Heat Pump Update: Week 2 – Radiators

Oct 26, 2025 | Batteries, Energy, Heat Pump, Octopus Energy, Solar

Forehead Thermometer

Heat Pump Update: Week 2 – Radiators, Batteries, and Beating the Chill

Last week, I shared the initial excitement (and a few teething problems) of installing my air-source heat pump over at Our Heartwarming Journey to a Greener Home with a Heat Pump. One week in, and the system is humming along nicely—proving that low-temperature heating can keep a home toasty without the drama of traditional boilers.

The “Cold” Radiator Myth

Walk up to any radiator in the house right now and slap a forehead thermometer on it: you’ll barely crack 30–35 °C. That’s not a fault. Heat pumps run water at 35–45 °C, far cooler than the 60–70 °C you’d see from a gas boiler. Yet the indoor temperature is a steady 20 °C while it’s hovering around 10 °C outside. The magic? Continuous, gentle heat transfer rather than short, scorching blasts. The house feels evenly warm—no cold spots, no roaring boiler cycling on and off.

Forehead Thermometer

Using a Forehead Thermometer to gauge the temperature of a Radiator on an Air Source Heat Pump

 

Consumption: A Slight Bump, but Still Impressive

Last week’s total draw was 33 kWh for the whole house (heat pump + everything else). This week, with overnight lows dipping a couple of degrees colder, we’re tracking toward the low 40s. That’s still a fraction of what the old oil boiler would have guzzled, and the coefficient of performance (COP) is sitting comfortably above 4 on milder days.

Night-Charged Batteries & Solar Top-Ups

Here’s the bit I love: virtually all of that electricity is coming from my home battery bank. The batteries charge overnight on the Octopus Go Faster tariff at 7 p/kWh, then discharge through the day to run the heat pump, lights, kettle—everything. On sunnier afternoons, the solar panels chip in a few extra kWh to keep the batteries topped up. Net result? My daytime grid draw is near zero, and the heat pump is effectively running on 7p electricity (or free sunshine).

Early Verdict

Two weeks in, the heat pump is living up to the hype. Comfortable heat, whisper-quiet operation, and bills that make me smile. Next update: I’ll dive into the detailed COP logs and see how the system behaves when we finally get a proper frost. Provisionally our consumption over the last 2 weeks have been as follows:

Energy used so far since 12/10/2025

  • 85 kwh energy consumed
  • Heat produced 402 kWh

Based on this data, the COP performance currently is 4.67 (so over 400% efficient!)

20 Degrees

If you’ve got a heat pump install on the horizon, drop your questions below—I’m happy to share the warts-and-all experience.

Or – you can get a quote from Octopus – free of charge by clicking this link – Get me a HeatPump Quote.