Free
£0
No account. No limits. Forever.
- Every calculator, in full
- Unlimited U-values, Ψ-values and fRsi on screen
- Condensation screening and the reverse solver
- Save, share and reload your models
Pay per report
£35+VAT a psi junction
Condensation reports £25 +VAT. No account needed.
- Building Control-ready PDF
- Verifiable printed report ID
- Free re-download for 24 hours
- Free re-export for genuine corrections
Most practices
Monkey Pro
£19/month +VAT
Or £190/year — two months free.
- Your practice on every report — logo, address, project references
- No Energycount marketing in the PDF
- Psi reports £15 instead of £35
- Condensation reports £10 instead of £25
- Covers every Monkey tool on your account
Start Monkey ProSign in first — no password
Pro Unlimited
£49/month +VAT
Or £490/year — two months free.
- Everything in Monkey Pro
- Unlimited psi reports — no per-junction charge
- Unlimited condensation reports
- Pays for itself at two reports a month
- Single named user; cancel any time
Start UnlimitedSign in first — no password
How to sign up
- Sign in with your email. There is no password — we send a one-time link that signs you in. Sign in or create an account →
- Pick a plan on your account page. Monthly or annual, Pro or Unlimited, all four buttons are there. Go to your account →
- Pay through Stripe. Add your company name and VAT number at checkout if you need them on the invoice — it is emailed automatically.
Your plan applies immediately, across every tool, on any browser you sign into. To change tier or cancel, use the same account page — cancelling is two clicks and takes effect at the end of the period you have already paid for. Nothing here is needed to use the calculators, or to buy a single report.
Which one is cheaper for you
Worth doing the arithmetic rather than guessing — for most people the answer is the free calculator, and for anyone issuing reports weekly it is Unlimited. All figures ex VAT, for psi junction reports.
| Junction reports a month | Pay per report | Monkey Pro £19 + £15 each | Pro Unlimited £49 flat |
|---|---|---|---|
| 0 | £0 | £19 | £49 |
| 1 | £35 | £34 | £49 |
| 2 | £70 | £49 | £49 |
| 4 | £140 | £79 | £49 |
| 8 | £280 | £139 | £49 |
| A 12-junction plot | £420 | £199 | £49 |
Cheapest option in each row is highlighted. If you have one plot to get through and no wish to subscribe, one month of Unlimited then cancelling is a perfectly sensible way to use this — it is not a trick, and we would rather you did that than paid £420.
Against a subscription-only tool
The closest comparison for thermal bridging is AutoPSI, at £59/month or £649/year for a single Professional licence at the time of writing (ex VAT). Monkey Pro Unlimited is £49/month or £490/year, and the U-value calculator comes with it. The bigger difference is that you can decline the subscription altogether: model everything free, and pay £35 for the one junction you actually need to submit. Please check AutoPSI's own site for their current pricing — ours is the number we can vouch for.
Against having them calculated for you
A consultancy will normally price a bespoke psi set at project level — figures around £3,000 for a five-unit scheme are typical, only dropping to a few pounds a junction when averaged across a large site. That is the right answer when you want somebody else to carry the professional responsibility, and our own SAP team will happily do exactly that. If you are competent to model your own details, this is the cheap way.
Frequently asked questions
Do I have to subscribe to use the tools?
No — and that is deliberate. Every calculator is free to use, with no account and no time limit: unlimited U-values, unlimited junction Ψ-values and f_Rsi, unlimited condensation screening, all on screen. You only pay when you want a formal PDF report to issue, and even then you can buy that one report outright. A subscription is a way to pay less if you produce a lot of them, never a gate on the calculation.
What is the difference between Pro and Pro Unlimited?
Both put your practice branding on every report and remove our marketing from it. Pro at £19/month then charges a member rate per report — psi reports £15 instead of £35, condensation reports £10 instead of £25. Pro Unlimited at £49/month includes those reports outright, however many you produce. If you issue two or more a month, Unlimited costs less.
Which tools does a subscription cover?
One subscription covers every Monkey tool on your account — U-Monkey and ΨMonkey today, and whatever we add next at no extra cost. There is no per-tool licence to buy or manage.
How does it compare with AutoPSI?
AutoPSI is the closest comparison for thermal bridging. Its published pricing at the time of writing (June 2026) is £59/month or £649/year for a single Professional licence, ex VAT. Monkey Pro Unlimited is £49/month or £490/year, includes the U-value calculator as well, and — unlike a subscription-only tool — you can skip it entirely and pay £35 for the one junction you need. Always check autopsi.co.uk for their current pricing.
What does "unlimited" actually mean?
It means what it says for one person doing their own work: export as many psi and condensation reports as your projects need. It is a single named user, not a shared login for a team or a bureau reselling reports — if that is what you need, call us and we will price it properly.
Can I cancel?
Yes, online from your account page in two clicks. It takes effect at the end of the period you have already paid for, and there is nothing to email or phone about. Reports you have already produced are yours and stay verifiable.
Can I switch between the tiers?
Yes, either way, at any time from your account. Stripe prorates the difference automatically, so upgrading part-way through a month only costs the balance.
Is VAT included?
No — every price here is ex VAT, which is the number a VAT-registered practice actually compares. UK VAT at 20% is added at checkout and itemised on the invoice, and you can add your company name and VAT number during payment.