New Zealand's short winter days are the main reason home gardeners reach for a grow light. Natural daylight in June and July can run well under nine hours in the southern half of the country, and much of that is low, weak, overcast light rather than strong direct sun. Starting seedlings indoors under a light rather than on a windowsill is the difference between sturdy young plants and pale, stretched ones that struggle once they're finally planted out.
Full-spectrum LED panels are the standard recommendation for home use now, and have largely replaced the fluorescent tube and HID setups gardeners used to rely on. LEDs run cooler, use less power for the same light output, and last for years without needing bulb replacements. A basic panel rated for seedlings and leafy greens is inexpensive and enough for most home setups; the more expensive high-output panels marketed for fruiting crops are only worth it if you're trying to grow something like tomatoes or capsicums to maturity entirely indoors, which is a much bigger undertaking than starting seedlings.
Distance from the plant matters more than most new growers expect. Too close and the light itself can scorch or bleach leaves, showing up as pale or crisped patches on the topmost growth. Too far away and the light is too weak to do its job properly, and the classic sign is exactly the problem a grow light is meant to solve: pale, thin, stretched ("leggy") seedlings straining upward toward the light source. Most LED panels list a recommended hanging distance for seedlings, usually somewhere in the 15-30cm range, and it's worth raising the light as the seedlings grow rather than leaving it fixed at the original height.
the classic sign is exactly the problem a grow light is meant to solve: pale, thin, stretched ("leggy") seedlings straining upward toward the light source
Duration matters as much as intensity. Artificial light is almost always weaker than direct sun, so seedlings under a grow light typically need more hours of light per day than they would outdoors to make up for the lower intensity, commonly 12-16 hours for vegetable and herb seedlings. A cheap plug-in timer is worth having from the start; it removes the daily job of remembering to switch the light on and off, and keeps the hours consistent, which matters more to seedlings than people often assume.
Grow lights are a genuine help for extending the growing season and getting a head start on spring planting, but they're not a full substitute for real sunlight once a plant is mature and ready to go outside. The realistic use case for most home gardeners is raising strong seedlings indoors through the coldest, darkest part of the year, then hardening them off and moving them into real daylight once the weather allows it, rather than trying to grow a plant to full maturity under lights alone.