How much does it cost to heat water with an electric water heater
An electric water heater for four people uses about 4,085 kWh of electricity a year, including about 491 kWh of losses from a 200 l tank. On the G11 tariff that is about 4,248 PLN, on G12 about 3,023 PLN. The calculator compares the heater on both tariffs with a hot water heat pump.
Example: 4 people, 47 l per person a day
Cheapest: Hot water heat pump, about 1,699 PLN a year
about 142 PLN a monthheat about 4,085 kWh/yrincl. tank about 491 kWh
- Hot water heat pump: about 1,699 PLN a year
- Electric water heater, G12: about 3,023 PLN a year
- Electric water heater, G11: about 4,248 PLN a year
Difference between the cheapest and the most expensive source: about 2,549 PLN a year.
Bar scale: up to 5,000 PLN/yrPrices from 11 October 2026, estimate
| Heat source | Yearly purchase | Yearly | Shower | Bath |
|---|---|---|---|---|
| Hot water heat pump | 1,634 kWh | 1,699 PLN | 0.93 PLN | 2.18 PLN |
| Electric water heater, G12 | 4,085 kWh | 3,023 PLN | 1.65 PLN | 3.88 PLN |
| Electric water heater, G11 | 4,085 kWh | 4,248 PLN | 2.32 PLN | 5.45 PLN |
Assumptions and formulaPrices from 11 October 2026
Heat in the water at the tap, your inputs
4 people × 47 l × 365 days × 4.19 kJ/(kg·K) × (55 − 10) K ÷ 3600 = 3,594 kWh/yr
Standing losses of the tank
200 l × 0.28 W/l × 8,760 h ÷ 1000 = 491 kWh/yr
Q = 3,594 + 491 = 4,085 kWh/yr
Yearly cost of each source
cost = Q ÷ efficiency × price
- Electric water heater, G11÷ 1.00 × 1.04 PLN/kWh
- Electric water heater, G12÷ 1.00 × 0.74 PLN/kWh
- Hot water heat pump÷ 2.50 × 1.04 PLN/kWh
One wash, water mixed to 40°C
64 l × 4.19 × (40 − 10) ÷ 3600 = 2.23 kWh
- Specific heat of water (1 l = 1 kg)
- 4.19 kJ/(kg·K)Energy performance certificate methodology, Polish Journal of Laws 2015 item 376
- Losses of a 200 l tank in a heated room
- 0.28 W/l with 100 mm, 0.40 W/l with 50 mmEnergy performance certificate methodology, Polish Journal of Laws 2015 item 376
- Electric heater: efficiency
- 100 %
- Hot water heat pump: yearly COP
- 2.5Example: yearly COP 2.5-3; Hewalex PCWU 200eK has COP 3.67 in test conditions
- Electricity price, G11
- 1.04 PLN/kWhURE G11 tariffs 2026 (PGE, Tauron, Enea, Energa), average with distribution
- Average electricity price, G12
- 0.74 PLN/kWhPGE 2026 tariff, G12, energy with variable charges, gross
- G12: cheaper zone share in the example
- 80 %Example from our guide: the water heater runs mostly at night
- Shower, example
- 64 l at 40°C (8 min × 8 l/min)
- Bath, example
- 150 l at 40°C
An estimate. Fixed charges, pipe and circulation losses, cold water and sewage and the device itself are not included.
How electricity, gas, pellet and coal prices have changed, month by month. Price history
Ready-made calculations
How to use the calculator
- Enter the number of people and how much hot water one person uses a day. If you have no reading, keep 47 l.
- Pick the tank insulation: a new heater has 100 mm, an older or cheaper one 50 mm.
- Enter the G11 price and the average G12 price from your bill, or keep the defaults.
- Click Calculate cost. To compare the heater with gas or pellets, switch those sources on.
How much electricity a water heater uses
An electric heater turns 1 kWh of electricity into 1 kWh of heat, so you buy as much electricity as the water needs, plus the tank losses. For four people using 47 l of 55°C water a day that is about 4,085 kWh a year, on average about 11.2 kWh and 11.64 PLN a day on G11.
A 200 l tank with 100 mm of insulation loses about 1.34 kWh a day, even when nobody opens a tap. Over a year that is about 491 kWh and 510 PLN. For one person the losses are about 35% of the electricity the heater uses, and the heater costs about 1,445 PLN a year.
A water heater on the G12 tariff
On G12 the heater can warm the water mostly at night. Example for the PGE network: 80% of the power in the cheaper zone at 0.6111 PLN and 20% in the day zone at 1.2490 PLN gives an average of about 0.74 PLN/kWh. Four people then pay about 3,023 PLN instead of about 4,248 PLN, about 1,225 PLN less a year.
G12 changes the price for the whole meter. Power used during the day, e.g. for cooking, costs more than on G11, so check whether it pays off for the whole house.
Electric water heater or hot water heat pump
A hot water heat pump with COP 2.5 uses about 1,634 kWh of electricity for four people and costs about 1,699 PLN a year. That is about 2,549 PLN less than an electric heater on G11 and about 1,324 PLN less than on G12.
Frequently asked questions
How much electricity does a 200 l water heater use a day?
For four people about 11.2 kWh a day, of which about 1.34 kWh are losses from a tank with 100 mm of insulation. At 1.04 PLN/kWh that is about 11.64 PLN a day.
How much does it cost to heat a 200 l tank?
Heating 200 l of water from 10 to 55°C takes about 10.5 kWh. On G11 that costs about 10.89 PLN, on G12 at an average of about 0.74 PLN/kWh about 7.75 PLN.
Does heating water at night pay off?
In the PGE example four people pay about 1,225 PLN less a year if 80% of the power for hot water falls in the cheaper zone. Whether G12 pays off depends on how much power the whole house uses during the day.