Construction crews know the gap between a finished wall with outlets and a bare jobsite with nothing but extension cords. Battery-powered inverters close part of that gap by converting the DC power in a cordless tool battery into the AC power that ordinary electronics expect. A compact inverter with a 120V AC outlet and USB ports fits in a tool bag and turns a spare battery into a power source for charging phones, running lights, and keeping laptops alive on site. Compact inverters in the 18V class typically deliver about 175W of continuous AC power, plus USB-A at 2.4A and USB-C Power Delivery at 45W, with separate switches for the AC and USB circuits. Before you rely on one, understand how multi-bay battery chargers sequence fast charging and top-off cycles, because an inverter session changes how quickly your packs drain and how often you rotate them through the charger.
What a Battery-Powered Inverter Does
A battery-powered inverter takes a single 18V pack and steps it up to 120V AC for lighter-duty electronics. It does not turn a battery into a generator. The 175W ceiling covers phone chargers, tablets, laptops under about 175W, LED work lights, radios, and small fans. It cannot run high-draw tools: a top-handle jigsaw needs far more than 175W at startup, so treat the AC port as a charging and lighting outlet rather than a tool outlet.
| Port | Output | Typical use |
|---|---|---|
| 120V AC | 175W max continuous | Laptop adapters, lights, radios |
| USB-A | 2.4A (about 12W) | Phones, earbuds, small devices |
| USB-C PD | 45W max | Fast-charging phones, tablets, some laptops |
| Controls | Separate AC and USB switches | Cut power per circuit, save battery |
Reading the port labels
USB-C Power Delivery negotiates wattage with the device instead of pushing a fixed current. The 45W rating charges most phones and tablets at full speed and tops up many laptops, though a 60W or 65W laptop still charges, just more slowly. If your laptop needs 130W, it will refuse a 45W port entirely and fall back to the AC outlet, so check the label before you depend on one port.
Surge versus continuous ratings
Inverters list a continuous wattage and often a higher surge that lasts a few seconds. The 175W figure is continuous. Electronics draw steady power, so the surge matters less for charging than it does for motors, which is another reason this class of inverter stays away from power tools.
Matching Inverter Capacity to Your Loads
Size the inverter to the single largest continuous load you plan to run, then add the rest. Watts on a device label tell you what it draws: a 65W laptop adapter plus a 20W phone charger plus a 10W light totals 95W, safely under 175W. Add loads up before plugging in, because an overloaded inverter shuts down or blows its fuse. Independent reviewers covered this class of inverter when it was sold separately, and Pro Tool Reviews confirmed the 175W rating in real-world use.
Calculating your load budget
- Read the wattage on each device adapter or label.
- Add the wattages of everything you will run at once.
- Keep the total at or below 80% of the inverter rating, about 140W here.
- Reserve headroom for the surge when devices start.
- Recheck the math whenever you add a device to the circuit.
| Device | Typical draw | Runs on a 175W inverter? |
|---|---|---|
| Phone charger | 5-20W | Yes |
| Tablet charger | 20-30W | Yes |
| Laptop adapter | 45-130W | Yes, up to the ceiling |
| LED work light | 10-50W | Yes |
| Jobsite radio | 5-30W | Yes |
| Small fan | 20-60W | Yes |
| Circular saw | 1200-1800W | No |
| Space heater | 1500W | No |
| Shop vacuum | 600-1400W | Usually no |
Runtime Math: Capacity, Load, and Efficiency
Runtime comes from the battery. A 5.0Ah 18V pack stores about 90 watt-hours (5.0 x 18). Divide by the load to get a theoretical runtime: 90 Wh divided by 45W is about 2 hours, and 90 divided by 175W is about 31 minutes. Real runtime runs 15 to 25% lower because the inverter loses energy converting DC to AC and the pack voltage sags under load. Expect about 20 to 25 minutes at full 175W load and close to 2 hours charging a laptop at 45W.
