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Appliance Energy & Electricity Bill Calculator: kWh, Inverter AC

Estimate appliance kWh, electricity units and bills from your own flat or slab rates. Compare fridge and inverter AC replacements using labels, duty cycles or seasonal ratings.

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Published 28. October 2026 · version 1

#appliance energy #duty cycle #electricity bill #inverter AC #ISEER #kWh #progressive tariffs #SEER

This electricity bill calculator estimates how much energy your home appliances use over a billing period and what that energy costs at prices you enter. It is for students learning power and energy, engineers checking household loads, and anyone comparing an old refrigerator or air conditioner with a replacement. One electricity unit means one kilowatt-hour (kWh); a watt is a rate of energy use, not a monthly unit.

Start with the number of billing days. Enter quantities, real input watts and daily operating hours for lights, fans, TVs and the two flexible appliance groups. The flexible groups can represent a kettle, router, water heater, pump, computer or another device. Use average daily hours for occasional use, and set an unused group’s quantity to zero. Other B is a simple combined-watts group with no standby model; set its watts to zero to omit it. Devices with different schedules should use separate groups. The initial household is illustrative, so replace its values with your own.

For a refrigerator, choose its annual kWh label whenever available. The tool apportions that energy across the billing days without applying another duty factor. If there is no label, use compressor-on watts, compressor-off watts and the fraction of the day spent cooling. Room temperature, thermostat setting, door opening and defrost all affect the result. A representative multi-day energy measurement is more useful than a guessed universal duty cycle.

For AC, the preferred route uses label kWh and the reference operating hours stated for that label. The tool scales to your enabled hours while assuming a comparable weather and load profile. Alternatively, estimate cooling energy from rated cooling capacity, hours and average cooling load fraction, then divide by ISEER or a seasonal efficiency ratio in equivalent units. US-style SEER and SEER2 in Btu/Wh are supported, but different rating procedures remain different. This answers questions such as “how many units does a 1.5 ton AC use per month” only after you specify its efficiency and load. A 1.5 ton cooling capacity is approximately 5.275 kW of cooling output; it is not 5.275 kW of electrical input.

This appliance power consumption calculator also accounts for enabled idle power and disabled standby without counting either twice. The bar chart and breakdown table show where the units go. Select a fridge or AC replacement to compare units and a fully recalculated bill; savings can be negative if the replacement uses more energy.

Enter a flat price or up to six progressive slabs, plus the fixed charge for this bill. All starting prices and thresholds are examples, with no stored utility tariff. Thresholds apply to the whole chosen period and are not automatically prorated. Use the same currency throughout. Taxes, fuel adjustments, subsidies, time-of-use pricing, non-progressive slab rules, demand charges and solar export are outside this estimate. It does not size wiring or protection; installation work belongs to a qualified person.

How it is calculated

Daily appliance energy is real input power multiplied by enabled time, quantity and repeated daily schedules. For a cycling device, $\bar P = dP_{on}+(1-d)P_{idle}$ . Disabled standby is added only during $24-h$ hours per day. These are energy-accounting equations; the Virginia Cooperative Extension BSE-301 worked examples (2020), p. 1, provide external numerical checks.

For fridges, annual label kWh is multiplied by billing days / 365 and overrides the cycling estimate. It already includes the label's compressor cycling and auxiliary energy. For an AC label, $E = E_{label} H/H_{label}$ ; this assumes the same weather/load profile as its reference hours. Enter zero additional disabled standby if the supplied kWh already includes it.

For the seasonal AC screening model, cooling energy is $Q_{rated} f H$ , and electrical energy is that cooling energy divided by the entered seasonal ratio. BEE Schedule 19 (29 June 2015), pp. 2–4, defines ISEER as seasonal cooling energy divided by seasonal electrical energy and refers to ISO 16358-1:2013. This tool uses an existing rating; it does not calculate or certify ISEER. US DOE FEMP's December 2024 AC guidance defines SEER2 in Btu/Wh and supplies the external 36,000 Btu/h, 3,409 h reference. Converting a ratio's units does not convert its test method.

A progressive bill sums the units inside each consecutive band times that band's price, then adds the user-entered fixed charge. The final band is unlimited. Replacement savings are the difference between two complete bills at the same tariff; they are not units saved times an average price.

Assumptions

All default powers, kWh labels, schedules, load fractions and prices are illustrative inputs, not a catalogue of appliances or utility rates. Each quantity group contains identical appliances; Other B instead combines steady loads with one schedule and excludes idle/standby draw. A daily schedule repeats throughout the billing period; fractional daily hours can represent intermittent use. Fridge annual labels use a fixed 365-day year.

The AC cooling load fraction is average required cooling divided by rated capacity during enabled hours. It is distinct from compressor on-time duty. Neither room temperature nor set temperature alone determines duty: insulation, solar gains, humidity, occupants and equipment behavior also matter. Choose measured duty/load for your actual conditions; no universal temperature correlation is imposed.

