How Many Watts Does a Microwave Use — and What Does a Reheat Cost? Input vs Output Power
Do microwaves use a lot of power — how many watts, how much per reheat? This page answers directly and clears up the biggest confusion: the “watts” on the door (700–1,100 W) is the OUTPUT power into the food, while the power actually drawn at the plug — the one the meter bills — is higher (~1,100–1,550 W). With a cost-per-minute and per-month table, and a straight comparison of microwave vs air-fryer vs oven.
A microwave really draws ~1,100–1,550 watts (input power). The 700–1,100 W on the door is the output power delivered into the food, which is lower than what is pulled from the plug — and the meter charges the input. But because a microwave runs for such a short time, reheating for 3–5 minutes costs only ~0.25–0.40 baht each, and at three uses a day that is just ~20–30 baht a month (at ~4 THB/unit). Compared with an air-fryer or an oven that must heat their own cavity and run far longer, the microwave is the cheapest way to reheat food — it puts heat straight into the food and runs briefly.
How Many Watts Does a Microwave Use (Input vs Output)?
| Microwave type | Output power | Input power (billed) |
|---|---|---|
| Solo, 17–23 L | 700–800 W | ~1,100–1,270 W |
| Large / high-power | 900–1,100 W | ~1,300–1,550 W |
| With grill — in grill mode | Grill element ~1,000–1,300 W | ~1,250–1,450 W |
| Convection — in oven mode | — | ~1,350–2,000 W |
How Much Is a Reheat — per Minute and per Use?
| Duration | Energy (units) | Approx cost |
|---|---|---|
| 1 minute | ~0.02 units | < 0.1 THB |
| 3 minutes | ~0.06 units | ~0.24 THB |
| 5 minutes | ~0.10 units | ~0.40 THB |
| Whole month (3×/day, ~3 min) | ~5.4 units | ~20–30 THB |
Microwave vs Air-Fryer vs Oven — Which Uses More Power?
| Appliance | Input power | Typical time | Cost per use |
|---|---|---|---|
| Microwave (reheat) | ~1,100–1,400 W | 3–5 min | ~0.25–0.40 THB |
| Air-fryer | ~1,400–1,800 W | 15–20 min | ~1.5–2.5 THB |
| Electric oven (+ preheat) | ~1,500–2,500 W | 30–45 min | ~4–7 THB |
Is a Microwave Really Power-Hungry (Standby / High Watts / Frequent Use)?
The common worries that make people hesitate to use a microwave — here is the reality, point by point:
“High watts means wasteful” — not necessarily. Cost = watts × time; a higher-power unit finishes faster, so the total energy is similar. What matters is how many minutes you run it, not the wattage number alone.
Left plugged in (standby) uses very little. The clock display / ready circuit draws only ~1–3 W — about ~1–2 units a month (a few baht). Unplug it if you rarely use it, but it is not a cause of a high bill.
Frequent reheating is still cheap. Several times a day for a whole month is only tens of baht, because each use is brief — trivial next to air-con or a water heater.
Reheat only what you will eat, for the least time = the most saving. Portion out just what you need, use a cover so heat spreads faster, and stir midway so it heats evenly without a long run.
How to Use a Microwave Efficiently
A microwave is already efficient, but a few habits make it more so:
Use the microwave to reheat instead of firing up the oven/air-fryer when you only need it hot — faster and several times cheaper.
Use a microwave cover to trap steam so food heats faster and runs shorter (and keeps the cavity clean).
Thaw frozen food in the fridge beforehand instead of relying on a long defrost cycle, so the reheat is quicker.
Reheat right-sized portions and stir midway rather than over-setting the timer, cutting wasted energy.
Unplug if unused for days to trim standby, and check the input power on the spec plate before buying a new unit.
A microwave is a very small load — a home's big bills usually come from air-con, water heaters and washing machines run on warm-wash/dry. To cut the whole-house bill seriously, rooftop solar is the better long-run option — talk to CapSolar for free.
About the Author
Compiled by the CapSolar team under Frank Lee (Founder). CapSolar is a commercial & industrial solar EPC/PPA provider in Thailand that explains electricity bills and home energy use from first-principles arithmetic so households and businesses can decide with confidence.
FAQ
Related Articles
Want to Cut the Whole-House Bill, Not Just the Kitchen?
Air-con, water heaters and dryers are the big bills. CapSolar gives you a free assessment from your actual bill of whether rooftop solar pays for your home or business.