USD 500-1,000/kW alkaline system mid-point minus its USD 270/kW stack, ECB 2020 rate) and O&M 1.5 % of CAPEX a year (IEA 2019) as the common cost base. Results: 67.6 t of H2 and 1,825 MWh discharged a year, 8,432 operating hours, 2,122 MWh/year of heat and losses, CAPEX 2,893 EUR/kW (85 % battery), electrode wear 442 equivalent cycles a year so a set lasts 4.5 years and 2.3 replacements are paid over 15 years (190,602 EUR/year), LCOWB = cost per MWh discharged = 193.9 EUR/MWh and LCOH 7.63 EUR/kg (capital 2.61, electricity 2.96, electrode replacement 1.67, O&M 0.38). The former default (Mulder's 80 % round trip with Barton's 70 % operating point) mixed two cells and gave 7.49 EUR/kg.

Bounds and domain. The LCOH bound 4.5-10.5 EUR/kg is the span of Total LCOH printed in the Hydrogen Observatory manual's conventional electrolysis use cases (4.51-10.23), transposed to a battolyser (evidence medium); specific energy is bounded 45-85 kWh/kg over 50-90 % efficiency, a domain statement from the model's own formula. Both hold on the nominal case and on every chart. Across the 192 valid corners of the input box the LCOH runs from about 3.0 to 29.0 EUR/kg with the model CAPEX, 24 % of them inside the band (2.8 to 53.4 EUR/kg with a Customized CAPEX): short storage, many electrolysis hours, cheap power, long-lived electrodes and cheap capital fall below it, and long storage with few cycles, few electrolysis hours, dear power and 500-cycle electrodes go far above it. The band was not widened to fit. The cost per MWh discharged has no market bound, since no accessible source prints a battolyser LCOS.

Limits a financier should know. The CAPEX is an equipment price level (IRENA's system figure excludes shipping, civil works and site preparation; installation, indirects and contingency are excluded; project mode adds them through battery_limit 'exfactory'). IRENA's 2020 figures are costs at the limit of zero profit, so a quoted price would be higher. Cost years: CAPEX EUR 2020, electricity EUR 2023, not indexed. The 51.11 EUR/MWh average covers the 4,000 cheapest hours while the model buys power for 6,607 h at the defaults, so the default price leans low. Not modelled: hourly dispatch and price arbitrage, efficiency drift between replacements, end-of-life cost or residual value (Jenkins' zero is for a lead-acid battolyser), self-discharge in the balance (1-2 %/day shown separately), Barton's lower 87 % faradaic efficiency (it would raise the specific energy by 15 %), water and oxygen values. 15 years at the default duty is about 6,600 equivalent deep cycles, 13 times the 500+ shown in the lab: the electrode life is the least grounded number in the calculator. The linear CAPEX law is prudent rather than neutral: IRENA 2020 (p.71, after Bohm et al. 2020) gives a cost exponent of 0.6-0.75 for a conventional electrolyser balance of plant, about 15 % of this CAPEX. Barton's battery price is a retail price, distribution margin included, so it leans high. The 70 % round trip was measured at C/5 (5 h) and is applied unchanged over the 2-6 h slider: at 2 h (C/2) it is optimistic, as Ni-Fe losses rise with current.

Model

148 variables — inputs, calculations and outputs, with their dependencies.

