January results - 61% bill reduction with Samsung + 60kWh battery + Home Assistant hybrid optimiser

Hardware Heatpump
1

Hi all,

Wanted to share my January 2026 results after running my Samsung heat pump through its first proper winter. The numbers have exceeded my expectations.

The setup:

  • Samsung heat pump (monitoring via OpenEnergyMonitor/Emoncms)

  • 60kWh battery storage

  • Existing gas boiler retained for hybrid operation

  • Home Assistant running a custom optimisation algorithm

January 2026 results:

  • Heat pump electric consumption: 1,329 kWh

  • Heat delivered by heat pump: 4,777 kWh

  • Gas boiler usage: 1,231 kWh

  • Monthly COP: 3.59 (space heating 3.65, DHW 3.09)

  • Outside temps ranged from -6.5°C to 10.3°C

  • House maintained at 20.8°C average

The cost comparison:

Jan 2025 Jan 2026
Gas £519 £74
Electricity (heating) - £126
Total £519 £200

That’s a 61% reduction - whilst actually delivering 46% more heat and running the house 1°C warmer than last year.

The plumbing setup:

The system uses a low loss header (LLH), but with a twist. When the heat pump is running solo, the LLH is bypassed entirely and two pumps run in series - this gives better flow rates and avoids the mixing losses you’d get through the header. When the gas boiler is called, the system switches back to operating via the LLH as normal.

The boiler isn’t just a dumb on/off backup either - I’ve set up custom weather compensation curves for it too, just like the heat pump. So when gas is running, it’s still modulating flow temps based on outside air temperature rather than blasting at 70°C. This keeps the boiler running more efficiently and means the heat pump can pick up seamlessly when it’s time to switch back.

How the Home Assistant hybrid optimiser works:

I’m on a tariff with overnight electricity at 5.041p/kWh vs 37.094p/kWh during the day. The 60kWh battery charges overnight and powers daytime loads - but I can’t run the heat pump flat out all day without depleting the battery.

So I built an automation that runs every hour and makes a plan:

  1. Fetches the hourly weather forecast for the day

  2. Calculates expected heat demand for each hour based on outdoor temp vs my balance point (using my measured heat loss coefficient)

  3. Estimates COP for each hour using a simple linear model (COP = a + b × outdoor_temp) - warmer hours have better COP

  4. Works out available battery budget = usable battery capacity minus house base load minus safety reserve

  5. Ranks all daytime hours by COP and selects the hours with the best efficiency that fit within the battery budget

  6. Hours that don’t make the cut → gas boiler

The overnight period (midnight to 7am) always runs the heat pump since I’m on cheap rate anyway.

The result: on mild days, the heat pump handles everything. On cold days, the system automatically picks the warmest hours (best COP) for the heat pump and lets gas cover the coldest hours where COP would be poor anyway.

Looking at my gas usage data, you can see the pattern - most gas consumption happens between 5pm and 11pm on cold days. Early January when we hit -6.5°C saw the heaviest gas usage. By mid-January as temps improved, gas usage dropped significantly - the last week had 4 days with virtually zero gas.

The economics:

At 5p overnight electricity and a COP of 3.59, I’m getting heat at roughly 1.4p/kWh equivalent when the heat pump runs. The gas backup costs more per kWh of heat, but it only kicks in during hours where running the heat pump would either drain the battery or operate at poor efficiency.

The 60kWh battery is the enabler - it time-shifts cheap overnight electricity to power the heat pump during the day without paying 37p/kWh.

Live data: https://emoncms.org/app/view?name=MyHeatpump&readkey=1c01a14f1832f562ac3dcba41fe23d2f

Happy to share the Home Assistant automation YAML if anyone wants to adapt it. The Samsung has been rock solid - COP drops a bit in the cold but it just keeps working.

For anyone wondering whether to keep their gas boiler: a hybrid setup lets you optimise for cost rather than forcing the heat pump to run at any price. Best of both worlds.

