How do I convert BTU to watts?

Watts = BTU/hr ÷ 3.412. Example: 12,000 BTU/hr AC = 12,000 ÷ 3.412 = 3,517 watts cooling capacity. Note this is thermal output, not electrical input. The electrical consumption depends on efficiency (EER/COP). A 12,000 BTU unit with EER 10 uses 1,200W electrical input.

What is the difference between BTU and watts?

BTU/hr measures thermal power (heating/cooling capacity). Watts measure electrical power consumed. AC units show both: 12,000 BTU/hr cooling output might use 1,200W electrical input. Efficiency = BTU output ÷ watts input × 3.412. Higher efficiency means more BTUs per watt consumed.

How many watts does a 5000 BTU window AC use?

5000 BTU window AC typically uses 400-550W electrical power, depending on efficiency. EER 10: 5000 ÷ 10 = 500W. EER 12: 5000 ÷ 12 = 417W. Older units (EER 8) use 625W. This is running watts - starting surge can be 2-3× higher. Size circuit for 125% of running current.

How do I calculate heating cost from BTU rating?

For electric heat: BTU/hr = Watts × 3.412. 5kW heater = 17,060 BTU/hr. Cost = kW × hours × rate. For gas: 100,000 BTU furnace at 80% efficiency delivers 80,000 BTU. Uses 100 cubic feet/hour. At $1/therm: $1/hour. Electric resistance heat is 100% efficient but costs 2-4× more than gas per BTU.

What is SEER vs EER for AC efficiency?

EER = BTU/hr ÷ watts at specific conditions (95°F). SEER = seasonal average including part-load operation. SEER 13 ≈ EER 11. Higher is better. SEER 16 uses 23% less power than SEER 13. New standards: SEER 14 minimum (South), SEER 13 (North). Mini-splits achieve SEER 20-30 for maximum efficiency.

BTU to Watts Calculator

Professional BTU/hr to watts converter for HVAC systems and electrical load calculations. Convert heating and cooling capacity to electrical power for proper circuit sizing.

Heat Output

BTU/hr thermal capacity

Cooling Power

AC & heat pump sizing

Electrical Load

Circuit requirements

BTU to Watts Calculator

Convert BTU ratings to electrical power requirements

Input Parameters

Use equipment preset

BTU Rating

Thermal energy rating

Time Unit

Efficiency

Equipment efficiency: Heat pumps 300-400%, Furnaces 80-98%

Voltage

Phase

Power Factor

Typical: 0.95 for modern equipment

Electricity Rate

$/kWh

Your local electricity rate

BTU Conversion

• 1 BTU/hr = 0.293 Watts (thermal)

• 1 Ton cooling = 12,000 BTU/hr

• 1 kW = 3,412 BTU/hr

• Efficiency affects electrical input

Typical Efficiencies

• Electric Resistance: 100% (1:1 conversion)

• Gas Furnace: 80-98% (combustion efficiency)

• Heat Pump (heating): 250-400% (COP 2.5-4.0)

• Air Conditioner: 300-500% (EER 10-17)

• Boiler: 85-95% (combustion efficiency)

Enter BTU rating to calculate power requirements

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Common BTU to Watts Conversions

Air Conditioner Sizes

Tons	BTU/hr	Thermal Watts	Elec. Watts (EER 10)	Circuit
0.75	9,000	2,638W	900W	15A/120V
1.0	12,000	3,517W	1,200W	15A/120V
1.5	18,000	5,275W	1,800W	20A/120V
2.0	24,000	7,034W	2,400W	15A/240V
2.5	30,000	8,792W	3,000W	20A/240V
3.0	36,000	10,551W	3,600W	20A/240V
3.5	42,000	12,309W	4,200W	25A/240V
4.0	48,000	14,067W	4,800W	30A/240V
5.0	60,000	17,584W	6,000W	35A/240V