148 variables shown of 148

Value	Unit	Depends on
1000	kW	—
5	h	—
365	cycles/year	—
4000	h/year	—
51.11	EUR/MWh	—
2000	cycles	—
0	—	—
2892.7	EUR/kW	—
6	%	—
15	years	—

Variable	Formula	Unit	Depends on
	`if((<=0)+(<)+(<0)+(<=0)+(<0)+(<)+(<0)+(>)+(<)+(*(+/max(,))+>)+(>=)((<)+(>))>0,1,0)`	bool
	`*`	ratio
	`*`	ratio
	`*`	ratio
	`*`	ratio
	`*`	ratio
	`/max(,)`	ratio
	`*/max(,)`	kg/year
	`(/)^(-)`	ratio
	`/max(+,)`	ratio

Variable	Formula	Unit	Depends on
	`*`	kWh
	`/max(,)`	1/h
	`*/`	MWh/year
	`/max(,)`	MWh/year
	`-`	MWh/year
	`/max(,)`	EUR/MWh
	`*/max(,)`	h/year
	`*/max(,)`	h/year
	`++`	h/year
	`-`	h/year
	`/*`	%
	`/*`	%
	`/max(,)`	V
	`-`	V
	`**/max(,)`	1/year
	`+`	1/year
	`/`	ratio
	`max(,/max(,))`	cycles/year
	`/max(,)`	years
	`*/max(,)`	sets
	`max(-,)`	sets
	`*/`	ratio
	`/max(*,)`	kWh/kg
	`(-)*`	%
	`*`	kWh/kg
	`(/-)*`	%
	`/max(,)*`	%
	`*/`	MWh/year
	`/max(,)`	kg/h
	`/`	t/year
	`*/`	MWh/year
	`*`	t/year
	`*`	t/year
	`+`	MWh/year
	`+`	MWh/year
	`-`	MWh/year
	`/max(,)*`	%
	`/max(,)*`	%
	`*/`	t
	`*/`	t
	`*//`	m3
	`**`	kWh/day
	`**`	kWh/day
	`if(<,/,(*(+)^)/max((+)^-,))`	1/year
	`clamp((+),,)`	EUR/kW
	`if(>=,,)`	EUR/kW
	`*`	EUR
	`*`	EUR
	`-`	EUR
	`**`	EUR
	`*/max(,)`	EUR/year
	`/max(,)*`	%
	`/max(,)`	EUR/kWh
	`*`	EUR/year
	`**`	EUR/year
	`*`	EUR/year
	`+++`	EUR/year
	`/max(,)`	EUR/MWh
		EUR/MWh
	`*/`	EUR/kg
	`/max(,)*/`	EUR/kg
	`/max(,)*/`	EUR/kg
	`/max(,)*/`	EUR/kg
	`/max(,)*/`	EUR/kg
	`*/`	EUR/kg

Assumptions

80 assumptions used in the calculations

Protects divisions; far below any physical value of the model.
Market range Not applicable.
0
OpenJack DSL convention
Unit multiplier used in the CRF, the BOP divisor and the guards.
Market range Exact by definition.
1
Numerical constant
Turns a percent input (0-100) into a fraction.
Market range Exact conversion, no range.
0.011/%
Unit conversion
Turns a fraction into a percent for display, and caps the discount rate guard at 100 %.
Market range Exact conversion factor.
100%
Unit conversion
Length of the year used by the time-budget check (charge + discharge + electrolysis hours).
Market range Exact convention.
8760h/year
Calendar convention
Converts MWh to kWh.
Market range Exact conversion factor.
1000kWh/MWh
Unit conversion
Converts kWh of storage to Wh for the volume estimate.
Market range Exact conversion factor.
1000Wh/kWh
Unit conversion
Converts litres to cubic metres.
Market range Exact conversion factor.
1000L/m3
Unit conversion
Converts kilograms to tonnes.
Market range Exact conversion factor.
1000kg/t
Unit conversion
Energy content used for the specific energy, the H2 thermal output and the LCOH = LCOWB x HHV conversion.
Market range No independent range cited; HHV basis throughout the calculator.
39.37kWh/kg
Jenkins et al. 2022, p.13
Voltage at which electrolysis efficiency is 100 % on an HHV basis; the implied cell voltage is 1.48 V divided by the voltage efficiency.
Market range No independent range cited; thermodynamic value.
1.48V
Mulder et al. 2017
Fully charged battery potential; the electrolysis cell voltage is shown as a margin above it.
Market range No independent range cited.
1.37V
Mulder et al. 2017
Charge-to-gas yield; multiplies the voltage efficiency in the stack specific consumption.
Market range 87 % (Barton 2020) to 100 % (Mulder 2017).
100%
Mulder et al. 2017 (Barton 2020 divergent)
Lower end of the lab overall efficiency; reference only, shown for comparison with the annual output efficiency.
Market range
80%
Mulder et al. 2017
Upper end of the lab overall efficiency; reference only.
Market range
90%
Mulder et al. 2017
Mulder's lab round trip, kept for reference only: the model uses Barton's 70 % (battery_rte_pct) so that the reference case comes from one cell.
Market range 70 % (Barton 2020, C/5) to 83 % (Mulder 2017, lab).
