Space Heater vs Electric Blanket: Yearly Cost Calculator

Why the blanket is so cheap

The whole gap is watts times hours. The heater draws 1,500 watts for 4 hours a day, 120 days a year: 1,500 × 4 × 120 ÷ 1,000 is 720.00 kWh a year, which at $0.17 per kWh is $122.40 a year. The blanket draws 100 watts for 8 hours a night, 120 nights a year: 100 × 8 × 120 ÷ 1,000 is 96.00 kWh a year, which at $0.17 is $16.32 a year. The saving is $106.08 a year. The blanket runs twice as long each night but draws a fifteenth of the watts — 100 against 1,500 — so it uses about a seventh of the energy: 96 kWh against 720. Per night the heater costs $1.02 and the blanket $0.136; per hour the heater costs $0.255 and the blanket $0.017. The blanket wins because it heats a few kilograms of person and bedding, not a whole roomful of air.

The whole debate is about $106.08

Step back from the percentages and look at the dollars: the heater costs $122.40 a year and the blanket $16.32, so the entire energy argument is worth $106.08 a year — $1,060.80 over a decade. The branches stay in the same range: 8 hours a day for the heater is $244.80 against $16.32, a saving of $228.48; a short 60-day season is $61.20 against $8.16, a saving of $53.04; a $0.30 rate is $216.00 against $28.80, a saving of $187.20; and a 750-watt heater on low is $61.20 against $16.32, a saving of $44.88. The gap is real money — unlike a kettle-versus-microwave debate worth four dollars — because heating a room is one of the hungriest jobs in a home. But the gap only exists if the blanket can do the job at all, and that depends on what needs warming.

Comfort vs cost: the room, not the bed

The blanket only warms the bed, not the room. If the room itself must stay warm — a baby sleeping in it, pipes that could freeze, or someone working from home in it all day — the heater is the only option, and the cost comparison breaks: you cannot save $106.08 by leaving a room cold when the room cannot be cold. The blanket is the right tool when the only thing that needs to be warm is the person in the bed: it pre-warms the sheets, holds a steady low heat all night, and lets the room sit a few degrees cooler, which is also how most people sleep best. The heater is the right tool when the room is the thing being used — an evening in the living room, a home office, a bathroom before a shower. The cheapest option of all is both: run the heater for an hour to take the chill off the room, then sleep under the blanket with the heater off — which is exactly the flip case below, where the heater costs $30.60 a year and the blanket $40.80.

The honest flip: blanket on high, heater on brief

There is one realistic way the heater wins on cost, and it is about how hard each one is pushed. Put the blanket on high — 200 watts — for 10 hours a night, and it uses 200 × 10 × 120 ÷ 1,000, or 240.00 kWh a year, which is $40.80 a year. Use the heater only to pre-warm the room for 1 hour a night, and it uses 1,500 × 1 × 120 ÷ 1,000, or 180.00 kWh a year, which is $30.60 a year. The heater saves $10.20 a year. A blanket on high all night costs more than a heater run briefly — because 200 watts for 10 hours is more energy than 1,500 watts for 1 hour. The lesson is not that the heater is cheap; it is that hours matter as much as watts. A blanket on its lowest setting, or switched off once you are warm, stays at $16.32 a year; a blanket cranked to high and left on all night costs two and a half times that.

Rounding convention, stated plainly: each kilowatt-hour figure is rounded to two decimals, each yearly cost is the rounded kilowatt-hours times the rate, rounded to cents, and the saving is the difference of the rounded yearly costs — so $122.40 minus $16.32 is exactly $106.08. Per-night costs are shown to three decimals where they need it ($1.02 against $0.136) because two decimals would round the blanket's $0.136 to $0.14 and hide the difference; per-hour costs are shown to three decimals ($0.255 against $0.017) for the same reason.

Output · formula · meaning

Who uses this

• The cold sleeper: wakes up cold every winter night and learns the blanket costs $16.32 a year against the heater's $122.40 — a saving of $106.08 — and that the blanket warms the bed, which is the only thing that needs warming at 2 a.m.
• The home-office worker: heats one room all day and learns the heater costs $244.80 a year at 8 hours a day — then checks whether a blanket over the legs and a heater run for an hour could do the same job for $30.60 plus a blanket.
• The short-season renter: only needs heat for 60 days and learns the gap shrinks to $61.20 against $8.16, a saving of $53.04 — still worth the blanket, but the heater's case gets better the shorter the season.
• The high-rate household: pays $0.30 per kWh and learns the gap widens to $216.00 against $28.80, a saving of $187.20 — the blanket matters more the dearer electricity gets.

Accuracy & limitations

This is a rated-watts model, not a meter reading. The default wattages are typical values — most portable space heaters run 750–1,500 W, and most electric blankets run 60–200 W — but a real heater cycles on and off once the room reaches temperature, and a real blanket's thermostat does the same, so the model charges full power for the whole run time and overstates both costs a little. The 120-day season is a rough four-month heating season; a mild climate needs fewer days and a cold one more. The model also excludes the purchase price — a good blanket costs $40–$80 and a heater $30–$100 — and it assumes the blanket is the only heat source at night: if the central heating also runs, the blanket's saving is smaller. Safety matters more than the dollars here: never leave a space heater unattended, keep it clear of bedding and curtains, and never fold or bunch an electric blanket while it is on. This page's safety notes are general guidance, not a substitute for the manufacturer's instructions.