6 Likes
2

Which tariff are you on out of interest and how many hours do you get off peak? I’m just ordering my 32kwh batteries today :slight_smile:

3

UW economy 7. So 7 hours :slight_smile:

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4

Interesting.

How big is the house?

How do you charge the batteries, 60kWh in 7 hours is charging at nearly 9kW

You don’t seem to have taken account of battery charging and discharging losses?

How have you sized the radiators?

Presumably, if the radiators are big enough to handle low flow temperatures with the heat pump they put out a massive amount of heat with the higher flow temperature of the gas boiler?

What flow temperatures do you run?

5

Blimey, incredible rate. Needs an E7 meter though which I don’t have. Shame they can’t do it with smart meters too.

6

I have a smart meter, they can easily swap it to e7 and back

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7

375 square metres

I have three inverters, so yes, 3.6kW*3 = 10.8kW

Heat pump peaks at 4kW + any house loads.

Under the 23kW limit, you can pull; you may be able to pull a little more, too. I think if we got an electric car, we are defo going to need to upgrade to three-phase.

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Your right thats about 10%

I sized for a flow temp of 42 at -4.

The gas boiler can operate effectively at the same flow temperatures as a heat pump. I am not even sure I could achieve a 70 °C flow with this much radiator heat sink. My controller sets the flow temp to the same for the heat pump and the gas boiler; you can’t tell the difference in the house when the gas is on.

I operated the boiler this way before installing a heat pump.

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8

Very interesting! I’ll be looking into this when the batteries are installed. That would save me another £250 a year :smiley:

9

How much is gas standing charge?

How does that compared to using daytime electricity when battery runs out?

How often do you use full battery capacity on consecutive days?

10

£120 a year

Any day you can see the line is a day the gas was used

If you say 1200kwh of gas. Which let’s say 96% efficiency 1152 of heat. Cop of 3.6 (which would prob be worse as I only use gas at the worse possible outdoor temps)

320 kWh of electricity at 37.09 £120

but I think the cop would more likely be down in the 2.9 range

400 kWh £150

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11

So can’t usefully have a battery larger then you can fully charge in single night.

But if the battery could be taken closer to 0% state of charge, so giving a few more kwh there are many days it helps.

12

Sorry did I miss explain. I do 100% change is everyday. The house electric demand the the heat bump demands decide this

13

That Economy 7 tariff is crazy good, but it’s a huge pity that they pay out so little on solar export (max 8p if you take out 2 more products with them), undoes all the benefit :frowning:

14

Unfortunately we have no solar so nothing to worry about. It’s annoying the other companies don’t have anything comparable for those with batteries but no electric cars

15

I was thinking that you can’t expand your battery much and still charge 100% each day without 3 phase.

16

Oh sorry I get you now.

I could add another 9.4kwh to each inverter but they would not fully charge every day

or add another inverter at 3.6kW but the draw would be getting pretty high 15kW before house or heat pump

plus the price of in for the 20 days a year ish when the rest of the year the batteries would be idle.

Plus if we ever sell the house we have both no one can complain :joy:

17

Spotted!

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18

Is this just an HA automation or did you write it in something else?

19

How much of the heat delivered was Space Heating?

What is the house fabric like?

20

Whilst this is an interesting setup and obviously works there are some issues that may not suit everybody regarding the hybrid setup.

The first and biggest issue is that it is not eligible for the BUS grant, that’s £7,500 gone before you start talking about the complexity of the installation compared to a direct replacement of gas with heat pump.

Also, whilst the COP is OK, it is not really good and could be better, especially considering you are not using the heat pump in the coldest of conditions. My COP for January in similar temperatures is 4.65 and that is used down to -6.5c as your would be.

If you were to run at a lower flow temperature with the heat pump you could get a better COP, it would use less electricity and negate the use of the gas boiler completely.

Taking everything into account, I suspect you could do as well and probably better with the heat pump on its own.

But as long as you are happy that is all that matters and thank you for sharing the setup with us.

5 Likes