80%
Mulder et al. 2017
Upper limit of the battery round-trip efficiency.
Market range
83%
Mulder et al. 2017
Barton's C/5 round trip: the value the model uses (battery_rte_pct).
Market range
70%
Barton et al. 2020
Lower limit of the input guard: below it the round-trip efficiency is outside anything published for Ni-Fe.
Market range
50%
Barton et al. 2020
Reference only: conventional Ni-Fe upper end.
Market range
80%
Barton et al. 2020
Lower end of the standby loss shown for a full battery; not part of the annual balance.
Market range
1%/day
Barton et al. 2020
Upper end of the standby loss shown for a full battery; not part of the annual balance.
Market range
2%/day
Barton et al. 2020
Barton's 70 % operating point (2.11 V, 83 mA/cm2): the value the model uses (elec_efficiency_hhv_pct), since the modelled current density sits below it.
Market range 50 % (Barton typical) to 90 % (Mulder max).
70%
Barton et al. 2020
Mulder's lab maximum: top of the specific-energy bound (45 kWh/kg); reference only, the efficiency is no longer an input.
Market range
90%
Mulder et al. 2017
Reference only: lab efficiency at the highest tested current density.
Market range
80%
Mulder et al. 2017
Barton's typical electrolysis efficiency, tied to no current density: reference only and the low end of the specific-energy bound. The model uses the 70 % point (elec_efficiency_hhv_pct).
Market range
50%
Barton et al. 2020
Reference cell voltage; the implied cell voltage of the model is compared with it.
Market range No independent range cited.
2.1V
Jenkins et al. 2022, p.13
Balance-of-plant divisor on the stack specific consumption (the load penalty of the electrolysis mode).
Market range No independent range cited.
95%
Jenkins et al. 2022, p.13
Reference specific energy; the model's deviation from it is shown.
Market range
58.8kWh/kg
Jenkins et al. 2022, p.13
Default storage duration (C/5).
Market range Duration of at least 1 h (charge rate below 1C).
5h
Barton et al. 2020
Input guard: a duration below 1 h would mean charging faster than 1C.
Market range No independent range cited.
1h
Barton et al. 2020
Default number of full battery cycles a year.
Market range No independent range cited.
365cycles/year
Derived from Barton et al. 2020
Default electrolysis hours a year.
Market range No independent range cited.
4000h/year
Hydrogen Observatory manual, Table 4
Source of the default battery capital cost, before conversion to EUR.
Market range No independent range cited.
440GBP/kWh
Barton et al. 2020
Converts Barton's 2020 GBP battery price to EUR 2020: 440 / 0.8897 = 494.5 EUR/kWh.
Market range Exact published average.
0.8897GBP/EUR
ECB SDW, EXR.A.GBP.EUR.SP00.A
Converts IRENA's 2020 USD electrolyser costs to EUR 2020, the same year as the battery part.
Market range Exact published average.
1.1422USD/EUR
ECB SDW, EXR.A.USD.EUR.SP00.A
Low end of the entire alkaline system cost; minus the stack it gives the low end of the electrolysis-part cost used in the Customized CAPEX lower bound.
Market range USD 500-1 000/kW (IRENA 2020, > 10 MW).
500USD/kW
IRENA 2020, Table ES1
High end of the entire alkaline system cost; taken whole (stack included) it gives the high end used in the Customized CAPEX upper bound.
Market range USD 500-1 000/kW (IRENA 2020, > 10 MW).
1000USD/kW
IRENA 2020, Table ES1
Removed from the system cost because the battolyser's Ni-Fe electrodes are its stack and are already costed in the battery part (Barton 2020: the battery price as an electrolyser stack excludes gas collection and compression).
Market range No independent range cited.
270USD/kW
IRENA 2020, Table ES1
Low end of the electrolysis-part cost (balance of plant only, the stack being the battery electrodes); enters the lower bound of the Customized CAPEX (494.5 x 2 h + 201.4 = 1,190.4 EUR/kW).
Market range
201.4EUR/kW
Derived from IRENA 2020 and ECB
High end of the electrolysis-part cost (the whole alkaline system, none of the stack in the battery price); enters the upper bound of the Customized CAPEX (494.5 x 6 h + 875.5 = 3,842.5 EUR/kW).
