Microwave Wattage and Cost to Run

The microwave is the clearest example of why wattage alone never tells you cost. It draws as much as a space heater, but only for the two minutes it takes to reheat coffee. High draw times tiny runtime equals pennies. There are two wrinkles worth knowing: the "watts" on the front (say, 1,000W) is the cooking output, while the unit actually pulls more from the wall to produce it; and the always-on clock and control panel sip a trickle of power 24/7 that, over a year, can rival the cooking itself.

How many watts does a microwave use?#

Two numbers get conflated. The advertised figure is cooking power; the input draw from the outlet is higher.

So a microwave labeled "1,000 watts" of cooking power draws somewhat more than that from the outlet while running — the difference is lost as heat in the electronics. Either way, the monthly energy is tiny because the magnetron is only energized for the few minutes a day you actually cook.

How much electricity (kWh) does a microwave use per month — and what does it cost?#

Standard formula, and the answer is close to a rounding error.

Monthly cost = kWh per month × your rate. At 5 kWh/month that is 5 × $0.17 = about 85 cents nationally, or 5 × $0.30 = $1.50 in California. Per use, reheating a plate costs a fraction of a cent.

For small reheats a microwave is actually the cheapest way to cook, because it heats the food directly and briefly rather than warming a large oven cavity. The one quiet cost is standby: a microwave that sits plugged in runs its clock and panel all year, which over twelve months can add up to a meaningful slice of its total energy.

When a high running cost signals a fault#

A microwave's energy is so small that a fault rarely moves your bill — but a couple of problems still matter:

• Food takes much longer to heat than it used to. A weakening magnetron produces less cooking power, so you run longer cycles for the same result — a sign the unit is aging out.
• The unit runs but does not heat, or trips the breaker. That points to a magnetron, diode, or capacitor fault.

Safety note: a microwave's internal capacitor can hold a lethal charge even when unplugged. This is never a DIY repair. For a countertop unit a magnetron failure usually means replacement, while an over-the-range or built-in model can justify a repair because a new one costs more to install — our repair-or-replace microwave guide walks through that split, and the microwave lifespan guide covers the typical 7-10 year life.

What does a microwave cost to run in California?#

Even at $0.30/kWh, a microwave costs only about $1-2.40 a month in California — small enough that timing does not matter for the cooking itself. The one California-relevant habit is unplugging a rarely-used second microwave, since standby draw runs at full-time rates too. For everyday use, the microwave is the appliance to reach for when you want to reheat something without paying oven or stovetop rates during peak hours.

The bottom line#

A microwave is among the cheapest appliances you own to run — well under $2.50 a month even in California — precisely because runtime, not wattage, drives cost. For small reheats it is the most efficient option in the kitchen. The only energy worth a second thought is the always-on clock, and only if the unit is rarely used.

When someone worries their microwave is "using a lot," I reassure them it is almost certainly not — but if it now takes three minutes to do what used to take ninety seconds, that is a fading magnetron, and on a countertop unit replacement is usually the call.

Microwave cost per day, per month, and per year#

Even at California rates the totals here are the smallest of any appliance in the kitchen — a reminder that runtime, not wattage, is what costs.

How to lower your microwave's running cost#

• Reach for it over the oven for small jobs. Reheating a plate or a single portion costs pennies where the oven costs many times more.
• Cover food. A lid or vented cover traps steam so food heats faster and you run shorter cycles.
• Unplug a rarely-used second unit. The clock and panel draw a trickle all year; on a spare microwave that standby is pure waste.
• Do not sweat the timing. The load is so small that off-peak scheduling makes no meaningful difference for a microwave.

Where a microwave ranks on your electric bill#

The microwave is the cheapest cooking appliance in the house, full stop. Its 3-8 kWh a month is a fraction of what an oven or cooktop uses, because it heats food directly for a couple of minutes instead of warming a cavity or a burner for much longer. That makes it the smart default for reheating and small portions — reaching for the oven to warm a single plate can cost many times more for the same result. The only microwave energy worth a thought is the always-on clock, and only on a spare unit that is rarely opened.

Frequently Asked Questions#

How much electricity does a microwave use?#

A microwave draws about 900-1,500 watts from the outlet while cooking but runs only minutes a day, so it uses just 3-8 kWh per month. Its high wattage is offset by very short runtime.

How much does it cost to run a microwave per month?#

Roughly under $1 to about $1.40 a month nationally at $0.17/kWh, or about $1 to $2.40 in California at $0.30/kWh. Per reheat the cost is a fraction of a cent.

Why is the input wattage higher than the label wattage?#

The label figure is cooking output — the microwave energy delivered to the food. Producing it is not perfectly efficient, so the unit draws somewhat more from the wall than its rated cooking power, with the difference lost as heat in the electronics.

Does leaving a microwave plugged in cost money?#

A little. The clock and control panel draw a few watts continuously, and over a full year that standby can add up to a noticeable share of a lightly-used microwave's total energy. Unplugging a rarely-used unit avoids it.

Is a microwave cheaper than the oven for reheating?#

Yes, clearly. A microwave heats the food directly for a couple of minutes, while an oven heats a large cavity for much longer. For small reheats and single portions the microwave is the cheapest option in the kitchen.