Seasonal efficiency is held constant in the approximate AC load model. Very low load cycling, hot-weather efficiency loss, fan speed and latent loads are not modeled separately. Running-watts mode can instead use measured average cooling-operation watts. Compressor-off and enabled idle power are included within their appliance groups; only disabled standby is in the separate standby group.

The replacement fridge uses its own annual label. A seasonal-mode AC replacement uses the same thermal demand and a new ratio from the same test procedure; other AC modes use the replacement label and its reference hours. Every unit in the selected group is replaced; disabled AC standby and fixed charges remain unchanged. No purchase cost or payback is assumed.

Where it applies

Use for household energy budgeting and comparisons with known labels or representative power measurements, not an exact utility invoice or HVAC sizing. Annual/seasonal label scaling cannot predict a particular hot month or a changed thermostat setting without a corresponding load assumption. Compare labels with compatible conditions and rating editions; ISEER, CSPF, SEER and SEER2 may differ in test climates and procedures.

Tariffs are supplied by the visitor; no jurisdiction or current price schedule is implemented. Method/source review: 26 October 2026. Slabs are strictly progressive marginal bands, with nonnegative rates and increasing cumulative thresholds supplied for the whole billing period. Lifeline eligibility, all-units slabs, rebates, taxes, time-of-use, demand charges, minimum bills, exports and late fees require separate treatment.

The historical BEE source explains seasonal terminology, not current star thresholds. Check against the standard in force when using a label for compliance. This is not an installation design tool; installation work belongs to a qualified person.

References

Virginia Cooperative Extension, BSE-301 (2020), Estimating Appliance and Home Electronic Energy Use, pp. 1–2. https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/2901/2901-9014/BSE-301.pdf
Bureau of Energy Efficiency, Schedule 19: Variable Capacity Air Conditioners, 29 June 2015, pp. 2–4 (ISEER definition and ISO 16358-1:2013 method reference). https://www.beestarlabel.com/content/files/inverter%20ac%20schedule%20final.pdf
US Department of Energy, FEMP, Purchasing Energy-Efficient Residential Central Air Conditioners, updated December 2024, Table 1 and energy-use assumptions. https://www.energy.gov/cmei/femp/purchasing-energy-efficient-residential-central-air-conditioners