Market range
875.5EUR/kW
Derived from IRENA 2020 and ECB
Source of the model's fixed O&M rate. The IEA figure is used rather than NREL's because NREL's 2.5 % is meant to cover capacity additions or replacements, which this calculator costs in its own electrode replacement line.
Market range 1.5 %/year (IEA 2019, electrolysis) to 2.5 %/year (NREL 2021, 4-hour battery incl. augmentation).
1.5%/year
IEA 2019 assumptions annex
Cost of one electrode and electrolyte set as a share of the battery-part CAPEX: electrodes and KOH electrolyte are replaced, cell casings, terminals, racking and the electrolysis-part balance of plant are kept.
Market range No independent range cited.
50%
OpenJack modelling assumption
Floor of the electrode life slider (lower values are refused) and the denominator of the lifetime-wear ratio.
Market range No independent range cited.
500cycles
Mulder et al. 2017
Charge throughput of Mulder's test; divided by its 500 cycles it converts a charge throughput into equivalent deep cycles of wear.
Market range No independent range cited.
1000capacities
Mulder et al. 2017
Sets the top of the electrode life slider: 20 years x 365 cycles = 7,300 equivalent cycles.
Market range
20years
Barton et al. 2020
Floor of the replacement count and of the O&M guard.
Market range Not applicable.
0
OpenJack DSL convention
Active nickel per kWh of storage.
Market range No independent range cited.
1.825kg/kWh
Mulder et al. 2017
Active iron per kWh of storage.
Market range No independent range cited.
0.868kg/kWh
Mulder et al. 2017
Energy density used for the indicative cell volume.
Market range 100 Wh/L now, 130-250 Wh/L practical limit (Mulder).
100Wh/L
Mulder et al. 2017
Oxygen co-produced per kg of hydrogen.
Market range Exact stoichiometry.
7.936kg/kg
IUPAC atomic weights
Water consumed by electrolysis per kg of hydrogen (minimum, before purification reject).
Market range Exact stoichiometric minimum.
8.936kg/kg
IUPAC atomic weights
Reference size of the CAPEX scaling law, at the bottom of the 1-5 MW design range (RWE press release 2023).
Market range Not applicable.
1000kW
OpenJack modelling choice
Exponent of the CAPEX scaling law, kept at 1: the battolyser is modular, scaled by module count (2.5 MW skids, 5 MW modules), and the Ni-Fe cells that carry about 85 % of the CAPEX are priced per kWh with no published size effect. The balance of plant could scale at 0.6-0.75 (IRENA 2020 after Bohm et al.), so the linear law is prudent on that 15 % (it may overstate the CAPEX at 5 MW), not neutral. The size slider is held to 1-5 MW, the range the cells are designed for.
Market range 1 (modular numbering-up); 0.6-0.75 for a conventional electrolyser balance of plant (IRENA 2020 p.71).
1
OpenJack modelling choice
Lower guard of the specific CAPEX clamp; never binds inside the declared domain (checked at the box corners).
Market range Not applicable.
100EUR/kW
OpenJack DSL convention
Upper guard of the specific CAPEX clamp; never binds inside the declared domain (checked at the box corners).
Market range Not applicable.
20000EUR/kW
OpenJack DSL convention
Default of the electricity price input, for both charging and electrolysis.
Market range No independent range cited; the slider runs 30-120 EUR/MWh as a sensitivity.
51.11EUR/MWh
Hydrogen Observatory manual, Table 7
Model value of the battery round-trip efficiency (reference case Barton 2020, tested 3 Ah cell). No longer an input: the reference case sets it.
Market range
70%
Barton et al. 2020
Model value of the electrolysis efficiency, HHV (reference case Barton 2020, tested 3 Ah cell, at the 2.11 V point printed by Barton). Its use at the model's lower current density is derived (evidence medium), not read. No longer an input: the reference case sets it. At Barton's typical 50 % (2.96 V, a high-current regime the cell does not reach at rated power) the LCOH would be 8.71 EUR/kg instead of 7.63.
Market range 50 % (Barton typical) to 90 % (Mulder lab maximum).
