Heiwit guides, calculators and tutorials

Tools and calculators

Calculators and games for comparing batteries and system choices using the figures from the datasheets. They run in your browser, with no registration.

• LCOS calculator: the real cost of every kWhCalculator

  Compare two batteries on the kWh delivered over their whole life and on the cost per kWh delivered. Editable sodium and lithium profiles.

• LCOS: the guide to the calculatorGuide

  Why the price per kWh is misleading, the formula using the four figures from the datasheet, and the sodium-lithium comparison.

• How to really compare battery pricesCalculator

  Cost per cycled kWh calculator: price, capacity, DoD, cycles and residual capacity compared with the Heiwit battery.

• Which battery is better value? The gameGame

  Three challenges between two 10 kWh batteries: cycles, depth of discharge and efficiency turn the price tag upside down.

• Retrofit or replacement? The gameGame

  Three existing systems and three different answers: a kit on the AC line, a new inverter or no work at all.

Choosing and sizing battery storage

Where to start when choosing a battery, pairing it with the inverter and working out whether a retrofit makes sense.

• Salt batteries for solar PV: the reference guideGuide

  What they are, how long they last according to field data, certifications, what determines the price and a comparison with lithium.

• The Heiwit sodium-ion rangeGuide

  10 kWh 48 V modules, up to three in parallel, Virgo and Lybra inverters, sodium-ion versus LFP, and FAQs.

• Heiwit battery: features, models and applications

  The 10 kWh module and configurations for homes, businesses and stationary storage.

• Compatible inverters: how to choose the configurationChecklist

  What to check before installing the battery, including on an existing system.

• Why Heiwit batteries only work with Heiwit inverters

  Charging profiles, protections and communication with the BMS: the full technical explanation.

• Retrofitting a battery to existing systemsGuide

  When a kit connected to the AC line is enough and when it is better to replace the inverter.

• Size and weight of storage batteriesComparison

  Eight home batteries on the same scale, with dimensions and weights taken from the datasheets.

• Industrial BESS: duration and safety before density

  What matters in energy storage for businesses and who benefits most.

• AI-Care smart quotation tool

  From your actual bill and roof to a solar PV design simulated on real data.

Costs, value and incentives

What stored energy really costs, when a battery pays for itself and which incentives are available today.

• Incentives for solar PV battery storage in 2026Guide

  IRPEF tax deduction, Transizione 5.0 for businesses, and the schemes that have closed or do not cover the battery, checked against official sources.

• Batteries for solar PV: are they really worth it?

  The two-minute calculation based on self-consumption, not on the list price.

• Do sodium batteries cost more than lithium ones?

  The right comparison is not on the list price but on the cost of stored energy.

• Cycle life: why it matters more than kWh

  Two storage systems with the same kWh can be worth different amounts: DoD, cycles and residual capacity.

Technology: how sodium batteries work

Chemistry, cells and BMS clearly explained, from the basics to the second polyanionic generation.

• How a sodium-ion battery worksGuide

  Anode and cathode chemistry, cell structure and the role of the BMS.

• Sodium-ion batteries: what they are and how they compare with lithium

  The basics: advantages, limitations and differences in safety, lifespan and cost.

• Complete technical guide: chemistries comparedGuide

  Sodium technologies, Heiwit layered oxide cells and the differences compared with lithium.

• Layered oxides in home battery storage

  Power, lifespan and use in the cold: a practical guide to choosing home battery storage.

• NFPP polyanionic cells: the second generationGuide

  NFPP cathode and layered oxides compared: rated cycles, performance at −20 °C and safety tests.

• The new Heiwit battery: 9,000 cycles at 95% DoD and 70% residual capacity

  What it means, under what conditions and when it will be available.

• Energy density versus lifespan

  Why Wh/kg matter little in stationary storage and which parameters to look at instead.

• High currents: how they cope with real-world stress

  Cold, deep cycles and high currents: how a storage system behaves outside ideal conditions.

