We've published a flow rate and pipe sizing calculator on the site. Your heat pump is rated at a specific output, but it can only hit that output if the primary pipework can actually move enough water to carry the heat. Get the primary pipe run wrong and the system is throttled before it's even switched on.

The calculator tells you the flow rate your system needs, checks whether your pipe diameter can deliver it, and shows you velocity and pressure drop across the run. Common copper and PEX sizes are preloaded.

https://renewableheatinghub.co.uk/is-poor-flow-throttling-your-heat-pump/

This tool currently runs two independent checks on a heat loss estimate (W/m² against property age and fabric, and a cross-reference against historical gas consumption) then asks four installer qualification questions covering controls, buffers and commissioning. The idea is to give homeowners enough grounding to push back on a quote before they sign anything.

It's in beta. The sizing logic is solid but the building categories and W/m² thresholds are still being refined. If you run it against a real installation (yours, a recent one you've been involved with or a horror story from the forum) and something doesn't look right, please say so here.

https://renewableheatinghub.co.uk/does-your-installers-heat-loss-figure-actually-stack-up

@editor in the spirit of helping out here. I ran the checks on our house, and it points to some inaccuracies in your sums(!) There’s two screenshots here, one our actual needed power, 8kW and one of the example quotes we had, 10kW. But the 8 should have showed as ok yet both show as a problem when the answer should be 6-9kW. Good luck finding it!.

@judith  very helpful, thank you. I know the ranges are out and we're working on getting them accurate.

A great idea, very useful tool. 🙂

Another example. In this one the wording does not seem perfect.

Perhaps it was me but the annual gas consumption does not seem to to be used.

@judith it may well be not be used in the logic of the applet, but given it is referred to in the wording, it can mislead. If that is the case, easily fixed by placing that comment on a final sentence.

We’ve just published a new interactive Weather Compensation Simulator.

Weather compensation is one of the most important heat pump settings, but it’s also one of the least understood for heat pump newbies. Our new tool lets you visualise how outdoor temperature, flow temperature and efficiency interact, and compare a weather-compensated system against a traditional fixed-flow approach.

Have a play with it here:
https://renewableheatinghub.co.uk/should-your-heat-pump-really-be-running-at-55c-weather-compensation-simulator/

Let us know what you think.

Sounds very useful. A couple of suggestions: 

It would be nice to have half degree options in the minimum temperature. 

And more importantly, electricity prices start much lower than 10p/kwh.. plenty around 8p and some of us are enjoying just above 3p..

@batpred I suspect others may know but could you explain how you manage 3p?  I can’t believe that is actually the unit price you are paying to your energy company.  Probably lots of storage and PV?  What have I missed?

Posted by: @davidb

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@batpred I suspect others may know but could you explain how you manage 3p?  I can’t believe that is actually the unit price you are paying to your energy company.  Probably lots of storage and PV?  What have I missed?

I was getting my leccy at 7p with the intelligent go from OE. When the some taxation was moved from electricity prices onto general taxation, we got a 3.5 discount, like many others on different tariffs..