Inputs

Input	Symbol	Unit	Default
Billing period Enter the days on your bill. Daily schedules repeat over this period.	`days`	day	30
Lights — quantity Set quantity to zero to omit this group.	`n_light`		6
Active power per appliance Use real input watts from a meter or label, not VA or cooling watts.	`P_light`	W	9
Daily active time Daily hours per appliance.	`h_light`	h	5
Fans — quantity Set quantity to zero to omit this group.	`n_fan`		2
Active power per appliance Use real input watts from a meter or label, not VA or cooling watts.	`P_fan`	W	65
Daily active time Daily hours per appliance.	`h_fan`	h	10
TVs — quantity Set quantity to zero to omit this group.	`n_tv`		1
Active power per appliance Use real input watts from a meter or label, not VA or cooling watts.	`P_tv`	W	100
Daily active time Daily hours per appliance.	`h_tv`	h	4
Standby power per TV Applies during the remaining hours. Enter zero if unplugged.	`Ps_tv`	W	1
Fridges — quantity Each fridge in this group uses the same inputs.	`n_fr`		1
Energy source A label includes cycling and auxiliaries; do not add a duty factor to its kWh.	`fr_mode`		Annual kWh label (preferred)
Annual label energy per fridge Illustrative value: replace with your label's kWh per year. Scaled by billing days / 365.	`E_fr_year`	kWh	250
Compressor-on input per fridge Whole-appliance real watts while cooling, including any simultaneous fans.	`P_fr`	W	150
Compressor duty fraction 0.35 means 35% of the day at compressor-on watts. Measure over several days at your room and set temperature; this is not universal.	`d_fr`		0.35
Compressor-off input per fridge Average watts during compressor-off time; include controls and allocate defrost here if not in running watts.	`Ps_fr`	W	3
ACs — quantity Identical units and schedules; set zero to omit.	`n_ac`		1
AC energy source Label kWh takes precedence. Seasonal mode is a screening estimate, not an instantaneous part-load performance map.	`ac_mode`		Cooling load / ISEER or SEER estimate
Daily AC enabled time Cooling time window, including compressor-off cycling within it.	`h_ac`	h	8
Label energy per AC Enter annual/seasonal active-cooling kWh from the label, together with its reference operating hours.	`E_ac_label`	kWh	850
Label reference operating hours Read the label/test basis. The BEE 2015 method uses 1600 h; other schemes differ. Scaling assumes the same weather/load profile.	`H_ac_label`	h	1600
Rated cooling capacity per AC Cooling output, not electrical input. 1 refrigeration ton = 3.51685 kW; 1.5 ton = 5.27528 kW. You can type a cooling capacity with units, for example 18000 BTU/h.	`Q_ac`	kW	5.275275
Average cooling load fraction 0.50 means an average cooling demand of half the rated capacity during enabled hours. Estimate from a load study or measurements at your room/set temperature; not a compressor on-time fraction.	`load_ac`		0.5
Seasonal rating units Use the numerical rating and units on the label. Converting units does not convert between different test standards.	`rating`		ISEER / CSPF / SEER expressed as W/W
Seasonal cooling efficiency ISEER is seasonal cooling energy divided by electrical energy, both in the same units.	`eta_ac`		4.5
SEER or SEER2 US-style seasonal rating. Btu/Wh is converted to the equivalent W/W energy ratio.	`seer_ac`	BTU/Wh	15.35
Compressor-on input per AC Measured/nameplate real input while cooling. Inverter watts vary; use an average over representative cooling operation.	`P_ac`	W	1500
Compressor-on duty fraction Fraction of enabled time at running watts. Tune from measurements for your room, set temperature and weather.	`d_ac`		0.6
Enabled but not cooling input Whole-unit fan/control input while the compressor is off within the enabled window.	`Pi_ac`	W	30
Disabled standby power per AC Only outside enabled hours, and only if connected to power. Enter zero if unplugged, or if your energy label already includes this off-period consumption.	`Ps_ac`	W	3
Other appliance A — quantity Flexible group; A starts as a kettle, B as an always-on router. Set zero to omit.	`n_a`		1
Running power per appliance Real electrical input watts. Replace the example with your device.	`P_a`	W	1500
Daily enabled time For occasional use, enter the average daily hours (for example 2 h/week = 0.286 h/day).	`h_a`	h	0.15
Running duty fraction Use 1 for steady devices. For thermostatic devices this fraction of enabled time draws running watts.	`d_a`		1
Enabled idle power per appliance Power during the rest of enabled time; use zero for a heater that cycles fully off.	`Pi_a`	W	0
Disabled standby per appliance Draw during the rest of the day. Use zero if disconnected.	`Ps_a`	W	0
Combined active power — Other B Sum steady devices with the same schedule. Starts as one router. This simple group has no idle/standby draw; use group A for those. Set watts to zero to omit.	`P_b`	W	12
Daily active time — Other B Hours per day at the combined watts. Use appliance A for cycling or standby loads.	`h_b`	h	24
Tariff model — enter your own prices No utility tariffs are stored. All prices use your own currency; starting values are illustrative only. Enter thresholds for this billing period.	`tariff`		Flat rate
Flat price per kWh — example Currency units per kWh. Replace 8 with your current rate. The 1/kWh unit is the physical rate factor; currency is a numeric label.	`r_flat`	1/kWh	8
Number of progressive slabs Each band charges only its own units, not the entire consumption.	`bands`		3
Slab 1 upper limit — example Cumulative kWh threshold for the complete billing period; thresholds are not prorated.	`b1`	kWh	100
Slab 2 upper limit — example Cumulative kWh threshold for the complete billing period; thresholds are not prorated.	`b2`	kWh	200
Slab 3 upper limit — example Cumulative kWh threshold for the complete billing period; thresholds are not prorated.	`b3`	kWh	300
Slab 4 upper limit — example Cumulative kWh threshold for the complete billing period; thresholds are not prorated.	`b4`	kWh	400
Slab 5 upper limit — example Cumulative kWh threshold for the complete billing period; thresholds are not prorated.	`b5`	kWh	500
Slab 1 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r1`	1/kWh	4
Slab 2 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r2`	1/kWh	6
Slab 3 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r3`	1/kWh	8
Slab 4 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r4`	1/kWh	10
Slab 5 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r5`	1/kWh	12
Slab 6 price per kWh — example Currency units per kWh in this band; the last active band has no upper limit.	`r6`	1/kWh	14
Fixed charge for this bill Currency units per billing period. Unchanged in the replacement scenario; no taxes or surcharges are added automatically.	`charge_fixed`		100
Replacement scenario Replaces every appliance in the selected group; quantities, daily use, thermal demand and tariff stay the same.	`replace`		Replace both groups
New fridge annual label energy Per replacement fridge, kWh per year. Compare labels with the same test basis.	`E_fr_new_year`	kWh	180
New AC seasonal efficiency W/W seasonal ratio using the SAME rating standard as the current AC. Same cooling load; no second duty factor.	`eta_ac_new`		5.5
New AC SEER or SEER2 Same test standard as the old AC; unit conversion alone does not make SEER and SEER2 comparable.	`seer_ac_new`	BTU/Wh	18.77
New AC label energy Per replacement AC, active-cooling energy over its reference hours. Used when the current AC is in label or running-watts mode.	`E_ac_new_label`	kWh	650
New AC label reference hours Use the basis of the replacement label. It must describe a comparable climate/load profile.	`H_ac_new_label`	h	1600