70%
Barton et al. 2020
REFERENCE CASE. 'Barton 2020 (Loughborough, 3 Ah cell) on a common cost base': round trip 70 %, electrolysis 70 % HHV (2.11 V) and the battery-part price (GBP 440/kWh = 494.5 EUR/kWh) come from Barton 2020, measured on one cell, except the faradaic efficiency (Mulder's 100 % rather than Barton's measured 87 %, declared as a modelling assumption); the electrolysis part (IRENA 2020, 420.2 EUR/kW) and the fixed O&M (IEA 2019, 1.5 %/year) are not in Barton and form a common cost base, named as such. It replaces the former default (RTE 80 % from Mulder, electrolysis 70 % from Barton's 2.11 V point, Barton's price), itself a mix of two cells: the nominal LCOH moves from 7.49 to 7.63 EUR/kg. Barton's price is a UK retail price of conventional Ni-Fe batteries, distribution margin included, so it leans high. battery_limit stays 'exfactory': Barton's is a purchase price before installation and IRENA's system cost excludes shipping, civil works and site preparation.
Market range Not applicable.
—
Barton 2020 + common cost base (IRENA 2020, IEA 2019)
Default 0: the model value (Barton 2020 on a common cost base).
Market range Not applicable.
—
OpenJack
Customized CAPEX per kW of rated power, EUR 2020, equipment price level (ex-works). Applied as entered at every size, with no scale law. The battery/electrolysis split, the electrode set and the fixed O&M follow it.
Market range 1,190.4-3,842.5 EUR/kW (see the two bound entries).
2,892.7EUR/kW
User input
Lower bound of the Customized CAPEX, identical in the guard, the slider and the help.
Market range Not applicable.
1,190.4EUR/kW
Derived from Barton 2020 + IRENA 2020
Upper bound of the Customized CAPEX, identical in the guard, the slider and the help.
Market range Not applicable.
3,842.5EUR/kW
Derived from Barton 2020 + IRENA 2020
Model value of the battery-part capital cost (reference case Barton 2020): equipment purchase price, EUR 2020; installation, indirects and contingency excluded. No longer an input: a different price goes through the Customized CAPEX.
Market range No independent range cited.
494.5EUR/kWh
Derived from Barton et al. 2020 and ECB
Model value of the electrolysis-part CAPEX (common cost base): rectifier, gas treatment and drying, water purification, cooling and commissioning of a conventional alkaline system, without the stack (the Ni-Fe electrodes, costed in the battery part). No longer an input.
Market range
420.2EUR/kW
Derived from IRENA 2020 and ECB
Model value of the fixed O&M (common cost base), applied to the CAPEX used, model or Customized; purchased electricity and electrode replacement are separate lines. No longer an input.
Market range 1.5 %/year (IEA 2019) to 2.5 %/year (NREL 2021, 4-hour battery incl. augmentation).
1.5%/year
IEA 2019 assumptions annex
Default electrode and electrolyte life in equivalent deep cycles; drives the number of replacements paid over the economic life.
Market range 500 (Mulder, demonstrated floor) to 7,300 (Barton, conventional Ni-Fe).
2000cycles
OpenJack modelling assumption on Mulder 2017 and Barton 2020
Default discount rate of the annuity.
Market range No independent range cited; slider 0-10 %.
6%
Hydrogen Observatory manual, Table 4
Default annuity horizon.
Market range No independent range cited; slider 10-20 years.
15years
Jenkins et al. 2022
STATUS. Pre-commercial technology with no current vendor offer. As of October 2026 no vendor sells a battolyser: there is no datasheet, no vendor price, and no vendor cost data exists. Battolyser Systems merged into Alquion, whose only product, the Flexolyser, is a flexible alkaline electrolyser with no battery function and no printed specifications (vendor status taken from the commissioning brief, not re-verified here). The physics comes from lab cells (Mulder 2017, 10 Ah, 18 months; Barton 2020, 3 Ah). The costs are declared approximations: a retail Ni-Fe battery price (Barton 2020), a conventional alkaline electrolyser (IRENA 2020), an electrolysis O&M rate (IEA 2019) and a declared electrode replacement share.
Market range Not applicable.
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Literature review
DEVICE. One Ni-Fe cell in KOH with a Zirfon diaphragm. Charging converts Fe(OH)2 to Fe and Ni(OH)2 to NiOOH; once charged, the same electrodes evolve H2 and O2. Efficiencies follow Mulder's definitions (eq. 5-7): battery efficiency = energy discharged / energy in; electrolysis efficiency = 1.48 V x charge to gas / energy in, i.e. 1.48 V divided by the cell voltage.
