The essentials in 30 seconds
- Pure sine is mandatory in marine use. Modified square-wave (quasi-sine) inverters damage laptop charger transformers and poorly power compressor fridges. Pure sine = 99% of sailboat use in 2026.
- Sizing = continuous power AND startup surge. A 1,200 W coffee machine draws 2,000 W at startup (3-5 sec). A "smooth" 1,200 W inverter will overload and shut down. Always plan for an inverter rated at 150% of continuous consumption.
- 2026 standards: Victron Phoenix 12/1600 Smart (~ $540 USD ex-works) for occasional use. MultiPlus 12/3000-120 for continuous use with shore power charger integrated.
- Idle loss matters. Inverter in standby consumes 0.3-0.8 A continuously. Over 24 h unused = 7-20 Ah loss. Always use an accessible ON/OFF switch.
- Skysat workshop install budget for 35-45 ft sailboat: ~ $800-$1,400 USD ex-works (inverter + wiring + protection + switch), excluding battery bank which depends on lithium pack sizing (see our sizing article).
The DC/AC inverter is the bridge between your 12/24 V battery bank and the 230 V world. It converts the DC voltage from the battery to a pure sine wave AC output, allowing household appliances (coffee machine, computer, absorption fridge, electronic chargers) to run. But without correct sizing, it is the most temperamental piece of equipment on board.
This article explains the difference between pure sine and quasi-sine, provides a sizing method, presents the Victron and Mastervolt ranges stocked by Skysat, and gives installation rules. For the battery bank that powers the inverter, see our lithium bank sizing article.
Why pure sine, not quasi-sine
Two inverter technologies exist: quasi-sine (modified square wave, stepped waveform) and pure sine (sine wave close to the EDF grid).
- Quasi-sine: cheaper, slightly higher efficiency, but high harmonic distortion. Damages: transformers (laptop chargers, camera chargers), induction motors (compressor fridges, fans), medical equipment.
- Pure sine: voltage identical to the grid, powers everything without issue. 20-30% surcharge vs quasi-sine, but a worthwhile investment as soon as you go beyond basic smartphone charging.
In modern sailboats in 2026, pure sine is the de facto standard. Unless you have a very specific use case (incandescent lighting only), go for pure sine.
Sizing — workshop method
Calculation in 4 steps:
- List all 230 V equipment used simultaneously. Coffee machine (1,000-1,500 W) + laptop (90 W) + absorption fridge (300 W at startup). Total continuous: ~1,400 W.
- Identify startup surge. For coffee machines and fridges, multiply continuous power by 1.5-2.0. Estimated surge: ~2,100 W.
- Choose an inverter rated at 150% of continuous consumption. Continuous consumption 1,400 W × 1.5 = minimum 2,100 W inverter. Round up to the next available size: 2,000-2,500 W inverter.
- Check the surge rating: a 2,000 W Victron inverter can handle a ~4,000 W surge for 1-2 seconds (datasheet). Compatible with coffee machine/fridge startup.
For light occasional use (laptop + USB chargers only): Phoenix 12/1600 Smart (~ $540 USD ex-works) is more than sufficient.
Victron Phoenix range
Entry and mid-market Victron range, pure sine, 12 V and 24 V.
- Phoenix 12/500 Smart: ~ $270 USD ex-works. Small uses: laptop, USB chargers, 230 V lighting.
- Phoenix 12/1200 Smart: ~ $470 USD ex-works. Light coffee machines, drills, small tools.
- Phoenix 12/1600 Smart: ~ $540 USD ex-works. Skysat’s workshop reference for 35-45 ft sailboats. 3,000 W surge (2-5 sec).
- Phoenix 24/1600 Smart: ~ $580 USD ex-works. 24 V version for sailboats with 24 V architecture.
- Phoenix 12/2000 Smart: ~ $850 USD ex-works. Compressor fridge + coffee machine + tools.
- Phoenix 12/3000 Smart: ~ $1,250 USD ex-works. Intensive continuous use.
Mastervolt Mass Sine range
Direct competitor to Victron with MasterBus / CZone integration for configured yachts.
- Mass Sine 12/1500: ~ $720 USD ex-works. More expensive than Victron at equivalent power, but native MasterBus integration.
- Mass Sine 12/2000: ~ $980 USD ex-works.
- Mass Sine 12/2500: ~ $1,250 USD ex-works.
Mastervolt is preferred on new Bénéteau/Jeanneau/Bavaria yachts equipped with CZone (native dashboard integration).
Inverter-charger combo
For intensive use and regular harbor stays, consider an inverter-charger combo in a single unit (Victron MultiPlus).
- MultiPlus 12/3000-120: 3,000 W inverter + 120 A shore charger in one box. ~ $1,850 USD ex-works. At the dock, it functions as a charger; at anchor, as an inverter. Automatic transfer in under 20 ms.
- MultiPlus II 48/3000: ~ $1,950 USD ex-works. 48 V version for large hybrid + solar banks.
If you plan to replace your shore charger and install an inverter, the MultiPlus saves on wiring and space.
