FAQ
TL;DR: Heating a 50 L electric boiler for 2 people adds ~100 PLN/month; “two people should not exceed 150 PLN” [Elektroda, oregon25, post #14381638] Pick G12/G12w tariffs and a timer to halve kWh price, aiming for 7–10 kWh/day.
Why it matters: Correct sizing, tariff choice and insulation can cut hot-water bills by 40 % or more.
Quick Facts
• 7–10 kWh/day for a 100 L tank = 1.8–2.5 PLN on cheap G12W rate [Elektroda, Bałdyzer, #17993092; kortyleski, #17993706]
• Stand-by loss: Ariston Velis 80 L ≈1.2 kWh/day at 60 °C [Elektroda, Radoslaw88, post #14381484]
• Typical annual energy per person: 500–1000 kWh [Elektroda, gaz4, post #14410717]
• G12 night rate ≈0.25 PLN/kWh vs G11 ≈0.60 PLN/kWh [Elektroda, Bałdyzer, #17993092]
• Flow heater needs ≥18 kW three-phase; single-phase limit 5 kW [Elektroda, jack63, post #14383417]
1. How much will an 80 L electric boiler cost for two adults each month?
Users report 7–8 kWh/day with timers, giving 210–240 kWh/month. At 0.25 PLN/kWh (G12 night) that is 53–60 PLN; at 0.60 PLN/kWh (G11) it rises to 126–144 PLN [Elektroda, Bałdyzer, #17993092; Radoslaw88, #14381484].
2. Which tariff is the cheapest for water heating?
G12 or G12w cuts night and weekend energy to ~0.25 PLN/kWh—about 60 % less than flat G11 [Elektroda, Bałdyzer, #17993092]. A timer ensures the heater only runs in cheap periods, maximising savings.
3. How quickly does hot water cool in a modern insulated cylinder?
Tests on a 200 L unit showed only 0.3 kWh loss overnight (≈1 °C drop) after extra insulation [Elektroda, gaz4, post #14408466] Factory data for an 80 L Velis lists 1.2 kWh/24 h at 60 °C [Elektroda, Radoslaw88, post #14381484]
4. Does a larger tank always cost more to run?
A bigger tank means more surface area, yet it lets you store water at a lower temperature. Lower ΔT offsets some surface loss, so running cost per litre can stay similar [Elektroda, jack63, post #14383417]
5. Is a flow (tankless) heater cheaper than storage?
Only if you already have three-phase power and high allocation. A 9 L/min shower needs 18 kW; 5.6 h/month of such load uses 108 kWh (~75 PLN) [Elektroda, Radoslaw88, post #14383112] Upgrading supply adds fixed fees that erase gains [Elektroda, jack63, post #14383417]
6. How many kWh per person per year should I budget for hot water?
Allow 500–1000 kWh. Careful users with efficient shower heads hit 500 kWh; long baths push the upper band [Elektroda, gaz4, post #14410717]
7. What element size suits a flow heater?
For endless hot water at 45 °C with 10 °C inlet, you need about 18 kW (three-phase). Single-phase 5 kW units give lukewarm flow only 4 L/min [Elektroda, jack63, post #14383417]
8. How do I quickly estimate daily boiler energy use?
- Multiply tank litres by 0.06 kWh to heat from 15 °C to 45 °C.
- Add standby loss (label value).
- Multiply by fills per day.
Example: 80 L ×0.06=4.8 kWh +1.2 kWh loss ≈6 kWh/day [Elektroda, Radoslaw88, post #14381484]
9. What edge case inflates bills unexpectedly?
Limescale on the heater element can raise energy use by 30 % because the element over-heats and cycles longer [Carbon Trust Hot Water Guide]. Descale yearly in hard-water areas.
10. Are heat-pump water heaters worth it?
They cut kWh by 50–65 % but cost several times more upfront. Viable for large households or when off-peak power is unavailable [Elektroda, jack63, post #14384541]
11. Is pellet or coal heating cheaper in summer?
One user spent 5 kg coal/day (~4 PLN) for 4 people; switching to a 2 kW electric element on G12W halved cost to ~60 PLN/month and removed maintenance work [Elektroda, Bałdyzer, #17993092].
12. How can I cut standby losses on an existing cylinder?
Wrap the jacket with aluminium-foil backed foam and seal the top lid. A user saw overnight drop fall to 1 °C after this DIY tweak [Elektroda, gaz4, post #14408466]
