Inverter guide
Solar inverter selection: pure sine, sizing, and surge math
The inverter converts your battery's DC power into the AC power that household appliances use. Get the wrong inverter and you'll either undersize and trip breakers constantly, oversize and waste money, or pick the wrong waveform and damage sensitive electronics. Here's the honest selection framework.
Step 1: Pure sine vs modified sine
Buy pure sine wave. Don't even consider modified sine in 2026.
Modified sine wave (square-wave-ish) inverters are cheaper but cause problems with:
- · Modern electronics (laptops, TVs, microwaves with digital controls)
- · Variable speed motor appliances (most modern refrigerators, mini-splits)
- · Battery chargers and power adapters
- · Inductive loads (anything with a motor)
The cost difference between modified and pure sine has shrunk to almost nothing in 2026. A quality 2,000W pure sine inverter from Renogy or AIMS Power costs $300-$450. The equivalent modified sine inverter is $150-$250. The savings aren't worth the appliance compatibility issues.
Step 2: Size continuous wattage
Continuous wattage = the maximum sustained load you'll run through the inverter. Add up the watts of everything that might run simultaneously, then add 25% headroom.
| Use case | Continuous load | Inverter size |
|---|---|---|
| Van life (laptop, lights, Starlink, fan) | ~400W | 1,000-1,500W |
| Van with induction cooktop | ~1,800W peak | 2,000-3,000W |
| Cabin with refrigerator + microwave | ~1,500W peak | 2,000-3,000W |
| Cabin with well pump + appliances | ~2,500W peak | 3,000-4,000W |
| Tiny home with mini-split AC | ~3,500W peak | 5,000W+ split phase |
| Full house backup (without electric heat) | ~6,000W peak | 8,000-12,000W split phase |
Step 3: Verify surge wattage
Surge wattage = the brief peak load when motors start. A 1,000W microwave might draw 1,500W for the first second. A well pump that runs at 600W continuous might surge to 2,400W at startup. Refrigerator compressors typically surge 3-5x their running wattage.
Quality pure sine inverters can handle 1.5-2x their continuous rating as a surge for ~5 seconds. A 2,000W inverter with 4,000W surge handles most residential surge events fine. Cheap inverters often advertise surge ratings they can't actually deliver — check independent reviews.
The "soft start" alternative: for high-surge equipment like well pumps or AC compressors, install soft-start devices ($150-$300) that smooth the inrush current. Cheaper than oversizing the inverter and works more reliably.
Step 4: Match input voltage to your battery bank
Inverters come in 12V, 24V, 48V (and 36V for some vehicle apps) input configurations. Match this to your battery bank voltage.
- · 12V systems: small vans, basic cabin use, anything under 2,000W inverter
- · 24V systems: medium vans, larger cabins, 2,000-3,500W inverter range
- · 48V systems: tiny homes, off-grid houses, anything above 3,500W inverter
Higher voltage is more efficient at higher power levels because cable losses scale with current (which decreases as voltage increases). A 4,000W load at 12V draws 333 amps; at 48V it draws 83 amps. The cable size, fuse rating, and conversion efficiency all improve dramatically.
Step 5: Hybrid inverter or standalone?
Hybrid inverters combine the charge controller, inverter, and grid-tie functionality into one unit. Examples: EG4 18kPV, Sol-Ark 15K, Schneider XW Pro, Outback Radian.
Standalone (or "off-grid") inverters just do DC-to-AC conversion. You pair them with a separate charge controller for the solar side.
When hybrid wins: grid-tied systems where you want backup power capability during outages. Whole-home backup setups. Anything with complex switching between solar, battery, and grid power.
When standalone wins: off-grid van and RV builds, simple cabin setups without grid connection, anyone who wants to mix-and-match components. Standalone inverters are dramatically cheaper for the same wattage rating.
Brands worth buying in 2026
Premium tier (5+ year warranty, exceptional reliability):
- · Victron Energy — MultiPlus and Quattro lines. Industry standard for European/marine applications. Bluetooth integration, robust, expensive.
- · Outback Power — FX series. American-made, long warranty, popular for rural off-grid.
- · Schneider Electric (Conext) — XW Pro hybrid. Large-system focus, excellent for whole-house backup.
- · Sol-Ark — 12K and 15K hybrid. Increasingly popular for grid-tied + backup applications.
Value tier (2-5 year warranty, good for the price):
- · EG4 — 18kPV hybrid is the DIY community favorite for whole-house off-grid in 2026. Excellent feature set per dollar.
- · Renogy — solid standalone inverters in the 2,000-3,000W range. Good for van and small cabin builds.
- · AIMS Power — wide range of standalone inverters. Quality varies by model; the higher-end LF series is solid.
- · Magnum Energy — MS series. Good price-to-quality, popular for RV and small home builds.
Skip: generic Chinese imports on Amazon under $300 for anything 2,000W+. They typically over-promise on surge ratings and have poor support when they fail.
Common sizing mistakes
- Undersizing the inverter for surge loads. Refrigerator startup, AC compressor cycling, well pump surges — these are where undersized inverters trip and frustrate owners.
- Oversizing the inverter dramatically. A 5,000W inverter running a 200W base load is inefficient — standby losses are typically 5-15W just being on. Match the inverter size to your actual loads.
- Wrong battery voltage match. Running a 12V inverter on a 24V battery bank destroys the inverter. Running a 48V inverter on a 12V bank does nothing. Verify the spec before purchase.
- Ignoring efficiency at low loads. Most inverters peak in efficiency around 50% of rated load. A 3,000W inverter running a 100W base load might be only 70% efficient. For low-base-load systems, smaller inverters are more efficient at typical loads.