Model comparison chart
| Model | Continuous power | Surge | Efficiency | Price ex-works |
|---|---|---|---|---|
| Victron Phoenix 12/500 | 500 W | 900 W | 89% | ~ $270 |
| Victron Phoenix 12/1200 | 1,200 W | 2,200 W | 91% | ~ $470 |
| Victron Phoenix 12/1600 | 1,600 W | 3,000 W | 92% | ~ $540 |
| Victron Phoenix 12/2000 | 2,000 W | 4,000 W | 92% | ~ $850 |
| Victron MultiPlus 12/3000-120 | 3,000 W + 120 A charger | 6,000 W | 93% | ~ $1,850 |
| Mastervolt Mass Sine 12/2000 | 2,000 W | 4,000 W | 93% | ~ $980 |
Workshop installation — technical rules
Skysat workshop rules
- DC side cable sized for max current. 12/1600 W inverter → 130 A continuous → 35 mm² cable minimum, length ≤ 1 m if possible. Too thin = voltage drop → inverter shuts down on low voltage.
- Fuse class T or MEGA in series with battery. Rated at 1.5× nominal current. 1,600 W inverter = 200 A class T fuse.
- Accessible ON/OFF switch. Inverter in standby consumes 0.3-0.8 A. Physical button at the helm = 5 min install = 100-300 Ah saved per year at anchor.
- Mandatory ventilation. 1,600 W inverter produces 100-150 W of heat at full load. Ventilated compartment required, never in a closed locker.
- AC earth bonding. The inverter’s 230 V output must be bonded to the boat’s ground for safety. ISO 13297 standard.
FAQ — Inverter in practice
12 V or 24 V inverter?
12 V if your bank is 12 V (95% of pleasure sailboats). 24 V if bank is 24 V (yachts ≥ 45 ft). Converting 12 → 24 V to power the inverter is inefficient; better to use an inverter directly on the bank voltage.
Can you use the inverter while sailing (engine running)?
Yes, and it’s optimal — the alternator recharges the bank while compensating for inverter consumption. Watch for startup surges: on small banks (< 200 Ah), voltage dips briefly and the alternator may overcompensate. Prefer starting the inverter with the engine running.
What is the standby loss of a modern inverter?
Victron Phoenix 12/1600 Smart: 0.4 A standby (4.8 W). Over 24 h unused = 9.6 Ah. Over 1 year at anchor = 3,500 Ah lost if never turned off. Hence the need for an ON/OFF switch.
Can the inverter power an air conditioner?
Theoretically yes, but not recommended. Marine air conditioning draws 500-1,500 W continuously. On batteries, autonomy is limited to a few hours max. Prefer a generator or shore power for extended air conditioning at anchor.
Inverter-charger combo or separate units?
Combo (MultiPlus) if you plan to use both intensively (long anchorages + port stays). Separate units if the shore charger is already in place and you only need to add an inverter. The combo wins on space and wiring, but loses in maintenance flexibility.
3 real-world workshop cases — inverter install
Case 1 — Bavaria 41 cruising family sailboat
Inverter installed in 2024: Victron Phoenix 12/1600 Smart (~ $540 USD ex-works) + accessible ON/OFF switch in cabin + 200 A class T fuse. Typical use: coffee machine (1,200 W at startup) in the morning at anchor, USB chargers while sailing. Average 24 h consumption: 30-40 Ah (including standby loss). The customer confirms: "Coffee at anchor changes the quality of the cruise."
Case 2 — Lagoon 42 catamaran offshore
Victron MultiPlus 12/3000-120 inverter-charger combo (~ $1,850 USD ex-works) replacing the existing shore charger. Benefits: automatic transfer shore↔battery in < 20 ms, continuous 230 V power at anchor (1,200 W air conditioning possible for 2-3 h), space saved in the technical locker. 6 h workshop install. Total install $2,200 USD ex-works.
Case 3 — 8 m coastal solo sailboat
Small need: laptop charging + phone chargers. Phoenix 12/500 Smart (~ $270 USD ex-works). 2 h install, 80 A class T fuse + switch. Total install ~ $380 USD ex-works. The customer confirms: "For my needs, it’s exactly the right power — not oversized, not frustrating."
Excluded alternatives — inverters not recommended
- Chinese quasi-sine inverters (250-350 USD ex-works for 2,000 W): avoid in marine use. Waveform degrades laptop chargers and fridge compressors within months. Attractive price, but reduced lifespan and risk of damaging powered equipment.
- "All-in-one" combo inverters (generator + inverter integrated): practical for very large units (yacht ≥ 60 ft), but expensive and complex to maintain. Prefer separate components under 50 ft.
- Inverters without integrated ON/OFF switch: some entry-level models lack a physical power button. Standby loss (0.5-1 A continuous) then consumes 4-8 kWh per month. Always choose a model with ON/OFF or add an external switch.
Specific case — powering an absorption fridge without shore power
An absorption fridge (Dometic, Vitrifrigo) draws 90-300 W in cycle, with a startup surge 2-3× continuous consumption. For a 200 W fridge on average:
- 24 h consumption: 200 W × 12 h cycle = 2.4 kWh = 200 Ah at 12 V.
- Inverter sizing: Phoenix 12/1200 minimum (for ~600 W startup surge).
- Battery bank: 400-500 Ah lithium minimum for 2-3 days autonomy without recharge.
For this specific use, the MultiPlus 12/3000-120 combo (~ $1,850 USD ex-works) is our standard: integrated 120 A shore charger + automatic transfer. The customer gets their 230 V coffee even on long anchorages.
Skysat distributes Victron Energy and Mastervolt. 2026 USD ex-works prices are indicative distributor pricing.
