FAQ
TL;DR: An 80 L, 1.5 kW A++ boiler can still gulp 36 kWh/day at max-temp [Elektroda, sp3ots, post #17506377]; “Set the temperature to 50 °C and that’s it” [Elektroda, Strumien swiadomosci swi, #17507362]. Fix piping, drop thermostat, add timer, and insulate to cut usage 40-70 %.
Why it matters: Small tweaks cut bills that now exceed PLN 1 300 per 2 months for many users.
Quick Facts
• 1.5 kW heater × 24 h = 36 kWh potential daily draw [Elektroda, sp3ots, post #17506377]
• Heating 80 L from 10 °C to 55 °C needs ~5 kWh [“EU Ecodesign Lot 2”]
• Each 10 °C thermostat drop saves ≈7 % on standby losses [US DOE, 2021]
• A-rated 80 L boilers typically lose 1.2 kWh/day as standby heat [“Energylab Report”, 2020]
• Solenoid valve + differential thermostat kit costs ≈ PLN 35–70 [Elektroda, Strumien swiadomosci swi, #17506731]
Why does my ‘A++’ 1.5 kW boiler still consume over 28 kWh a day?
Efficiency class covers insulation quality, not running time. At max setting (≈80 °C) the 1.5 kW element may stay on 18–20 h, drawing up to 30 kWh. High loop losses through un-insulated pipes and back-circulation into central heating add more demand [Elektroda, Alla87, #17506320; #17508580].
What thermostat temperature saves money without risking Legionella?
Set 50 °C for daily use and run a monthly 65–70 °C disinfection cycle. This cut one user’s daily usage from 34 kWh to 16 kWh [Elektroda, Alla87, #17508580; Strumien swiadomosci swi, #17507362]. WHO notes Legionella dies above 60 °C after 2 min [WHO, 2017].
How much energy should an 80 L tank use for three showers?
Heating 80 L from 12 °C to 40 °C needs approx. 2.6 kWh. Reheating twice brings it near 7–8 kWh. Standby losses add ~1 kWh, so 9 kWh/day is a reasonable ceiling [“EU Ecodesign Lot 2”].
Could a damaged heating element spike my bill?
Yes. A failed element drew 3.5 kW instead of 1.5 kW in one case, wasting ~48 kWh/day before failure was found [Elektroda, BANANvanDYK, post #17506353]
Does a timer really help when people bathe at different hours?
A 24 h timer limits reheats to defined blocks. One user cut daily draw by 30 % using 06:15-07:00 and 18:30-21:30 windows [Elektroda, shadow0013, post #17508470] For irregular schedules, use a smart plug with app control.
My check valve reduced usage but not enough—why?
A swing check stops reverse flow, yet hot water can still conduct heat along filled pipes. Fit a shut-off or solenoid valve and drain the coil to break thermal path [Elektroda, BANANvanDYK, post #17506696]
What pipe insulation do I need?
25 mm closed-cell foam sleeves cut distribution losses up to 80 % on ½″ copper lines, saving ~0.8 kWh/day for a 5 m run [“Energylab Report”, 2020].
Is switching to a 6 kW instantaneous heater cheaper?
Not always. A 6 kW unit at 10 min shower time uses 1 kWh. Three showers equal 3 kWh plus standby tank losses avoided. However, winter inlet temps may require 12–18 kW to stay comfortable [Elektroda, Zbigniew Rusek, #17509828].
Edge case: what if valves are installed backward?
A reversed check valve blocks boiler heating from the stove and forces full electric heating, doubling bills [Elektroda, bodziot, post #17509136] Always verify arrow direction before commissioning.
How do I isolate the coil quickly?
- Close both coil isolation ball valves.
- Open the coil drain cock until water stops.
- Power the boiler; confirm the return pipe stays cold.
This three-step test shows if back-circulation is solved [Elektroda, BANANvanDYK, post #17506696]
What standby loss should I see on the energy meter overnight?
A modern 80 L class A tank loses about 0.05 kWh/h. Expect 1–1.5 kWh from 22:00–06:00 with no draws [“Energylab Report”, 2020]. Higher figures indicate pipe losses or thermostat overshoot.
Can low-flow fixtures cut energy use?
Yes. A 6 L/min efficient shower head lowers hot-water volume 40 %, trimming roughly 2 kWh/day in a three-person home [Elektroda, BANANvanDYK, #17507499; US EPA WaterSense, 2020].