Heating Equipment

Equipment	BTU/hr	kW Heat	Elec. Draw	Efficiency
Space Heater	5,120	1.5kW	1.5kW	100%
Baseboard 4ft	3,413	1.0kW	1.0kW	100%
Heat Pump 2T	24,000	7.0kW	2.3kW	COP 3.0
Heat Pump 3T	36,000	10.5kW	3.0kW	COP 3.5
Furnace 60k	60,000	17.6kW	0.6kW	Gas 95%
Furnace 80k	80,000	23.4kW	0.8kW	Gas 95%
Furnace 100k	100,000	29.3kW	1.0kW	Gas 95%
Elec Furnace	68,260	20kW	20kW	100%

Real-World BTU to Watts Examples

Mini-Split Installation

Equipment: 18,000 BTU mini-split

SEER Rating: 20

Thermal Output:

18,000 BTU × 0.293071 = 5,275W
(5.3kW cooling capacity)

Electrical Consumption:

EER = SEER × 0.875 = 17.5
Watts = 18,000 ÷ 17.5 = 1,029W

Circuit: 15A @ 240V

Wire Size: 14 AWG
Disconnect: 30A fused
MCA: 8.6A | MOP: 15A

Heat Pump Upgrade

Old Unit: 3-ton, SEER 10

New Unit: 3-ton, SEER 18

Capacity: 36,000 BTU/hr

Old Power Draw:

36,000 ÷ (10 × 0.875) = 4,114W
Current = 4,114W ÷ 240V = 17.1A

New Power Draw:

36,000 ÷ (18 × 0.875) = 2,286W
Current = 2,286W ÷ 240V = 9.5A

Energy Savings: 44%

Annual Savings: ~$650
Existing Circuit: Adequate
ROI: 5-7 years

Commercial Kitchen HVAC

Kitchen Size: 2,000 sq ft

Equipment Heat: 150,000 BTU/hr

Required Cooling:

Base: 2,000 × 40 = 80,000 BTU
Equipment: + 150,000 BTU
Total: 230,000 BTU/hr (19 tons)

Electrical Load:

230,000 ÷ 11 EER = 20,909W
Three units @ 7kW each

Power: 3× 40A @ 240V

Makeup Air: Required
Exhaust CFM: 8,000

Server Room Cooling

IT Load: 20kW

Heat Generation:

20kW × 3,412 = 68,240 BTU/hr
Safety Factor × 1.3 = 88,712 BTU
Required: 7.4 tons cooling

CRAC Unit Sizing:

2× 5-ton units (redundancy)
60,000 BTU each @ EER 12
Power: 5kW each unit

Total Cooling Power: 10kW

PUE: 1.5 (good efficiency)
Circuit: 2× 30A @ 240V
UPS Protected: Yes

Warehouse Unit Heaters

Space: 10,000 sq ft × 20ft ceiling

Heat Loss: 400,000 BTU/hr

Gas vs Electric:

Gas: 5× 80,000 BTU units
Electric: 0.5kW each (fans)
Total Electric: 2.5kW

All Electric Alternative:
400,000 BTU × 0.293 = 117kW
Current: 282A @ 480V 3-phase

Gas: More economical

Operating Cost: $2,400/mo vs $8,500/mo
Installation: Gas piping required

Pool Heat Pump Sizing

Pool: 20,000 gallons

Temperature Rise: 15°F

Heat Required:

20,000 gal × 8.33 lb/gal × 15°F
= 2,499,000 BTU total
24hr heating = 104,125 BTU/hr

Heat Pump Selection:

120,000 BTU/hr unit
COP 5.0 @ 80°F ambient
Power: 120,000 ÷ (5×3,412)
= 7.03kW electrical

Circuit: 40A @ 240V

Wire: 8 AWG THWN
Runtime: 20 hrs initial
Daily Cost: ~$8.50

Understanding HVAC Efficiency Ratings

Cooling Efficiency Metrics

EER (Energy Efficiency Ratio)

BTU/hr cooling ÷ Watts input at 95°F

Standard: 8-12High-Eff: 12-16

SEER (Seasonal EER)

Seasonal average efficiency

Minimum: 14ENERGY STAR: 15+

SEER to EER Conversion

EER ≈ SEER × 0.875

SEER 14	EER 12.3
SEER 16	EER 14.0
SEER 20	EER 17.5
SEER 25	EER 21.9

Heating Efficiency Metrics

COP (Coefficient of Performance)