Results

With the default inputs above, the calc gives:

Result	Value
Electricity units this billing period	237.75 kWh
Estimated bill — currency units	2,002.02
AC units including disabled standby	142.11 kWh
Disabled standby units	2.04 kWh
Units after selected replacement	206.42 kWh
Bill after replacement — currency units	1,751.37
Units saved (negative = increase)	31.33 kWh
Bill savings — currency units (negative = increase)	250.64

Checked against sources

Each case below was calculated by this calc and agrees with the value from its source (within the tolerance where one is shown).

Virginia Tech: 200 W window fan, 120 days

Source: Virginia Cooperative Extension BSE-301 (2020), p. 1: 200 W window fan, 4 h/day, 120 days, 0.085 USD/kWh; published 96 kWh and 8.16 USD. Historical example only, not a stored utility tariff.

Inputs: Lights — quantity = 0; Fans — quantity = 1; TVs — quantity = 0; Fridges — quantity = 0; ACs — quantity = 0; Other appliance A — quantity = 0; Fixed charge for this bill = 0; Replacement scenario = No replacement; Active power per appliance = 200 W; Daily active time = 4 h; Billing period = 120 day; Flat price per kWh — example = 0.085 1/kWh; Combined active power — Other B = 0 W; the others as above.

Result	Source	This calc
Electricity units this billing period	96 kWh	96 kWh
Estimated bill — currency units	8.16	8.16

Virginia Tech: computer and monitor, rounding retained

Source: Virginia Cooperative Extension BSE-301 (2020), p. 1: 120 W computer plus 150 W monitor, 4 h/day for 365 days. Published energy is rounded to 394 kWh; unrounded correct energy is 394.2 kWh and cost 33.507 USD. Tolerances retain the publication's rounding.

Inputs: Lights — quantity = 0; Fans — quantity = 0; TVs — quantity = 0; Fridges — quantity = 0; ACs — quantity = 0; Fixed charge for this bill = 0; Replacement scenario = No replacement; Running power per appliance = 270 W; Daily enabled time = 4 h; Billing period = 365 day; Flat price per kWh — example = 0.085 1/kWh; Combined active power — Other B = 0 W; the others as above.

Result	Source	This calc
Electricity units this billing period	394 kWh	394.2 kWh
Estimated bill — currency units	33.51	33.507

DOE FEMP: SEER2 23.5 AC, Southeast example

Source: US DOE FEMP, Purchasing Energy-Efficient Residential Central Air Conditioners (updated December 2024), Table 1: 23.5 SEER2, 36,000 Btu/h and 3,409 annual operating hours give published 5,222 kWh. Here full-load-equivalent hours reproduce that reference; no claim of an instantaneous SEER map. Q=10.55055 kW is 36,000 Btu/h. Historical example only.

Inputs: Lights — quantity = 0; Fans — quantity = 0; TVs — quantity = 0; Fridges — quantity = 0; Other appliance A — quantity = 0; Fixed charge for this bill = 0; Replacement scenario = No replacement; Rated cooling capacity per AC = 10.551 kW; Average cooling load fraction = 1; Seasonal rating units = SEER / SEER2 expressed as Btu/Wh; SEER or SEER2 = 23.5 BTU/Wh; Daily AC enabled time = 9.34 h; Disabled standby power per AC = 0 W; Billing period = 365 day; Flat price per kWh — example = 0.11 1/kWh; Combined active power — Other B = 0 W; the others as above.

Result	Source	This calc
Selected AC energy during enabled hours	5,222 kWh	5,222 kWh
Electricity units this billing period	5,222 kWh	5,222 kWh

DOE FEMP: annual kWh label overrides watts estimate

Source: Transfer of DOE FEMP Table 1's published annual energy of 5,222 kWh as an annual-energy input at its stated 3,409 h basis. Checks label precedence and normalization; it is a transfer check, not independent validation of the label or its test procedure.

Inputs: Lights — quantity = 0; Fans — quantity = 0; TVs — quantity = 0; Fridges — quantity = 0; Other appliance A — quantity = 0; Fixed charge for this bill = 0; Replacement scenario = No replacement; AC energy source = Label kWh and reference hours (preferred); Label energy per AC = 5,222 kWh; Label reference operating hours = 3,409 h; Daily AC enabled time = 9.34 h; Disabled standby power per AC = 0 W; Billing period = 365 day; Flat price per kWh — example = 0.11 1/kWh; Combined active power — Other B = 0 W; the others as above.