Market range Not applicable.
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Mulder et al. 2017
SCHEDULE. Annual steady state, no hourly dispatch. Battery mode: cycles x usable kWh discharged, divided by the round-trip efficiency for the energy charged, both at rated power. Electrolysis mode: rated power x electrolysis hours. Charge + discharge + electrolysis hours must fit in 8,760 h; above it the inputs are refused. At the defaults the year holds 8,432 h.
Market range Not applicable.
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OpenJack model
ALLOCATION. Adapted from Jenkins 2022 eq. 7 (LCOWB): one levelised cost per MWh of useful output, electricity discharged plus hydrogen HHV. Two departures from Jenkins: eq. 7 leaves the charging electricity out (free energy from the wind farm) and puts the wind farm in the capital cost; here bought electricity is in the annual cost and no generator capital is. The cost per MWh discharged equals this LCOWB: it is a joint allocation, not Jenkins' LCOS (eq. 5 divides by electricity discharged only) and not a stand-alone battery LCOS. LCOH = LCOWB x 39.37/1000 per kg. End-of-life cost and residual value are not modelled (0): Jenkins sets end of life to 0 because it assumes a lead-acid battolyser feeding the lead-acid recycling chain, which is not established for Ni-Fe. The annual cost is CRF x CAPEX + fixed O&M + electrode replacement provision + electricity, the structure of the Hydrogen Observatory LCOH manual eq. 1, 8-14 (other OPEX and stack replacement as a share of CAPEX), with replacements paid pro-rata rather than as the manual's rounded-down count.
Market range Not applicable.
—
Adapted from Jenkins 2022 + Hydrogen Observatory
REPLACEMENT. Electrode wear per year = the larger of the battery cycles and the charge throughput divided by 2, the capacities of charge per deep cycle in Mulder's test (1000/500). Electrolysis charge counts in battery capacities as hours x C-rate x 1.37 V / cell voltage (current at rated power = power / cell voltage; capacity in Ah taken at the 1.37 V OCV). Sets used over the life = lifetime x wear / electrode life; the first set is in the CAPEX and the rest are paid pro-rata, the last one only for the part used, with no lump at the end of life. One set costs 50 % of the battery-part CAPEX (declared), itself the model's battery share of the CAPEX used. The provision is the replacements used x set cost / lifetime, a constant EUR 2020 cash amount per year, never discounted, so it does not move with the discount rate. Project mode does not replace the set (it replaces only the whole asset), so this line is what a project figure omits. At the defaults: 442 equivalent cycles a year, a set lasts 4.5 years, 2.3 replacements, 190,602 EUR/year. It rises with battery cycles and electrolysis hours: over the cycles slider (200 to 365 at the defaults) it goes from 139,607 to 190,602 EUR/year, 1.50 to 1.67 EUR/kg. The total LCOH still falls there (8.16 to 7.63 EUR/kg) because each extra cycle spreads the capital over more output, but less than with no replacement (6.66 to 5.96 in the 7,300-cycle case); with 500-cycle electrodes and 1,000 electrolysis hours the wear wins and it rises slightly (20.75 to 21.28).
Market range Not applicable.
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OpenJack model on Mulder 2017, Barton 2020 and the Hydrogen Observatory structure
CAPEX BOUNDARY. The CAPEX is an equipment price level: retail Ni-Fe battery price (Barton 2020) plus the alkaline electrolysis balance of plant (IRENA 2020 system cost minus stack). IRENA's system figure excludes shipping, civil works and site preparation, and the retail battery price excludes installation; indirects, owner's costs and contingency are in neither. costs.capex.battery_limit is therefore 'exfactory' and project mode adds its cost layers and contingency. A bidirectional converter for battery discharge is not costed separately; IRENA's rectifier stands in for the power electronics. The calculator's own LCOH carries no uplift, so it is a screening figure that project mode will raise. Electrode replacements are not in the CAPEX: they are a separate annual provision. A Customized CAPEX must sit at the same level and in EUR 2020: Barton's figure is a retail price (distribution margin included, so it leans high), and a quote at another year or an installed price would be escalated and marked up a second time by project mode.