• How much raw material sodium batteries need

  The scientific calculation on raw materials, explained simply.

• Sodium batteries and the supply chain

  Supply chain risks, water impact and price volatility in solar PV battery storage.

• Sodium-ion battery glossaryGlossary

  35 terms in one or two sentences: NFPP, BMS, SoC, DoD, cycle life, MPPT, CEI 0-21.

Safety, lifespan and field data

Cell tests, cycles measured across the installed base and real data from installed systems.

• Safety of sodium cells: what the tests showTests

  Nail penetration, overcharge, crush, oven and thermal control at 300 °C.

• Is sodium safer than lithium? What the research says

  Thermal runaway, thermal stability and behaviour under extreme conditions.

• Battery safety: what happens when they heat up

  What thermal runaway is and how to assess whether a battery storage system is safe.

• Real safety, not just promises

  How sodium chemistry behaves under critical conditions.

• NFPP cells in the cold: 95% capacity at −20 °CTests

  Cold qualification tests, with a comparison against a reference LFP cell.

• How long do Heiwit batteries last? Real cycles across the fleetData

  Over 6,500 cycles (NA-48V210Ah, layered oxide cells) in the endurance test, and the cycles accumulated by the installed fleet.

• 20,000 cycles reached by the battery fleetData

  The installed fleet's milestone and what it says about service life.

• Self-discharge: only 6% lost in 539 daysData

  Measured on real batteries at room temperature.

• High self-consumption: data from an Italian fleet of systemsStudy

  Observational study: self-consumption levels, methodology and limitations.

• 92% of solar potential put to useData

  AI-Care data from hundreds of systems with a Heiwit battery.

Regulations and certifications

What the standards say and which certificates Heiwit batteries and inverters hold.

• Battery CE marking, document by document

  CEI 0-21, Low Voltage, EMC and TÜV SÜD tests.

• Temperature range: charging, discharging and TÜV SÜD tests

  Discharging from −25 to +60 °C, charging from 0 to +60 °C: what the document says.

• RED III Directive: what changes

  Targets, timelines and what changes for renewables, energy storage and self-consumption.

• Solar PV and regulations: the laws you need to know

  Permits, landscape restrictions, grid connection and obligations.

• Energy-intensive companies: what they are and what obligations they have

  Sectors, definition and obligations in Italy and the European Union.

PDF documents

• TÜV SÜD CEI 0-21 certification for Virgo inverters and battery, document D 132944 0003
• TÜV Rheinland CEI 0-21 certification for Lybra inverters and battery, certificate A3 50741827 0001
• TÜV SÜD VDE-AR-N 4105:2018 certificate for Virgo inverters (Germany)
• VDE-AR-N 4105:2018 certificate for the grid and system protection integrated into Virgo inverters
• CEI 0-21 certification for the NA-48V210Ah battery

AI-Care and energy management

Monitoring, self-consumption optimisation and selling energy when it is worth most.

• SoP, State of Panels: the panel health indexGuide

  How AI-Care measures module output against its reference under the same sun and temperature: filtering out inverter curtailment, year-on-year comparison and three checks on strings, shading and voltage.

• AI-Care, Smart Energy Manager

  The AI-powered monitoring and optimisation platform.

• AI-Care: smart monitoring

  It interprets system data and flags anomalies to the installer and the customer.

• Energy Manager AI: selling energy when it is worth most

  Using, storing or exporting energy according to the hourly price.

• How AI-Care optimises self-consumption

  Artificial intelligence and solar PV: how it works.

• AI storage and GSE revenue

  How an AI-managed battery storage system can increase revenue.

• Distributed BESS: daytime sun becomes useful energy in the evening

  The Heiwit distributed energy storage model.

Tutorials and support

Step-by-step procedures for inverters, the app and data, and the explanations our support team gives most often.

• Reconnecting the inverter Wi-Fi after changing your router or passwordVideo

  Step-by-step guide with video, from the Bluetooth connection to the 2.4 GHz network.

