Posted by Matt Bebbington on 19th Jan 2026
Technical Guide
A Technical Guide to RV Inverters
Understanding DC-to-AC power for your motorhome or caravan.
A DC-to-AC inverter is an essential piece of kit for many RV owners. It lets appliances designed for
household electricity run from your RV's battery system — giving you 230-volt power
even when you're completely off-grid.
In simple terms, an inverter converts direct current (DC) from your house batteries into alternating current (AC) — the same type of electricity supplied through wall sockets at home. That makes it possible to use everyday appliances like TVs, coffee machines and chargers while travelling.
How Does an Inverter Work?
An inverter takes the low-voltage DC power supplied by the batteries (typically 12 volts in most RVs) and electronically boosts and transforms it into 230-volt AC power.
The name "inverter" has an interesting origin. Early electrical converters were designed to change AC power into DC. Eventually, someone realised these devices could be run in reverse — producing AC power from a DC source.
Choosing the Right Inverter
Input Voltage
The first consideration is input voltage. The inverter must match the voltage of your battery system — most Kiwi RVs use 12 volts, though some larger systems run at 24 volts.
Output Wattage
Next, work out the required output wattage. This must cover both the running wattage and the start-up (surge) wattage of your appliances. Running wattage is usually on the appliance label; surge wattage — a brief spike when appliances start — can be harder to find, but is often available from the manufacturer or retailer.
If you plan to run several appliances at once, add their wattages together. For example, a TV drawing 50 watts and a capsule coffee machine drawing 1,000 watts require a combined running load of 1,050 watts. (A coffee capsule machine typically uses around 1,200 watts.)
Surge Capability Explained
Inverter surge capability is rated in both watts and time. A 1,200-watt inverter may tolerate a 30% overload — around 1,560 watts — for up to 10 seconds.
Order matters: if the coffee machine has a 500-watt surge for 10 seconds and the TV has a 150-watt surge for five, and the coffee machine is already past its surge phase when the TV is switched on, a 1,200-watt inverter may be sufficient.
As a general rule, higher-quality inverters tolerate larger surge loads for longer. Running an inverter well within its rated capacity keeps temperatures down, improves reliability and extends its lifespan.
Battery Capacity Considerations
Inverters place heavy demands on house batteries, causing rapid voltage drops under load. Most inverters include a low-voltage cut-off — typically between 10 and 11 volts — to protect the inverter itself. However, that voltage is often too low to adequately protect the batteries.
Some inverters let you adjust this cut-off point closer to 12 volts, which can significantly improve battery life.
Battery Capacity Rule of Thumb
12V systems: Total Wattage ÷ 5 = Required Ah
24V systems: Total Wattage ÷ 10 = Required Ah
Example: 1,400W ÷ 5 = 280Ah battery capacity needed (12V system)
For example, a continuous load of 1,400 watts on a 12-volt system would need roughly 280 amp-hours of battery capacity (1,400 ÷ 5 = 280) to run effectively until the desired depth of discharge is reached.
Battery Upgrade Recommended?
If your calculations show you need more battery capacity, we can help. See our RV Battery Upgrade services for lithium and AGM options.
Installation Essentials
An inverter should be installed as close to the batteries as possible, to minimise voltage drop and reduce heat caused by resistance. Heavy-duty cabling of the correct size is essential.
Appropriate circuit protection must also be installed — a heavy-duty fuse or circuit breaker — to protect both the inverter and the electrical system.
Professional Installation Recommended
Installing an inverter can be a rewarding DIY project, but there are pitfalls. Incorrect cable sizing, poor connections or inadequate circuit protection can lead to fire hazards, equipment damage and premature battery failure.
If you're unsure, professional advice and installation is well worth seeking. Our team at RV Solutions in Christchurch has extensive experience with inverter installations and can ensure your system is safe, compliant and optimised for your needs.
Final Thoughts
A correctly selected and installed inverter provides reliable 230-volt power and helps maximise the life of your house batteries. Get it wrong, and the result can be costly equipment damage and premature battery failure. When choosing an inverter, remember to:
- Match the input voltage to your battery system (12V or 24V)
- Calculate total running wattage plus surge requirements
- Ensure adequate battery capacity using the formulas above
- Install close to the batteries with proper cable sizing
- Include appropriate circuit protection
- Consider professional installation for safety and reliability
Need Help With Your Inverter Installation?
Our team in Christchurch can help you choose the right inverter, calculate your power requirements, and install it professionally.
This article is general guidance to help you plan, not specific electrical advice for your vehicle. Inverter sizing and installation depend on your exact loads, battery bank and cabling — always have 230V work carried out by a qualified professional.