Efficiency losses and double conversion
Charging a laptop through the AC port converts DC to AC in the inverter, then AC back to DC in the laptop’s power brick. That double conversion wastes 10 to 20% of the energy. USB-C Power Delivery avoids the second conversion, so a 45W USB-C port often charges a compatible laptop more efficiently than the AC port with the laptop’s own brick. Battery chemistry matters too: modern lithium packs do not need to be drained before recharging, and the battery memory myth about draining packs applies to older nickel chemistries, not the cells in today’s tools.
| Load | Theoretical runtime (5.0Ah) | Realistic runtime |
|---|---|---|
| 175W full AC | 31 min | 20-25 min |
| 100W | 54 min | 40-45 min |
| 45W USB-C | 2.0 hr | 1.6-1.8 hr |
| 20W phone charging | 4.5 hr | 3.5-4 hr |
| 10W light | 9 hr | 7-8 hr |
Buying Smart: Bare Tools, Bundles, and Cost Per Amp-Hour
The inverter typically sells for about $99 as a bare tool. Bundles add a battery: one common deal pairs it with a 5.0Ah pack for $149, which prices the battery at roughly $50. Promotions frequently sell two 3.0Ah packs for $99 to $100, about $50 per pack. A 5.0Ah battery at regular retail runs about $139 for one or $199 for two. The bundle’s effective $50 for a 5.0Ah pack beats both the per-pack promo price and regular retail, so the deal makes sense when you need the inverter and a larger pack at the same time.
Cost per amp-hour math
Cost per amp-hour normalizes battery prices across capacities. Larger packs shift the math again, and 9.0 Ah battery cost and value for professionals explains when the bigger pack pays for itself through fewer mid-day swaps.
| Pack | Typical price | Cost per Ah |
|---|---|---|
| 3.0Ah (promo, 2-pack) | $50 per pack | $16.7/Ah |
| 5.0Ah (bundle) | $50 effective | $10.0/Ah |
| 5.0Ah (regular retail) | $139 | $27.8/Ah |
| 5.0Ah (2-pack retail) | $100 per pack | $20.0/Ah |
Field Power: Storage, Charging, and Off-Grid Use
An inverter makes a battery useful in places with no outlet, but the battery still needs care. Lithium packs lose capacity in extreme heat and discharge slowly in cold, so store them inside the cab or trailer rather than on a metal toolbox in the sun. Rotate packs so the inverter draws from a charged spare while another charges, which is exactly the rhythm that multi-bay chargers support with their top-off cycles. The same principles scale up: battery storage for off-grid homes covers sizing, temperature, and depth-of-discharge rules that apply to a single tool pack in miniature.
Keeping packs healthy between uses
Store packs at partial charge, roughly 30 to 60%, for weeks of inactivity. Charge them fully the night before a big day. If a pack sits unused for months, recharge it before expecting full runtime.
Temperature rules
Most packs charge only between about 0 C and 40 C and refuse to charge when frozen. In winter, warm the pack in the cab before charging. In summer, keep the inverter and packs out of direct sun, since heat accelerates cell aging faster than any other single factor.
Choosing a Battery Platform for the Long Term
The inverter is one accessory in a bigger decision: which battery platform you commit to. A $99 accessory is cheap; the packs and the tools that share them are the real investment. Check whether the platform’s packs work across tool generations, whether the charger handles the newest high-capacity packs, and whether the voltage line is still current. Battery systems evolve through voltage transitions, compatibility changes, and new management electronics, and how cordless power tool battery systems evolve shows why a pack bought today should still fit the tools you buy in three years.
- Does the inverter fit every pack size you own?
- Does the charger support the largest pack you plan to buy?
- Can you run the inverter’s AC and USB ports independently?
- Is the platform still actively supported with new tools?
A portable inverter earns its place in the truck when it turns a battery you already own into a power source at the top of a ladder, in a crawl space, or on a roof. Match the capacity to the loads, do the runtime math, and buy the battery where the cost per amp-hour works in your favor.