Market range Not applicable.
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Barton 2020 + IRENA 2020
COST YEAR. CAPEX in EUR 2020: battery part from Barton's 2020 GBP at the ECB 2020 rate, electrolysis part from IRENA's 2020 USD at the ECB 2020 rate; fixed O&M and the replacement set are shares of that CAPEX. Electricity is EUR 2023 (Observatory, ENTSO-E 2023), not indexed. The meta declares 2020, and a Customized CAPEX must be entered in EUR 2020 ex-works for the same reason. No escalation applies to any line, so the discount rate is used as a real rate.
Market range Not applicable.
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ECB + Observatory
LIMITS. Not modelled: hourly prices and arbitrage (discharged electricity is not credited at a different price), efficiency drift between electrode replacements, end-of-life cost or residual value (Jenkins' zero is for a lead-acid battolyser), self-discharge in the balance (shown as a standby figure), Barton's 87 % faradaic efficiency (Mulder's 100 % kept), water and oxygen values, grid fees, and land. The default price is the 4,000-cheapest-hours average while the model buys power for 6,607 h, so it leans low. Lifetime 15 years at the default duty means about 6,600 equivalent deep cycles, 13 times the 500+ shown in the lab: the electrode life input is the least grounded number and the replacement provision follows it. Size is held to 1-5 MW, the range the cells are designed for (RWE 2023); the CAPEX is linear in size (modular numbering-up), while IRENA 2020 (p.71, after Bohm et al. 2020) gives 0.6-0.75 for a conventional electrolyser balance of plant, so at 5 MW the electrolysis part may be overstated. The 70 % round trip was measured at C/5 (5 h) and is applied unchanged over the 2-6 h slider: at 2 h (C/2) it is optimistic, as Ni-Fe losses rise with current.
Market range Not applicable.
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OpenJack model
BOUNDS. LCOH bound 4.5-10.5 EUR/kg = lowest (4.51) and highest (10.23) Total LCOH printed in the Hydrogen Observatory manual use cases with default 2024 data (p.37, 40), conventional low-temperature electrolysis transposed to a battolyser: evidence medium. The reference case (Barton 2020 cell, 7.63 EUR/kg) sits inside it, just above its mid-point. Specific energy bound 45-85 kWh/kg = 39.37/(efficiency x 0.95) over 90 % to 50 %: a domain statement from the model's own formula, not an external check. Both hold on the nominal case and on every charted sweep; the reference case leaves the band above about 100 EUR/MWh or below about 1,050 electrolysis hours, and the charts (price 40-75 EUR/MWh, hours 2,000-4,300 h) stay well inside it. They do not hold across the whole input box, and the bound was not widened to fit: over its 192 valid corners with the model CAPEX the LCOH runs from about 3.0 to 29.0 EUR/kg and 24 % of corners sit inside the band (2.8 to 53.4 EUR/kg over the 384 valid corners with a Customized CAPEX). The cheap end combines 2 h, 365 cycles, 6,000 electrolysis hours, 30 EUR/MWh, 7,300-cycle electrodes, 0 % and 20 years; the dear end combines 6 h, 200 cycles, 1,000 electrolysis hours, 120 EUR/MWh, 500-cycle electrodes, 10 % and 10 years. The cost per MWh discharged has no market bound: no accessible source prints a Ni-Fe battolyser LCOS.
Market range Not applicable.
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Hydrogen Observatory manual + model
CHAINING. Electricity appears on both sides of this asset. The inlet 'Electricity (charging and electrolysis)' (annual_electricity_input_mwh / 8760) takes upstream generation, PV, wind or a grid supply, and pays for both battery charging and electrolysis. The outlet 'Electricity discharged (battery mode)' (annual_discharged_mwh / 8760) may feed a downstream electricity load, or stay unlinked as a by-product. The two are never netted against each other: never link the discharged outlet back to this asset's own inlet, nor to the upstream source that charges it, or the netting cancels charge against discharge and the levelised cost loses its meaning. Hydrogen, the main product, is linked downstream on its own.
Market range Not applicable (chaining rule).
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Chaining doctrine written 2026-10-04 for the battolyser, following the same-commodity converter rule of calcs 303 and 431.