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How much am I ‘saving’?

 
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Electricity, Tariffs, Monitoring, Electrics & Providers
Last Post by Tim441 11 months ago
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Toodles
 Toodles
(@toodles)
Famed Member Contributor
Joined: 4 years ago
Posts: 2825
Topic starter 13/08/2025 3:24 pm  

@tim441 Indeed, so many variables! At present, I export solar energy and am paid 15 pence per KWh but I don’t feel it worthwhile to grid-charge the battery at 13 point summat pence, allow ~10% loses for AC-DC-AC conversion to export again at 15 pence; there is no real value in that candle! (We are on Cosy tariff) Regards, Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
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 Tim441
(@tim441)
Honorable Member Contributor
Joined: 4 years ago
Posts: 427
13/08/2025 3:37 pm  

@toodles agreed... probably worth effort at sub 10p? 

IOG is 7p+ vat overnight. Other benefit is ensuring I maximise pv solar prod via exports - not using myself or filling batteries .. say mid May to mid Oct


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8.7kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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 Old_Scientist
(@old_scientist)
Honorable Member Member
Joined: 2 years ago
Posts: 452
13/08/2025 5:20 pm  

We are currently generating and consuming roughly 7000kWh per year, net exporting for the 6 months April to Sept, and net importing October through to March. We have an ASHP, no EV, 7.2kWp solar and a 13.5kW battery.

Predicted generation/consumption:

Net export 2675kWh during summer on IOF at an average of ~26p per kWh = £695

Net import ~2070kWh during winter on Cosy (assuming we self consume all solar generation) at ~13p = £269

Our SC is 365 x 47.53p = £173.50

£695 export - £269 import - £173.50 SC = £252.50 predicted credit for the year

So we are predicted to be running a positive balance of around £250/year giving scope to crank the heating up a little if it gets very cold this winter. That £252.50 could buy us another 1942kWh of heat in winter, giving me confidence that we can probably crank the thermostat up to 20C having run at a miserly 19-19.5C last winter, or maybe turn the DHW up by a couple of degrees. I've already increased our predicted usage a little as I accept we ran on bare minimum during our first winter as we didn't know where the costs/usage would be. I'm not looking to make a profit, if we are net zero cost I'm very happy.


This post was modified 11 months ago by Old_Scientist

Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.


   
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 Tim441
(@tim441)
Honorable Member Contributor
Joined: 4 years ago
Posts: 427
13/08/2025 5:38 pm  

@old_scientist like for like comparisons are almost impossible...

My estimates do not include SC.

Other factors:

We work from home and heat main rooms to 21 deg 

Secondary rooms and bedrooms much cooler

Half building is very old & inefficient. Half is modern and well insulated. We mostly heat the newer part to 21 deg plus kitchen in old.

SW England,.. Somerset .. probably milder than some.

 


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8.7kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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