Heat output ÷ Energy input

Resistance: 1.0Heat Pump: 2.5-4.5

HSPF (Heating Seasonal Performance Factor)

BTU heating ÷ Watt-hours (seasonal)

Minimum: 8.2High-Eff: 10+

AFUE (Annual Fuel Utilization Efficiency)

For gas/oil furnaces

Standard	80%
High-Efficiency	90-95%
Condensing	95-98%

Heat Load Calculation Guidelines

Residential Rules of Thumb

Cooling (South)600 sq ft/ton

Cooling (North)800 sq ft/ton

Heating (Mild)25 BTU/sq ft

Heating (Moderate)35 BTU/sq ft

Heating (Cold)45 BTU/sq ft

Heating (Extreme)55 BTU/sq ft

Commercial Spaces

Office250-300 sq ft/ton

Retail200-250 sq ft/ton

Restaurant150-200 sq ft/ton

Data Center150 sq ft/ton

Warehouse500-800 sq ft/ton

Manufacturing300-400 sq ft/ton

Additional Factors

Windows (std)+1,000 BTU ea

Windows (south)+2,000 BTU ea

People+600 BTU ea

Kitchen+4,000 BTU

Computers+400 BTU ea

Poor Insulation+30%

HVAC Electrical Requirements by BTU Rating

BTU Rating	Tons	Typical Watts	MCA	MOP/Breaker	Wire Size	Voltage
9,000 BTU	0.75	900W	7.5A	15A	14 AWG	120V
12,000 BTU	1.0	1,200W	10A	15A	14 AWG	120V
18,000 BTU	1.5	1,800W	8.6A	15A	14 AWG	240V
24,000 BTU	2.0	2,400W	11.5A	20A	12 AWG	240V
30,000 BTU	2.5	3,000W	14.4A	20A	12 AWG	240V
36,000 BTU	3.0	3,600W	17.3A	25A	10 AWG	240V
48,000 BTU	4.0	4,800W	23A	30A	10 AWG	240V
60,000 BTU	5.0	6,000W	28.8A	40A	8 AWG	240V

* MCA = Minimum Circuit Ampacity | MOP = Maximum Overcurrent Protection
* Values shown for typical SEER 14-16 equipment. High-efficiency units may require less power.

Heating Cost Comparison by Fuel Type

Cost to generate 1 million BTU of heat (assuming $0.12/kWh electricity, $1.50/therm gas, $3.00/gal propane):

Heating Method	Efficiency	Cost/Million BTU	Annual Cost*	CO₂ Impact
Heat Pump (COP 3.5)	350%	$10.05	$1,005	Low-Medium
Heat Pump (COP 2.5)	250%	$14.07	$1,407	Medium
Natural Gas (95%)	95%	$15.79	$1,579	Medium
Natural Gas (80%)	80%	$18.75	$1,875	Medium-High
Propane (95%)	95%	$34.48	$3,448	High
Electric Resistance	100%	$35.17	$3,517	Highest
Oil (85%)	85%	$25.49	$2,549	High

* Annual cost based on 100 million BTU/year (typical 2,000 sq ft home in moderate climate)

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Industry Standards & References

ASHRAE Standards

Heating, ventilation, air conditioning, and refrigeration engineering standards

ENERGY STAR

Energy efficiency ratings and certified HVAC equipment database

ACCA Manuals

Manual J load calculations and HVAC system design standards

Carrier Corporation

HVAC equipment specifications and sizing resources

Trane Technologies

Heat pump and air conditioning technical resources

NFPA 90A

Installation standards for air-conditioning and ventilation systems

Professional HVAC Installation Required

BTU calculations are critical for proper HVAC system sizing. Undersized equipment won't maintain comfort, while oversized systems short-cycle, reducing efficiency and lifespan. Electrical circuits must be sized per NEC Article 440 for air conditioning equipment. Always perform Manual J load calculations for accurate sizing. Installation requires EPA 608 certification for refrigerant handling and electrical licensing for power connections. Consult qualified HVAC professionals for system design and installation.