A tiny house is an RV that never moves, or a cabin that arrived on wheels, depending on who you ask. Electrically it is one of three things, and the inverter-charger choice follows from which.
Which of the three you are
Off-grid, with a generator for backup. Solar and batteries carry the house; a generator runs a few hours on the worst days. This is the cabin-forum case, and it wants the largest battery and a 48 volt system.
Parked with a 30 amp hookup. A tiny house on wheels on a lot, a family property or an RV site with a 30 amp pedestal. The inverter-charger's job is to make 30 amps feel like more, and to keep the house running when the pedestal is switched off.
A park model on a 50 amp, 120/240 volt pedestal. Park models are built to RV standards but wired like a small house, with split-phase service. This is the case people get wrong, because a single 120 volt inverter-charger does not feed a 240 volt panel.
The off-grid tiny house: go to 48 volts
An off-grid house runs its inverter around the clock, so two things dominate the choice: the inverter's idle draw, which you pay for every hour of the year, and cable current, which at 12 volts becomes absurd for a house.
The MultiPlus-II 48/3000 draws 11 to 13 watts at zero load and reaches 96 percent efficiency, the best figures in the range. Its 48/5000 sibling covers a house with an electric water heater, a well pump or a mini-split, at 15 to 24 watts idle. Both have the AES and search modes that cut idle draw further overnight.
The bank is Victron NG 51.2 volt lithium modules, 100 amp-hours each, which is about 5 kilowatt-hours per module. A modest off-grid house is two to four modules; the exact count comes from your daily watt-hours, which our how many lithium batteries guide walks through.
Solar on a house roof is more than an RV carries, and at 48 volts the SmartSolar MPPT RS 450/100 takes a high-voltage string of panels straight in, which keeps the array wiring small.
The generator connects to the MultiPlus-II's AC input. When you start it, the inverter-charger passes generator power through to the house and charges the bank at the same time; with a Cerbo GX it can start a compatible generator itself when the bank is low.
The 30 amp hookup: PowerAssist is the whole point
Thirty amps at 120 volts is 3,600 watts. A tiny house with a mini-split, a water heater and a kettle passes that in a morning. The MultiPlus-II's PowerAssist adds battery power on top of the pedestal's 30 amps for the minutes the load exceeds it, then recharges the bank from the pedestal when the load drops. The pedestal breaker stops tripping, and the house runs through a pedestal outage without noticing.
For this case the system voltage follows the house. A 12/3000 MultiPlus-II suits a house that was built as an RV with 12 volt lighting and pumps; a 48/3000 suits one built as a house with 120 volt everything and a bigger bank. Either way, set the input current limit to 30 amps, or a little under if the pedestal wiring is old, and PowerAssist does the rest.
The park model on 50 amps: split-phase, two ways
A 50 amp RV pedestal delivers two 120 volt legs, 240 volts between them. A park model's panel uses both. Two Victron layouts feed that panel correctly:
One inverter-charger with two outputs. The MultiPlus-II 2x120V and the Quattro-II 2x120V are built for North American 50 amp split-phase. They pass both legs through from the pedestal, and when the pedestal drops, they invert on one leg and use an internal arrangement to keep both legs live for 120 volt loads. The Quattro-II adds a second AC input for a generator, switched automatically.
An autotransformer. Where a single 120 volt inverter-charger already exists, the Victron Autotransformer splits its output into two balanced legs for the panel, in 32, 50 and 100 amp sizes. It is also the fix when the loads on the two legs are badly unbalanced and one keeps tripping.
True 240 volt loads, an electric range or a dryer, need two units in split-phase or a Quattro pair; that is a larger system and a conversation, not a product page.
Fusing a house-size lithium bank
Everything in the cabin-forum fusing threads is right: a lithium bank this size needs a Class T fuse at the bank, because its short-circuit current is beyond what MEGA or ANL fuses can interrupt. The Lynx Class-T Power In holds it, the Lynx Distributor fuses the inverter, MPPT and DC branches behind it. Our lithium fusing guide lays out the layers.
Monitoring, because a house is unattended more than an RV
A Cerbo GX with a GX Touch display on the wall shows the household its state of charge and solar yield at a glance, and puts the same on your phone from anywhere. For a house left empty in winter, the low-battery alert and the generator auto-start are the features that matter.
Code, listing and the electrician
A tiny house that is a permanent dwelling is subject to local electrical code, and a park model in a park is subject to the park's rules as well. We carry UL-listed variants of the MultiPlus-II and MultiPlus for installations where the inspector will ask; which listing applies is a question for the electrician doing the AC side, and we would rather you asked before buying than after.
Our MultiPlus-II sizing guide and MultiPlus versus MultiPlus-II versus Quattro comparison cover the models in more depth. Send us the panel type, the daily loads and where the power comes from, and we will spec the system. Everything ships from Upland, California.