• Accessing your inverter data via API (Data Act)Tutorial

  Tokens, available data, limits and examples with Home Assistant, Excel and Python.

• Why the state of charge (SoC) percentage sometimes jumps

  How the BMS estimates the state of charge and why it also happens with lithium batteries.

Technical documentation

Product pages with specifications and FAQs, datasheets and manuals in PDF with selectable text.

• Sodium-ion batteryProduct page

  Product page with specifications, datasheet, manual and TÜV certification.

• Virgo single-phase hybrid inverterProduct page

  Specifications, FAQs, datasheet, manual and CEI 0-21 and VDE-AR-N 4105 certificates.

• Lybra three-phase hybrid inverterProduct page

  Specifications, FAQs, datasheet and TÜV Rheinland CEI 0-21 certificate.

PDF documents

• NA-48V210Ah battery datasheet, July 2026
• NA-48V210Ah battery manual
• Virgo 3K-S, 4K6-S and 6K-S inverter datasheet
• Virgo 6K-S inverter user manual
• Lybra 6K-T, 10K-T and 12K-T inverter datasheet
• Heiwit brochure

For installers

How to join the network, the badge to display and the course materials.

• How to become a Heiwit certified installerGuide

  The four steps, the free course of around two hours and answers to new partners' questions.

• Certified installer badge

  The badge to add to your website, with ready-to-paste code.

• Installer course, 30 September 2026Video

  Course recording and slides.

• Installer course, 18 November 2025Video

  Recording and slides of the course on the residential battery.

• Webinar, 28 January 2026Video

  Recording and presentation of the product webinar.

• Installer Portal

  Restricted area with price list and documentation.

Solar PV: the basics

Articles from 2024 written for businesses, still useful today for getting to grips with panels, roofs and costs.

• What a solar panel looks like and how it works

  Cells, layers, the photovoltaic effect and the real output of a module.

• Guide to solar panel types

  Monocrystalline, polycrystalline, thin film: how to choose.

• Roof requirements for solar panels

  Surface area, orientation, structural load capacity and condition of the roof.

• Sizing a solar PV system: calculating the output

  Output based on consumption, available area and self-consumption profile.

• Installation on a business roof: the guide

  Site survey, design, permits, grid connection and realistic timescales.

• How much does a photovoltaic system cost per year

  Maintenance, insurance and monitoring compared with the savings.

• Maintaining a system on a business roof

  What it involves, how often it should be done and how much it affects costs.

• Photovoltaic system: 5 myths to dispel

  Real-world yield, land use, maintenance, disposal and cost-effectiveness.

• How much can you save with photovoltaics?

  How to calculate a business's savings on its energy bill.

• Industrial solar PV systems: benefits and opportunities

  Typical sizes, payback periods and incentives for businesses.

• How much CO2 a system on a business roof avoids

  Calculating avoided emissions.

Studies and research

The Heiwit study on the solar PV potential of public administration roofs, with method, results and sources. All the studies, including those on fleet data and cell tests, are collected on the page Studies and research.

• The solar PV potential of Italian public administration roofsStudy

  The study of 41,254 buildings: potential, PNIEC, methodology, limitations and sources.

• How much public roofs can contribute to the PNIEC 2030

  Data, limitations and scenarios for the contribution of schools, hospitals and town halls to the 2030 target.

• How we estimated the potential of 41,254 buildings

  Bottom-up method: sample, Google Solar API, PVGIS, bootstrap and stated limitations.

• 5.68 GW and 7.53 TWh on public administration roofs

  The model's results and what they mean.

• How much it costs to put solar on public roofs

  €6.8 billion CAPEX, LCOE and economic variables.

• Can the public administration become self-sufficient?

  Energy, self-consumption and emissions: what 7.53 TWh means.

• From potential to operational plan

  Six-phase roadmap: EPBD, ESCos, CERs and governance.